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C# passing property of viewmodel into dispatcher

I have a method which updates the contents of a WriteableBitmap (FrameDataNew) which is a property in my viewmodel (VM):
public WriteableBitmap FrameDataNew
{
get { return frameDataNew; }
set
{
frameDataNew = value;
OnProptertyChanged("FrameDataNew");
}
}
private WriteableBitmap frameDataNew = null;
When I receive a new Bitmap from a gstreamer class I have written I update FrameDataNew in order to show the latest frame onscreen. the window is a simple Image control which has its source bound to FrameDataNew.
The following code works fine to do this in my event handler:
/// <summary>
/// BitmapCaptured event handler for when a new video frame is received from the IP source
/// </summary>
/// <param name="sender">The originating source of the event</param>
/// <param name="NewBitmap">The new frame in Bitmap form</param>
private void PipeLine_BitmapCaptured(object sender, Bitmap NewBitmap)
{
// render to the screen
Dispatcher.Invoke(() =>
{
// check the existence of the WriteableBitmap and also the dimensions, create a new one if required
if ((VM.FrameDataNew == null) || (VM.FrameDataNew.Width != NewBitmap.Width) || (VM.FrameDataNew.Height != NewBitmap.Height))
VM.FrameDataNew = new WriteableBitmap(NewBitmap.Width, NewBitmap.Height, NewBitmap.HorizontalResolution, NewBitmap.VerticalResolution, PixelFormats.Bgr24, null);
// lock the bitmap data so we can use it
BitmapData data = NewBitmap.LockBits(new Rectangle(0, 0, NewBitmap.Width, NewBitmap.Height), ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
// lock the backbuffer of the WritebaleBitmap so we can modify it
VM.FrameDataNew.Lock();
// Copy the bitmap's data directly to the on-screen buffers
CopyMemory(VM.FrameDataNew.BackBuffer, data.Scan0, (data.Stride * data.Height));
// Moves the back buffer to the front.
VM.FrameDataNew.AddDirtyRect(new Int32Rect(0, 0, data.Width, data.Height));
// unlock the back buffer again
VM.FrameDataNew.Unlock();
//
//NewBitmap.UnlockBits(data);
});
}
[DllImport("Kernel32.dll", EntryPoint = "RtlMoveMemory")]
public static extern void CopyMemory(IntPtr Destination, IntPtr Source, int Length);
Now I want to update my program to handle multiple pipelines and WriteableBitmaps so I can show several video feeds. The first thing I did was create a static utilities class so I can pass in the new bitmap (NewBitmap) and the WriteableBitmap (VM.FrameDataNew) I wish to update. This I then called as required when the new frame arrives:
The utilities class (just the code concerned with my question):
public static class Utils
{
/// <summary>
/// Inject the source Bitmap into the Destination WriteableBitmap
/// </summary>
/// <param name="Src">The source Bitmap</param>
/// <param name="Dest">The destination WriteableBitmap</param>
public static void InjectBitmap(Bitmap Src, WriteableBitmap Dest)
{
if ((Dest == null) || (Dest.Width != Src.Width) || (Dest.Height != Src.Height))
Dest = new WriteableBitmap(Src.Width, Src.Height, Src.HorizontalResolution, Src.VerticalResolution, PixelFormats.Bgr24, null);
BitmapData data = Src.LockBits(new Rectangle(0, 0, Src.Width, Src.Height), ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
Dest.Lock();
// Copy the bitmap's data directly to the on-screen buffers
CopyMemory(Dest.BackBuffer, data.Scan0, (data.Stride * data.Height));
// Moves the back buffer to the front.
Dest.AddDirtyRect(new Int32Rect(0, 0, data.Width, data.Height));
Dest.Unlock();
//
Src.UnlockBits(data);
}
[DllImport("Kernel32.dll", EntryPoint = "RtlMoveMemory")]
public static extern void CopyMemory(IntPtr Destination, IntPtr Source, int Length);
}
...and the way I call it:
/// <summary>
/// BitmapCaptured event handler for when a new video frame is received from the IP source
/// </summary>
/// <param name="sender">The originating source of the event</param>
/// <param name="NewBitmap">The new frame in Bitmap form</param>
private void PipeLine_BitmapCaptured(object sender, Bitmap NewBitmap)
{
// render to the screen
Dispatcher.Invoke(() =>
{
Utils.InjectBitmap(NewBitmap, VM.FrameDataNew);
});
}
The image no longer appears onscreen. Stepping through the code it looks like every time InjectBitmap() is called the destination WriteableBitmap is null? The code creates a new one in the first if statement but VM.FrameDataNew remains null?
I'm definitely at the edge of my experience with this so any help would be much appreciated.
Edit: The aim is to have an observable collection of WriteableBitmaps so I can handle several of these efficiently.

The reason is simple: you don't assign the newly created object to the FrameDataNew property, so its value remains null.
Don't forget that in C# the reference type instances are passed by reference.
So in your method you're doing the following:
void InjectBitmap(Bitmap Src, WriteableBitmap Dest)
{
if (Dest == null)
Dest = new WriteableBitmap(/* ... */);
}
But Dest is just a local variable inside of your method - the method's arguments can be seen as method's local variables.
So you assign a newly created instance to a local variable that will of course be lost when the method returns.
What you need here is a ref parameter:
void InjectBitmap(Bitmap src, ref WriteableBitmap dest)
{
if (dest == null)
dest = new WriteableBitmap(/* ... */);
}
Note that I changed the parameter name casing to match the C# style guide.
However, this won't work for properties, so InjectBitmap(NewBitmap, VM.FrameDataNew) won't compile if FrameDataNew is a property.
You could make the FrameDataNew to a field, but having a non-private mutable field is a bad idea.
You could use a temporary local variable, but it's somehow ugly:
var copy = VM.FrameDataNew;
InjectBitmap(NewBitmap, ref copy);
if (copy != VM.FrameDataNew)
VM.FrameDataNew = copy;
I would rethink your design so that you don't need all that stuff.
By the way, having multiple calls to Dispatcher.Invoke in a multithreaded environment (especially if the invoked methods are slow, and yours are) will drop your app's performance and make the UI unresponsive.

How can I update this kinect depth-basics code so that i can save raw depth data such as uint16 format in C#?

I want to change this code so it can save raw depth data as uint16 format. but at this stage, it saves the image in uint8 format by converting the values 0-255. but i need to save the value as it come from camera or kinect such as uint16 format.
Code:depthBasics:
//------------------------------------------------------------------------------
// <copyright file="MainWindow.xaml.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
namespace Microsoft.Samples.Kinect.DepthBasics
{
using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Windows;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using Microsoft.Kinect;
/// <summary>
/// Interaction logic for MainWindow
/// </summary>
public partial class MainWindow : Window, INotifyPropertyChanged
{
/// <summary>
/// Map depth range to byte range
/// </summary>
private const int MapDepthToByte = 8000 ;
/// <summary>
/// Active Kinect sensor
/// </summary>
private KinectSensor kinectSensor = null;
/// <summary>
/// Reader for depth frames
/// </summary>
private DepthFrameReader depthFrameReader = null;
/// <summary>
/// Description of the data contained in the depth frame
/// </summary>
private FrameDescription depthFrameDescription = null;
/// <summary>
/// Bitmap to display
/// </summary>
private WriteableBitmap depthBitmap = null;
/// <summary>
/// Intermediate storage for frame data converted to color
/// </summary>
private byte[] depthPixels = null;
/// <summary>
/// Current status text to display
/// </summary>
private string statusText = null;
/// <summary>
/// Initializes a new instance of the MainWindow class.
/// </summary>
public MainWindow()
{
// get the kinectSensor object
this.kinectSensor = KinectSensor.GetDefault();
// open the reader for the depth frames
this.depthFrameReader = this.kinectSensor.DepthFrameSource.OpenReader();
// wire handler for frame arrival
this.depthFrameReader.FrameArrived += this.Reader_FrameArrived;
// get FrameDescription from DepthFrameSource
this.depthFrameDescription = this.kinectSensor.DepthFrameSource.FrameDescription;
// allocate space to put the pixels being received and converted
this.depthPixels = new byte[this.depthFrameDescription.Width * this.depthFrameDescription.Height];
// create the bitmap to display
this.depthBitmap = new WriteableBitmap(this.depthFrameDescription.Width, this.depthFrameDescription.Height, 96.0, 96.0, PixelFormats.Gray8, null);
// set IsAvailableChanged event notifier
this.kinectSensor.IsAvailableChanged += this.Sensor_IsAvailableChanged;
// open the sensor
this.kinectSensor.Open();
// set the status text
this.StatusText = this.kinectSensor.IsAvailable ? Properties.Resources.RunningStatusText
: Properties.Resources.NoSensorStatusText;
// use the window object as the view model in this simple example
this.DataContext = this;
// initialize the components (controls) of the window
this.InitializeComponent();
}
/// <summary>
/// INotifyPropertyChangedPropertyChanged event to allow window controls to bind to changeable data
/// </summary>
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Gets the bitmap to display
/// </summary>
public ImageSource ImageSource
{
get
{
return this.depthBitmap;
}
}
/// <summary>
/// Gets or sets the current status text to display
/// </summary>
public string StatusText
{
get
{
return this.statusText;
}
set
{
if (this.statusText != value)
{
this.statusText = value;
// notify any bound elements that the text has changed
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs("StatusText"));
}
}
}
}
/// <summary>
/// Execute shutdown tasks
/// </summary>
/// <param name="sender">object sending the event</param>
/// <param name="e">event arguments</param>
private void MainWindow_Closing(object sender, CancelEventArgs e)
{
if (this.depthFrameReader != null)
{
// DepthFrameReader is IDisposable
this.depthFrameReader.Dispose();
this.depthFrameReader = null;
}
if (this.kinectSensor != null)
{
this.kinectSensor.Close();
this.kinectSensor = null;
}
}
/// <summary>
/// Handles the user clicking on the screenshot button
/// </summary>
/// <param name="sender">object sending the event</param>
/// <param name="e">event arguments</param>
private void ScreenshotButton_Click(object sender, RoutedEventArgs e)
{
if (this.depthBitmap != null)
{
// create a png bitmap encoder which knows how to save a .png file
BitmapEncoder encoder = new PngBitmapEncoder();
// create frame from the writable bitmap and add to encoder
encoder.Frames.Add(BitmapFrame.Create(this.depthBitmap));
string time = System.DateTime.UtcNow.ToString("hh'-'mm'-'ss", CultureInfo.CurrentUICulture.DateTimeFormat);
string myPhotos = Environment.GetFolderPath(Environment.SpecialFolder.MyPictures);
string path = Path.Combine(myPhotos, "KinectScreenshot-Depth-" + time + ".png");
// write the new file to disk
try
{
// FileStream is IDisposable
using (FileStream fs = new FileStream(path, FileMode.Create))
{
encoder.Save(fs);
}
this.StatusText = string.Format(CultureInfo.CurrentCulture, Properties.Resources.SavedScreenshotStatusTextFormat, path);
}
catch (IOException)
{
this.StatusText = string.Format(CultureInfo.CurrentCulture, Properties.Resources.FailedScreenshotStatusTextFormat, path);
}
}
}
/// <summary>
/// Handles the depth frame data arriving from the sensor
/// </summary>
/// <param name="sender">object sending the event</param>
/// <param name="e">event arguments</param>
private void Reader_FrameArrived(object sender, DepthFrameArrivedEventArgs e)
{
bool depthFrameProcessed = false;
using (DepthFrame depthFrame = e.FrameReference.AcquireFrame())
{
if (depthFrame != null)
{
// the fastest way to process the body index data is to directly access
// the underlying buffer
using (Microsoft.Kinect.KinectBuffer depthBuffer = depthFrame.LockImageBuffer())
{
// verify data and write the color data to the display bitmap
if (((this.depthFrameDescription.Width * this.depthFrameDescription.Height) == (depthBuffer.Size / this.depthFrameDescription.BytesPerPixel)) &&
(this.depthFrameDescription.Width == this.depthBitmap.PixelWidth) && (this.depthFrameDescription.Height == this.depthBitmap.PixelHeight))
{
// Note: In order to see the full range of depth (including the less reliable far field depth)
// we are setting maxDepth to the extreme potential depth threshold
ushort maxDepth = ushort.MaxValue;
// If you wish to filter by reliable depth distance, uncomment the following line:
//// maxDepth = depthFrame.DepthMaxReliableDistance
this.ProcessDepthFrameData(depthBuffer.UnderlyingBuffer, depthBuffer.Size, depthFrame.DepthMinReliableDistance, maxDepth);
depthFrameProcessed = true;
}
}
}
}
if (depthFrameProcessed)
{
this.RenderDepthPixels();
}
}
/// <summary>
/// Directly accesses the underlying image buffer of the DepthFrame to
/// create a displayable bitmap.
/// This function requires the /unsafe compiler option as we make use of direct
/// access to the native memory pointed to by the depthFrameData pointer.
/// </summary>
/// <param name="depthFrameData">Pointer to the DepthFrame image data</param>
/// <param name="depthFrameDataSize">Size of the DepthFrame image data</param>
/// <param name="minDepth">The minimum reliable depth value for the frame</param>
/// <param name="maxDepth">The maximum reliable depth value for the frame</param>
private unsafe void ProcessDepthFrameData(IntPtr depthFrameData, uint depthFrameDataSize, ushort minDepth, ushort maxDepth)
{
// depth frame data is a 16 bit value
ushort* frameData = (ushort*)depthFrameData;
// convert depth to a visual representation
for (int i = 0; i < (int)(depthFrameDataSize / this.depthFrameDescription.BytesPerPixel); ++i)
{
// Get the depth for this pixel
ushort depth = frameData[i];
// To convert to a byte, we're mapping the depth value to the byte range.
// Values outside the reliable depth range are mapped to 0 (black).
this.depthPixels[i] = (byte)(depth >= minDepth && depth <= maxDepth ? (depth / MapDepthToByte) : 0);
}
}
/// <summary>
/// Renders color pixels into the writeableBitmap.
/// </summary>
private void RenderDepthPixels()
{
this.depthBitmap.WritePixels(
new Int32Rect(0, 0, this.depthBitmap.PixelWidth, this.depthBitmap.PixelHeight),
this.depthPixels,
this.depthBitmap.PixelWidth,
0);
}
/// <summary>
/// Handles the event which the sensor becomes unavailable (E.g. paused, closed, unplugged).
/// </summary>
/// <param name="sender">object sending the event</param>
/// <param name="e">event arguments</param>
private void Sensor_IsAvailableChanged(object sender, IsAvailableChangedEventArgs e)
{
// on failure, set the status text
this.StatusText = this.kinectSensor.IsAvailable ? Properties.Resources.RunningStatusText
: Properties.Resources.SensorNotAvailableStatusText;
}
}
}

private unsafe void ProcessDepthFrameData(IntPtr depthFrameData, uint depthFrameDataSize, ushort minDepth, ushort maxDepth)
{
// CONVERT IN TO ANY VALID FORMAT YOU WANT
// THEN HERE YOU HAVE DEPTH DATA ARRAY, SAVE IT AS YOU LIKE
ushort* frameData = (ushort*)depthFrameData;
}
If you need more efficiency, you can try something like
depthFrame.CopyFrameDataToBuffer(buffer);
In Reader_FrameArrived function.

The example provided in the Kinect SDK saves the PNG's in 8-bit format (0-255) therefore you loose the depth values. The issue is that WPF(?) cannot display 16-bit image data on screen (i believe due to GDI+ restrictions as mentioned in another SO question)
To save the depth images as Raw 16-bit PNG's; a couple of things need to be done.
WriteableBitmap item with PixelFormats.Gray16 needs to be declared, instead of the PixelFormats.Gray8
Two separate WritePixels need to be called, one for displaying the image in (byte) format and another for saving the depth image in 16-bit (ushort) format
Lastly, the depth data acquired needs to be processed twice, once in a byte array for displaying on screen, and once in ushort array for saving.
Note that the above can be modified as required (or for performance reasons if req) but for me, this works just fine and i can display the depth images and save the raw depth data aswell.
The code is as follows:
Initialize a new var:
private ushort[] raw = null;
private WriteableBitmap rawPNG = null;
In MainWindow Create two writeableBitmap's
this.depthBitmap = new WriteableBitmap(this.depthFrameDescription.Width, this.depthFrameDescription.Height, 96.0, 96.0, PixelFormats.Gray8, null);
this.rawPNG= new WriteableBitmap( this.depthFrameDescription.Width, this.depthFrameDescription.Height, 96.0, 96.0, PixelFormats.Gray16, null );
In ProcessDepthFrameData assign the values:
// FOR DISPLAYING ON SCREEN:
// To convert to a byte, we're mapping the depth value to the byte range.
// Values outside the reliable depth range are mapped to 0 (black).
this.depthPixels[i] = (byte)(depth >= minDepth && depth <= maxDepth ? (depth / MapDepthToByte) : 0);
// FOR SAVING RAW PNG 16-BIT DATA
// Keeping the raw depth values after clipping them to the max depth. The data is converted to ushort which is 16bit data
raw[i] = (ushort)(depth >= minDepth && depth <= maxDepth ? (depth) : 0);
In RenderDepthPixels, create teh two images:
// Rendering frame for displaying on the screen, in 8-Bit grayscale format
depthBitmap.WritePixels(
new Int32Rect( 0, 0, depthBitmap.PixelWidth, depthBitmap.PixelHeight ),
depthPixels,
depthBitmap.PixelWidth,
0 );
// Rendering frame for saving as raw-16-bit PNG file
rawPNG.WritePixels(
new Int32Rect( 0, 0, depthBitmap.PixelWidth, depthBitmap.PixelHeight ),
raw,
depthBitmap.PixelWidth * 2,
0 );
And lastly, in ScreenshotButton_Click, save the file:
// TO SAVE THE DISPLAYED 8-BIT PNG
//encoder.Frames.Add( BitmapFrame.Create( this.depthBitmap) );
// TO SAVE THE RAW 16-BIT PNG
encoder.Frames.Add( BitmapFrame.Create( this.rawPNG ) );
The results can be verified by loading the depth image in Matlab. Imread shows a Uint16 image format and the depth values are retained in the matrix. Or by just checking the png file properties :)
I have shared the complete code that is working for me at Pastebin. Hopefully it should work for you aswell, and solves the issue.

What is the replacement of Graphics and Pen class in uwp app?

This is a WinForm code
private EasyScript eScript;
/// <summary>
/// Graphics object we'll draw on to in order to produce a signature
/// image.
/// </summary>
private Graphics graphics;
/// <summary>
/// Raster backing the graphics object.
/// </summary>
private Bitmap raster;
/// <summary>
/// Pen we'll use to create strokes on our graphics object.
/// </summary>
private Pen pen;
/// <summary>
/// The last point we captured.
/// </summary>
private Coordinate lastPoint = null;
/// <summary>
/// Whether or not the next event we receive should clear the signature.
/// </summary>
private bool clearOnNext = false;
/// <summary>
/// The current stroke count.
/// </summary>
private int strokeCount = 0;
/// <summary>
/// The amount to scale the coordinates by.
/// </summary>
private double scaleFactor = 1;
/// <summary>
/// Initializes a new instance of the <see cref="ExampleForm"/> class.
/// </summary>
public ExampleForm()
{
//Create a new EasyScript object.
this.eScript = new EasyScript();
//Register ourselves as a signature listener.
eScript.AddListener(this);
//Initialize our form.
this.InitializeComponent();
//Initialize our drawing components.
raster = new Bitmap(signaturePictureBox.Width, signaturePictureBox.Height);
graphics = Graphics.FromImage(raster);
//Enable high quality drawing.
graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
graphics.CompositingQuality = CompositingQuality.HighQuality;
graphics.SmoothingMode = SmoothingMode.AntiAlias;
pen = new Pen(Brushes.Black);
//Calculate our scale factor based on the size of the picture box.
scaleFactor = signaturePictureBox.Width / eScript.GetSignatureProtocol().GetWidth();
//Clear the picture box.
ClearSignatureBox();
// this allows the form to preview all keyboard events before other parts of the form are allowed
// to get them. If a particular keyboard event is from a ScripTouch device,
// we can prevent the event from propogating to other form elements, such as a TextBox.
this.KeyPreview = true;
this.cardSwipeInfoTextBox.ReadOnly = true;
this.signatureInfoTextBox.ReadOnly = true;
}
I need to convert this in my UWP app. However i can use WriteableBitmap in place of Bitmap and SolidColorBrush in place of Pen. But what should be for Graphics class.
Anyhow everything is solved if i consider graphics as a WriteableBitmap apart from these below lines
graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
graphics.CompositingQuality = CompositingQuality.HighQuality; graphics.SmoothingMode = SmoothingMode.AntiAlias;
and
graphics.FillRectangle(Colors.White, 0, 0, signature.Width, signature.Height);
and
graphics.DrawLine(pen, (float)(lastPoint.X * scaleFactor), (float)(lastPoint.Y * scaleFactor), (float)(coordinate.X * scaleFactor), (float)(coordinate.Y * scaleFactor));
signature is my image object.
Thanks in advance.

The Graphics class under System.Drawing namespace is more like CanvasDrawingSession class of Win2D. Win2D is an easy-to-use Windows Runtime API for immediate mode 2D graphics rendering with GPU acceleration which is available for UWP app.
For example, for graphics.InterpolationMode property you may try CanvasImageInterpolation instead. The Antialiasing property of CanvasDrawingSession defined similar features as SmoothingMode has. CanvasDrawingSession also has FillRectangle and Drawline methods as you showed above from Graphics.
So you can try to use Win2D library in UWP app to implement the same features. For more details about how to use Win2D please reference the README.md of the official site and for samples please reference the official samples.

Try using the WritableBitmapEx library
https://www.nuget.org/packages/WriteableBitmapEx
You can add this package to your project using nuget.
With WritableBitmapEx, it is really easy to Draw polygons, shapes, lines etc, directly on images.
E.g.
bmp.DrawRectangle(cornerPoints[0].X, cornerPoints[0].Y, cornerPoints[2].X, cornerPoints[2].Y, Colors.Red);
You can find tons of drawing examples with WritableBitmapEx on github
https://github.com/reneschulte/WriteableBitmapEx

HUD basics using SharpDX: How to Draw over the screen surface?

Scenario
I'm planning to learn the basics about how to develop a custom HUD for a 3rd party PC-game (free, legal), my intention is to develop an application that will draw/show additional info on the screen (by reading mem addresses).
So I've researched for profesional projects and I've found TurboHUD that uses SharpDX library to draw objects/overlays/text over the screen using that DirectX based library and the results are very good (it does not loose performancy at any moment when drawing multiple objects on the screen),
but, since the author of that project does not provide a source to understand how they did it then I'm trying to learn by myself to use the same professional technics.
Question
If I'm on the wrong way or I missed some other better alternatives than SharpDX to develop this, please let me know.
My main question is:
In C# or preferably VB.Net, how I could just draw efficiently a custom string over the screen using SharpDX?.
Note that I could set the Form's oppacity to 0 but I think it should exists a proper way and I'm asking to know that proper way to draw directlly on the "desktop" screen.
My expects are to launch that PC-Game, then launch my custom HUD that will draw over the "desktop" screen surface to add additional info on the game, I hope you understand me.
Research
I should clarify that I'm totally unexperienced whit this kind of DirectX libs, and I'm using the SharpDX samples package to try learn its usage.
Since all the samples are in C# its more difficult to learn its usage under VB.Net.
Inside the SharpDX samples package there is an 'AdvancedTextRenderingApp' C# project, but as its name says it is an advanced example and also it instances a custom Form (a SharpDX.Windows.RenderForm) to draw on that Form.
This is the an VB.Net code translation of that C# project that I mentioned:
http://pastebin.com/KG2c3v09
UPDATE:
Just with the intention to comment about a research I did:
I recentlly discovered this useful GitHub repository, however, it fails to compile in Visual Studio 2015 (because missing namespace usings, that when added they generate more compiler errors), also it is oriented for advanced SharpDX users, and after analyzed the full sample I still don't have any idea of how to write/draw over the surface of a 3rd part process window ...also the C# syntax difficults me the overall understanding of SharpDX usage, because also the author did custom implementations a big variety of SharpDX members, then... I'm more than lost with all those examples.
The official SharpDX samples are another of those things that seems very useful ...maybe for advanced users. Some samples seems that demonstrates how to render a custom window/surface (with 500 tedious and incomprehensible lines of code to do it. And their "Hello world" sample is a nightmare for me.), however, what I would like to acchieve as I explained in my question is to draw on the surface of an existing window of another process, and I'm aware that probablly for that I would need to render a "surface" from scratch with SharpDX, then positionate it in the target window, then make invisible the surface, then draw on it, but I don't know how to do those things.

It took me a while to find how to load the font in XNA to draw the text but everything works fine.
You need 4 things:
Make form topmost
Extend aero glass style to whole form (for transparency to work)
Initialize XNA, Microsoft XNA Game Studio 4.0
Draw the texture and text
One limitation
The game must not be in fullscreen mode. The same as the TurboHUD limitation
Form1.cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using System.IO;
using System.Windows.Forms;
using System.Threading;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using System.Runtime.InteropServices;
using System.Drawing;
namespace XNATransparentWindow
{
public partial class Form1 : Form
{
private ContentBuilder contentBuilder;
public Form1()
{
InitializeComponent();
TopMost = true;
FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
MARGINS margins = new MARGINS();
margins.leftWidth = 0;
margins.rightWidth = 0;
margins.topHeight = this.Width;
margins.bottomHeight = this.Height;
// Extend aero glass style to whole form
DwmExtendFrameIntoClientArea(this.Handle, ref margins);
//Load XNA directX
this.contentBuilder = new ContentBuilder();
graphicsDeviceService = GraphicsDeviceService.AddRef(Handle, ClientSize.Width, ClientSize.Height);
//Register the service, so components like ContentManager can find it.
services.AddService<IGraphicsDeviceService>(graphicsDeviceService);
//Get the Graphics device
dev = graphicsDeviceService.GraphicsDevice;
if(dev == null){/*error message*/}
//Load texture
int bufferSize;
System.IO.MemoryStream memoryStream;
Bitmap img;
using (img = new Bitmap(#"C:\...\.png"))
{
bufferSize = img.Height * img.Width * 4;
memoryStream = new System.IO.MemoryStream(bufferSize);
img.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Png);
memoryStream.Seek(0, SeekOrigin.Begin);
texture = Texture2D.FromStream(dev, memoryStream, img.Width, img.Height, false);
memoryStream.Close();
if(texture == null){/*error message*/}
}
//Create sprite
s_Batch = new SpriteBatch(dev);
if(s_Batch == null){/*error message*/}
FontPos = new Vector2(270.0F, 110.0F);
//Load font
contentManager = new ContentManager(services, this.contentBuilder.OutputDirectory);
this.contentBuilder.Clear();
this.contentBuilder.Add(#"C:\...\my_font1.spritefont","my_font1", "FontDescriptionImporter", "FontDescriptionProcessor");
//Build spritefont to get the .xbn file
string error = this.contentBuilder.Build();
//If build fail
if (!String.IsNullOrEmpty(error))
{
MessageBox.Show(error);
return;
}
//Load the .xbn file
Font1 = contentManager.Load<SpriteFont>("my_font1");
if(Font1 == null){/*error message*/}
}
[DllImport("dwmapi.dll")]
static extern int DwmExtendFrameIntoClientArea(IntPtr hWnd, ref MARGINS margin);
[DllImport("user32.dll")]
static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, Int32 wParam, Int32 lParam);
[StructLayout(LayoutKind.Sequential)]
public struct MARGINS
{
public int leftWidth;
public int rightWidth;
public int topHeight;
public int bottomHeight;
}
public ServiceContainer Services
{
get { return services; }
}
ServiceContainer services = new ServiceContainer();
GraphicsDevice dev;
SpriteFont Font1;
Vector2 FontPos;
SpriteBatch s_Batch;
Texture2D texture;
ContentManager contentManager;
GraphicsDeviceService graphicsDeviceService;
private const UInt32 WM_NCLBUTTONDOWN = 0xA1;
private const Int32 HTCAPTION = 0x2;
private void Form1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == System.Windows.Forms.MouseButtons.Right)
{
this.Close();
}
else //to move the form
{
this.Capture = false;
SendMessage(this.Handle, WM_NCLBUTTONDOWN, HTCAPTION, 0);
}
}
private void Form1_Paint(object sender, PaintEventArgs e)
{
//There are two buffers. One offscreen-backbuffer and the
//frontbuffer which is the actual form in this example. The
//drawings are done to the backbuffer and in the end the two
//buffers flip. The backbuffer becomes frontbuffer and the
//frontbuffer becomes backbuffer.
//The drawing should start when the last resource is loaded.
//Since Font1 is the last one in this example I check for this
if (Font1 == null)
{
return;
}
//clear the backbuffer with transparent color.
dev.Clear(Microsoft.Xna.Framework.Color.Transparent);
//Do all your drawings here
//draw texture and text with the sprite
s_Batch.Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend);
s_Batch.Draw(texture, new Microsoft.Xna.Framework.Rectangle(0, 0, this.Width, this.Height), Microsoft.Xna.Framework.Color.White);
s_Batch.DrawString(Font1, #"XNA FRAMEWORK", FontPos, Microsoft.Xna.Framework.Color.Black);
s_Batch.End();
//here the flip is performed
dev.Present();
}
//Release resources
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
graphicsDeviceService.GraphicsDevice.Dispose();
graphicsDeviceService.Release(true);
s_Batch.Dispose();
texture.Dispose();
}
}
}
The following classes are just copy-paste from an example XNA 4.0 Content Compiler I found(with minor adjustments). They are used just to load the font for drawing the text:
GraphicsDeviceService.cs
#region File Description
//-----------------------------------------------------------------------------
// GraphicsDeviceService.cs
//
// Microsoft XNA Community Game Platform
// Copyright (C) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
#endregion
#region Using Statements
using System;
using System.Threading;
using Microsoft.Xna.Framework.Graphics;
#endregion
// The IGraphicsDeviceService interface requires a DeviceCreated event, but we
// always just create the device inside our constructor, so we have no place to
// raise that event. The C# compiler warns us that the event is never used, but
// we don't care so we just disable this warning.
#pragma warning disable 67
namespace XNATransparentWindow
{
/// <summary>
/// Helper class responsible for creating and managing the GraphicsDevice.
/// All GraphicsDeviceControl instances share the same GraphicsDeviceService,
/// so even though there can be many controls, there will only ever be a single
/// underlying GraphicsDevice. This implements the standard IGraphicsDeviceService
/// interface, which provides notification events for when the device is reset
/// or disposed.
/// </summary>
class GraphicsDeviceService : IGraphicsDeviceService
{
#region Fields
// Singleton device service instance.
static GraphicsDeviceService singletonInstance;
// Keep track of how many controls are sharing the singletonInstance.
static int referenceCount;
#endregion
/// <summary>
/// Constructor is private, because this is a singleton class:
/// client controls should use the public AddRef method instead.
/// </summary>
GraphicsDeviceService(IntPtr windowHandle, int width, int height)
{
parameters = new PresentationParameters();
parameters.BackBufferWidth = Math.Max(width, 1);
parameters.BackBufferHeight = Math.Max(height, 1);
parameters.BackBufferFormat = SurfaceFormat.Vector4; // SurfaceFormat.Color;
parameters.DeviceWindowHandle = windowHandle;
parameters.PresentationInterval = PresentInterval.Immediate;
parameters.IsFullScreen = false;
graphicsDevice = new GraphicsDevice(GraphicsAdapter.DefaultAdapter, GraphicsProfile.Reach, parameters);
}
/// <summary>
/// Gets a reference to the singleton instance.
/// </summary>
public static GraphicsDeviceService AddRef(IntPtr windowHandle,
int width, int height)
{
// Increment the "how many controls sharing the device" reference count.
if (Interlocked.Increment(ref referenceCount) == 1)
{
// If this is the first control to start using the
// device, we must create the singleton instance.
singletonInstance = new GraphicsDeviceService(windowHandle,
width, height);
}
return singletonInstance;
}
/// <summary>
/// Releases a reference to the singleton instance.
/// </summary>
public void Release(bool disposing)
{
// Decrement the "how many controls sharing the device" reference count.
if (Interlocked.Decrement(ref referenceCount) == 0)
{
// If this is the last control to finish using the
// device, we should dispose the singleton instance.
if (disposing)
{
if (DeviceDisposing != null)
DeviceDisposing(this, EventArgs.Empty);
graphicsDevice.Dispose();
}
graphicsDevice = null;
}
}
/// <summary>
/// Resets the graphics device to whichever is bigger out of the specified
/// resolution or its current size. This behavior means the device will
/// demand-grow to the largest of all its GraphicsDeviceControl clients.
/// </summary>
public void ResetDevice(int width, int height)
{
if (DeviceResetting != null)
DeviceResetting(this, EventArgs.Empty);
parameters.BackBufferWidth = Math.Max(parameters.BackBufferWidth, width);
parameters.BackBufferHeight = Math.Max(parameters.BackBufferHeight, height);
graphicsDevice.Reset(parameters);
if (DeviceReset != null)
DeviceReset(this, EventArgs.Empty);
}
/// <summary>
/// Gets the current graphics device.
/// </summary>
public GraphicsDevice GraphicsDevice
{
get { return graphicsDevice; }
}
GraphicsDevice graphicsDevice;
// Store the current device settings.
PresentationParameters parameters;
// IGraphicsDeviceService events.
public event EventHandler<EventArgs> DeviceCreated;
public event EventHandler<EventArgs> DeviceDisposing;
public event EventHandler<EventArgs> DeviceReset;
public event EventHandler<EventArgs> DeviceResetting;
}
}
ServiceContainer.cs
#region File Description
//-----------------------------------------------------------------------------
// ServiceContainer.cs
//
// Microsoft XNA Community Game Platform
// Copyright (C) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
#endregion
#region Using Statements
using System;
using System.Collections.Generic;
#endregion
namespace XNATransparentWindow
{
/// <summary>
/// Container class implements the IServiceProvider interface. This is used
/// to pass shared services between different components, for instance the
/// ContentManager uses it to locate the IGraphicsDeviceService implementation.
/// </summary>
public class ServiceContainer : IServiceProvider
{
Dictionary<Type, object> services = new Dictionary<Type, object>();
/// <summary>
/// Adds a new service to the collection.
/// </summary>
public void AddService<T>(T service)
{
services.Add(typeof(T), service);
}
/// <summary>
/// Looks up the specified service.
/// </summary>
public object GetService(Type serviceType)
{
object service;
services.TryGetValue(serviceType, out service);
return service;
}
}
}
ContentBuilder.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Diagnostics;
using Microsoft.Build.Construction;
using Microsoft.Build.Evaluation;
using Microsoft.Build.Execution;
using Microsoft.Build.Framework;
namespace XNATransparentWindow
{
public class ContentBuilder : IDisposable
{
#region Fields
// What importers or processors should we load?
const string xnaVersion = ", Version=4.0.0.0, PublicKeyToken=842cf8be1de50553";
static string[] pipelineAssemblies =
{
"Microsoft.Xna.Framework.Content.Pipeline.FBXImporter" + xnaVersion,
"Microsoft.Xna.Framework.Content.Pipeline.XImporter" + xnaVersion,
"Microsoft.Xna.Framework.Content.Pipeline.TextureImporter" + xnaVersion,
"Microsoft.Xna.Framework.Content.Pipeline.EffectImporter" + xnaVersion,
"Microsoft.Xna.Framework.Content.Pipeline.AudioImporters" + xnaVersion,
"Microsoft.Xna.Framework.Content.Pipeline.VideoImporters" + xnaVersion,
// If you want to use custom importers or processors from
// a Content Pipeline Extension Library, add them here.
//
// If your extension DLL is installed in the GAC, you should refer to it by assembly
// name, eg. "MyPipelineExtension, Version=1.0.0.0, PublicKeyToken=1234567812345678".
//
// If the extension DLL is not in the GAC, you should refer to it by
// file path, eg. "c:/MyProject/bin/MyPipelineExtension.dll".
};
// MSBuild objects used to dynamically build content.
Project buildProject;
ProjectRootElement projectRootElement;
BuildParameters buildParameters;
List<ProjectItem> projectItems = new List<ProjectItem>();
//ErrorLogger errorLogger;
// Temporary directories used by the content build.
string buildDirectory;
string processDirectory;
string baseDirectory;
// Generate unique directory names if there is more than one ContentBuilder.
static int directorySalt;
// Have we been disposed?
bool isDisposed;
#endregion
#region Properties
/// Gets the output directory, which will contain the generated .xnb files.
public string OutputDirectory
{
get { return Path.Combine(buildDirectory, "bin/Content"); }
}
#endregion
#region Initialization
/// Creates a new content builder.
public ContentBuilder()
{
CreateTempDirectory();
CreateBuildProject();
}
/// Finalizes the content builder.
~ContentBuilder()
{
Dispose(false);
}
/// Disposes the content builder when it is no longer required.
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
/// Implements the standard .NET IDisposable pattern.
protected virtual void Dispose(bool disposing)
{
if (!isDisposed)
{
isDisposed = true;
DeleteTempDirectory();
}
}
#endregion
#region MSBuild
/// Creates a temporary MSBuild content project in memory.
void CreateBuildProject()
{
string projectPath = Path.Combine(buildDirectory, "content.contentproj");
string outputPath = Path.Combine(buildDirectory, "bin");
// Create the build project.
projectRootElement = ProjectRootElement.Create(projectPath);
// Include the standard targets file that defines how to build XNA Framework content.
projectRootElement.AddImport("$(MSBuildExtensionsPath)\\Microsoft\\XNA Game Studio\\" +
"v4.0\\Microsoft.Xna.GameStudio.ContentPipeline.targets");
buildProject = new Project(projectRootElement);
buildProject.SetProperty("XnaPlatform", "Windows");
buildProject.SetProperty("XnaProfile", "Reach");
buildProject.SetProperty("XnaFrameworkVersion", "v4.0");
buildProject.SetProperty("Configuration", "Release");
buildProject.SetProperty("OutputPath", outputPath);
// Register any custom importers or processors.
foreach (string pipelineAssembly in pipelineAssemblies)
{
buildProject.AddItem("Reference", pipelineAssembly);
}
// Hook up our custom error logger.
//errorLogger = new ErrorLogger();
buildParameters = new BuildParameters(ProjectCollection.GlobalProjectCollection);
//buildParameters.Loggers = new ILogger[] { errorLogger };
}
/// Adds a new content file to the MSBuild project. The importer and
/// processor are optional: if you leave the importer null, it will
/// be autodetected based on the file extension, and if you leave the
/// processor null, data will be passed through without any processing.
public void Add(string filename, string name, string importer, string processor)
{
ProjectItem item = buildProject.AddItem("Compile", filename)[0];
item.SetMetadataValue("Link", Path.GetFileName(filename));
item.SetMetadataValue("Name", name);
if (!string.IsNullOrEmpty(importer))
item.SetMetadataValue("Importer", importer);
if (!string.IsNullOrEmpty(processor))
item.SetMetadataValue("Processor", processor);
projectItems.Add(item);
}
/// Removes all content files from the MSBuild project.
public void Clear()
{
buildProject.RemoveItems(projectItems);
projectItems.Clear();
}
/// Builds all the content files which have been added to the project,
/// dynamically creating .xnb files in the OutputDirectory.
/// Returns an error message if the build fails.
public string Build()
{
// Create and submit a new asynchronous build request.
BuildManager.DefaultBuildManager.BeginBuild(buildParameters);
BuildRequestData request = new BuildRequestData(buildProject.CreateProjectInstance(), new string[0]);
BuildSubmission submission = BuildManager.DefaultBuildManager.PendBuildRequest(request);
submission.ExecuteAsync(null, null);
// Wait for the build to finish.
submission.WaitHandle.WaitOne();
BuildManager.DefaultBuildManager.EndBuild();
// If the build failed, return an error string.
if (submission.BuildResult.OverallResult == BuildResultCode.Failure)
{
//return string.Join("\n", errorLogger.Errors.ToArray());
}
return null;
}
#endregion
#region Temp Directories
/// Creates a temporary directory in which to build content.
void CreateTempDirectory()
{
// Start with a standard base name:
//
// %temp%\WinFormsContentLoading.ContentBuilder
baseDirectory = Path.Combine(Path.GetTempPath(), GetType().FullName);
// Include our process ID, in case there is more than
// one copy of the program running at the same time:
//
// %temp%\WinFormsContentLoading.ContentBuilder\<ProcessId>
int processId = Process.GetCurrentProcess().Id;
processDirectory = Path.Combine(baseDirectory, processId.ToString());
// Include a salt value, in case the program
// creates more than one ContentBuilder instance:
//
// %temp%\WinFormsContentLoading.ContentBuilder\<ProcessId>\<Salt>
directorySalt++;
buildDirectory = Path.Combine(processDirectory, directorySalt.ToString());
// Create our temporary directory.
Directory.CreateDirectory(buildDirectory);
PurgeStaleTempDirectories();
}
/// <summary>
/// Deletes our temporary directory when we are finished with it.
/// </summary>
void DeleteTempDirectory()
{
Directory.Delete(buildDirectory, true);
// If there are no other instances of ContentBuilder still using their
// own temp directories, we can delete the process directory as well.
if (Directory.GetDirectories(processDirectory).Length == 0)
{
Directory.Delete(processDirectory);
// If there are no other copies of the program still using their
// own temp directories, we can delete the base directory as well.
if (Directory.GetDirectories(baseDirectory).Length == 0)
{
Directory.Delete(baseDirectory);
}
}
}
/// <summary>
/// Ideally, we want to delete our temp directory when we are finished using
/// it. The DeleteTempDirectory method (called by whichever happens first out
/// of Dispose or our finalizer) does exactly that. Trouble is, sometimes
/// these cleanup methods may never execute. For instance if the program
/// crashes, or is halted using the debugger, we never get a chance to do
/// our deleting. The next time we start up, this method checks for any temp
/// directories that were left over by previous runs which failed to shut
/// down cleanly. This makes sure these orphaned directories will not just
/// be left lying around forever.
/// </summary>
void PurgeStaleTempDirectories()
{
// Check all subdirectories of our base location.
foreach (string directory in Directory.GetDirectories(baseDirectory))
{
// The subdirectory name is the ID of the process which created it.
int processId;
if (int.TryParse(Path.GetFileName(directory), out processId))
{
try
{
// Is the creator process still running?
Process.GetProcessById(processId);
}
catch (ArgumentException)
{
// If the process is gone, we can delete its temp directory.
Directory.Delete(directory, true);
}
}
}
}
#endregion
}
}
The font which you are loading is an xml file: any_name.spritefont
Example:
<?xml version="1.0" encoding="utf-8"?>
<!--
This file contains an xml description of a font, and will be read by the XNA
Framework Content Pipeline. Follow the comments to customize the appearance
of the font in your game, and to change the characters which are available to draw
with.
-->
<XnaContent xmlns:Graphics="Microsoft.Xna.Framework.Content.Pipeline.Graphics">
<Asset Type="Graphics:FontDescription">
<!--
Modify this string to change the font that will be imported.
-->
<FontName>Segoe UI Mono</FontName>
<!--
Size is a float value, measured in points. Modify this value to change
the size of the font.
-->
<Size>14</Size>
<!--
Spacing is a float value, measured in pixels. Modify this value to change
the amount of spacing in between characters.
-->
<Spacing>0</Spacing>
<!--
UseKerning controls the layout of the font. If this value is true, kerning information
will be used when placing characters.
-->
<UseKerning>true</UseKerning>
<!--
Style controls the style of the font. Valid entries are "Regular", "Bold", "Italic",
and "Bold, Italic", and are case sensitive.
-->
<Style>Regular</Style>
<!--
If you uncomment this line, the default character will be substituted if you draw
or measure text that contains characters which were not included in the font.
-->
<!-- <DefaultCharacter>*</DefaultCharacter> -->
<!--
CharacterRegions control what letters are available in the font. Every
character from Start to End will be built and made available for drawing. The
default range is from 32, (ASCII space), to 126, ('~'), covering the basic Latin
character set. The characters are ordered according to the Unicode standard.
See the documentation for more information.
-->
<CharacterRegions>
<CharacterRegion>
<Start> </Start>
<End>~</End>
</CharacterRegion>
</CharacterRegions>
</Asset>
</XnaContent>
If you want the form to be click-through then you need to add a random
transparency key color to form and:
[DllImport("user32.dll", EntryPoint="GetWindowLong")]
static extern IntPtr GetWindowLongPtr(IntPtr hWnd, int nIndex);
[DllImport("user32.dll")]
static extern int SetWindowLong(IntPtr hWnd, int nIndex, IntPtr dwNewLong);
In public Form1()
IntPtr initialStyle = GetWindowLongPtr(this.Handle, -20);
SetWindowLong(this.Handle, -20, (IntPtr)((int)initialStyle | 0x20));
Feel free to correct any mistakes I have made.

After Writing to a RenderTarget, How to Efficiently Clone the Output?

XNA noob here, learning every day. I just worked out how to composite multiple textures into one using a RenderTarget2D. However, while I can use the RenderTarget2D as a Texture2D for most purposes, there's a critical difference: these rendered textures are lost when the backbuffer is resized (and no doubt under other circumstances, like the graphics device running low on memory).
For the moment, I'm just copying the finished RenderTarget2D into a new non-volatile Texture2D object. My code to do so is pretty fugly, though. Is there a more graceful way to do this? Maybe I'm just tired but I can't find the answer on Google or SO.
Slightly simplified:
public static Texture2D MergeTextures(int width, int height, IEnumerable<Tuple<Texture2D, Color>> textures)
{
RenderTarget2D buffer = new RenderTarget2D(_device, width, height);
_device.SetRenderTarget(buffer);
_device.Clear(Color.Transparent);
SpriteBatch spriteBatch = new SpriteBatch(_device);
spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.NonPremultiplied);
// Paint each texture over the one before, in the appropriate color
Rectangle rectangle = new Rectangle(0, 0, width, height);
foreach (Tuple<Texture2D, Color> texture in textures)
spriteBatch.Draw(texture.Item1, rectangle, texture.Item2);
spriteBatch.End();
_device.SetRenderTarget((RenderTarget2D)null);
// Write the merged texture to a Texture2D, so we don't lose it when resizing the back buffer
// This is POWERFUL ugly code, and probably terribly, terribly slow
Texture2D mergedTexture = new Texture2D(_device, width, height);
Color[] content = new Color[width * height];
buffer.GetData<Color>(content);
mergedTexture.SetData<Color>(content);
return mergedTexture;
}
I suppose I should check for IsContentLost and re-render as needed, but this happens in the middle of my main drawing loop, and of course you can't nest SpriteBatches. I could maintain a "render TODO" list, handle those after the main SpriteBatch ends, and then they'd be available for the next frame. Is that the preferred strategy?
This code is only called a few times, so performance isn't a concern, but I'd like to learn how to do things right.

Actually your code is not so bad if you're generating textures in a once-off process when you'd normally load content (game start, level change, room change, etc). You're transferring textures between CPU and GPU, same thing you'd be doing loading plain ol' textures. It's simple and it works!
If you're generating your textures more frequently, and it starts to become a per-frame cost, rather than a load-time cost, then you will want to worry about its performance and perhaps keeping them as render targets.
You shouldn't get ContentLost in the middle of drawing, so you can safely just respond to that event and recreate the render targets then. Or you can check for IsContentLost on each of them, ideally at the start of your frame before you render anything else. Either way everything should be checked before your SpriteBatch begins.
(Normally when using render targets you're regenerating them each frame anyway, so you don't need to check them in that case.)

Replace
Texture2D mergedTexture = new Texture2D(_device, width, height);
Color[] content = new Color[width * height];
buffer.GetData<Color>(content);
mergedTexture.SetData<Color>(content);
return mergedTexture;
with
return buffer;
Because RenderTarget2D extends Texture2D you will just get Texture2D class data returned. Also in case you are interested here's a class i made for building my GUI library's widgets out of multiple textures. In case you need to be doing this sort of thing a lot.
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using System.IO;
namespace Voodo.Utils {
/// <summary>
///
/// </summary>
public class TextureBaker {
private readonly SpriteBatch _batch;
private readonly RenderTarget2D _renderTarget;
private readonly GraphicsDevice _graphicsDevice;
/// <summary>
///
/// </summary>
public Rectangle Bounds {
get { return _renderTarget.Bounds; }
}
/// <summary>
///
/// </summary>
/// <param name="graphicsDevice"></param>
/// <param name="size"></param>
public TextureBaker(GraphicsDevice graphicsDevice, Vector2 size) {
_graphicsDevice = graphicsDevice;
_batch = new SpriteBatch(_graphicsDevice);
_renderTarget = new RenderTarget2D(
_graphicsDevice,
(int)size.X,
(int)size.Y);
_graphicsDevice.SetRenderTarget(_renderTarget);
_graphicsDevice.Clear(Color.Transparent);
_batch.Begin(
SpriteSortMode.Immediate,
BlendState.AlphaBlend,
SamplerState.LinearClamp,
DepthStencilState.Default,
RasterizerState.CullNone);
}
#region Texture2D baking
/// <summary>
///
/// </summary>
/// <param name="texture"></param>
public void BakeTexture(Texture2D texture) {
_batch.Draw(
texture,
new Rectangle(0, 0, Bounds.Width, Bounds.Height),
Color.White);
}
/// <summary>
///
/// </summary>
/// <param name="texture"></param>
/// <param name="destination"></param>
public void BakeTexture(Texture2D texture, Rectangle destination) {
_batch.Draw(
texture,
destination,
Color.White);
}
/// <summary>
///
/// </summary>
/// <param name="texture"></param>
/// <param name="destination"></param>
/// <param name="source"></param>
public void BakeTexture(Texture2D texture, Rectangle destination, Rectangle source) {
_batch.Draw(
texture,
destination,
source,
Color.White);
}
/// <summary>
///
/// </summary>
/// <param name="texture"></param>
/// <param name="sourceModification"></param>
/// <param name="destination"></param>
public void BakeTexture(Texture2D texture, System.Drawing.RotateFlipType sourceModification, Rectangle destination) {
Stream sourceBuffer = new MemoryStream();
texture.SaveAsPng(sourceBuffer, texture.Width, texture.Height);
System.Drawing.Image sourceImage = System.Drawing.Image.FromStream(sourceBuffer);
sourceBuffer = new MemoryStream();
sourceImage.RotateFlip(sourceModification);
sourceImage.Save(sourceBuffer, System.Drawing.Imaging.ImageFormat.Png);
_batch.Draw(
Texture2D.FromStream(_graphicsDevice, sourceBuffer),
destination,
Color.White);
}
/// <summary>
///
/// </summary>
/// <param name="texture"></param>
/// <param name="sourceModification"></param>
/// <param name="destination"></param>
/// <param name="source"></param>
public void BakeTexture(Texture2D texture, System.Drawing.RotateFlipType sourceModification, Rectangle destination, Rectangle source) {
Stream sourceBuffer = new MemoryStream();
texture.SaveAsPng(sourceBuffer, texture.Width, texture.Height);
System.Drawing.Image sourceImage = System.Drawing.Image.FromStream(sourceBuffer);
sourceBuffer = new MemoryStream();
sourceImage.RotateFlip(sourceModification);
sourceImage.Save(sourceBuffer, System.Drawing.Imaging.ImageFormat.Png);
_batch.Draw(
Texture2D.FromStream(_graphicsDevice, sourceBuffer),
destination,
source,
Color.White);
}
#endregion
#region SpriteFont baking
/// <summary>
///
/// </summary>
/// <param name="font"></param>
/// <param name="text"></param>
/// <param name="location"></param>
/// <param name="textColor"></param>
public void BakeText(SpriteFont font, string text, Vector2 location, Color textColor) {
_batch.DrawString(font, text, location, textColor);
}
/// <summary>
///
/// </summary>
/// <param name="font"></param>
/// <param name="text"></param>
/// <param name="location"></param>
public void BakeTextCentered(SpriteFont font, string text, Vector2 location, Color textColor) {
var shifted = new Vector2 {
X = location.X - font.MeasureString(text).X / 2,
Y = location.Y - font.MeasureString(text).Y / 2
};
_batch.DrawString(font, text, shifted, textColor);
}
#endregion
/// <summary>
///
/// </summary>
/// <returns></returns>
public Texture2D GetTexture() {
_batch.End();
_graphicsDevice.SetRenderTarget(null);
return _renderTarget;
}
}
}

if you are having problems with your rendertarget being dynamically resized when drawing it somewhere else, you could just have an off-screen rendertarget with a set size that you copy your finished RT to like this:
Rendertarget2D offscreenRT = new RenderTarget2D(_device, width, height);
_device.SetRenderTarget(offscreenRT);
_device.Clear(Color.Transparent);
SpriteBatch spriteBatch = new SpriteBatch(_device);
spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.NonPremultiplied);
spriteBatch.Draw(buffer, Vector2.Zero, Color.White);
spriteBatch.End();
_device.SetRenderTarget(null);