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Rotate a Gmap marker (bitmap) by any degree in C#

I'm using GMaps for using google maps on c#. I write latitude and langitude values and press the load button. Then the code put a marker(like arrow) that point. I want to rotate that marker for any degree like google maps'. I don't have any sensors so I can write the degree in a textbox and press a rotate button. How can i do that? This code shows how I create markers and put them into my map. I know bitmap a little but not too much and sorry for my bad english. I hope you'll understand what I want.
`double lat = Convert.ToDouble(txtLat.Text);
double lng = Convert.ToDouble(txtLong.Text);
map.Position = new PointLatLng(lat, lng);
//custom marker
Bitmap bmpMarker = (Bitmap)Image.FromFile("img/arrow.png");
PointLatLng point = new PointLatLng(lat, lng);
GMap.NET.WindowsForms.GMapMarker marker = new GMarkerGoogle(point, bmpMarker);
//1. Create a Overlay
GMapOverlay markers = new GMapOverlay("markers");
map.ZoomAndCenterMarkers("markers");
//2. Add all available markers to that Overlay
markers.Markers.Add(marker);
//3. Cover map with Overlay
map.Overlays.Add(markers);
//RotateImage(bmpMarker, 180.0f);
marker.ToolTipText = map.Position.ToString();`

Try to set the Bitmap image again with the rotation because it is not a reference type:
GMap.NET.WindowsForms.GMapMarker marker = new GMarkerGoogle(point, RotateImg(bmpMarker,45));
Suggestion to rotate the bitmap:
public Bitmap RotateImg(Bitmap bmpimage, float angle)
{
int w = bmpimage.Width;
int h = bmpimage.Height;
PixelFormat pf;
pf = bmpimage.PixelFormat;
Bitmap tempImg = new Bitmap(w, h, pf);
Graphics g = Graphics.FromImage(tempImg);
g.DrawImageUnscaled(bmpimage, 1, 1);
g.Dispose();
GraphicsPath path = new GraphicsPath();
path.AddRectangle(new RectangleF(0.0F, 0.0F, w, h));
Matrix mtrx = new Matrix();
mtrx.Rotate(angle);
RectangleF rct = path.GetBounds(mtrx);
Bitmap newImg = new Bitmap(Convert.ToInt32(rct.Width), Convert.ToInt32(rct.Height), pf);
g = Graphics.FromImage(newImg);
g.TranslateTransform(-rct.X, -rct.Y);
g.RotateTransform(angle);
g.InterpolationMode = InterpolationMode.HighQualityBilinear;
g.DrawImageUnscaled(tempImg, 0, 0);
g.Dispose();
tempImg.Dispose();
return newImg;
}

Cropping Image(From Screen)

I have read many question about this. But my question is little bit different. What i need to do crop image from screen.
There is my codes
Bitmap photo = new Bitmap(Screen.PrimaryScreen.Bounds.Width,Screen.primaryScreen.Bounds.Height)
Graphics gr = Graphics.FromImage(photo);
gr.CopyFromScreen(0,0,0,0 new size(foto.Width,foto.Height));
picturebox1.Image = photo;
And there my crop codes
Rectangle cropRec = new Rectangle(1,1,1,1);
Bitmap target = new Bitmap(cropRec.Width,cropRec.Height);
using(Graphics g = Graphics.FromImage(target))
{
g.DrawImage(photo,new Rentangle(0,0,target.Width,target.Height),cropRec,GraphicsUnit.Pixel);
}
I want to crop middle part of this photo and compare with itself.
Thanks n advance

To symmetrically crop your image as shown in the following sketch, try creating a Bitmap with margins in the X and Y axis and then cropping the screenshot image by using those margins in CopyFromScreen():
Bitmap printscreen = new Bitmap(Screen.PrimaryScreen.Bounds.Width - 2 * xmargin, Screen.PrimaryScreen.Bounds.Height - 2 * ymargin);
Graphics graphics = Graphics.FromImage(printscreen as Image);
graphics.CopyFromScreen(xmargin, ymargin, 0, 0, printscreen.Size);

Reading System.Drawing.Bitmap into OpenCV / Emgu to find contours

My code is divided in three parts: PART 1) Drawing in a bitmap, PART 2) Saving the bitmap as a jpg image, PART 3) Reading the jpg file and find contours using Emgu.
These three parts work separately but I cannot make them work together. Particularly, my problem is how to input the System.Drawing.Bitmap of PART 1 into PART 3 which input is an Image<Bgr, Byte>.
So far I have tried to read the Bitmap "target" in Part 1 directly into Part 3 doing Image<Bgr, Byte> imageFrame = new Image<Bgr, Byte>(target) with no success (it doen't identify any contours)
I have also tried to create an intermediate .jpg file (Part 2) they can share with no success either (it doen't identify any contours either).
The only way that I can make this work is:
i) Run Part 1 and Part 2
ii) Open the resultant jpg image using Paint, hit "Save" and close Paint. I have done this manually.
iii) Run Part 3.
Doing this the contour is identified. However this is not a valid solutions since the step ii) is not automated. However this might help illustrating what the problem is.
Can someone help?
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;
using Emgu.CV;
using Emgu.CV.Structure;
namespace Contouring
{
class Program
{
static void Main(string[] args)
{
//--------------------------------------PART 1 : DRAWING STUFF IN A BITMAP------------------------------------------------------------------------------------
Pen blackPen = new Pen(Color.FromArgb(255, 0, 0, 0), 1);
Bitmap bmp = new Bitmap(1000, 1000);
Graphics g = Graphics.FromImage(bmp);
//This is just an example using three rectangles for illustration purposes.
//In reality I have a set of arbitrary lines defining complex polygons.
g.DrawRectangle(blackPen, new Rectangle(10, 10, 200, 100)); //rectangle 1
g.DrawRectangle(blackPen, new Rectangle(20, 20, 50, 30)); //rectangle 2
g.DrawRectangle(blackPen, new Rectangle(200, 10, 25, 25)); //rectangle 3
Rectangle r = new Rectangle(10, 10, 250, 250); //bounding box of the 3 rectangles
Rectangle rcrop = new Rectangle(r.X, r.Y, r.Width + 10, r.Height + 10);//This is the cropping rectangle (bonding box adding 10 extra units width and height)
//Crop the model from the bmp
Bitmap src = bmp;
Bitmap target = new Bitmap(r.Width, r.Height);
using (Graphics gs = Graphics.FromImage(target))
{
gs.DrawImage(src, new Rectangle(5, 5, 250, 250), rcrop, GraphicsUnit.Pixel);
gs.Dispose();
}
//--------------------------------------PART 2 : SAVING THE BMP AS JPG------------------------------------------------------------------------------------
target.Save("test.jpg");
//--------------------------------------PART 3 : USING THE SAVED PICTURE AND FIND CONTOURS ----------------------------------------------------------------
Image<Bgr, Byte> imageFrame = new Image<Bgr, Byte>("test.jpg");
//Image<Bgr, Byte> imageFrame = new Image<Bgr, Byte>(target);
//Find contours
Image<Gray, byte> grayFrame = imageFrame.Convert<Gray, byte>();
List<Contour<Point>> result = new List<Contour<Point>>();
using (MemStorage storage = new MemStorage()) //allocate storage for contour approximation
for (Contour<Point> contours = grayFrame.FindContours(Emgu.CV.CvEnum.CHAIN_APPROX_METHOD.CV_CHAIN_APPROX_SIMPLE, Emgu.CV.CvEnum.RETR_TYPE.CV_RETR_LIST, storage); contours != null; contours = contours.HNext)
{
//here i do stuff with the contours and add them to the list result
result.Add(contours);
}
//Write to console
Console.WriteLine(result.Count + " NO. contours have been identified");
}//endmain
}//endprogram
}//endNamespace

Well, I think that trouble is in transparent. EmguCV doesn't understand images with transparent. I updated your code, so, now it work without saving. Does it help or you need transparent images?
//--------------------------------------PART 1 : DRAWING STUFF IN A BITMAP------------------------------------------------------------------------------------
var blackPen = new Pen(Color.FromArgb(255, 0, 0, 0), 1);
var bmp = new Bitmap(1000, 1000, PixelFormat.Format32bppArgb);
using (var g = Graphics.FromImage(bmp))
{
g.Clear(Color.White);
//This is just an example using three rectangles for illustration purposes.
//In reality I have a set of arbitrary lines defining complex polygons.
g.DrawRectangle(blackPen, new Rectangle(10, 10, 200, 100)); //rectangle 1
g.DrawRectangle(blackPen, new Rectangle(20, 20, 50, 30)); //rectangle 2
g.DrawRectangle(blackPen, new Rectangle(200, 10, 25, 25)); //rectangle 3
}
var r = new Rectangle(10, 10, 250, 250); //bounding box of the 3 rectangles
var rcrop = new Rectangle(r.X, r.Y, r.Width + 10, r.Height + 10);//This is the cropping rectangle (bonding box adding 10 extra units width and height)
//Crop the model from the bmp
var src = bmp;
var target = new Bitmap(r.Width, r.Height);
using (var gs = Graphics.FromImage(target))
{
gs.DrawImage(src, new Rectangle(5, 5, 250, 250), rcrop, GraphicsUnit.Pixel);
gs.Dispose();
}
//--------------------------------------PART 3 : USING THE SAVED PICTURE AND FIND CONTOURS ----------------------------------------------------------------
var imageFrame = new Image<Bgr, Byte>(target);
//Find contours
var grayFrame = imageFrame.Convert<Gray, byte>();
var result = new List<Contour<Point>>();
using (var storage = new MemStorage()) //allocate storage for contour approximation
for (var contours = grayFrame.FindContours(CHAIN_APPROX_METHOD.CV_CHAIN_APPROX_SIMPLE, RETR_TYPE.CV_RETR_LIST, storage); contours != null; contours = contours.HNext)
{
//here i do stuff with the contours and add them to the list result
result.Add(contours);
}

Finding contour points in emgucv

I am working with emguCV for finding contours essential points then saving this point in a file and user redraw this shape in future. so, my goal is this image:
example
my solution is this:
1. import image to picturebox
2. edge detection with canny algorithm
3. finding contours and save points
I found a lot of points with below codes but i can't drawing first shape with this point!
using Emgu.CV;
using Emgu.Util;
private void button1_Click(object sender, EventArgs e)
{
Bitmap bmp = new Bitmap(pictureBox1.Image);
Image<Bgr, Byte> img = new Image<Bgr, byte>(bmp);
Image<Gray, Byte> gray = img.Convert<Gray, Byte>().PyrDown().PyrUp();
Gray cannyThreshold = new Gray(80);
Gray cannyThresholdLinking = new Gray(120);
Gray circleAccumulatorThreshold = new Gray(120);
Image<Gray, Byte> cannyEdges = gray.Canny(cannyThreshold, cannyThresholdLinking).Not();
Bitmap color;
Bitmap bgray;
IdentifyContours(cannyEdges.Bitmap, 50, true, out bgray, out color);
pictureBox1.Image = color;
}
public void IdentifyContours(Bitmap colorImage, int thresholdValue, bool invert, out Bitmap processedGray, out Bitmap processedColor)
{
Image<Gray, byte> grayImage = new Image<Gray, byte>(colorImage);
Image<Bgr, byte> color = new Image<Bgr, byte>(colorImage);
grayImage = grayImage.ThresholdBinary(new Gray(thresholdValue), new Gray(255));
if (invert)
{
grayImage._Not();
}
using (MemStorage storage = new MemStorage())
{
for (Contour<Point> contours = grayImage.FindContours(Emgu.CV.CvEnum.CHAIN_APPROX_METHOD.CV_CHAIN_APPROX_SIMPLE, Emgu.CV.CvEnum.RETR_TYPE.CV_RETR_LIST, storage); contours != null; contours = contours.HNext)
{
Contour<Point> currentContour = contours.ApproxPoly(contours.Perimeter * 0.015, storage);
if (currentContour.BoundingRectangle.Width > 20)
{
CvInvoke.cvDrawContours(color, contours, new MCvScalar(255), new MCvScalar(255), -1, 1, Emgu.CV.CvEnum.LINE_TYPE.EIGHT_CONNECTED, new Point(0, 0));
color.Draw(currentContour.BoundingRectangle, new Bgr(0, 255, 0), 1);
}
Point[] pts = currentContour.ToArray();
foreach (Point p in pts)
{
//add points to listbox
listBox1.Items.Add(p);
}
}
}
processedColor = color.ToBitmap();
processedGray = grayImage.ToBitmap();
}

In your code you have added contour approximation operation
Contour<Point> currentContour = contours.ApproxPoly(contours.Perimeter * 0.015, storage);
This contour approximation will approximate your Contour to a nearest polygon & so your actual points got shifted. If you want to reproduce the same image you need not to do any approximation.
Refer this thread.

c# write text on bitmap

I have following problem. I want to make some graphics in c# windows form.
I want to read bitmap to my program and after it write some text on this bitmap. In the end I want this picture load to pictureBox. And it's my question. How can I do it?
example, how must it work:
Bitmap a = new Bitmap(#"path\picture.bmp");
a.makeTransparent();
// ? a.writeText("some text", positionX, positionY);
pictuteBox1.Image = a;
Is it possible do to?

Bitmap bmp = new Bitmap("filename.bmp");
RectangleF rectf = new RectangleF(70, 90, 90, 50);
Graphics g = Graphics.FromImage(bmp);
g.SmoothingMode = SmoothingMode.AntiAlias;
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.PixelOffsetMode = PixelOffsetMode.HighQuality;
g.DrawString("yourText", new Font("Tahoma",8), Brushes.Black, rectf);
g.Flush();
image.Image=bmp;

Very old question, but just had to build this for an app today and found the settings shown in other answers do not result in a clean image (possibly as new options were added in later .Net versions).
Assuming you want the text in the centre of the bitmap, you can do this:
// Load the original image
Bitmap bmp = new Bitmap("filename.bmp");
// Create a rectangle for the entire bitmap
RectangleF rectf = new RectangleF(0, 0, bmp.Width, bmp.Height);
// Create graphic object that will draw onto the bitmap
Graphics g = Graphics.FromImage(bmp);
// ------------------------------------------
// Ensure the best possible quality rendering
// ------------------------------------------
// The smoothing mode specifies whether lines, curves, and the edges of filled areas use smoothing (also called antialiasing).
// One exception is that path gradient brushes do not obey the smoothing mode.
// Areas filled using a PathGradientBrush are rendered the same way (aliased) regardless of the SmoothingMode property.
g.SmoothingMode = SmoothingMode.AntiAlias;
// The interpolation mode determines how intermediate values between two endpoints are calculated.
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
// Use this property to specify either higher quality, slower rendering, or lower quality, faster rendering of the contents of this Graphics object.
g.PixelOffsetMode = PixelOffsetMode.HighQuality;
// This one is important
g.TextRenderingHint = TextRenderingHint.AntiAliasGridFit;
// Create string formatting options (used for alignment)
StringFormat format = new StringFormat()
{
Alignment = StringAlignment.Center,
LineAlignment = StringAlignment.Center
};
// Draw the text onto the image
g.DrawString("yourText", new Font("Tahoma",8), Brushes.Black, rectf, format);
// Flush all graphics changes to the bitmap
g.Flush();
// Now save or use the bitmap
image.Image = bmp;
References
https://msdn.microsoft.com/en-us/library/system.drawing.graphics.smoothingmode(v=vs.110).aspx
https://msdn.microsoft.com/en-us/library/system.drawing.drawing2d.interpolationmode(v=vs.110).aspx
https://msdn.microsoft.com/en-us/library/system.drawing.graphics.pixeloffsetmode(v=vs.110).aspx
https://msdn.microsoft.com/en-us/library/system.drawing.graphics.textrenderinghint(v=vs.110).aspx
https://msdn.microsoft.com/en-us/library/system.drawing.stringformat(v=vs.110).aspx
https://msdn.microsoft.com/en-us/library/21kdfbzs(v=vs.110).aspx

You need to use the Graphics class in order to write on the bitmap.
Specifically, one of the DrawString methods.
Bitmap a = new Bitmap(#"path\picture.bmp");
using(Graphics g = Graphics.FromImage(a))
{
g.DrawString(....); // requires font, brush etc
}
pictuteBox1.Image = a;

var bmp = new Bitmap(#"path\picture.bmp");
using( Graphics g = Graphics.FromImage( bmp ) )
{
g.DrawString( ... );
}
picturebox1.Image = bmp;

If you want wrap your text, then you should draw your text in a rectangle:
RectangleF rectF1 = new RectangleF(30, 10, 100, 122);
e.Graphics.DrawString(text1, font1, Brushes.Blue, rectF1);
See: https://msdn.microsoft.com/en-us/library/baw6k39s(v=vs.110).aspx