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How to do Bitmap processing using BitmapData?

I've built a small test example where the goal is to change all pixels in my .png to white. I'm doing it using BitmapData, because as I understand it, the performance is better. If I can get it working; then I can change which pixels I'm changing and add different conditions to altering a pixel color. But I'm stuck on just this simple test.
Here's my C# :
public static void TestConvertAllBlackBitmapToAllWhite()
{
string allBlackPNGFullFilePath = #"C:\Users\{Username}\Desktop\50x50AllBlack.png";
Bitmap allBlackBitmap = new Bitmap(allBlackPNGFullFilePath);
Bitmap newBitmap = (Bitmap)allBlackBitmap.Clone();
Size size = newBitmap.Size;
PixelFormat pixelFormat = newBitmap.PixelFormat;
byte bitDepth = (byte)(pixelFormat == PixelFormat.Format32bppArgb ? 4 : 3);
Rectangle rectangle = new Rectangle(Point.Empty, size);
BitmapData bitmapData = newBitmap.LockBits(rectangle, ImageLockMode.ReadOnly, pixelFormat);
int dataSize = bitmapData.Stride * bitmapData.Height;
byte[] data = new byte[dataSize];
Marshal.Copy(bitmapData.Scan0, data, 0, dataSize);
Color white = Color.White;
for (int y = 0; y < size.Height; y++)
{
for (int x = 0; x < size.Width; x++)
{
// Get Index
int index = y * bitmapData.Stride + x * bitDepth;
// Set Pixel Color
data[index] = white.B;
data[index + 1] = white.G;
data[index + 2] = white.R;
}
}
Marshal.Copy(data, 0, bitmapData.Scan0, data.Length);
newBitmap.UnlockBits(bitmapData);
// Save New Converted Bitmap
string originalFileName = Path.GetFileNameWithoutExtension(allBlackPNGFullFilePath);
string directory = Path.GetDirectoryName(allBlackPNGFullFilePath);
string newBitmapFileName = originalFileName + "_Converted";
string newBitmapFullFileName = directory + Path.DirectorySeparatorChar.ToString() + newBitmapFileName + ".png";
newBitmap.Save(newBitmapFullFileName, ImageFormat.Png);
}
My input is an all black 50x50 .png :
The problem is the output I'm getting is another all black .png instead of an all white one.
How can I fix up my simple example code to produce an all white .png as a result?
Any help / guidance will be really appreciated.

As pointed out by #Taw
It's a little thing on this line :
BitmapData bitmapData = newBitmap.LockBits(rectangle, ImageLockMode.ReadOnly, pixelFormat);
The ImageLockMode is set to ReadOnly. Since I'm making changes to the BitmapData while looping; the ImageLockMode should be ReadWrite

Marshal.Copy() is not copying to bitmap

I'm working on an image processing project, and I've read that the fastest way to manipulate a bitmap image is to copy it from a byte array using Marshal.Copy(). However, for whatever reason, nothing is being copied from my byte array to my Bitmap, and there's not a clear reason why. This is the code I'm using to copy into my Bitmap:
public void UpdateImage()
{
var data = image.LockBits(
new Rectangle(Point.Empty, image.Size),
ImageLockMode.WriteOnly,
PixelFormat.Format32bppArgb);
Marshal.Copy(backBuffer, 0, data.Scan0, backBuffer.Length);
image.UnlockBits(data);
Console.WriteLine("UpdateImage");//For debugging purposes
}
I'm attempting to fill the image with complete black, and looking at the data of the backBuffer, it appears to be correct, and as expected, where as when I check any pixel of 'image' it is completely blank. I have no idea why nothing is happening. Any advice would be much appreciated!
Edit: I apologize, I'm a bit new around here, let me provide some more information. Specifically, I am working on some GPU accelerated image processing using Cloo/OpenCL. I wanted to fill the screen with black to make sure that I am doing things correctly, although I am evidently not. Here is the entire class file I'm using:
public class RenderTarget
{
public GraphicsDevice GraphicsDevice;
private byte[] backBuffer;
public Bitmap image;
private ComputeKernel fillKernel;
private ComputeProgram fillProgram;
public void UpdateImage()
{
var data = image.LockBits(
new Rectangle(Point.Empty, image.Size),
ImageLockMode.WriteOnly,
PixelFormat.Format32bppArgb);
Marshal.Copy(backBuffer, 0, data.Scan0, backBuffer.Length);
image.UnlockBits(data);
Console.WriteLine("UpdateImage");
}
//Test method ONLY
public void FillScreen(Color color)
{
if (fillProgram == null)//temporary, all kernels should be compiled on start up. In fact, these probably should be static
{
string fillText = #"
kernel void fillScreen(global uchar* data_out, int from, int to, uchar a, uchar r, uchar g, uchar b){
for (int i = from; i < to; i += 4){
data_out[i] = a;
data_out[i + 1] = r;
data_out[i + 2] = g;
data_out[i + 3] = b;
}
}";
fillProgram = new ComputeProgram(GraphicsDevice.context, fillText);
fillProgram.Build(null, null, null, IntPtr.Zero);
fillKernel = fillProgram.CreateKernel("fillScreen");
}
ComputeBuffer<byte> backBufferBuffer = new ComputeBuffer<byte>(GraphicsDevice.context, ComputeMemoryFlags.ReadOnly | ComputeMemoryFlags.UseHostPointer, backBuffer);
fillKernel.SetMemoryArgument(0, backBufferBuffer);
for (int i = 0; i < backBuffer.Length / 10000; i++)
{
fillKernel.SetValueArgument<int>(1, i * 10000);
fillKernel.SetValueArgument<int>(2, (i + 1) * 10000);
fillKernel.SetValueArgument<byte>(3, color.A);
fillKernel.SetValueArgument<byte>(4, color.R);
fillKernel.SetValueArgument<byte>(5, color.G);
fillKernel.SetValueArgument<byte>(6, color.B);
GraphicsDevice.queue.ExecuteTask(fillKernel, null);
}
GraphicsDevice.queue.ReadFromBuffer(backBufferBuffer, ref backBuffer, false, null);
GraphicsDevice.queue.Finish();
}
public RenderTarget(int Width, int Height, GraphicsDevice device)
{
image = new Bitmap(Width, Height);
backBuffer = new byte[4 * Width * Height];
GraphicsDevice = device;
//Fill the screen with black
FillScreen(Color.Black);
UpdateImage();
Console.WriteLine(image.GetPixel(0, 0).A);
}
}
I have checked to make absolutely sure that the backBuffer is correct. (The values I expected were 255, 0, 0, 0 for the first four elements of the backBuffer).

Okay, I figured out what was going wrong. I had the format in the backBuffer wrong. I was expecting it to be ARGB when it should be ordered RGBA. So, it was a problem with my code in 'fillText'.

c# merge images sent over socket

im trying to send screenshots over socket so i use unsafe pointers to send only the differences:
private unsafe Bitmap GetDiffBitmap(Bitmap bmp, Bitmap bmp2)
{
bmpRes = new Bitmap(1920, 1080,bmp.PixelFormat);
bmData = bmp.LockBits(new Rectangle(0, 0, 1920, 1080), System.Drawing.Imaging.ImageLockMode.ReadOnly, bmp.PixelFormat);
bmData2 = bmp2.LockBits(new Rectangle(0, 0, bmp2.Width, bmp2.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, bmp2.PixelFormat);
bmDataRes = bmpRes.LockBits(new Rectangle(0, 0, bmpRes.Width, bmpRes.Height), System.Drawing.Imaging.ImageLockMode.ReadWrite, PixelFormat.Format32bppRgb);
IntPtr scan0 = bmData.Scan0;
IntPtr scan02 = bmData2.Scan0;
IntPtr scan0Res = bmDataRes.Scan0;
int stride = bmData.Stride;
int stride2 = bmData2.Stride;
int strideRes = bmDataRes.Stride;
int nWidth = bmp.Width;
int nHeight = bmp.Height;
//for(int y = 0; y < nHeight; y++)
System.Threading.Tasks.Parallel.For(0, nHeight, y =>
{
//define the pointers inside the first loop for parallelizing
byte* p = (byte*)scan0.ToPointer();
p += y * stride;
byte* p2 = (byte*)scan02.ToPointer();
p2 += y * stride2;
byte* pRes = (byte*)scan0Res.ToPointer();
pRes += y * strideRes;
for (int x = 0; x < nWidth; x++)
{
//always get the complete pixel when differences are found
if (p[0] != p2[0] || p[1] != p2[1] || p[2] != p2[2])
{
pRes[0] = p2[0];
pRes[1] = p2[1];
pRes[2] = p2[2];
//alpha (opacity)
pRes[3] = p2[3];
}
p += 4;
p2 += 4;
pRes += 4;
}
});
bmp.UnlockBits(bmData);
bmp2.UnlockBits(bmData2);
bmpRes.UnlockBits(bmDataRes);
return bmpRes;
}
this is the call on the client:
private void startSend()
{
Bitmap curr;
Bitmap pre = screenshot();
byte []bmpBytes = imageToByteArray(pre);
SendVarData(handler, bmpBytes);// this is the first send of the whole screen
while (true)
{
curr = screenshot();
Bitmap diff = GetDiffBitmap(pre, curr);//generate differences.
bmpBytes = imageToByteArray(diff);
SendVarData(handler, bmpBytes);//sending the diff image.
pre = curr;
}
}
SendVarData is a method which send the bytes array over the socket it is not the problem here-leave it.
this is how i get the data in the server side:
public void startListening()
{
Bitmap merge = new Bitmap(1920, 1080);
Graphics g = Graphics.FromImage(merge);
Bitmap prev = byteArrayToImage(ReceiveVarData(client.Client)) as Bitmap;//getting the first full size image.
theImage.Image = prev;//assisning it to picturebox.
while (true)
{
byte[]data = ReceiveVarData(client.Client);
Bitmap curr = byteArrayToImage(data) as Bitmap;//here is the diffrent image
//merge and apply differences
g.DrawImage(prev, 0, 0,1920, 1080);
g.DrawImage(curr, 0, 0, 1920,1080);
theImage.Image = merge;
count++;
prev = merge;
}
}
my problem is that eventhough i merge the two images with the Graphics.Draw it still(after the first dataReceive) looks like not full... this is actually what i see on the server..
i dont know what's wrong here... can anyone light my eyes? :D
#DmitriTrofimov
if (p[0] != p2[0] || p[1] != p2[1] || p[2] != p2[2])
{
pRes[0] = p2[0];
pRes[1] = p2[1];
pRes[2] = p2[2];
//alpha (opacity)
pRes[3] = p2[3];
}
else
pRes[0] = 0;

This is what you get when you keep pixel opacity. You should set Alpha to zero on the pixels that are not different and make sure you are working with 32-bit images (refer to PixelFormat parameter of Bitmap constructor).
P.S. Make sure you compress the diff bitmap otherwise it's no use.

unsafe image noise removal in c# (error : Bitmap region is already locked)

public unsafe Bitmap MedianFilter(Bitmap Img)
{
int Size =2;
List<byte> R = new List<byte>();
List<byte> G = new List<byte>();
List<byte> B = new List<byte>();
int ApetureMin = -(Size / 2);
int ApetureMax = (Size / 2);
BitmapData imageData = Img.LockBits(new Rectangle(0, 0, Img.Width, Img.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppRgb);
byte* start = (byte*)imageData.Scan0.ToPointer ();
for (int x = 0; x < imageData.Width; x++)
{
for (int y = 0; y < imageData.Height; y++)
{
for (int x1 = ApetureMin; x1 < ApetureMax; x1++)
{
int valx = x + x1;
if (valx >= 0 && valx < imageData.Width)
{
for (int y1 = ApetureMin; y1 < ApetureMax; y1++)
{
int valy = y + y1;
if (valy >= 0 && valy < imageData.Height)
{
Color tempColor = Img.GetPixel(valx, valy);// error come from here
R.Add(tempColor.R);
G.Add(tempColor.G);
B.Add(tempColor.B);
}
}
}
}
}
}
R.Sort();
G.Sort();
B.Sort();
Img.UnlockBits(imageData);
return Img;
}
I tried to do this. but i got an error call "Bitmap region is already locked" can anyone help how to solve this. (error position is highlighted)

GetPixel is the slooow way to access the image and doesn't work (as you noticed) anymore if someone else starts messing with the image buffer directly. Why would you want to do that?
Check Using the LockBits method to access image data for some good insight into fast image manipulation.
In this case, use something like this instead:
int pixelSize = 4 /* Check below or the site I linked to and make sure this is correct */
byte* color =(byte *)imageData .Scan0+(y*imageData .Stride) + x * pixelSize;
Note that this gives you the first byte for that pixel. Depending on the color format you are looking at (ARGB? RGB? ..) you need to access the following bytes as well. Seems to suite your usecase anyway, since you just care about byte values, not the Color value.
So, after having some spare minutes, this is what I'd came up with (please take your time to understand and check it, I just made sure it compiles):
public void SomeStuff(Bitmap image)
{
var imageWidth = image.Width;
var imageHeight = image.Height;
var imageData = image.LockBits(new Rectangle(0, 0, imageWidth, imageHeight), ImageLockMode.ReadOnly, PixelFormat.Format32bppRgb);
var imageByteCount = imageData.Stride*imageData.Height;
var imageBuffer = new byte[imageByteCount];
Marshal.Copy(imageData.Scan0, imageBuffer, 0, imageByteCount);
for (int x = 0; x < imageWidth; x++)
{
for (int y = 0; y < imageHeight; y++)
{
var pixelColor = GetPixel(imageBuffer, imageData.Stride, x, y);
// Do your stuff
}
}
}
private static Color GetPixel(byte[] imageBuffer, int imageStride, int x, int y)
{
int pixelBase = y*imageStride + x*3;
byte blue = imageBuffer[pixelBase];
byte green = imageBuffer[pixelBase + 1];
byte red = imageBuffer[pixelBase + 2];
return Color.FromArgb(red, green, blue);
}
This
Relies on the PixelFormat you used in your sample (regarding both the pixelsize/bytes per pixel and the order of the values). If you change the PixelFormat this will break.
Doesn't need the unsafe keyword. I doubt that it makes a lot of difference, but you are free to use the pointer based access instead, the method would be the same.

convert bitonal TIFF to bitonal PNG in C#

I need to convert bitonal (black and white) TIFF files into another format for display by a web browser, currently we're using JPGs, but the format isn't crucial. From reading around .NET doesn't seem to easily support writing bitonal images, so we're ending up with ~1MB files instead of ~100K ones. I'm considering using ImageMagick to do this, but ideally i'd like a solution which doesn't require this if possible.
Current code snippet (which also does some resizing on the image):
using (Image img = Image.FromFile(imageName))
{
using (Bitmap resized = new Bitmap(resizedWidth, resizedHeight)
{
using (Graphics g = Graphics.FromImage(resized))
{
g.DrawImage(img, new Rectangle(0, 0, resized.Width, resized.Height), 0, 0, img.Width, img.Height, GraphicsUnit.Pixel);
}
resized.Save(outputFilename, System.Drawing.Imaging.ImageFormat.Jpeg);
}
}
Is there any way to achieve this?
Thanks.

I believe the problem can be solved by checking that resized bitmap is of PixelFormat.Format1bppIndexed. If it's not, you should convert it to 1bpp bitmap and after that you can save it as black and white png without problems.
In other words, you should use following code instead of resized.Save(outputFilename, System.Drawing.Imaging.ImageFormat.Jpeg);
if (resized.PixelFormat != PixelFormat.Format1bppIndexed)
{
using (Bitmap bmp = convertToBitonal(resized))
bmp.Save(outputFilename, System.Drawing.Imaging.ImageFormat.Png);
}
else
{
resized.Save(outputFilename, System.Drawing.Imaging.ImageFormat.Png);
}
I use following code for convertToBitonal :
private static Bitmap convertToBitonal(Bitmap original)
{
int sourceStride;
byte[] sourceBuffer = extractBytes(original, out sourceStride);
// Create destination bitmap
Bitmap destination = new Bitmap(original.Width, original.Height,
PixelFormat.Format1bppIndexed);
destination.SetResolution(original.HorizontalResolution, original.VerticalResolution);
// Lock destination bitmap in memory
BitmapData destinationData = destination.LockBits(
new Rectangle(0, 0, destination.Width, destination.Height),
ImageLockMode.WriteOnly, PixelFormat.Format1bppIndexed);
// Create buffer for destination bitmap bits
int imageSize = destinationData.Stride * destinationData.Height;
byte[] destinationBuffer = new byte[imageSize];
int sourceIndex = 0;
int destinationIndex = 0;
int pixelTotal = 0;
byte destinationValue = 0;
int pixelValue = 128;
int height = destination.Height;
int width = destination.Width;
int threshold = 500;
for (int y = 0; y < height; y++)
{
sourceIndex = y * sourceStride;
destinationIndex = y * destinationData.Stride;
destinationValue = 0;
pixelValue = 128;
for (int x = 0; x < width; x++)
{
// Compute pixel brightness (i.e. total of Red, Green, and Blue values)
pixelTotal = sourceBuffer[sourceIndex + 1] + sourceBuffer[sourceIndex + 2] +
sourceBuffer[sourceIndex + 3];
if (pixelTotal > threshold)
destinationValue += (byte)pixelValue;
if (pixelValue == 1)
{
destinationBuffer[destinationIndex] = destinationValue;
destinationIndex++;
destinationValue = 0;
pixelValue = 128;
}
else
{
pixelValue >>= 1;
}
sourceIndex += 4;
}
if (pixelValue != 128)
destinationBuffer[destinationIndex] = destinationValue;
}
Marshal.Copy(destinationBuffer, 0, destinationData.Scan0, imageSize);
destination.UnlockBits(destinationData);
return destination;
}
private static byte[] extractBytes(Bitmap original, out int stride)
{
Bitmap source = null;
try
{
// If original bitmap is not already in 32 BPP, ARGB format, then convert
if (original.PixelFormat != PixelFormat.Format32bppArgb)
{
source = new Bitmap(original.Width, original.Height, PixelFormat.Format32bppArgb);
source.SetResolution(original.HorizontalResolution, original.VerticalResolution);
using (Graphics g = Graphics.FromImage(source))
{
g.DrawImageUnscaled(original, 0, 0);
}
}
else
{
source = original;
}
// Lock source bitmap in memory
BitmapData sourceData = source.LockBits(
new Rectangle(0, 0, source.Width, source.Height),
ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
// Copy image data to binary array
int imageSize = sourceData.Stride * sourceData.Height;
byte[] sourceBuffer = new byte[imageSize];
Marshal.Copy(sourceData.Scan0, sourceBuffer, 0, imageSize);
// Unlock source bitmap
source.UnlockBits(sourceData);
stride = sourceData.Stride;
return sourceBuffer;
}
finally
{
if (source != original)
source.Dispose();
}
}

Have you tried saving using the Image.Save overload with Encoder parameters?
Like the Encoder.ColorDepth Parameter?

Trying jaroslav's suggestion for color depth doesn't work:
static void Main(string[] args)
{
var list = ImageCodecInfo.GetImageDecoders();
var jpegEncoder = list[1]; // i know this is the jpeg encoder by inspection
Bitmap bitmap = new Bitmap(500, 500);
Graphics g = Graphics.FromImage(bitmap);
g.DrawRectangle(new Pen(Color.Red), 10, 10, 300, 300);
var encoderParams = new EncoderParameters();
encoderParams.Param[0] = new EncoderParameter(Encoder.ColorDepth, 2);
bitmap.Save(#"c:\newbitmap.jpeg", jpegEncoder, encoderParams);
}
The jpeg is still a full color jpeg.
I don't think there is any support for grayscale jpeg in gdi plus. Have you tried looking in windows imaging component?
http://www.microsoft.com/downloads/details.aspx?FamilyID=8e011506-6307-445b-b950-215def45ddd8&displaylang=en
code example: http://www.codeproject.com/KB/GDI-plus/windows_imaging.aspx
wikipedia: http://en.wikipedia.org/wiki/Windows_Imaging_Component

This is an old thread. However, I'll add my 2 cents.
I use AForge.Net libraries (open source)
use these dlls. Aforge.dll, AForge.Imaging.dll
using AForge.Imaging.Filters;
private void ConvertBitmap()
{
markedBitmap = Grayscale.CommonAlgorithms.RMY.Apply(markedBitmap);
ApplyFilter(new FloydSteinbergDithering());
}
private void ApplyFilter(IFilter filter)
{
// apply filter
convertedBitmap = filter.Apply(markedBitmap);
}

Have you tried PNG with 1 bit color depth?
To achieve a size similar to a CCITT4 TIFF, I believe your image needs to use a 1-bit indexed pallette.
However, you can't use the Graphics object in .NET to draw on an indexed image.
You will probably have to use LockBits to manipulate each pixel.
See Bob Powell's excellent article.