I'm currently writing a C# implementation of a little program which I have written in Java.
I had used BufferedImage.getRGB(int startX, int startY, int w, int h, int[] rgbArray, int offset, int scansize) function in my Java app. But I couldn't exactly find a version of this in C# and I am not sure how to write it manually.
There's not a direct equivalent in the .NET Framework to this method. However, if your image is a System.Drawing.Bitmap, you can call the LockBits method, and this will return a BitmapData structure that contains the address of the first scanline. You can then use it to create what should be an API-compatible wrapper. I'm assuming you're using C# 3.5 or greater, so I'm using an extension method - if you're using an older flavor, change this to a regular method by dropping the 'this' from the Bitmap argument:
public static void getRGB(this Bitmap image, int startX, int startY, int w, int h, int[] rgbArray, int offset, int scansize)
{
const int PixelWidth = 3;
const PixelFormat PixelFormat = PixelFormat.Format24bppRgb;
// En garde!
if (image == null) throw new ArgumentNullException("image");
if (rgbArray == null) throw new ArgumentNullException("rgbArray");
if (startX < 0 || startX + w > image.Width) throw new ArgumentOutOfRangeException("startX");
if (startY < 0 || startY + h > image.Height) throw new ArgumentOutOfRangeException("startY");
if (w < 0 || w > scansize || w > image.Width) throw new ArgumentOutOfRangeException("w");
if (h < 0 || (rgbArray.Length < offset + h * scansize) || h > image.Height) throw new ArgumentOutOfRangeException("h");
BitmapData data = image.LockBits(new Rectangle(startX, startY, w, h), System.Drawing.Imaging.ImageLockMode.ReadOnly, PixelFormat);
try
{
byte[] pixelData = new Byte[data.Stride];
for (int scanline = 0; scanline < data.Height; scanline++)
{
Marshal.Copy(data.Scan0 + (scanline * data.Stride), pixelData, 0, data.Stride);
for (int pixeloffset = 0; pixeloffset < data.Width; pixeloffset++)
{
// PixelFormat.Format32bppRgb means the data is stored
// in memory as BGR. We want RGB, so we must do some
// bit-shuffling.
rgbArray[offset + (scanline * scansize) + pixeloffset] =
(pixelData[pixeloffset * PixelWidth + 2] << 16) + // R
(pixelData[pixeloffset * PixelWidth + 1] << 8) + // G
pixelData[pixeloffset * PixelWidth]; // B
}
}
}
finally
{
image.UnlockBits(data);
}
}
This wrapper can now be called like this:
Bitmap foo = Bitmap.FromFile(@"somefile.jpg") as Bitmap;
int[] rgbArray = new int[100];
foo.getRGB(1, 1, 10, 10, rgbArray, 0, 10);
Hope this helps, and welcome to .NET!
You'd use Bitmap.LockBits to get direct access to the pixels in a bitmap. Here's a sample implementation, it returns one scanline from the passed bitmap as an int[]:
int[] getRGB(Bitmap bmp, int line) {
var data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height),
System.Drawing.Imaging.ImageLockMode.ReadOnly,
System.Drawing.Imaging.PixelFormat.Format32bppRgb);
try {
var ptr = (IntPtr)((long)data.Scan0 + data.Stride * (bmp.Height - line - 1));
var ret = new int[bmp.Width];
System.Runtime.InteropServices.Marshal.Copy(ptr, ret, 0, ret.Length * 4);
return ret;
}
finally {
bmp.UnlockBits(data);
}
}
I think the closest one is Bitmap.GetPixel(x,y) that return a single pixel color at a point.
In order to simulate the java function, you will need to write some helper.
It depends how fast you need to do it.
Bitmap has GetPixel() method which works fine for a pixel.
If you need to do fast image processing you need to use LockBits which you can find a sample here.
Bitmap img = (Bitmap) Image.FromFile(imageFileName);
BitmapData data = img.LockBits(new Rectangle(0,0,img.Width, img.Height), ImageLockMode.ReadWrite, img.PixelFormat);
byte* ptr = (byte*) data.Scan0;
for (int j = 0; j < data.Height; j++)
{
byte* scanPtr = ptr + (j * data.Stride);
for (int i = 0; i < data.width; i++, scanPtr+=NO_OF_CHANNELS)
{
for (int m = 0; m < NO_OF_CHANNELS; m++)
Console.WriteLine(*scanPtr); // value of each channel
}
}
img.UnlockBits(data);
