Question

I am trying to extract R G B values from a pixel in the following code:

for ( int i=0; i < pixeldata.length; i++)
    {
        IntPtr ptr = bmd.Scan0+i;
        byte* pixel = (byte*)ptr;

        //here is the problem :O

        float r = pixel[1];
        float g = pixel[2];
        float b = pixel[3];
     }
....

where bmd is an array of pixels data:

BitmapData bmd = source.LockBits(rect, ImageLockMode.ReadOnly, source.PixelFormat);

and source is the Bitmap of my input, which is an image.
I am trying to avoid the use of Color object. I have already done that and it works, I want to use this other way, but the issue is that ptr is a number and I have to extract the R G B from it.

Answer 1

This is the solution that gives you the right answer.

Bitmap source = new Bitmap(image);

            Rectangle rect = new Rectangle(0, 0, source.Width, source.Height);

            BitmapData bmd = source.LockBits(rect, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

            int totalPixels = rect.Height * rect.Width;
            int[] pixelData = new int[totalPixels];
            for (int i = 0; i < totalPixels; i++)
            {
                byte* pixel = (byte*)bmd.Scan0;
                pixel = pixel + (i * 4);

                byte b = pixel[0];
                byte g = pixel[1];
                byte r = pixel[2];

                int luma = (int)(r * 0.3 + g * 0.59 + b * 0.11);
                pixelData[i] = luma;
            }