C# TUTORIAL: HOW TO APPLY EROSION TO AN IMAGE

float rgb;
for (int i = 0; i < bytes; i += 4)
{
    rgb = pixelBuffer[i] * .071f;
    rgb += pixelBuffer[i + 1] * .71f;
    rgb += pixelBuffer[i + 2] * .21f;
    pixelBuffer[i] = (byte)rgb;
    pixelBuffer[i + 1] = pixelBuffer[i];
    pixelBuffer[i + 2] = pixelBuffer[i];
    pixelBuffer[i + 3] = 255;
}

int kernelSize = 3;
int kernelOffset = (kernelSize - 1) / 2;
int calcOffset = 0;
int byteOffset = 0;

for (int y = kernelOffset; y < height - kernelOffset; y++)
{
    for (int x = kernelOffset; x < width - kernelOffset; x++)
    {
        byte value = 255;
        byteOffset = y * srcData.Stride + x * 4;
        for (int ykernel = -kernelOffset; ykernel <= kernelOffset; ykernel++)
        {
            for (int xkernel = -kernelOffset; xkernel <= kernelOffset; xkernel++)
            {
                if (kernel[ykernel + kernelOffset,xkernel + kernelOffset] == 1)
                {
                    calcOffset = byteOffset + ykernel * srcData.Stride + xkernel * 4;
                    value = Math.Min(value, pixelBuffer[calcOffset]);
                }
                else
                {
                    continue;
                }
            }
        }
        resultBuffer[byteOffset] = value;
        resultBuffer[byteOffset + 1] = value;
        resultBuffer[byteOffset + 2] = value;
        resultBuffer[byteOffset + 3] = 255;
    }
}

    Bitmap result = new Bitmap(width, height);
    BitmapData resultData = result.LockBits(canvas, ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);
    Marshal.Copy(resultBuffer, 0, resultData.Scan0, bytes);
    result.UnlockBits(resultData);
    return result;