Question

I had a situation to duplicate an image with the help of bitmap data, below is the code i used to do the same, am I wrong anywhere, please help me.. Try drawing this image
https://i.stack.imgur.com/VCSoQ.png in the bmp format

private void button1_Click(object sender, EventArgs e)
{
Bitmap mask = Image.FromFile("../../Data/mask.bmp") as Bitmap;
BitmapData data = mask.LockBits(new Rectangle(0, 0, mask.Width, mask.Height), ImageLockMode.ReadWrite, mask.PixelFormat);
int bytes = Math.Abs(data.Stride) * mask.Height;
byte[] outPut = new byte[bytes];
Marshal.Copy(data.Scan0, outPut, 0, bytes);

Bitmap test = new Bitmap(mask.Width, mask.Height, mask.PixelFormat);
BitmapData testData = test.LockBits(new Rectangle(0, 0, test.Width, test.Height),
ImageLockMode.ReadWrite, test.PixelFormat);
Marshal.Copy(outPut, 0, testData.Scan0, bytes);
test.UnlockBits(testData);
test.Save("test.jpg");
}

Thanks,
Suresh

Answer 1

There is problem in getting the color palette of the image through BitmapData, on replacing the color palette of the new image with the old, we could get the same image.

Bitmap mask = Image.FromFile("../../Data/mask.bmp") as Bitmap;
        BitmapData data = mask.LockBits(new Rectangle(0, 0, (int)mask.PhysicalDimension.Width, (int)mask.PhysicalDimension.Height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);
        int bytes = Math.Abs(data.Stride) * mask.Height;            
        byte[] outPut = new byte[bytes];
        Marshal.Copy(data.Scan0, outPut, 0, bytes);
        Marshal.Copy(outPut, 0, data.Scan0, bytes);
        mask.UnlockBits(data);

        Bitmap test = new Bitmap(mask.Width, mask.Height, PixelFormat.Format8bppIndexed);
        test.Palette = mask.Palette;
        BitmapData testData = test.LockBits(new Rectangle(0, 0, mask.Width, mask.Height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);
        Marshal.Copy(outPut, 0, testData.Scan0, bytes);
        test.UnlockBits(data);
        test.Save("test.jpg");