So, I am very confused over a quick test that I just ran. I am doing some image processing in C#. Get/SetPixel() have proven to be too slow, so I am using LockBits to get at the raw data.
However, I seem to have hit a situation which I can't figure out. While scanning the image, it seems that each pixel is laid out as Bgra, that is, blue byte, green byte, red byte, and alpha, in that order. I was under the impression that they would be laid out in Argb order. here is a sample of the code that I am using.
BitmapData baseData =
m_baseImage.LockBits(new Rectangle(new Point(0, 0), m_baseImage.Size),
ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
Bitmap test = new Bitmap(m_baseImage.Width, m_baseImage.Height);
byte* ptr = (byte*)baseData.Scan0;
for (int y = 0; y < m_baseImage.Height; ++y)
{
for (int x = 0; x < m_baseImage.Width; ++x)
{
// this works, image is copied correctly
Color c1 = Color.FromArgb(*(ptr + 3), *(ptr + 2), *(ptr + 1), *ptr);
// below does not work! Bytes are reversed.
//Color c1 = Color.FromArgb(*ptr, *(ptr + 1), *(ptr + 2), *(ptr + 3));
test.SetPixel(x, y, c1);
ptr += 4;
}
}
m_baseImage.UnlockBits(baseData);
pictureBox1.Image = m_baseImage;
pictureBox2.Image = test;
The first line which grabs the color of the base image works, the second does not. I am pretty sure that I am missing something very obvious here.