Saving Bitmap as 32bpp doesn't keep transparency

Question

using (var bmp = new Bitmap(image.Width, image.Height, PixelFormat.Format32bppArgb))
using (var g = Graphics.FromImage(bmp))
{
    g.Clear(Color.Transparent);
    g.         


        

Answer 1

It's because by default the bmp file format doesn't support transparency while the png file format does.

If you want transparency you are going to have to use png. The compression algorithms are lossless so you're not going to get artefacts in your image. The file will take up less space on disk too.