Changing the Opacity of a Bitmap image

Question

I have a form which has a image. I am using a slider to change the opacity of the image. So in the \"ValueChanged\" event of the slider I am calling the following method to

Answer 1

The ImageAttributes method will work fine with PNG as the original post has it listed, but for JPEG you need to flood fill the graphics canvas with a color first. Since this can leave a tiny undesired border, only do it if the opacity is something less than 1.0:

if(opacity < 1.0)
{
    // g is a Graphics object
    g.Clear(Color.White);
}
// set color matrix and draw image as shown in other posts
// ...