Remove transparency in images with C#

Question

Hello there,

does anyone know a smooth / fast way of removing transparency from e.g. pngs/tiffs etc and replacing it with a white background?

Basically what I need this for is I need to create PDF/A compatible images, which may, according to the spec, have -no- transparency (and therefore a fixed white background is fine).

Any ideas / suggestions?

Cheers & thanks, -Jörg

Answer 1

1) Create a bitmap with a white background and with the same size as your image
2) Load you image and paint it on top of your "white" bitmap
3) Save the newly created image

Answer 2

You could create a bitmap the same size as the png, draw a white rectangle and then draw the image on top of it.

void RemTransp(string file) {
    Bitmap src = new Bitmap(file);
    Bitmap target = new Bitmap(src.Size.Width,src.Size.Height);
    Graphics g = Graphics.FromImage(target);
    g.DrawRectangle(new Pen(new SolidBrush(Color.White)), 0, 0, target.Width, target.Height);
    g.DrawImage(src, 0, 0);
    target.Save("Your target path");
}

Answer 3

PNGs have alpha channel, so simple recoloring won't do. Create white image of same size, and create composite image overlay your image over it.