Detecting if a PNG image file is a Transparent image?

Question

I am looking for a way to quickly determine if a PNG image has transparent features. That is, whether any portion of the image is translucent or displays the background in any way. Does anyone one know a simple way to detect this?

UPDATE: OK, is there a less complicated way then to pull out the PNG specification and hacking code?

Answer 1

Why not just loop through all of the pixels in the image and check their alpha values?

    bool ContainsTransparent(Bitmap image)
    {
        for (int y = 0; y < image.Height; ++y)
        {
            for (int x = 0; x < image.Width; ++x)
            {
                if (image.GetPixel(x, y).A != 255)
                {
                    return true;
                }
            }
        }
        return false;
    }