使用非黑色背景颜色将透明PNG转换为JPG

Question

我在.Net中使用System.Drawing.Image进行从png到jpeg的简单转换.我基本上只使用这两行代码:

Image img = Image.FromFile(filename);
img.Save(newFilename, System.Drawing.Imaging.ImageFormat.Jpeg);

它工作正常,除了png文件由于alpha通道包含透明度.在这种情况下,转换的jpeg具有黑色背景.有没有办法让背景变白？

Answer 1

// Assumes myImage is the PNG you are converting
using (var b = new Bitmap(myImage.Width, myImage.Height)) {
    b.SetResolution(myImage.HorizontalResolution, myImage.VerticalResolution);

    using (var g = Graphics.FromImage(b)) {
        g.Clear(Color.White);
        g.DrawImageUnscaled(myImage, 0, 0);
    }

    // Now save b as a JPEG like you normally would
}