使用C#删除图像中的透明度

Question

有没有人知道一个平滑/快速的方法来删除透明度,例如pngs/tiffs等,并用白色背景替换它？

基本上我需要的是我需要创建PDF/A兼容图像,根据规范,它可能具有-no-透明度(因此固定的白色背景很好).

有什么想法/建议吗？

干杯和谢谢,-Jörg

Answer 1

您可以创建一个与png大小相同的位图,绘制一个白色矩形,然后在其上绘制图像.

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 2

您必须删除Alpha通道.否则你仍然会有一个透明的图像 - 只是没有透明的区域.

class Program
{
    static void Main(string[] args)
    {
        //this also works for different file formats
        ReplaceTransparency(@"C:\Y\transparent.png", System.Drawing.Color.White).Save(@"C:\Y\no_transparency.png");
        ReplaceTransparency(@"C:\Y\transparent.gif", System.Drawing.Color.White).Save(@"C:\Y\no_transparency.gif");
    }

    public static System.Drawing.Bitmap ReplaceTransparency(string file, System.Drawing.Color background)
    {
        return ReplaceTransparency(System.Drawing.Image.FromFile(file), background);
    }

    public static System.Drawing.Bitmap ReplaceTransparency(System.Drawing.Image image, System.Drawing.Color background)
    {
        return ReplaceTransparency((System.Drawing.Bitmap)image, background);
    }

    public static System.Drawing.Bitmap ReplaceTransparency(System.Drawing.Bitmap bitmap, System.Drawing.Color background)
    {
        /* Important: you have to set the PixelFormat to remove the alpha channel.
         * Otherwise you'll still have a transparent image - just without transparent areas */
        var result = new System.Drawing.Bitmap(bitmap.Size.Width, bitmap.Size.Height, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
        var g = System.Drawing.Graphics.FromImage(result);

        g.Clear(background);
        g.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceOver;
        g.DrawImage(bitmap, 0, 0);

        return result;
    }
}