C# 将透明水印（png）图像添加到其他图像

我需要添加一个透明水印到一个更大的图像。通过谷歌搜索，我找到了你 代码似乎可以工作，但水的图像没有被正确放置，似乎扭曲和失去透明度。请告诉我如何纠正这个问题。如果有更好的方法来实现这一点，请让我知道

主图像640x480

水印图像100x86

public static class ImageHelper
{
    #region Public Methods and Operators

    public static Bitmap BitmapSourceToBitmap(BitmapSource bitmapsource)
    {
        Bitmap bitmap;
        using (var outStream = new MemoryStream())
        {
            BitmapEncoder enc = new BmpBitmapEncoder();
            enc.Frames.Add(BitmapFrame.Create(bitmapsource));
            enc.Save(outStream);
            bitmap = new Bitmap(outStream);
        }

        return bitmap;
    }

    public static BitmapSource BitmapToBitmapSource(Bitmap source)
    {
        return Imaging.CreateBitmapSourceFromHBitmap(
            source.GetHbitmap(), 
            IntPtr.Zero, 
            Int32Rect.Empty, 
            BitmapSizeOptions.FromEmptyOptions());
    }

    #endregion

    #region Methods

    public static Image BitmapSourceToImage(BitmapSource image)
    {
        var ms = new MemoryStream();
        var encoder = new BmpBitmapEncoder();
        encoder.Frames.Add(BitmapFrame.Create(image));
        encoder.Save(ms);
        ms.Flush();
        return Image.FromStream(ms);
    }

    public static Bitmap Superimpose(Bitmap largeBmp, Bitmap smallBmp)
    {
        Graphics g = Graphics.FromImage(largeBmp);
        g.CompositingMode = CompositingMode.SourceOver;

        // smallBmp.MakeTransparent();
        int margin = 5;
        int x = largeBmp.Width - smallBmp.Width - margin;
        int y = largeBmp.Height - smallBmp.Height - margin;
        g.DrawImage(smallBmp, new Point(x, y));
        return largeBmp;
    }

    #endregion
}

呼叫代码

        var fs = new FileStream(path, FileMode.Create);

        BitmapSource bitmap = new BitmapImage(new Uri(ImagePath, UriKind.Absolute));
        BitmapSource Logobitmap = new BitmapImage(new Uri(logoPath, UriKind.Absolute));

        bitmap =
            ImageHelper.BitmapToBitmapSource(
                ImageHelper.Superimpose(
                    ImageHelper.BitmapSourceToBitmap(bitmap), 
                    ImageHelper.BitmapSourceToBitmap(Logobitmap)));
        var encoder = new PngBitmapEncoder();
        encoder.Frames.Add(BitmapFrame.Create(bitmap));
        encoder.Save(fs);
        fs.Close();

---

为任何需要它的人修复了它（请阅读：）

呼叫码

        string logoPath =  "watermark.png";

        var fs = new FileStream(path, FileMode.Create);

        BitmapSource bitmap = [LoadImage]

        if (Settings.Default.AddWaterMark)
        {
            BitmapSource logobitmap = new BitmapImage(new Uri(logoPath, UriKind.Absolute));
            Bitmap mainImgeBitmap = ImageHelper.BitmapSourceToBitmap(bitmap);
            Bitmap logoImageBitmap = ImageHelper.BitmapSourceToBitmap(logobitmap, ImageHelper.ImageType.PNG);
            logoImageBitmap = ImageHelper.SetBitmapResolution(
                logoImageBitmap,
                (float)bitmap.DpiX,
                (float)bitmap.DpiY);
            bitmap = ImageHelper.BitmapToBitmapSource(ImageHelper.Superimpose(mainImgeBitmap, logoImageBitmap));
        }

        var encoder = new PngBitmapEncoder();
        encoder.Frames.Add(BitmapFrame.Create(bitmap));
        encoder.Save(fs);
        fs.Close();

---

确保两个位图具有相同的dpi设置；最好设置它！在不透明位图上使用半透明位图绘制将生成不透明位图，根据每个像素的透明度级别混合颜色。如果你想得到一个半透明的水印，你需要用setpixel改变像素。对于这样一个小的水印图像不是一个大问题，除非您需要快速更改很多图像。那你就要用锁具了。。

        string logoPath =  "watermark.png";

        var fs = new FileStream(path, FileMode.Create);

        BitmapSource bitmap = [LoadImage]

        if (Settings.Default.AddWaterMark)
        {
            BitmapSource logobitmap = new BitmapImage(new Uri(logoPath, UriKind.Absolute));
            Bitmap mainImgeBitmap = ImageHelper.BitmapSourceToBitmap(bitmap);
            Bitmap logoImageBitmap = ImageHelper.BitmapSourceToBitmap(logobitmap, ImageHelper.ImageType.PNG);
            logoImageBitmap = ImageHelper.SetBitmapResolution(
                logoImageBitmap,
                (float)bitmap.DpiX,
                (float)bitmap.DpiY);
            bitmap = ImageHelper.BitmapToBitmapSource(ImageHelper.Superimpose(mainImgeBitmap, logoImageBitmap));
        }

        var encoder = new PngBitmapEncoder();
        encoder.Frames.Add(BitmapFrame.Create(bitmap));
        encoder.Save(fs);
        fs.Close();