在高質量的圖像上設置水印

Question

我有一個處理器在圖像上設置水印。問題是質量不太好。 這是代碼：

byte[] imageBytes = null; 

    using (Graphics G = Graphics.FromImage(ImageToWatermark)) 
    { 
     using (ImageAttributes IA = new ImageAttributes()) 
     { 
      ColorMatrix CM = new ColorMatrix(); 
      CM.Matrix33 = Opacity; 
      IA.SetColorMatrix(CM); 
      G.DrawImage(Watermark, new Rectangle(WatermarkPosition, Watermark.Size), 0, 0, Watermark.Width, Watermark.Height, GraphicsUnit.Pixel, IA); 
     } 
    } 

    using (MemoryStream memoryStream = new MemoryStream()) 
    { 
     ImageToWatermark.Save(memoryStream, GetImageFormat(context.Request.PhysicalPath)); 
     imageBytes = memoryStream.ToArray(); 
    } 

如何設置結果的質量？

謝謝 阿麗娜

Answer 1

如果您的圖像格式是JPEG，這時你可以手動使用此樣本的方法來保存到磁盤設置輸出質量：

public void SaveJpg(string path, Bitmap img, long quality) { 
     // Encoder parameter for image quality 
     EncoderParameter qualityParam = new EncoderParameter(Encoder.Quality, quality); 

     // Jpeg image codec 
     ImageCodecInfo jpegCodec = this.getEncoderInfo("image/jpeg"); 

     EncoderParameters encoderParams = new EncoderParameters(1); 
     encoderParams.Param[0] = qualityParam; 

     img.Save(path, jpegCodec, encoderParams); 
    } 

或者，在情況下，使用下面的代碼段：

using (MemoryStream memoryStream = new MemoryStream()) 
    { 
     EncoderParameter qualityParam = new EncoderParameter(Encoder.Quality, 80); // edit image quality here 
     ImageCodecInfo jpegCodec = this.getEncoderInfo("image/jpeg"); 
     EncoderParameters encoderParams = new EncoderParameters(1); 
     encoderParams.Param[0] = qualityParam; 

     ImageToWatermark.Save(memoryStream, encoderParams); 
     imageBytes = memoryStream.ToArray(); 
    } 

通常，60〜100質量應產生用於屏幕輸出足夠好JPEG圖像。