在C＃中使用圖像。調整一個GIF並保存爲JPEG

您好我使用C＃和Asp.Net4。在C＃中使用圖像。調整一個GIF並保存爲JPEG

我創建了一個重新調整源圖像大小的類。代碼工作的偉大與JPEG文件，但如果我上傳一個GIF我收到此錯誤：

A Graphics object cannot be created from an image that has an indexed pixel format.

這裏我的代碼..任何想法？

異常行：SD.Graphics newImage = SD.Graphics.FromImage(temp);

private static ImageCodecInfo GetEncoderInfo(String mimeType) 
    { 
     int j; 
     ImageCodecInfo[] encoders; 
     encoders = ImageCodecInfo.GetImageEncoders(); 
     for (j = 0; j < encoders.Length; ++j) 
     { 
      if (encoders[j].MimeType == mimeType) 
       return encoders[j]; 
     } 
     return null; 
    } 


    protected void ResizeImageWithAspect(string fileName, string outputFileName, int newWidth, int newResolution, string newCodec, int qualityLevel) 
    { 
     // Original Image 
     SD.Image original = SD.Image.FromFile(fileName); 

     // Find image aspect ratio computed by image height and width. 
     float aspect = (float)original.Height/(float)original.Width; 

     // Calculate the new height using the aspect ratio and the desired new width. 
     int newHeight = (int)(newWidth * aspect); 

     // Create a bitmap of the correct size. Bitmap it is used for image manipolation. 
     SD.Bitmap temp = new SD.Bitmap(newWidth, newHeight, original.PixelFormat); 

     // Setting the Encoder for the image. 
     ImageCodecInfo myImageCodecInfo; 
     Encoder myEncoder; // Guid Encoder 
     EncoderParameter myEncoderParameter; // Pass a value to an Image Encoder 
     EncoderParameters myEncoderParameters; //Encapsulates an array of EncoderParameter objects 

     // Get an ImageCodecInfo object that represents the JPEG codec. 
     myImageCodecInfo = GetEncoderInfo(newCodec); 
     // Create an Encoder object based on the GUID 
     // for the Quality parameter category. 
     myEncoder = Encoder.Quality; 
     // Create an EncoderParameters object. 
     // An EncoderParameters object has an array of EncoderParameter 
     // objects. In this case, there is only one 
     // EncoderParameter object in the array. 
     myEncoderParameters = new EncoderParameters(1); 
     myEncoderParameter = new EncoderParameter(myEncoder, qualityLevel); 
     myEncoderParameters.Param[0] = myEncoderParameter; 

     //Set image resolution (horizontal and vertical) 
     temp.SetResolution(newResolution, newResolution); 

     //Get a Graphics object from the bitmap. 
     SD.Graphics newImage = SD.Graphics.FromImage(temp); 
     // Quality settings output image 
     newImage.SmoothingMode = SmoothingMode.AntiAlias; 
     newImage.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality; 
     newImage.InterpolationMode = InterpolationMode.HighQualityBicubic; 
     newImage.PixelOffsetMode = PixelOffsetMode.HighQuality; 

     //Draw the image with the new width/height 
     newImage.DrawImage(original, 0, 0, newWidth, newHeight); 

     //Save the bitmap with appropirate Codec 
     temp.Save(outputFileName, myImageCodecInfo, myEncoderParameters); 

     //Dispose of our objects. 
     original.Dispose(); 
     temp.Dispose(); 
     newImage.Dispose(); 
    }

來源

2011-04-04 GibboK

哪行給出了錯誤？由於GIF圖像使用索引來指定每個像素的顏色，而不是顯式的RGB值，所以您需要使用不同的方法來讀取它。 – ChrisF 2011-04-04 09:13:28

SD.Graphics newImage = SD.Graphics.FromImage（temp）; – GibboK 2011-04-04 09:18:13

上面的行創建錯誤。你能給我一個不同方法的例子嗎？我是否也有與PNG文件相同的問題？ – GibboK 2011-04-04 09:19:11

只是改變這一行：

SD.Bitmap temp = new SD.Bitmap(newWidth, newHeight, original.PixelFormat);

到

SD.Bitmap temp = new SD.Bitmap(newWidth, newHeight, PixelFormat.Format24bppRgb);

來源

2011-04-04 09:20:43

非常感謝作品！ – GibboK 2011-04-04 09:39:18

，我認爲這就是問題所在：

SD.Bitmap temp = new SD.Bitmap(newWidth, newHeight, original.PixelFormat);

您正在使用你剛纔讀入的圖像的像素格式 - 在這種情況下，GIF，所以這是失敗的。

您需要爲此使用非索引像素格式。

來源

2011-04-04 09:18:14 ChrisF

在C＃中使用圖像。調整一個GIF並保存爲JPEG

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