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Graphics使用InterpolationMode.High缩放图像黑图的问题 RRS feed

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    Graphics使用InterpolationMode.High将两张特定的图片缩放到特定大小时，得到的是一张黑图。而其他类似的图片却能正常缩放。

    请问是什么原因？

    原图是89.1kb（91276字节） 1028*768 96dpi*96dpi 24色深的pnｇ图片。

    至于图片，因为不知道怎么上传附件，所以暂时不传。

    缩放代码如下：

    FileStream fileStream = new FileStream(@"C:\i0000440.png");//取得图片的文件流
Bitmap bitMap = new Bitmap(fileStream);//创建bitmap
fileSream.Dispse();

int x = 0;
int y = 0;
int width = 548;//缩放后的图的高，1280缩小成这个特定的高度
int height = 329;//缩放后的图的宽，768缩小成这个特定的宽度
Bitmap bitMap2 = new Bitmap(width, height, PixelFormat.Format32bppArgb);//缩放后的新图

Graphics gImg = Graphics.FromImage(bitMap2);
gImg.CompositingQuality = CompositingQuality.HighQuality;
gImg.InterpolationMode = InterpolationMode.High;// 指定高质量插值法。 指定这个算法缩放图片后，得到的这张特定图片是黑图，而指定高质量的双三次插值法InterpolationMode.HighQualityBicubic也会生成黑图，而指定其他算法就没有问题。另外，缩放成其他大小也没有问题，比如width=547, height=328。
gImg.SmoothingMode = SmoothingMode.HighQuality;
gImg.Clear(Color.Transparent);
gImg.DrawImage(bitmap, x, y, width, height);
bitMap2.Save((@"C:\i0000440-2.png");//保存新图的位置没有特殊要求
bitMap.Dispose();
gImg.Dispose();
bitMap2.Dispose();
    2011年4月14日 1:46
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答案

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    你好
    试试下面的代码，注意把保存为jpeg 的地方改成png就可以了。有些代码可以不要，参考下。
    using System; 
    using     System.Collections.Generic; 
    using     System.Drawing; 
    using     System.Drawing.Imaging; 
     
    namespace     DoctaJonez.Drawing.Imaging 
    { 
            /// <summary> 
            /// Provides various image untilities, such as high quality resizing and the ability to save a JPEG. 
            /// </summary> 
            public static class ImageUtilities 
            {     
                /// <summary> 
                /// A quick lookup for getting image encoders 
                /// </summary> 
                private static Dictionary<string, ImageCodecInfo> encoders = null; 
     
                /// <summary> 
                /// A quick lookup for getting image encoders 
                /// </summary> 
                public static Dictionary<string, ImageCodecInfo> Encoders 
                { 
                    //get accessor that creates the dictionary on demand 
                get 
                    { 
                        //if the quick lookup isn't initialised, initialise it 
                        if (encoders == null) 
                        { 
                        encoders     = new Dictionary<string, ImageCodecInfo>(); 
                        } 
     
                        //if there are no codecs, try loading them 
                        if (encoders.Count == 0) 
                        { 
                            //get all the codecs 
                            foreach (ImageCodecInfo codec in ImageCodecInfo.GetImageEncoders()) 
                            { 
                                //add each codec to the quick lookup 
                            encoders    .Add(codec.MimeType.ToLower(), codec); 
                            } 
                        } 
     
                        //return the lookup 
                        return encoders; 
                    } 
                } 
     
                /// <summary> 
                /// Resize the image to the specified width and height. 
                /// </summary> 
                /// <param name="image">The image to resize.</param> 
                /// <param name="width">The width to resize to.</param> 
                /// <param name="height">The height to resize to.</param> 
                /// <returns>The resized image.</returns> 
                public static System.Drawing.Bitmap ResizeImage(System.Drawing.Image image, int width, int height) 
                { 
                    //a holder for the result 
                    Bitmap result = new Bitmap(width, height); 
     
                    //use a graphics object to draw the resized image into the bitmap 
                using     (Graphics graphics = Graphics.FromImage(result)) 
                    { 
                        //set the resize quality modes to high quality 
                    graphics    .CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality; 
                    graphics    .InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; 
                    graphics    .SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; 
                        //draw the image into the target bitmap 
                    graphics    .DrawImage(image, 0, 0, result.Width, result.Height); 
                    } 
     
                    //return the resulting bitmap 
                    return result; 
                } 
     
                /// <summary>  
                /// Saves an image as a jpeg image, with the given quality  
                /// </summary>  
                /// <param name="path">Path to which the image would be saved.</param>  
                /// <param name="quality">An integer from 0 to 100, with 100 being the  
                /// highest quality</param>  
                /// <exception cref="ArgumentOutOfRangeException"> 
                /// An invalid value was entered for image quality. 
                /// </exception> 
                public static void SaveJpeg(string path, Image image, int quality) 
                { 
                    //ensure the quality is within the correct range 
                    if ((quality < 0) || (quality > 100)) 
                    { 
                        //create the error message 
                        string error = string.Format("Jpeg image quality must be between 0 and 100, with 100 being the highest quality.  A value of {0} was specified.", quality); 
                        //throw a helpful exception 
                        throw new ArgumentOutOfRangeException(error); 
                    } 
     
                    //create an encoder parameter for the image quality 
                    EncoderParameter qualityParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality); 
                    //get the jpeg codec 
                    ImageCodecInfo jpegCodec = GetEncoderInfo("image/jpeg"); 
     
                    //create a collection of all parameters that we will pass to the encoder 
                    EncoderParameters encoderParams = new EncoderParameters(1); 
                    //set the quality parameter for the codec 
                encoderParams    .Param[0] = qualityParam; 
                    //save the image using the codec and the parameters 
                image    .Save(path, jpegCodec, encoderParams); 
                } 
     
                /// <summary>  
                /// Returns the image codec with the given mime type  
                /// </summary>  
                public static ImageCodecInfo GetEncoderInfo(string mimeType) 
                { 
                    //do a case insensitive search for the mime type 
                    string lookupKey = mimeType.ToLower(); 
     
                    //the codec to return, default to null 
                    ImageCodecInfo foundCodec = null; 
     
                    //if we have the encoder, get it to return 
                    if (Encoders.ContainsKey(lookupKey)) 
                    { 
                        //pull the codec from the lookup 
                    foundCodec     = Encoders[lookupKey]; 
                    } 
     
                    return foundCodec; 
                }  
            } 
    } 
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    • 已标记为答案 Cookie Luo 2011年4月25日 2:47
    2011年4月15日 7:21
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