Question

我发布了这个其他主题，得到了一些温和的回复，但虽然答案解决了问题的质量方面，但他们用kb中的图像大小创建了另一个问题。 Asp.net image resizing quality

这是问题所在。

我有一个2MB的图像，我想减少到480px的宽度。

我使用了三种不同的方法来调整它的大小：

1）在Fileupload上运行此代码：

System.IO.Stream st = FileUploadPost.PostedFile.InputStream;
myImage = System.Drawing.Image.FromStream(st);
thumb = myImage.GetThumbnailImage(newWidth, newHeight, null, System.IntPtr.Zero);
thumb.Save(myPath);

好处：kb的尺寸变小（约80Kb）。

缺点：视觉质量太可怕了

2）在Fileupload上运行此代码（在上述帖子中提供的解决方案）：

 Bitmap newImg = new Bitmap(newWidth, newHeight,    System.Drawing.Imaging.PixelFormat.Format24bppRgb);                            
 Graphics newGraphic = Graphics.FromImage(newImg);
 newGraphic.DrawImage(myImage, 0, 0, newWidth, newHeight);
 newGraphic.Dispose();
 newImg.Save(myPath);

好处：视觉质量很好

下行：规模持续很大（约400kb）

3）使用Windows Paint软件并“手动”将图像缩小为480px宽度

好处：1）和2）的好处 - ＆gt;视觉质量良好，尺寸减小到约80kb

问题是：

什么是重现第3项行为的代码（良好的视觉质量和较小的kb尺寸）？

由于

Answer 1

尝试以下方法之一：

 Bitmap newImg = new Bitmap(newWidth, newHeight, System.Drawing.Imaging.PixelFormat.Format16bppRgb555);                            
 Graphics newGraphic = Graphics.FromImage(newImg);
 newGraphic.DrawImage(myImage, 0, 0, newWidth, newHeight);
 newGraphic.Dispose();
 newImg.Save(myPath);

或

 Bitmap newImg = new Bitmap(newWidth, newHeight, System.Drawing.Imaging.PixelFormat.Format16bppArgb1555);                            
 Graphics newGraphic = Graphics.FromImage(newImg);
 newGraphic.DrawImage(myImage, 0, 0, newWidth, newHeight);
 newGraphic.Dispose();
 newImg.Save(myPath);

或

 Bitmap newImg = new Bitmap(newWidth, newHeight, System.Drawing.Imaging.PixelFormat.Format8bppIndexed);                            
 Graphics newGraphic = Graphics.FromImage(newImg);
 newGraphic.DrawImage(myImage, 0, 0, newWidth, newHeight);
 newGraphic.Dispose();
 newImg.Save(myPath);

这应该只会略微降低质量并大幅减小尺寸，但我不确定哪一种会更好。

以下是一大堆其他选项：

http://msdn.microsoft.com/en-us/library/system.drawing.imaging.pixelformat%28v=vs.110%29.aspx

Answer 2

   protected void Page_Load(object sender, EventArgs e)
    {
        //BR**
        string filePath = "";//Source file path with image name
        int CompressLevel = 50;//Image compression leve as per our requirement
        string DestintionPath = "";//Destination file path
        string Filename = "";//Output image name to save in destination path

        Stream bmpStream = System.IO.File.Open(filePath, System.IO.FileMode.Open);
        Bitmap bmp1 = new Bitmap(bmpStream);

        ImageCodecInfo jpgEncoder = GetEncoder(ImageFormat.Jpeg);
        System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
        EncoderParameters myEncoderParameters = new EncoderParameters(1);
        EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, CompressLevel);
        myEncoderParameters.Param[0] = myEncoderParameter;
        bmp1.Save(DestintionPath + "\\" + Filename, jpgEncoder, myEncoderParameters);
        //BR**
        bmpStream.Close();
        string lblmsg = "Compressed Sucessfully with Compression Level { " + CompressLevel.ToString() + " }";
    }

    private ImageCodecInfo GetEncoder(ImageFormat format)
    {
        /*/ Hope this will work.Thanks in advance /*/
        ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();

        foreach (ImageCodecInfo codec in codecs)
        {
            if (codec.FormatID == format.Guid)
            {
                return codec;
            }
        }
        return null;
    }

Asp.net以kb缩小图像大小

2 个答案: