c# GDI+ Image.Save()或者Bitmap.Save()方法保存高质量图片

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GDI+保存质量比较高的图片的方法，使用Image或者Bitmap的Save方法调节图像保存的质量。

Image.Save方法共有五种重载

其中Save(String, ImageCodecInfo, EncoderParameters)和Save(Stream, ImageCodecInfo,EncoderParameters)这两种方法课以调节图像质量。

Save.(string ,ImageCodeInfo,EncoderParameters) 使用方法：

参数：

filename 类型：System.String 字符串，包含要将此 Image 保存到的文件的名称。

encoder 类型：System.Drawing.Imaging.ImageCodecInfo 此 Image 的 ImageCodecInfo。

encoderParams 类型：System.Drawing.Imaging.EncoderParameters 用于该 Image 的 EncoderParameters。

步骤：

①获得编码器的函数，

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;    }

    可以直接复制过去使用。

②获取编码器

    ImageCodecInfo myImageCodecInfo;

    //获得JPEG格式的编码器

    myImageCodecInfo = GetEncoderInfo("image/jpeg");

③设置图像质量

    System.Drawing.Imaging.Encoder myEncoder;
    EncoderParameter myEncoderParameter;
    EncoderParameters myEncoderParameters;

    // for the Quality parameter category.

    myEncoder = System.Drawing.Imaging.Encoder.Quality;

    // EncoderParameter object in the array.

    myEncoderParameters = new EncoderParameters(1);

    //设置质量 数字越大质量越好，但是到了一定程度质量就不会增加了，MSDN上没有给范围，只说是32为非负整数

    myEncoderParameter = new EncoderParameter(myEncoder, 100L);

    myEncoderParameters.Param[0] = myEncoderParameter;

④保存图像

    bitmap.Save(@"D:\Users\Administrator\Desktop\Piexl1.jpeg", myImageCodecInfo, myEncoderParameters);

MSDN上的给的例子：

using System;using System.Drawing;using System.Drawing.Imaging;class Example_SetJPEGQuality{    public static void Main()    {        Bitmap myBitmap;        ImageCodecInfo myImageCodecInfo;        Encoder myEncoder;        EncoderParameter myEncoderParameter;        EncoderParameters myEncoderParameters;        // Create a Bitmap object based on a BMP file.        myBitmap = new Bitmap("Shapes.bmp");        // Get an ImageCodecInfo object that represents the JPEG codec.        myImageCodecInfo = GetEncoderInfo("image/jpeg");        // 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);        // Save the bitmap as a JPEG file with quality level 25.        myEncoderParameter = new EncoderParameter(myEncoder, 25L);        myEncoderParameters.Param[0] = myEncoderParameter;        myBitmap.Save("Shapes025.jpg", myImageCodecInfo, myEncoderParameters);        // Save the bitmap as a JPEG file with quality level 50.        myEncoderParameter = new EncoderParameter(myEncoder, 50L);        myEncoderParameters.Param[0] = myEncoderParameter;        myBitmap.Save("Shapes050.jpg", myImageCodecInfo, myEncoderParameters);        // Save the bitmap as a JPEG file with quality level 75.        myEncoderParameter = new EncoderParameter(myEncoder, 75L);        myEncoderParameters.Param[0] = myEncoderParameter;        myBitmap.Save("Shapes075.jpg", myImageCodecInfo, myEncoderParameters);    }    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;    }}

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