C＃中保存的JPG的质量

Z时代
2024-01-10
分类：问答

我制作了一个小型C＃应用，以创建.jpg格式的图像。

pictureBox.Image.Save(name,ImageFormat.Jpeg);

图像创建成功。我输入了原始图片，并对其做了一些处理并保存。但是，此新图片的质量低于原始图片的质量。

有什么方法可以设置所需的质量？

回答：

下面的代码示例演示如何使用EncoderParameter构造函数创建EncoderParameter。要运行此示例，请粘贴代码并调用VaryQualityLevel方法。

本示例需要位于c：的名为TestPhoto.jpg的图像文件。

private void VaryQualityLevel()
{
    // Get a bitmap.
    Bitmap bmp1 = new Bitmap(@"c:\TestPhoto.jpg");
    ImageCodecInfo jgpEncoder = GetEncoder(ImageFormat.Jpeg);
    // Create an Encoder object based on the GUID
    // for the Quality parameter category.
    System.Drawing.Imaging.Encoder myEncoder =
        System.Drawing.Imaging.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.
    EncoderParameters myEncoderParameters = new EncoderParameters(1);
    EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, 
        50L);
    myEncoderParameters.Param[0] = myEncoderParameter;
    bmp1.Save(@"c:\TestPhotoQualityFifty.jpg", jgpEncoder, 
        myEncoderParameters);
    myEncoderParameter = new EncoderParameter(myEncoder, 100L);
    myEncoderParameters.Param[0] = myEncoderParameter;
    bmp1.Save(@"c:\TestPhotoQualityHundred.jpg", jgpEncoder, 
        myEncoderParameters);
    // Save the bitmap as a JPG file with zero quality level compression.
    myEncoderParameter = new EncoderParameter(myEncoder, 0L);
    myEncoderParameters.Param[0] = myEncoderParameter;
    bmp1.Save(@"c:\TestPhotoQualityZero.jpg", jgpEncoder, 
        myEncoderParameters);
}
private ImageCodecInfo GetEncoder(ImageFormat format)
{
    ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();
    foreach (ImageCodecInfo codec in codecs)
    {
        if (codec.FormatID == format.Guid)
        {
            return codec;
        }
    }
    return null;
}