C#压缩图片的方法

/// 

/// 图片压缩
/// 
/// 图片文件路径
/// 保存文件夹
/// 压缩质量
/// 压缩后的文件名后缀（防止直接覆盖原文件）
public static void CompressionImage(string imagePath, string targetFolder, long quality, string fileSuffix = "Demo")
{
    if (!System.IO.File.Exists(imagePath))
    {
        throw new FileNotFoundException();
    }
    if (!Directory.Exists(targetFolder))
    {
        Directory.CreateDirectory(targetFolder);
    }
    var fileInfo = new FileInfo(imagePath);
    var fileName = fileInfo.Name.Replace(fileInfo.Extension, "");
    var fileFullName = Path.Combine($"{targetFolder}", $"{fileName}_{fileSuffix}{fileInfo.Extension}");

    var imageByte = CompressionImage(imagePath, quality);
    var ms = new MemoryStream(imageByte);
    var image = Image.FromStream(ms);
    image.Save(fileFullName);
    ms.Close();
    ms.Dispose();
    image.Dispose();
}

/// 

/// 设置图片质量
/// 
/// 
/// 范围0~100，越大质量越高
/// 
private static byte[] CompressionImage(string imagePath, long quality)
{
    using (var fileStream = new FileStream(imagePath, FileMode.Open))
    {
        using (var img = Image.FromStream(fileStream))
        {
            using (var bitmap = new Bitmap(img))
            {
                ImageCodecInfo codecInfo = GetEncoder(img.RawFormat);
                var myEncoder = System.Drawing.Imaging.Encoder.Quality;
                var myEncoderParameters = new EncoderParameters(1);
                var myEncoderParameter = new EncoderParameter(myEncoder, quality);
                myEncoderParameters.Param[0] = myEncoderParameter;
                using (var ms = new MemoryStream())
                {
                    bitmap.Save(ms, codecInfo, myEncoderParameters);
                    myEncoderParameters.Dispose();
                    myEncoderParameter.Dispose();
                    return ms.ToArray();
                }
            }
        }
    }
}

/// 

/// Guid
/// 
/// 
/// 
private static ImageCodecInfo GetEncoder(ImageFormat format)
{
    var codecs = ImageCodecInfo.GetImageDecoders();
    return codecs.FirstOrDefault(codec => codec.FormatID == format.Guid);
}
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调用方法：

CompressionImage("C:\\Users\\admin\\Desktop\\画图\\1.jpg", "C:\\Users\\admin\\Desktop\\画图\\Demo", 50, "Demo");
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