C# 图片缩略图

1/// <summary>
2        /// 生成缩略图
3        /// </summary>
4        /// <param name="sourceFile">原始图片文件</param>
5        /// <param name="quality">质量压缩比</param>
6        /// <param name="multiple">收缩倍数</param>
7        /// <param name="outputFile">输出文件名</param>
8        /// <returns>成功返回true,失败则返回false</returns>
9        public static bool getThumImage(string sourceFile, long quality, int multiple, string outputFile)
10        {
11            try
12            {
13                long imageQuality = quality;
14                Bitmap sourceImage = new Bitmap(sourceFile);
15                ImageCodecInfo myImageCodecInfo = GetEncoderInfo("image/jpeg");
16                Encoder myEncoder = Encoder.Quality;
17                EncoderParameters myEncoderParameters = new EncoderParameters(1);
18                EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, imageQuality);
19                myEncoderParameters.Param[0] = myEncoderParameter;
20                float xWidth = sourceImage.Width;
21                float yWidth = sourceImage.Height;
22                Bitmap newImage = new Bitmap((int)(xWidth / multiple), (int)(yWidth / multiple));
23                Graphics g = Graphics.FromImage(newImage);
24                g.DrawImage(sourceImage, 0, 0, xWidth / multiple, yWidth / multiple);
25                g.Dispose();
26                newImage.Save(outputFile, myImageCodecInfo, myEncoderParameters);
27                return true;
28            }
29            catch (Exception ex)
30            {
31                return false;
32            }
33        }
34
35        /// <summary>
36        /// 获取图片编码信息
37        /// </summary>
38        private static ImageCodecInfo GetEncoderInfo(string mimeType)
39        {
40            int j;
41            ImageCodecInfo[] encoders;
42            encoders = ImageCodecInfo.GetImageEncoders();
43            for (j = 0; j < encoders.Length; ++j)
44            {
45                if (encoders[j].MimeType == mimeType)
46                    return encoders[j];
47            }
48            return null;
49        }