by kevin
20.
八月 2013 21:44
>
最近在开发65emall的时候，发现产品的缩略图每个都有几十KB，检查了下，发现，在生成缩略图的时候，代码里只是设置了InterpolationMode，如下 1: g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.Low;
其实这样的压缩，非常有限，所以文件还是非常大。
其实，要真正压缩jpg文件，还是要降低图片的质量，这里我们设置了50%，结果图片大小缩小了80-90%。
具体的代码如下
1: private static ImageCodecInfo GetEncoder(ImageFormat format)
2: {
3: ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();
4: foreach (ImageCodecInfo codec in codecs)
5: {
6: if (codec.FormatID == format.Guid)
7: {
8: return codec;
9: }
10: }
11: return null;
12: }
13:
14: private static void CreateImage(int oldWidth, int oldHeight, int limitWidth, int limitHeight,
15: System.Drawing.Image oldImage, string path, string fileName)
16: {
17: if (!System.IO.Directory.Exists(path))
18: {
19: System.IO.Directory.CreateDirectory(path);
20: }
21: int createWidth, createHeight;
22: ImageSize(oldWidth, oldHeight, limitWidth, limitHeight, out createWidth, out createHeight);
23:
24: System.Drawing.Bitmap createImage = new System.Drawing.Bitmap(createWidth, createHeight);
25: System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(createImage);
26: g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.Low;
27: g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
28: g.Clear(System.Drawing.Color.Transparent);
29: g.DrawImage(oldImage, new System.Drawing.Rectangle(0, 0, createWidth, createHeight),
30: new System.Drawing.Rectangle(0, 0, oldImage.Width, oldImage.Height),
31: System.Drawing.GraphicsUnit.Pixel);
32: ImageCodecInfo jgpEncoder = GetEncoder(ImageFormat.Jpeg);
33: System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
34: EncoderParameters myEncoderParameters = new EncoderParameters(1);
35: EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, 50L);
36: myEncoderParameters.Param[0] = myEncoderParameter;
37: createImage.Save(path + fileName, jgpEncoder, myEncoderParameters);
38: g.Dispose();
39: createImage.Dispose();
40: }
参考资料：
How to: Set JPEG Compression Level
How to: Use Interpolation Mode to Control Image Quality During Scaling