c#实现图片生成缩略图
1，判断图片的宽和高的比例，然后进行缩放，以便于使缩略图不变形。
2，DrawImage方法为缩略图绘制边框，这样，浏览起来比较美观。
3，调用Save方法将生成的缩略图保存到指定的目录下。
private void MakeThumbnail(string sourcePath, string newPath, int width, int height) { System.Drawing.Image ig = System.Drawing.Image.FromFile(sourcePath); int towidth = width; int toheight = height; int x = 0; int y = 0; int ow = ig.Width; int oh = ig.Height; if ((double)ig.Width / (double)ig.Height > (double)towidth / (double)toheight) { oh = ig.Height; ow = ig.Height * towidth / toheight; y = 0; x = (ig.Width - ow) / 2; } else { ow = ig.Width; oh = ig.Width * height / towidth; x = 0; y = (ig.Height - oh) / 2; } System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight); System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap); g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; g.Clear(System.Drawing.Color.Transparent); g.DrawImage(ig, new System.Drawing.Rectangle(0, 0, towidth, toheight), new System.Drawing.Rectangle(x, y, ow, oh), System.Drawing.GraphicsUnit.Pixel); try { bitmap.Save(newPath, System.Drawing.Imaging.ImageFormat.Jpeg); } catch (Exception ex) { throw ex; } finally { ig.Dispose(); bitmap.Dispose(); g.Dispose(); } }