| 标题 | C#实现图片压缩方法 |
| 内容 | 这个是未经优化的简单实现 public static System.Drawing.Image GetImageThumb(System.Drawing.Image sourceImg, int width, int height) { System.Drawing.Image targetImg = new System.Drawing.Bitmap(width, height); using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(targetImg)) { g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality; g.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality; g.DrawImage(sourceImg, new System.Drawing.Rectangle(0, 0, width, height), new System.Drawing .Rectangle(0, 0, sourceImg.Width, sourceImg.Height), System.Drawing.GraphicsUnit.Pixel); g.Dispose(); } return targetImg; } 这个方法比较简单，用到的是高质量压缩。经过这个方法压缩后，200K的图片只能压缩到160k左右。 经过改写代码实现了如下的方法 public Bitmap GetImageThumb(Bitmap mg, Size newSize) { double ratio = 0d; double myThumbWidth = 0d; double myThumbHeight = 0d; int x = 0; int y = 0; Bitmap bp; if ((mg.Width / Convert.ToDouble(newSize.Width)) > (mg.Height / Convert.ToDouble(newSize.Height))) ratio = Convert.ToDouble(mg.Width) / Convert.ToDouble(newSize.Width); else ratio = Convert.ToDouble(mg.Height) / Convert.ToDouble(newSize.Height); myThumbHeight = Math.Ceiling(mg.Height / ratio); myThumbWidth = Math.Ceiling(mg.Width / ratio); Size thumbSize = new Size((int)newSize.Width, (int)newSize.Height); bp = new Bitmap(newSize.Width, newSize.Height); x = (newSize.Width - thumbSize.Width) / 2; y = (newSize.Height - thumbSize.Height); System.Drawing.Graphics g = Graphics.FromImage(bp); g.SmoothingMode = SmoothingMode.HighQuality; g.InterpolationMode = InterpolationMode.HighQualityBicubic; g.PixelOffsetMode = PixelOffsetMode.HighQuality; Rectangle rect = new Rectangle(x, y, thumbSize.Width, thumbSize.Height); g.DrawImage(mg, rect, 0, 0, mg.Width, mg.Height, GraphicsUnit.Pixel); return bp; } 这样实现的压缩使压缩率大幅度上升。其实代码并没有变多少，最主要的是在保存的时候要是用jpg格式， 如果不指定格式，默认使用的是png格式。 下面这个是园友写的根据设置图片质量数值来压缩图片的方法： public static bool GetPicThumbnail(string sFile, string outPath, int flag) { System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile); ImageFormat tFormat = iSource.RawFormat; //以下代码为保存图片时，设置压缩质量 EncoderParameters ep = new EncoderParameters(); long[] qy = new long[1]; qy[0] = flag;//设置压缩的比例1-100 EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy); ep.Param[0] = eParam; try { ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders(); ImageCodecInfo jpegICIinfo = null; for (int x = 0; x < arrayICI.Length; x++) { if (arrayICI[x].FormatDescription.Equals("JPEG")) { jpegICIinfo = arrayICI[x]; break; } } if (jpegICIinfo != null) { iSource.Save(outPath, jpegICIinfo, ep);//dFile是压缩后的新路径 } else { iSource.Save(outPath, tFormat); } return true; } catch { return false; } finally { iSource.Dispose(); iSource.Dispose(); } } |
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