一般在web应用中,对客户端提交上来的图片肯定需要进行压缩的。尤其是比较大的图片,如果不经过压缩会导致页面变的很大,打开速度比较慢,当然了如果是需要高质量的图片也得需要生产缩略图。
下面贴出我自己琢磨的图片压缩算法,首先这个是未经优化的简单实现:
代码如下:
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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:
代码如下:
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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。
下面这个是根据设置图片质量数值来压缩图片写的的方法:
代码如下:
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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(); } } |
以上就是c# 如何实现图片压缩的详细内容,更多关于c# 图片压缩的资料请关注服务器之家其它相关文章!
原文链接:https://www.cnblogs.com/1175429393wljblog/p/5871248.html