知识大全 C#实现图片压缩方法

Posted 2022-07-17 知

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　　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 Drawing D InterpolationMode High; g SmoothingMode = System Drawing Drawing D SmoothingMode HighQuality; g InterpolationMode = System Drawing Drawing D InterpolationMode HighQualityBicubic; g CompositingQuality = System Drawing Drawing D CompositingQuality HighQuality; g PixelOffsetMode = System Drawing Drawing D PixelOffsetMode HighQuality; g DrawImage(sourceImg new System Drawing Rectangle( width height) new System Drawing Rectangle( 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 K的图片只能压缩到 k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 = d; double myThumbWidth = d; double myThumbHeight = d; int x = ; int y = ; 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) / ; 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 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

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