c# 如何實現(xiàn)圖片壓縮

更新時間：2022年04月19日 10:23:45 作者：龍騎科技

這篇文章主要介紹了c# 實現(xiàn)圖片壓縮的示例，幫助大家更好的理解和學習c#，感興趣的朋友可以了解下

一般在web應用中，對客戶端提交上來的圖片肯定需要進行壓縮的。尤其是比較大的圖片，如果不經(jīng)過壓縮會導致頁面變的很大，打開速度比較慢，當然了如果是需要高質(zhì)量的圖片也得需要生產(chǎn)縮略圖。

下面貼出我自己琢磨的圖片壓縮算法，首先這個是未經(jīng)優(yōu)化的簡單實現(xiàn)：

代碼如下:

        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;
??????? }

這個方法比較簡單，用到的是高質(zhì)量壓縮。經(jīng)過這個方法壓縮后，200K的圖片只能壓縮到160k左右。經(jīng)過改寫代碼實現(xiàn)了如下的方法：

代碼如下:

        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;

??????? }

這樣實現(xiàn)的壓縮使壓縮率大幅度上升。其實代碼并沒有變多少，最主要的是在保存的時候要是用jpg格式，如果不指定格式，默認使用的是png格式。

下面這個是根據(jù)設置圖片質(zhì)量數(shù)值來壓縮圖片寫的的方法：

代碼如下:

        public static bool GetPicThumbnail(string sFile, string outPath, int flag)
??????? {
??????????? System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile);
??????????? ImageFormat tFormat = iSource.RawFormat;
??????????? //以下代碼為保存圖片時，設置壓縮質(zhì)量?
??????????? EncoderParameters ep = new EncoderParameters();
??????????? long[] qy = new long[1];
??????????? qy[0] = flag;//設置壓縮的比例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是壓縮后的新路徑?
??????????????? }
??????????????? else
??????????????? {
??????????????????? iSource.Save(outPath, tFormat);
??????????????? }
??????????????? return true;
??????????? }
??????????? catch
??????????? {
??????????????? return false;
??????????? }
??????????? finally
??????????? {
??????????????? iSource.Dispose();
??????????????? iSource.Dispose();
??????????? }
??????? }

以上就是c# 如何實現(xiàn)圖片壓縮的詳細內(nèi)容，更多關(guān)于c# 圖片壓縮的資料請關(guān)注腳本之家其它相關(guān)文章！

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