C#图片截取压缩(百分比压缩/大小压缩)实现代码

<br>View Code <br>/// <summary> <br>/// 按照比例缩小图片 <br>/// </summary> <br>/// <param name="srcImage">要缩小的图片</param> <br>/// <param name="percent">缩小比例</param> <br>/// <returns>缩小后的结果</returns> <br>public static Bitmap PercentImage(Image srcImage, double percent) <br>{ <br>// 缩小后的高度 <br>int newH = int.Parse(Math.Round(srcImage.Height * percent).ToString()); <br>// 缩小后的宽度 <br>int newW = int.Parse(Math.Round(srcImage.Width * percent).ToString()); <br>try <br>{ <br>// 要保存到的图片 <br>Bitmap b = new Bitmap(newW, newH); <br>Graphics g = Graphics.FromImage(b); <br>// 插值算法的质量 <br>g.InterpolationMode = InterpolationMode.Default; <br>g.DrawImage(srcImage, new Rectangle(0, 0, newW, newH), new Rectangle(0, 0, srcImage.Width, srcImage.Height), GraphicsUnit.Pixel); <br>g.Dispose(); <br>return b; <br>} <br>catch (Exception) <br>{ <br>return null; <br>} <br>} <br> <br>2.按照指定像素大小截图 <br><span><u></u></span> 代码如下:<pre class="brush:php;toolbar:false layui-box layui-code-view layui-code-notepad"><ol class="layui-code-ol"><li><br>View Code <br>/// <summary> <br>/// 按照指定大小缩放图片 <br>/// </summary> <br>/// <param name="srcImage"></param> <br>/// <param name="iWidth"></param> <br>/// <param name="iHeight"></param> <br>/// <returns></returns> <br>public static Bitmap SizeImage(Image srcImage, int iWidth, int iHeight) <br>{ <br>try <br>{ <br>// 要保存到的图片 <br>Bitmap b = new Bitmap(iWidth, iHeight); <br>Graphics g = Graphics.FromImage(b); <br>// 插值算法的质量 <br>g.InterpolationMode = InterpolationMode.HighQualityBicubic; <br>g.DrawImage(srcImage, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(0, 0, srcImage.Width, srcImage.Height), GraphicsUnit.Pixel); <br>g.Dispose(); <br>return b; <br>} <br>catch (Exception) <br>{ <br>return null; <br>} <br>} <br> <br>3.按照指定像素大小截图（但为了保证图片的原始比例，将对图片从中心进行截取，达到图片不被拉伸的效果） <br><span><u></u></span> 代码如下:<pre class="brush:php;toolbar:false layui-box layui-code-view layui-code-notepad"><ol class="layui-code-ol"><li><br>View Code <br>/// <summary> <br>/// 按照指定大小缩放图片，但是为了保证图片宽高比自动截取 <br>/// </summary> <br>/// <param name="srcImage"></param> <br>/// <param name="iWidth"></param> <br>/// <param name="iHeight"></param> <br>/// <returns></returns> <br>public static Bitmap SizeImageWithOldPercent(Image srcImage, int iWidth, int iHeight) <br>{ <br>try <br>{ <br>// 要截取图片的宽度（临时图片） <br>int newW = srcImage.Width; <br>// 要截取图片的高度（临时图片） <br>int newH = srcImage.Height; <br>// 截取开始横坐标（临时图片） <br>int newX = 0; <br>// 截取开始纵坐标（临时图片） <br>int newY = 0; <br>// 截取比例（临时图片） <br>double whPercent = 1; <br>whPercent = ((double)iWidth / (double)iHeight) * ((double)srcImage.Height / (double)srcImage.Width); <br>if (whPercent > 1) <br>{ <br>// 当前图片宽度对于要截取比例过大时 <br>newW = int.Parse(Math.Round(srcImage.Width / whPercent).ToString()); <br>} <br>else if (whPercent < 1) <br>{ <br>// 当前图片高度对于要截取比例过大时 <br>newH = int.Parse(Math.Round(srcImage.Height * whPercent).ToString()); <br>} <br>if (newW != srcImage.Width) <br>{ <br>// 宽度有变化时，调整开始截取的横坐标 <br>newX = Math.Abs(int.Parse(Math.Round(((double)srcImage.Width - newW) / 2).ToString())); <br>} <br>else if (newH == srcImage.Height) <br>{ <br>// 高度有变化时，调整开始截取的纵坐标 <br>newY = Math.Abs(int.Parse(Math.Round(((double)srcImage.Height - (double)newH) / 2).ToString())); <br>} <br>// 取得符合比例的临时文件 <br>Bitmap cutedImage = CutImage(srcImage, newX, newY, newW, newH); <br>// 保存到的文件 <br>Bitmap b = new Bitmap(iWidth, iHeight); <br>Graphics g = Graphics.FromImage(b); <br>// 插值算法的质量 <br>g.InterpolationMode = InterpolationMode.Default; <br>g.DrawImage(cutedImage, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(0, 0, cutedImage.Width, cutedImage.Height), GraphicsUnit.Pixel); <br>g.Dispose(); <br>return b; <br>} <br>catch (Exception) <br>{ <br>return null; <br>} <br>} <br> <br>4.jpeg图片质量压缩，压缩的比例参数在1-100之间。（适量的压缩对于肉眼来说没有什么明显的区别，但是能够大大的减小图片的占用大小） <br><span><u></u></span> 代码如下:<pre class="brush:php;toolbar:false layui-box layui-code-view layui-code-notepad"><ol class="layui-code-ol"><li><br>View Code <br>/// <summary> <br>/// jpeg图片压缩 <br>/// </summary> <br>/// <param name="sFile"></param> <br>/// <param name="outPath"></param> <br>/// <param name="flag"></param> <br>/// <returns></returns> <br>public static bool GetPicThumbnail(string sFile, string outPath, int flag) <br>{ <br>System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile); <br>ImageFormat tFormat = iSource.RawFormat; <br>//以下代码为保存图片时，设置压缩质量 <br>EncoderParameters ep = new EncoderParameters(); <br>long[] qy = new long[1]; <br>qy[0] = flag;//设置压缩的比例1-100 <br>EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy); <br>ep.Param[0] = eParam; <br>try <br>{ <br>ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders(); <br>ImageCodecInfo jpegICIinfo = null; <br>for (int x = 0; x < arrayICI.Length; x++) <br>{ <br>if (arrayICI[x].FormatDescription.Equals("JPEG")) <br>{ <br>jpegICIinfo = arrayICI[x]; <br>break; <br>} <br>} <br>if (jpegICIinfo != null) <br>{ <br>iSource.Save(outPath, jpegICIinfo, ep);//dFile是压缩后的新路径 <br>} <br>else <br>{ <br>iSource.Save(outPath, tFormat); <br>} <br>return true; <br>} <br>catch <br>{ <br>return false; <br>} <br>finally <br>{ <br>iSource.Dispose(); <br>iSource.Dispose(); <br>} <br>} <br> <br>PS：之上用的CutImage方法的补充 <br><span><u></u></span> 代码如下:<pre class="brush:php;toolbar:false layui-box layui-code-view layui-code-notepad"><ol class="layui-code-ol"><li><br>View Code <br>/// <summary> <br>/// 剪裁 -- 用GDI+ <br>/// </summary> <br>/// <param name="b">原始Bitmap</param> <br>/// <param name="StartX">开始坐标X</param> <br>/// <param name="StartY">开始坐标Y</param> <br>/// <param name="iWidth">宽度</param> <br>/// <param name="iHeight">高度</param> <br>/// <returns>剪裁后的Bitmap</returns> <br>public static Bitmap CutImage(Image b, int StartX, int StartY, int iWidth, int iHeight) <br>{ <br>if (b == null) <br>{ <br>return null; <br>} <br>int w = b.Width; <br>int h = b.Height; <br>if (StartX >= w || StartY >= h) <br>{ <br>// 开始截取坐标过大时，结束处理 <br>return null; <br>} <br>if (StartX + iWidth > w) <br>{ <br>// 宽度过大时只截取到最大大小 <br>iWidth = w - StartX; <br>} <br>if (StartY + iHeight > h) <br>{ <br>// 高度过大时只截取到最大大小 <br>iHeight = h - StartY; <br>} <br>try <br>{ <br>Bitmap bmpOut = new Bitmap(iWidth, iHeight); <br>Graphics g = Graphics.FromImage(bmpOut); <br>g.DrawImage(b, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(StartX, StartY, iWidth, iHeight), GraphicsUnit.Pixel); <br>g.Dispose(); <br>return bmpOut; <br>} <br>catch <br>{ <br>return null; <br>} <br>} <br> <br>再次记录下截取的代码，虽然简单，如果重写还是需要花费时间。</li><li>            </li><li>                                </li></ol></pre></li></ol></pre></li></ol></pre></li></ol></pre>