C#图片处理之:图片缩放和剪裁

粗糙成比例放大

string strFileNameOld = @"D:/png/fenge/129267877539521154.png"; string strFileNameNew = @"D:/png/fenge/"+DateTime.Now.ToFileTime().ToString()+".png "; int iWidth, iHeight, iMagnify; Color myColor; int i, j, i0, j0, i1, j1; iMagnify = 8; Bitmap bmpTmp = (Bitmap)System.Drawing.Image.FromFile(strFileNameOld); Bitmap bmpNew = new Bitmap(bmpTmp.Width * iMagnify, bmpTmp.Height * iMagnify); Graphics g = Graphics.FromImage(bmpNew); iWidth = bmpTmp.Width; iHeight = bmpTmp.Height; try { for (i = 0; i < iWidth; i++) { i0 = i * iMagnify; for (j = 0; j < iHeight; j++) { j0 = j * iMagnify; myColor = bmpTmp.GetPixel(i, j); for (i1 = i0; i1 < i0 + iMagnify; i1++) for (j1 = j0; j1 < j0 + iMagnify; j1++) bmpNew.SetPixel(i1, j1, myColor); } } } catch { string errormsg; errormsg = "hi "; } bmpTmp.Dispose(); g.Dispose(); bmpNew.Save(strFileNameNew, System.Drawing.Imaging.ImageFormat.Bmp); 应听众点播要求，今天说说用C#做图片的缩放和剪裁，相信很多人会对这部分内容感兴趣，毕竟这个操作太实用了。 其实在GDI+中，缩放和剪裁可以看作同一个操作，无非就是原始区域的选择不同罢了。空口无凭，先看具体算法可能更好理解。 /// <summary> /// Resize图片 /// </summary> /// <param name="bmp">原始Bitmap</param> /// <param name="newW">新的宽度</param> /// <param name="newH">新的高度</param> /// <param name="Mode">保留着，暂时未用</param> /// <returns>处理以后的图片</returns> public static Bitmap KiResizeImage(Bitmap bmp, int newW, int newH, int Mode) { try { Bitmap b = new Bitmap(newW, newH); Graphics g = Graphics.FromImage(b); // 插值算法的质量 g.InterpolationMode = InterpolationMode.HighQualityBicubic; g.DrawImage(bmp, new Rectangle(0, 0, newW, newH), new Rectangle(0, 0, bmp.Width, bmp.Height), GraphicsUnit.Pixel); g.Dispose(); return b; } catch { return null; } } // =============================== /// <summary> /// 剪裁 -- 用GDI+ /// </summary> /// <param name="b">原始Bitmap</param> /// <param name="StartX">开始坐标X</param> /// <param name="StartY">开始坐标Y</param> /// <param name="iWidth">宽度</param> /// <param name="iHeight">高度</param> /// <returns>剪裁后的Bitmap</returns> public static Bitmap KiCut(Bitmap b, int StartX, int StartY, int iWidth, int iHeight) { if (b == null) { return null; } int w = b.Width; int h = b.Height; if (StartX >= w || StartY >= h) { return null; } if (StartX + iWidth > w) { iWidth = w - StartX; } if (StartY + iHeight > h) { iHeight = h - StartY; } try { Bitmap bmpOut = new Bitmap(iWidth, iHeight, PixelFormat.Format24bppRgb); Graphics g = Graphics.FromImage(bmpOut); g.DrawImage(b, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(StartX, StartY, iWidth, iHeight), GraphicsUnit.Pixel); g.Dispose(); return bmpOut; } catch { return null; } } 注意到区别了吗？提示，g.DrawImage中第二个new Rectangle。 目标其实都是new Rectangle(0, 0, iWidth, iHeight)，缩放算法把整个原始图都往目标区域里塞new Rectangle(0, 0, bmp.Width, bmp.Height)，而剪裁只是把原始区域上等宽等高的那个区域new Rectangle(StartX, StartY, iWidth, iHeight)1:1的塞到目标区域里。很容易吧。