【转】C#中Bitmap类实现对图像操作的一些方法

http://hi.baidu.com/donetsky/blog/item/e95ab635eb7af21090ef3984.html

导入以下两个包：

     System.Drawing;

     System.Drawing.Imaging;

建产对象：

     Bitmap bm = new Bitmap("c:/1.bmp");

缩放：

     Bitmap bm1 = new Bitmap(bm,width,height);

格式转换：

     bm.save("c:/1.jpg",ImageFromat.Jpeg);

     bm1.Save("c:/1.gif", ImageFormat.Gif);

剪切一个区域：

     //剪切大小

     int cutwidth;  

     int cutheight;

     Graphics g;

     //以大小为剪切大小，像素格式为32位RGB创建一个位图对像

     Bitmap bm1 = new Bitmap(width,height,PixelFormat.Format32bppRgb) ;

     //定义一个区域

     Rectangle rg = new Rectangle(0,0,cutwidth,cutheight);

     //要绘制到的位图

     g = Graphics.FromImage(bm1);

     //将bm内rg所指定的区域绘制到bm1

     g.DrawImage(bm,rg)

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C#Bitmap代替另一个Bitmap的某部分
Bitmap bm = new Bitmap(宽度, 高度);// 新建一个 Bitmap 位图
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bm); // 根据新建的 Bitmap 位图，创建画布
g.Clear(System.Drawing.Color.Black);// 使用黑色重置画布
g.DrawImage(源位图, ......); // 绘制“源位图”，后面有若干参数控制大小、坐标等等功能。

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C# 图片处理之：旋转图片任意角度

     /// <summary>
        /// 任意角度旋转
        /// </summary>
        /// <param name="bmp">原始图Bitmap</param>
        /// <param name="angle">旋转角度</param>
        /// <param name="bkColor">背景色</param>
        /// <returns>输出Bitmap</returns>
        public static Bitmap KiRotate(Bitmap bmp, float angle, Color bkColor)
        ...{
            int w = bmp.Width + 2;
            int h = bmp.Height + 2;

             PixelFormat pf;

            if (bkColor == Color.Transparent)
            ...{
                 pf = PixelFormat.Format32bppArgb;
             }
            else
            ...{
                 pf = bmp.PixelFormat;
             }

             Bitmap tmp = new Bitmap(w, h, pf);
             Graphics g = Graphics.FromImage(tmp);
             g.Clear(bkColor);
             g.DrawImageUnscaled(bmp, 1, 1);
             g.Dispose();

             GraphicsPath path = new GraphicsPath();
             path.AddRectangle(new RectangleF(0f, 0f, w, h));
             Matrix mtrx = new Matrix();
             mtrx.Rotate(angle);
             RectangleF rct = path.GetBounds(mtrx);

             Bitmap dst = new Bitmap((int)rct.Width, (int)rct.Height, pf);
             g = Graphics.FromImage(dst);
             g.Clear(bkColor);
             g.TranslateTransform(-rct.X, -rct.Y);
             g.RotateTransform(angle);
             g.InterpolationMode = InterpolationMode.HighQualityBilinear;
             g.DrawImageUnscaled(tmp, 0, 0);
             g.Dispose();

             tmp.Dispose();

            return dst;
         }