图片旋转算法

本文为转载文章，但是希望更多的朋友来优化该算法。

转载地址：http://www.cnblogs.com/ice6/archive/2010/08/19/rotating-an-image-in-silverlight-without-cropping.html

旋转算法如下：

Rotation[degrees counterclockwise]Subscript Manipulation using Pixels0Out[i, j] = In[i, j]90Out[j, Right-i-1] = In[i, j]180Out[Right-i-1, Bottom-j-1] = In[i, j]270Out[Bottom-j-1,i] = In[i, j]
i代表x轴的值，j代表Y轴上的值

 privateWriteableBitmap WBRotate(WriteableBitmap wb, intCounterclockwiseAngle)

 {

     int[,] wb_arr = newint[wb.PixelWidth, wb.PixelHeight];

     //导致许多缺页中断的初始化循环

     //for (int r = 0; r < wb.PixelHeight; r++)// r=row    c=column

     //{

     //    for (int c = 0; c < wb.PixelWidth; c++)

     //    {

     //        wb_arr[c, r] = wb.Pixels[wb.PixelWidth * r + c];

     //    }

     //}

     //导致较少缺页中断的初始化循环 对上面代码的简单优化

     for(intc = 0; c < wb.PixelWidth; c++)// r=row    c=column

     {

         for(intr = 0; r < wb.PixelHeight; r++)

         {

             wb_arr[c, r] = wb.Pixels[wb.PixelWidth * r + c];

         }

     }

 

     WriteableBitmap wb2;

     int[,] wb_arr_2;

 

     if(CounterclockwiseAngle == 0 || CounterclockwiseAngle == 360 || CounterclockwiseAngle == -360)//0度 360度

     {

         wb2 = newWriteableBitmap(wb.PixelWidth, wb.PixelHeight);

         wb_arr_2 = newint[wb.PixelWidth, wb.PixelHeight];

         wb_arr_2 = wb_arr;

     }

     elseif(CounterclockwiseAngle == 90 || CounterclockwiseAngle == -270)//90 -270//Math.Sin(

     {

         wb2 = newWriteableBitmap(wb.PixelHeight, wb.PixelWidth);

         wb_arr_2 = newint[wb.PixelHeight, wb.PixelWidth];

         for(intc = 0; c < wb_arr.GetLength(0); c++)//width  i

         {

             for(intr = 0; r < wb_arr.GetLength(1); r++)//height j

             {

                 wb_arr_2[r, wb_arr.GetLength(0) - c - 1] = wb_arr[c, r]; //90 Out[j, Right-i-1] = In[i, j]  Right代表真个宽度

             }

         }

     }

     elseif(CounterclockwiseAngle == 180 || CounterclockwiseAngle == -180)//180 -180

     {

         wb2 = newWriteableBitmap(wb.PixelWidth, wb.PixelHeight);

         wb_arr_2 = newint[wb.PixelWidth, wb.PixelHeight];

         for(intc = 0; c < wb_arr.GetLength(0); c++)//width  i

         {

             for(intr = 0; r < wb_arr.GetLength(1); r++)//height j

             {

                 wb_arr_2[wb_arr.GetLength(0) - c - 1, wb_arr.GetLength(1) - r - 1] = wb_arr[c, r]; //180 Out[Right-i-1, Bottom-j-1] = In[i, j] 

             }

         }

     }

     elseif(CounterclockwiseAngle == 270 || CounterclockwiseAngle == -90)//270 -90

     {

         wb2 = newWriteableBitmap(wb.PixelHeight, wb.PixelWidth);

         wb_arr_2 = newint[wb.PixelHeight, wb.PixelWidth];

         for(intc = 0; c < wb_arr.GetLength(0); c++)//width  i

         {

             for(intr = 0; r < wb_arr.GetLength(1); r++)//height j

             {

                 wb_arr_2[wb_arr.GetLength(1) - r - 1, c] = wb_arr[c, r]; //270 Out[Bottom-j-1,i] = In[i, j]

             }

         }

     }

     else

     {

         returnnull;//如果是其他角度 就直接返回null

     }

     //将二位数组转换成Pixels

     for(intr = 0; r < wb_arr_2.GetLength(1); r++)// r=row    c=column

     {

         for(intc = 0; c < wb_arr_2.GetLength(0); c++)

         {

             wb2.Pixels[wb2.PixelWidth * r + c] = wb_arr_2[c, r];

         }

     }

     returnwb2;

 }