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李現路:DSP6000圖像位置移動與變形的典型算法（三）

三、圖像的水平鏡像變換算法

數學表達式原理：

設圖像高度為IHeight，寬度為IWidth，原圖中（x0,y0）經過水平鏡像后從未將變為

（IWidth-x0，y0），其表達式為：

X0=IWidth-y1; y0=y1

算法的C語言代碼：

/*水平鏡像變換處理*/

void horizTranspose()

{

         int i,j;

         for(i=0;i<numLines;i++)

         {            

              /*前半部分為原始圖像*/

              //傳送臨時Y緩沖區

                   DAT_copy((void *)(capYbuffer + i * numPixels),

                      (void *)(tempYbuffer + i * numPixels),

                      numPixels>>1);                                                       

             //傳送臨時Cb緩沖區

             DAT_copy((void *)(capCbbuffer + i * (numPixels >> 1)),

                      (void *)(tempCbbuffer + i * (numPixels >> 1)),

                      numPixels>>2);        

             //傳送臨時Cr緩沖區

             DAT_copy((void *)(capCrbuffer + i * (numPixels >> 1)),

                      (void *)(tempCrbuffer + i * (numPixels >> 1)),

                      numPixels>>2);                                                                          

                   /*后半部分為水平鏡像圖像*/

                   for(j=numPixels/2;j<numPixels;j++)

                   {

                            //傳送臨時Y緩沖區               

                            *(Uint8 *)(tempYbuffer + i*numPixels + j) = *(Uint8 *)(capYbuffer + i*numPixels + numPixels-1-j);             

                   }

             for(j=(numPixels>>2);j<(numPixels>>1);j++)

                   {

                            //傳送臨時Cb緩沖區

                            *(Uint8 *)(tempCbbuffer + i*(numPixels>>1) + j) = *(Uint8 *)(capCbbuffer + i*(numPixels>>1) + (numPixels>>1)-1-j);                   

                            //傳送臨時Cr緩沖區

                            *(Uint8 *)(tempCrbuffer + i*(numPixels>>1) + j) = *(Uint8 *)(capCrbuffer + i*(numPixels>>1) + (numPixels>>1)-1-j);                   

                   }

          }

}

四、圖像的縮放算法

數學表達式原理：

假設圖像x軸方向縮放比率fx，y軸方向縮放比率是fy，那么原圖中點（x0，y0）對應

于新圖中的點（x1，y1）的轉換表達式為：

X0=x1/fx; y0=y1/fy

算法的C語言代碼：

/*圖像縮放參數*/

Float fXZoomRatio=0.5; //水平縮放比率

Float fYZoomRatio=0.5; //垂直縮放比率

/*縮放處理函數*/

/*縮放處理*/

void zoom()

{

         int i,j;

         int intCapX,intCapY;

         for(i=0;i<numLines;i++)

         {

             for(j=0;j<numPixels;j++)

             {                    

            intCapX = (int)(j/fYZoomRatio+0.5);

            intCapY = (int)(i/fXZoomRatio+0.5);          

            //判斷是否在原圖范圍內

            if((intCapX>=0) && (intCapX<numPixels))  

            {  

                     if((i<numLines/2) && (intCapY>=0) && (intCapY<numLines/2))

                     {

                                         //傳送亮度信號

                                         *(Uint8 *)(tempYbuffer + i*numPixels + j) = *(Uint8 *)(capYbuffer + intCapY*numPixels + intCapX); 

                                }

                                else if((i>=numLines/2) && (i<numLines) && (intCapY>=numLines/2) && (intCapY<numLines))

                                {

                                             //傳送亮度信號

                                         *(Uint8 *)(tempYbuffer + i*numPixels + j) = *(Uint8 *)(capYbuffer + intCapY*numPixels + intCapX);                        

                                }

                                else

                                {

                                    *(Uint8 *)(tempYbuffer + i*numPixels + j) = 0xFF;

                                }                                                                                  

                 }

            else

            {

                      *(Uint8 *)(tempYbuffer + i*numPixels + j) = 0xFF;

            }                                             

                   }       

         }

}