李現路:DSP6000圖像位置移動與變形的典型算法（四）

五、圖像的旋轉實驗

數學表達式原理：

下面我們來推導一下旋轉運算的變換公式。如下圖所示，點（x0，y0）經過旋轉θ度后

坐標變成（x1，y1）。其數學表達式為：

X0=x1cos(θ)+y1sin(θ)+ccos(θ)-dsin(θ)+a ;

Y0=-xsin(θ)+y1cos(θ)+csin(θ)-dcos(θ)+ b

算法的C語言代碼：

/*圖像旋轉參數*/

Float fAngle=3.1415927/3; //旋轉的角度

*畫矩形邊框函數*/

Void drawRectangle();

*計算圖像旋轉參數*/

Void computeParameter();

/*進行圖像旋轉處理*/

void rotate()

{

         int i,j,intInc;

         int intCapYInc;

         int intCapX,intCapY;

         /*進行圖像旋轉，重新賦值*/

         //方框內奇數行

         for(i=intALines;i<intDLines;i++)

         {

             for(j=intAPixels;j<intDPixels;j++)

             {

            intInc = i*2;  

            intCapX    = (int)(j*cosAngle + intInc*sinAngle + f1 + 0.5);

            intCapYInc = (int)(intInc*cosAngle - j*sinAngle + f1 + 0.5);          

            if((intCapYInc%2)==0)

            {

                     intCapY = intCapYInc/2;

            }

            else

            {

                     intCapY = (intCapYInc-1)/2+numLines/2;

            }

            //判斷是否在原圖范圍內

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

            }

                   }       

         }

         //方框內偶數行

         for(i=numLines/2+intALines;i<numLines/2+intDLines;i++)

         {

             for(j=intAPixels;j<intDPixels;j++)

             {                

            intInc = (i-numLines/2)*2 + 1;

            intCapX    = (int)(j*cosAngle + intInc*sinAngle + f1 + 0.5);

            intCapYInc = (int)(intInc*cosAngle - j*sinAngle + f1 + 0.5);          

            if((intCapYInc%2)==0)

            {

                     intCapY = intCapYInc/2;

            }

            else

            {

                     intCapY = (intCapYInc-1)/2+numLines/2;

            }            

            //判斷是否在原圖范圍內

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

            }

                   }       

         }       

}

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