李现路:DSP6000图像位置移动与变形的典型算法（四）

五、图像的旋转实验

数学表达式原理：

下面我们来推导一下旋转运算的变换公式。如下图所示，点（x0，y0）经过旋转θ度后

坐标变成（x1，y1）。其数学表达式为：

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

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

算法的C语言代码：

/*图像旋转参数*/

Float fAngle=3.1415927/3; //旋转的角度

*画矩形边框函数*/

Void drawRectangle();

*计算图像旋转参数*/

Void computeParameter();

/*进行图像旋转处理*/

void rotate()

{

         int i,j,intInc;

         int intCapYInc;

         int intCapX,intCapY;

         /*进行图像旋转，重新赋值*/

         //方框内奇数行

         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;

            }

            //判断是否在原图范围内

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

            {

                                //传送亮度信号

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

                 }

            else

            {

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

            }

                   }       

         }

         //方框内偶数行

         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;

            }            

            //判断是否在原图范围内

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

            {

                                //传送亮度信号

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

                 }

            else

            {

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

            }

                   }       

         }       

}

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