镜头桶形失真校正算法 镜头径向畸变校正

短焦镜头通常会产生桶形失真，以下是校正算法的matlab代码：

 %% 镜头桶形失真校正(短焦镜头)

 img_origin1 = imread('Still001.bmp');
 img_origin = rgb2gray(img_origin1);

 k1 = -0.00000037;   % 形变参数，根据实际情况调整
 k2 = -0.00000037;

 img_size = size( img_origin );
 img_undist = zeros( img_size );
 img_undist = uint8( img_undist );


 for l1 = 1:img_size(1)  % 垂直方向

     y = l1 - img_size(1)/2;

     for l2 = 1:img_size(2)  % 水平方向

         x = l2 - img_size(2)/2;

         x1 = round( x * ( 1 + k1 * x * x + k2 * y * y ) );
         y1 = round( y * ( 1 + k1 * x * x + k2 * y * y ) );
         y1 = y1 + img_size(1)/2;
         x1 = x1 + img_size(2)/2;

         img_undist(l1,l2) = img_origin(y1, x1);

     end
 end


 figure(1);
 subplot(121); imshow(img_origin);
 subplot(122); imshow(img_undist);

 imwrite(img_origin,'1.bmp');
 imwrite(img_undist,'2.bmp');

在实时视频处理中，如果对每帧图像都要重复进行坐标转换运算，就是个很大的浪费，我们可以在初始化过程中先将坐标对应关系建立一个二维查找表，之后每帧处理只需要查表，C++代码如下（用到了OpenCV）：

 // 镜头校正查找表
 CvPoint CorrInd[480][640];

 // 镜头径向畸变校正初始化
 void LensCorrectInit( double k1 = -0.00000035, double k2 = -0.00000035 );


 // 镜头径向畸变校正初始化
 void LensCorrectInit( double k1, double k2 )
 {
     int imgWidth = camera.GetWidth();   // 获得摄像头图像尺寸
     int imgHeight = camera.GetHeight();

     int imgWd2 = imgWidth>>1;
     int imgHd2 = imgHeight>>1;

     int it;
     int jt;
     int it2;
     int jt2;

     for( int i=0; i<imgHeight; i++ )
     {
         it = ( i + 1 ) - imgHd2; // (i+1) 是其真正的图像坐标
         for( int j=0; j<imgWidth; j++ )
         {
             double temp;

             jt = ( j + 1 ) - imgWd2; // (j+1) 是其真正的图像坐标
             temp = 1 + k1*it*it + k2*jt*jt;
             it2 = (int)(temp * it);
             jt2 = (int)(temp * jt);

             it2 = it2 + imgHd2 + 1;
             jt2 = jt2 + imgWd2 + 1;

             CorrInd[i][j].x = jt2;
             CorrInd[i][j].y = it2;
         }
     }
 }




 // 镜头径向畸变校正
 void LensCorrect( IplImage* src, IplImage* dst )
 {
     int imgWidth = dst->width;
     int imgHeight = dst->height;

     int it2;
     int jt2;

     for( int i=0; i<imgHeight; i++ )
     {
         uchar *pdstdata = (uchar*)(dst->imageData) + i*dst->widthStep;

         for( int j=0; j<imgWidth; j++ )
         {
             it2 = CorrInd[i][j].y;
             jt2 = CorrInd[i][j].x;

             uchar * psrcdata = cvPtr2D( src, it2, jt2 );

             *(pdstdata++) = *(psrcdata++);
             *(pdstdata++) = *(psrcdata++);
             *(pdstdata++) = *(psrcdata++);
         }
     }
 }