opencv 旋转图片

旋转图像

有几种方法旋转OpenCV的图像。旋转图像中的主要问题是它会留下一些空白图像的四个角。有几种方法来应对的空白区域

下面是一个例子，旋转图像，同时保留它的大小。 

#include <opencv/cv.h>#include <opencv/highgui.h>IplImage *rotateImage(const IplImage *src, int angleDegrees){        IplImage *imageRotated = cvCloneImage(src);    if(angleDegrees!=0){        CvMat* rot_mat = cvCreateMat(2,3,CV_32FC1);            // Compute rotation matrix        CvPoint2D32f center = cvPoint2D32f( cvGetSize(imageRotated).width/2, cvGetSize(imageRotated).height/2 );        cv2DRotationMatrix( center, angleDegrees, 1, rot_mat );        // Do the transformation        cvWarpAffine( src, imageRotated, rot_mat );    }    return imageRotated;}int main(){                    IplImage* img;          IplImage* rotated_img;          int angle=0;                    //creating the window with a track bar          cvNamedWindow("MyWindow");          cvCreateTrackbar("Angle", "MyWindow", &angle, 360, 0);                    while(true){              //load the original image              img = cvLoadImage("d:/1.jpg");                            //rotate the image              rotated_img=rotateImage(img,angle);              //display the rotated image              cvShowImage("MyWindow", rotated_img);               //clean up              cvReleaseImage(&img);              cvReleaseImage(&rotated_img);                            //if user press 'ESC' button, program quit the while loop              int c=cvWaitKey(50);                             if(c==27) break;          }                              cvDestroyWindow("MyWindow");                    return 0;}

Explanation

Here are the new OpenCV functions, found in the above example.

• cvCloneImage(const IplImage* src)

Makes a identical(cloned) copy of the 'src' image including header and region of interrest(ROI) 

Returns IplImage* points to the cloned image

Arguements -

• IplImage* src - source image to be cloned

•  cvCreateMat(int rows, int columns, int types)

Creates matrix header and allocates matrix data
Returns CvMat* points to the matrix

Arguements -

• int rows - number of rows of the matrix
• int columns - number of columns of the matrix
• int types - CV_<no. of bits of the image data><data type of image data>C<no. of channel>

                             <no. of bits of the image data>  = 8,16,32, ....
                             <data type of image data> = 'S' for signed data, 'U' for unsigned data and  'F' for float data
                             <no. of channel> = 1,2,3
                             
                             eg. : CV_8UC1 = 8 bit unsigned image with a single channel
                                     CV_32FC3 = 32 bit float image with 3 channels

• cvPoint2D32f (float x, float y)

It is a basic structure for 2D point with floating point cordinates
            
             typedef struct CvPoint2D32f
            {
                float x;
                float y;
            }
            CvPoint2D32f;

/* Constructor */
inline CvPoint2D32f cvPoint2D32f( double x, double y );

• cv2DRotationMatrix(CvPoint2D32f center, double angle, double scale, CvMat* mapMatrix)

Computes affine matrix of 2D rotation

Arguements - 

• CvPoint2D32f center - specifies the ceter of rotation
• double angle - rotation angle in degrees (Positive value means counter clockwise rotation and negative value means clockwise rotation)
• double scale -Isotrophic scale factor
• CvMat* mapMatrix - the pointer to the resultant matrix which should be 2x3 matrix

• cvWarpAffine(const CvArr* src, CvArr* dst, const CvMat* mapMatrix)

Applies an affine transformation to the source image

Arguements -

• const CvArr* src - source image
• CvArr* dst - destination image which is the affine transformed image of the source image
•  const CvMat* mapMatrix - 2x3 transformation matrix

#include <opencv/cv.h>#include <opencv/highgui.h>IplImage *rotateImage(const IplImage *src, int angleDegrees, double zoom){        IplImage *imageRotated = cvCloneImage(src);        CvMat* rot_mat = cvCreateMat(2,3,CV_32FC1);        // Compute rotation matrix    CvPoint2D32f center = cvPoint2D32f( cvGetSize(imageRotated).width/2, cvGetSize(imageRotated).height/2 );    cv2DRotationMatrix( center, angleDegrees, zoom, rot_mat );    // Do the transformation    cvWarpAffine( src, imageRotated, rot_mat );        return imageRotated;}int main(){                    IplImage* img;          IplImage* rotated_img;          int angle=0;          int zoom=24;                    //creating the window with 2 track bars          cvNamedWindow("MyWindow");          cvCreateTrackbar("Angle", "MyWindow", &angle, 360, 0);          cvCreateTrackbar("Zoom", "MyWindow", &zoom, 99, 0);                    while(true){              //load the original image              img = cvLoadImage("d:/lena.jpg");                            //rotate the image              rotated_img=rotateImage( img, angle, (zoom+1)/25.0 );              //display the rotated image              cvShowImage("MyWindow", rotated_img);               //clean up              cvReleaseImage(&img);              cvReleaseImage(&rotated_img);                            //if user press 'ESC' button, program quit the while loop              int c=cvWaitKey(50);                             if(c==27) break;          }                              cvDestroyWindow("MyWindow");                    return 0;} 

旋转填充式：

#include <opencv/cv.h>#include <opencv/highgui.h>IplImage* rotateImage(const IplImage* src, int angleDegrees){    //take the dimention of original image    int w = src->width;    int h = src->height;     // Make a new image for the result    CvSize newSize;    newSize.width = cvRound(w);    newSize.height = cvRound(h);    IplImage *imageRotated = cvCreateImage( newSize, src->depth, src->nChannels );            // Create a map_matrix, where the left 2x2 matrix is the transform and the right 2x1 is the dimensions.    float m[6];    CvMat M = cvMat(2, 3, CV_32F, m);        float angleRadians = angleDegrees * ((float)CV_PI / 180.0f);    m[0] = (float)( cos(angleRadians) );    m[1] = (float)( sin(angleRadians) );    m[3] = -m[1];    m[4] = m[0];    m[2] = w*0.5f;      m[5] = h*0.5f;      // Transform the image    cvGetQuadrangleSubPix( src, imageRotated, &M);    return imageRotated;}int main(){                    IplImage* img;          IplImage* rotated_img;          int angle=0;                  //creating the window with a track bar          cvNamedWindow("MyWindow");          cvCreateTrackbar("Angle", "MyWindow", &angle, 360, 0);                    while(true){              //load the original image              img = cvLoadImage("d:/lena.jpg");                            //rotate the image              rotated_img=rotateImage(img,angle);              //display the rotated image              cvShowImage("MyWindow", rotated_img);               //clean up              cvReleaseImage(&img);              cvReleaseImage(&rotated_img);                            //if user press 'ESC' button, program quit the while loop              int c=cvWaitKey(50);                             if(c==27) break;          }                              cvDestroyWindow("MyWindow");                    return 0;}