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*
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;
}
