對於二維圖像,Log-Polar表示從笛卡爾座標到極座標的變換。
OpenCV中對於數極座標轉換的函數是cvLogPolar():
void cvLogPolar(const CvArr * src , CvArr * det , CvPoint2D32f center , double n , int flags = CV_INTER_LINEAR | CV_WARP_FILL_OUTLIERS)
src 和 dst是單通道或三通道的彩色或灰度圖像。
center是對數極座標變換的中心點;
m是縮放比例;
下面以《學習OpenCV》課後題10爲例子進行練習
10.進行LogPolar轉換
a:如果logPolar的中心點在正方形的一角,畫出log-polar的結果;
b:如果中心點在圓裏邊靠近邊緣,那麼log-polar變換中的圓的外觀?
c:如果中心點在圓的外邊,畫出圓的外觀
#include <iostream>
#include <opencv2/opencv.hpp>
#include <opencv2/highgui.hpp>
using namespace std;
using namespace cv;
int main(int argc, const char * argv[]) {
/*1、生成一個圖像*/
IplImage * Src1 = cvCreateImage(cvSize(250,250), IPL_DEPTH_32F, 1);
cvSetZero(Src1);
/*2、克隆圖像Src2 和 Src3,生成矩形和圓*/
IplImage * Src2 = cvCloneImage(Src1);
Src2->origin = Src1->origin; //設置相同原點
cvSetZero(Src2);
cvRectangle(Src1, cvPoint(100, 100), cvPoint(200, 200), CV_RGB(255, 255, 255));
cvCircle(Src2, cvPoint(150, 150), 50, CV_RGB(255,255,255));
cvShowImage("Rect_1", Src1);
cvShowImage("Circle", Src2);
double M = 50; //縮放比例
/*3、中心點在正方形的中心進行極座標變換 */
IplImage * Ipolar1 = cvCloneImage(Src1);
Ipolar1->origin = Src1->origin;
cvSetZero(Ipolar1);
CvPoint2D32f center1 = cvPoint2D32f(150, 150); //在矩形中心
cvLogPolar(Src1, Ipolar1, center1, M , CV_INTER_LINEAR | CV_WARP_FILL_OUTLIERS);
cvShowImage("Ipolar1", Ipolar1);
/*4、中心點在正方形的一角進行極座標變換*/
IplImage * Ipolar2 = cvCloneImage(Src1);
Ipolar2->origin = Src1->origin;
cvSetZero(Ipolar2);
CvPoint2D32f center2 = cvPoint2D32f(100, 100); //矩形邊角
cvLogPolar(Src1,Ipolar2 , center2, M , CV_INTER_LINEAR | CV_WARP_FILL_OUTLIERS);
cvShowImage("Ipolar2", Ipolar2);
/*5、中心點在圓裏面靠近邊緣進行極座標變換*/
IplImage * Ipolar3 = cvCloneImage(Src2);
Ipolar3->origin = Src2->origin;
cvSetZero(Ipolar3);
CvPoint2D32f center3 = cvPoint2D32f(150, 102);
cvLogPolar(Src2, Ipolar3, center3, M , CV_INTER_LINEAR | CV_WARP_FILL_OUTLIERS);
cvShowImage("Ipolar3", Ipolar3);
/*6、中心點在圓裏面外邊邊緣進行極座標變換*/
IplImage * Ipolar4 = cvCloneImage(Src2);
Ipolar4->origin = Src2->origin;
cvSetZero(Ipolar4);
CvPoint2D32f center4 = cvPoint2D32f(150, 98);
cvLogPolar(Src2, Ipolar4, center4, M , CV_INTER_LINEAR | CV_WARP_FILL_OUTLIERS);
cvShowImage("Ipolar4", Ipolar4);
cvWaitKey(0);
cvReleaseImage(&Src1);
cvReleaseImage(&Src2);
cvReleaseImage(&Ipolar1);
cvReleaseImage(&Ipolar2);
cvReleaseImage(&Ipolar3);
cvReleaseImage(&Ipolar4);
return 0;
}