用OpenCV裁剪图像
问题描述：
我在使用iPhone上的OpenCV库裁剪图像时遇到了问题。我有一个与选定区域的图像，我想裁剪该区域的图像。但新图像不是映射到矩形，新图像也是蓝色文本。用OpenCV裁剪图像
我使用该代码即可裁剪图片：
IplImage *src = [OpenCV CreateIplImageFromUIImage:image];
NSValue *val = [corners objectAtIndex:0];
CGPoint p1 = [val CGPointValue];
val = [corners objectAtIndex:1];
CGPoint p2 = [val CGPointValue];
val = [corners objectAtIndex:2];
CGPoint p3 = [val CGPointValue];
val = [corners objectAtIndex:3];
CGPoint p4 = [val CGPointValue];
float minX = fmin(fmin(p1.x, p2.x), fmin(p3.x, p4.x));
float minY = fmin(fmin(p1.y, p2.y), fmin(p3.y, p4.y));
float maxX = fmax(fmax(p1.x, p2.x), fmax(p3.x, p4.x));
float maxY = fmax(fmax(p1.y, p2.y), fmax(p3.y, p4.y));
CGFloat width = maxX - minX;
CGFloat height = maxY - minY;
IplImage *dst = cvCreateImage(cvSize(width, height), 8, 3);
p1 = CGPointMake(p1.x - minX, p1.y - minY);
p2 = CGPointMake(p2.x - minX, p2.y - minY);
p3 = CGPointMake(p3.x - minX, p3.y - minY);
p4 = CGPointMake(p4.x - minX, p4.y - minY);
IplImage* cropped = cvCreateImage(cvSize(width, height), src->depth, src->nChannels);
cvSetImageROI(src, cvRect(minX, minY, width, height));
cvCopy(src, cropped, NULL);
cvResetImageROI(src);
cvReleaseImage(&src);
CvMat* mmat = cvCreateMat(3, 3, CV_32FC1);
CvPoint2D32f *c1 = (CvPoint2D32f *)malloc(4 * sizeof(CvPoint2D32f));
CvPoint2D32f *c2 = (CvPoint2D32f *)malloc(4 * sizeof(CvPoint2D32f));
c1[0].x = p1.x; c1[0].y = p1.y;
c1[1].x = p4.x; c1[1].y = p4.y;
c1[2].x = p2.x; c1[2].y = p2.y;
c1[3].x = p3.y; c1[3].y = p3.y;
c2[0].x = 0; c2[0].y = 0;
c2[1].x = width; c2[1].y = 0;
c2[2].x = 0; c2[2].y = height;
c2[3].x = width; c2[3].y = height;
mmat = cvGetPerspectiveTransform(c1, c2, mmat);
cvWarpPerspective(cropped, dst, mmat, CV_INTER_LINEAR+CV_WARP_FILL_OUTLIERS, cvScalarAll(0));
我会感谢任何帮助。
答
我的代码有错误。如果有人对此感兴趣，请点击这里工作代码：
IplImage *src = [OpenCV CreateIplImageFromUIImage:image];
IplImage *dst = cvCloneImage(src);
dst->origin = src->origin;
dst->nChannels = src->nChannels;
dst->depth = src->depth;
cvZero(dst);
NSValue *val = [corners objectAtIndex:0];
CGPoint p1 = [val CGPointValue];
val = [corners objectAtIndex:1];
CGPoint p2 = [val CGPointValue];
val = [corners objectAtIndex:2];
CGPoint p3 = [val CGPointValue];
val = [corners objectAtIndex:3];
CGPoint p4 = [val CGPointValue];
CGFloat width = src->width;
CGFloat height = src->height;
CvMat* mmat = cvCreateMat(3, 3, CV_32FC1);
CvPoint2D32f *c1 = (CvPoint2D32f *)malloc(4 * sizeof(CvPoint2D32f));
CvPoint2D32f *c2 = (CvPoint2D32f *)malloc(4 * sizeof(CvPoint2D32f));
c1[0].x = round(p1.x); c1[0].y = round(p1.y);
c1[1].x = round(p4.x); c1[1].y = round(p4.y);
c1[2].x = round(p2.x); c1[2].y = round(p2.y);
c1[3].x = round(p3.x); c1[3].y = round(p3.y);
c2[0].x = 0; c2[0].y = 0;
c2[1].x = width -1; c2[1].y = 0;
c2[2].x = 0; c2[2].y = height - 1;
c2[3].x = width - 1; c2[3].y = height - 1;
mmat = cvGetPerspectiveTransform(c1, c2, mmat);
free(c1);
free(c2);
cvWarpPerspective(src, dst, mmat, CV_INTER_LINEAR+CV_WARP_FILL_OUTLIERS, cvScalarAll(0));
cvReleaseImage(&src);
cvReleaseMat(&mmat);
UIImage *newImage = [OpenCV UIImageFromIplImage:dst];
cvReleaseImage(&dst);
为什么不尝试在不使用扭曲的情况下看到裁剪后的图像？ – rics 2010-09-25 20:11:27
选中的不能是矩形。它可以是任何四边形，我想先将该图像裁剪到该四边形，然后将该四边形映射到矩形。但有了上述功能，我只能将图像裁剪到矩形区域，并且翘曲不起作用。 – 2010-09-27 07:41:50
我们如何检测角落？你能给我提供指导方针或一点点代码吗？ – QueueOverFlow 2012-10-27 09:24:04