从原始UIImage裁剪圆形或椭圆形图像

如何解决从原始UIImage裁剪圆形或椭圆形图像

| 我正在开发用于检测人脸的openCV。我希望在检测到人脸后对其进行裁剪。直到现在我已经获得了人脸并在iPhone上标记了周围的矩形/椭圆形。 请帮我把脸剪成圆形/椭圆形

 (UIImage *) opencvFaceDetect:(UIImage *)originalImage 
 {

cvSetErrMode(CV_ErrModeParent);

IplImage *image = [self CreateIplImageFromUIImage:originalImage];

// Scaling down

/*
Creates IPL image (header and data) ----------------cvCreateImage
CVAPI(IplImage*)  cvCreateImage( CvSize size,int depth,int channels );
*/

IplImage *small_image = cvCreateImage(cvSize(image->width/2,image->height/2),IPL_DEPTH_8U,3);

/*SMOOTHES DOWN THYE GUASSIAN SURFACE--------:cvPyrDown*/
cvPyrDown(image,small_image,CV_GAUSSIAN_5x5);
int scale = 2;

// Load XML
NSString *path = [[NSBundle mainBundle] pathForResource:@\"haarcascade_frontalface_default\" ofType:@\"xml\"];
CvHaarClassifierCascade* cascade = (CvHaarClassifierCascade*)cvLoad([path cStringUsingEncoding:NSASCIIStringEncoding],NULL,NULL);

// Check whether the cascade has loaded successfully. Else report and error and quit

if( !cascade )
{
    NSLog(@\"ERROR: Could not load classifier cascade\\n\");
    //return;
}

//Allocate the Memory storage
CvMemStorage* storage = cvCreateMemStorage(0);

// Clear the memory storage which was used before
cvClearMemStorage( storage );

CGColorSpaceRef colorSpace;
CGContextRef contextRef;


CGRect face_rect;
// Find whether the cascade is loaded,to find the faces. If yes,then:
if( cascade )
{
CvSeq* faces = cvHaarDetectObjects(small_image,cascade,storage,1.1f,3,cvSize(20,20));
cvReleaseImage(&small_image);

// Create canvas to show the results
 CGImageRef imageRef = originalImage.CGImage;
 colorSpace = CGColorSpaceCreateDeviceRGB();
 contextRef = CGBitmapContextCreate(NULL,originalImage.size.width,originalImage.size.height,8,originalImage.size.width * 4,colorSpace,kCGImageAlphaPremultipliedLast|kCGBitmapByteOrderDefault);
//VIKAS
CGContextDrawImage(contextRef,CGRectMake(0,originalImage.size.height),imageRef);



CGContextSetLineWidth(contextRef,4);
CGContextSetRGBStrokeColor(contextRef,1.0,0.5);




// Draw results on the iamge:Draw all components of face in the form of small rectangles

// Loop the number of faces found.

for(int i = 0; i < faces->total; i++) 
    {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    // Calc the rect of faces
    // Create a new rectangle for drawing the face

    CvRect cvrect = *(CvRect*)cvGetSeqElem(faces,i);
    //  CGRect face_rect = CGContextConvertRectToDeviceSpace(contextRef,//                          CGRectMake(cvrect.x * scale,cvrect.y * scale,cvrect.width * scale,cvrect.height * scale));


     face_rect = CGContextConvertRectToDeviceSpace(contextRef,CGRectMake(cvrect.x*scale,cvrect.y,cvrect.width*scale,cvrect.height*scale*1.25
                                                                    ));

    facedetectapp=(FaceDetectAppDelegate *)[[UIApplication sharedApplication]delegate];
    facedetectapp.grabcropcoordrect=face_rect;

    NSLog(@\"  FACE off %f %f %f %f\",facedetectapp.grabcropcoordrect.origin.x,facedetectapp.grabcropcoordrect.origin.y,facedetectapp.grabcropcoordrect.size.width,facedetectapp.grabcropcoordrect.size.height);
    CGContextStrokeRect(contextRef,face_rect);
        //CGContextFillEllipseInRect(contextRef,face_rect);
    CGContextStrokeEllipseInRect(contextRef,face_rect);


    [pool release];
}

}
CGImageRef imageRef = CGImageCreateWithImageInRect([originalImage CGImage],face_rect);
    UIImage *returnImage = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);


CGContextRelease(contextRef);
CGColorSpaceRelease(colorSpace);

cvReleaseMemStorage(&storage);
cvReleaseHaarClassifierCascade(&cascade);

   return returnImage;
}


}

谢谢 维卡斯     

解决方法

        有很多混合模式可供选择，其中一些对“遮罩”很有用。我相信这应该可以大致满足您的要求：

CGContextSaveGState(contextRef);
CGContextSetBlendMode(contextRef,kCGBlendModeDestinationIn);
CGContextFillEllipseInRect(contextRef,face_rect);
CGContextRestoreGState(contextRef);

\“大约\”，因为它每次都会掩盖整个上下文的内容，因此对一张以上的脸做错了。要处理这种情况，请在循环中使用CGContextAddEllipseInRect（），最后使用CGContextFillPath（）。 您可能还需要查看CGContextBeginTransparencyLayerWithRect（）。     ,        以下是我在如何将UIImage裁剪为椭圆形或圆形时给出的答案？使图像转圈。这个对我有用.. 从URL http://vocaro.com/trevor/blog/2009/10/12/resize-a-uiimage-the-right-way/下载支持存档文件

#import \"UIImage+RoundedCorner.h\"
#import \"UIImage+Resize.h\"

以下几行用于调整图像大小并转换为半径的圆角

UIImage *mask = [UIImage imageNamed:@\"mask.jpg\"];

mask = [mask resizedImage:CGSizeMake(47,47) interpolationQuality:kCGInterpolationHigh ];
mask = [mask roundedCornerImage:23.5 borderSize:1];

希望对您有所帮助。