从原始UIImage裁剪圆形或椭圆形图像

 (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, 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, 0, 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, 0, originalImage.size.width, originalImage.size.height), imageRef);



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


}