Select and crop face image from photo image (ios) - ios

Question

I'm trying to get cropped image from photo. I have the following code that crop image that was got from ios face detection sdk:
- (UIImage *)scaleAndRotateImage:(CIFeature *)ciFeature image:(UIImage *)image {
static int kMaxResolution = 640;
CGImageRef imgRef = image.CGImage;
CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);
CGAffineTransform transform = CGAffineTransformIdentity;
CGRect bounds = CGRectMake(0, 0, width, height);
if (width > kMaxResolution || height > kMaxResolution) {
CGFloat ratio = width/height;
if (ratio > 1) {
bounds.size.width = kMaxResolution;
bounds.size.height = bounds.size.width / ratio;
} else {
bounds.size.height = kMaxResolution;
bounds.size.width = bounds.size.height * ratio;
}
}
CGFloat scaleRatio = bounds.size.width / width;
UIImageOrientation orient = image.imageOrientation;
switch(orient) {
case UIImageOrientationUp:
transform = CGAffineTransformIdentity;
break;
default:
[NSException raise:NSInternalInconsistencyException
format:#"Invalid image orientation"];
}
UIGraphicsBeginImageContext(bounds.size);
CGContextRef context = UIGraphicsGetCurrentContext();
if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {
CGContextScaleCTM(context, -scaleRatio, scaleRatio);
CGContextTranslateCTM(context, -height, 0);
} else {
CGContextScaleCTM(context, scaleRatio, -scaleRatio);
CGContextTranslateCTM(context, 0, -height);
}
CGContextConcatCTM(context, transform);
CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
UIImage *returnImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return returnImage;
}
But how can I crop only face from the image (Like face image in box) because for now it changes original resolution of image?

Answer 1

If you want to crop your image with more conveniently and more user-defined, I recommend you to use the RSKImageCropper, its github location is here:https://github.com/ruslanskorb/RSKImageCropper
Because you want to crop the face's position, so the system's default method is not satisfy your requirement, you can learn from here:https://developer.apple.com/library/content/documentation/AudioVideo/Conceptual/CameraAndPhotoLib_TopicsForIOS/Articles/PickinganItemfromthePhotoLibrary.html#//apple_ref/doc/uid/TP40010408-SW1
The Core Graphic's crop image method:CGImageCreateWithImageInRect, is not easy to confirm the rect you want, because you for get the position of the face you should do a lot of work, the RSKImageCropper may be your convenient choise.