Cropping an image without using an image mask? - ios

Question

I'm trying to add a feature in my iPhone app that allows users to record the screen. To do this, I used an open source class called ScreenCaptureView that compiles a series of screenshots of the main view through the renderInContext: method. However, this method ignores masked CALayers, which is key to my app.
EDIT:
I need a way to record the screen so that the masks are included. Although this question specifically asks for a way to create the illusion of an image mask, I'm open to any other modifications I can make to record the screen successfully.
APP DESCRIPTION
In the app, I take a picture and create the effect of a moving mouth by animating the position of the jaw region, as shown below.
Currently, I have the entire face as one CALayer, and the chin region as a separate CALayer. To make the chin layer, I mask the chin region from the complete face using a CGPath. (This path is an irregular shape and must be dynamic).
- (CALayer *)getChinLayerFromPic:(UIImage *)pic frame:(CGRect)frame {
CGMutablePathRef mPath = CGPathCreateMutable();
CGPathMoveToPoint(mPath, NULL, p0.x, p0.y);
CGPoint midpt = CGPointMake( (p2.x + p0.x)/2, (p2.y+ p0.y)/2);
CGPoint c1 = CGPointMake(2*v1.x - midpt.x, 2*v1.y - midpt.y); //control points
CGPoint c2 = CGPointMake(2*v2.x - midpt.x, 2*v2.y - midpt.y);
CGPathAddQuadCurveToPoint(mPath, NULL, c1.x, c1.y, p2.x, p2.y);
CGPathAddQuadCurveToPoint(mPath, NULL, c2.x, c2.y, p0.x, p0.y);
CALayer *chin = [CALayer layer];
CAShapeLayer *chinMask = [CAShapeLayer layer];
chin.frame = frame;
chin.contents = (id)[pic CGImageWithProperOrientation];
chinMask.path = mPath;
chin.mask = chinMask;
CGPathRelease(mPath);
return chin;
}
I then animate the chin layer with a path animation.
As mentioned before, the renderInContext: method ignores the mask, and returns an image of the entire face instead of just the chin. Is there any way I can create an illusion of masking the chin? I would like to use CALayers if possible, since it would be most convenient for animations. However, I'm open to any ideas, including other ways to capture the video. Thanks.
EDIT:
I'm turning the cropped chin into a UIImage, and then setting that new image as the layers contents, instead of directly masking the layer. However, the cropped region is the reverse of the specified path.
CALayer *chin = [CALayer layer];
chin.frame = frame;
CGImageRef imageRef = [pic CGImage];
CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef);
int targetWidth = frame.size.width;
int targetHeight = frame.size.height;
CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
CGContextRef bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);
CGContextAddPath(bitmap, mPath);
CGContextClip(bitmap);
CGContextDrawImage(bitmap, CGRectMake(0, 0, targetWidth, targetHeight), imageRef);
CGImageRef ref = CGBitmapContextCreateImage(bitmap);
UIImage *chinPic = [UIImage imageWithCGImage:ref];
chin.contents = (id)[chinPic CGImageWithProperOrientation];

Answer 1

Why don't you draw the CALayer of the chin into a seperate CGImage and make a new UIImage with that?
Then you can add this CGImage to a seperate UIImageView, which you can just move around with a PanGestureRecognizer for example?

Answer 2

I suggest that you draw each part alone(you don't need masks), the face without a chin, and the chin, both with alpha pixels around, then just draw the chin over and move it on your path ..
Please inform me if this wasn't helpful to you, regards

Answer 3

If you just need this in order to capture the screen, it is much easier to use a programme such as
http://www.airsquirrels.com/reflector/
that connects your device to the computer via AirPlay, and then record the stream on the computer. This particular programme has screen recording built in, extremely convenient. I think there is a trial version you can use for recordings of up to 10 minutes.

Answer 4

Have you tried taking a look at layer.renderInContext doesn't take layer.mask into account? ?
In particular (notice the coordinate flip):
//Make the drawing right with coordinate switch
CGContextTranslateCTM(context, 0, cHeight);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextClipToMask(context, CGRectMake(maskLayer.frame.origin.x * mod, maskLayer.frame.origin.y * modTwo, maskLayer.frame.size.width * mod,maskLayer.frame.size.height * modTwo), maskLayer.image.CGImage);
//Reverse the coordinate switch
CGAffineTransform ctm = CGContextGetCTM(context);
ctm = CGAffineTransformInvert(ctm);
CGContextConcatCTM(context, ctm);