Using renderInContext: for masks created by cgpaths - ios

Question

I recently found out that the renderinContext: method ignores any layer masks. I am trying to capture a video of my app's screen, in which I animate the path of a masked CALayer.
To record the screen, I am using the ScreenCaptureView class, found online. The view takes a "screenshot" of it's subviews every x seconds and compiles them into a video.
In the drawRect method, I call
[[self.layer presentationLayer] renderInContext:context];
After looking online, I found someone's solution; however, it applies for masks that are images. (My mask is a CGPath).
-(UIImage*) imageFromView:(UIView*)originalView
{
//Creating a fakeView which is initialized as our original view.
//Actually i render images on a fakeView and take screenshot of this fakeView.
UIView *fakeView = [[UIView alloc] initWithFrame:originalView.frame];
[fakeView.layer setMasksToBounds:originalView.layer.masksToBounds];
//Getting subviews of originalView.
for (UIView *view in originalView.subviews)
{
//Getting screenshot of layer of view.
UIGraphicsBeginImageContext(view.bounds.size);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *imageLayer = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
//If it is masked view, then get masked image.
if (view.layer.mask)
{
//getting screenshot of masked layer.
UIGraphicsBeginImageContext(view.bounds.size);
[view.layer.mask renderInContext:UIGraphicsGetCurrentContext()];
//PNG Representation is most important. otherwise this masked image will not work.
UIImage *maskedLayerImage=[UIImage imageWithData:UIImagePNGRepresentation(UIGraphicsGetImageFromCurrentImageContext())];
UIGraphicsEndImageContext();
//getting image by masking original image.
imageLayer = [self maskImage:imageLayer withMask:maskedLayerImage];
}
//If imageLayer is pointing to a valid object, then setting this image to UIImageView, our UIImageView frame having exactly as view.frame.
if (imageLayer)
{
UIImageView *imageView = [[UIImageView alloc] initWithFrame:view.frame];
[imageView setImage:imageLayer];
[fakeView addSubview:imageView];
}
}
//At the end, taking screenshot of fakeView. This will get your Original Image.
UIGraphicsBeginImageContext(fakeView.bounds.size);
[fakeView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *previewCapturedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return previewCapturedImage;
}
}
//Method is used to get masked image.
- (UIImage*) maskImage:(UIImage *)image withMask:(UIImage *)maskImage
{
CGImageRef maskRef = maskImage.CGImage;
CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef),
CGImageGetHeight(maskRef),
CGImageGetBitsPerComponent(maskRef),
CGImageGetBitsPerPixel(maskRef),
CGImageGetBytesPerRow(maskRef),
CGImageGetDataProvider(maskRef), NULL, false);
CGImageRef masked = CGImageCreateWithMask([image CGImage], mask);
return [UIImage imageWithCGImage:masked];
}
Can I do something similar for masks from cgpaths?

Answer 1

You can use CGContextClip() in renderInContext: to clip to a path:
- (void)renderInContext:(CGContextRef)context {
// Assign maskPath to whatever path you want to mask to (Here, it's assumed that your layer's mask is a CAShapeLayer)
CGPathPathRef maskPath = [(CAShapeLayer *)self.mask path];
CGContextAddPath(context, maskPath);
CGContextClip(context);
// Do drawing code here
}