Overlay Image from VNTextObservation

OverlayImageWithVNTextObservation.m

- (UIImage *)overlayImageWithTextObservations:(NSArray<VNTextObservation *> *)results size:(CGSize)size
{
    UIGraphicsImageRenderer *renderer = [[UIGraphicsImageRenderer alloc] initWithSize:size];
    UIImage *overlayImage = [renderer imageWithActions:^(UIGraphicsImageRendererContext * _Nonnull rendererContext) {
        CGAffineTransform t = CGAffineTransformIdentity;
        t = CGAffineTransformScale(t, size.width, -size.height);
        t = CGAffineTransformTranslate(t, 0, -1);
        for (VNTextObservation *textObservation in results) {
            [[UIColor redColor] setStroke];
            [[UIBezierPath bezierPathWithRect:CGRectApplyAffineTransform(textObservation.boundingBox, t)] stroke];
            for (VNRectangleObservation *rectangleObservation in textObservation.characterBoxes) {
                [[UIColor blueColor] setStroke];
                [[UIBezierPath bezierPathWithRect:CGRectApplyAffineTransform(rectangleObservation.boundingBox, t)] stroke];
            }
        }
    }];
    return overlayImage;
}