Error when trying to merge two UIImages into an UIImageView - ios

Question

I'm trying to merge a couple photos (UIImages) into a Image View. I'm using this method:
- (UIImage *) addImageToImage:(UIImage *)img withImage2:(UIImage *)img2{
CGSize size = CGSizeMake(finalPhoto.image.size.width, finalPhoto.image.size.height);
UIGraphicsBeginImageContext(size);
CGPoint pointImg1 = CGPointMake(0,0);
[img drawAtPoint:pointImg1];
CGPoint pointImg2 = CGPointMake(0,0);
[img2 drawAtPoint: pointImg2];
UIImage* result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
The problem is that it cant make the merge because it doesn't have the corrects points (I guess...) Here is the log:
Jan 17 09:35:20 <Error>: CGContextSaveGState: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextSetBlendMode: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextSetAlpha: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextTranslateCTM: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextScaleCTM: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextConcatCTM: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextDrawImage: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextRestoreGState: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextSaveGState: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextSetBlendMode: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextSetAlpha: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextTranslateCTM: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextScaleCTM: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextConcatCTM: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextDrawImage: invalid context 0x0
Jan 17 09:35:20 <Error>: CGContextRestoreGState: invalid context 0x0
This problems happens on iOS 6 and iOS 7. Is there a posible solution? Thanks.

Answer 1

Use below code:
- (UIImage *) addImageToImage:(UIImage *)img withImage2:(UIImage *)img2{
//merge two images for this code
CGSize newSize = CGSizeMake(512,512); // Set your bottom image size
UIGraphicsBeginImageContext(newSize);
// Use existing opacity as is
[img drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];///1st image set frame
// Apply supplied opacity if applicable
[img2 drawInRect:CGRectMake(165,332,165,120) blendMode:kCGBlendModeNormal alpha:1];//2nd image set frame with alpha value
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage; //return UIImage
}

Answer 2

My guess is that your images are nil pointers, so the rectangle you're using to create your context is empty. Check the value of size before you create your context:
NSLog(#"Size = %#", NSStringFromCGSize(size));