Building an Image From Multiple UIImageViews - iphone

Question

I am interested in building a Collage style app for the IPhone and IPad. I have been looking at other apps and trying to work out the method that they use to create the final image.
I am guessing that the app has a UIView and then each individual image is a UIImageView and is a subview of the main UIView. The user is then able to move each UIImageView and position them as they intend.
Now my question is, after the user has positioned all the UIImageViews on screen how do you then create the final image from what is on the screen. This of course takes into account that you will be upscaling the images to create lets say an A4 sized final print.
Can anyone share some information?
Thanks

Answer 1

You should take a look at CGContext Reference. You can do something like the following to combine imageView 1 and 2 to imageView 3.
Sample Code :
UIGraphicsBeginImageContext(imageView1.image.size);
CGRect rect = CGRectMake(0, 0, imageView1.image.size.width, imageView1.image.size.height);
[imageView1.image drawInRect:rect];
[imageView2.image drawInRect:rect blendMode:kCGBlendModeScreen alpha:0.5];
UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[imageView3 setImage:resultingImage];
GoodLuck !!!

Answer 2

If you use an UIView to include more 2 Images to merge, that you can try to capture the view to be an image to use.
//Capture View to Image
-(UIImage *)captureImageFromView
{
UIView *theView = self; //self extends UIView
if( NULL != UIGraphicsBeginImageContextWithOptions )
{
UIGraphicsBeginImageContextWithOptions(theView.bounds.size, NO, 2.0f);
}
else
{
//iOS 4.0
UIGraphicsBeginImageContext(theView.frame.size);
}
[theView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *captureImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return captureImage;
}
//Merge 2 Images to be an Image.
-(UIImage *)mergeBaseImage:(UIImage *)_baseImage
underImage:(UIImage *)_underImage
matchBaseImageSize:(BOOL)_matchBaseImageSize
{
UIGraphicsBeginImageContext(_baseImage.size);
[_baseImage drawInRect:CGRectMake(0, 0, _baseImage.size.width, _baseImage.size.height)];
if( _matchBaseImageSize )
{
[_underImage drawInRect:CGRectMake(0, 0, _baseImage.size.width, _baseImage.size.height)];
}
else
{
[_underImage drawInRect:CGRectMake(0, 0, _underImage.size.width, _underImage.size.height)];
}
UIImage *_mergedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return _mergedImage;
}
Wish it can help you.