How to take screenshot of a user defined rectangular area in cocos2d - cocos2d-iphone

Question

I need to take the screenshot in my cocos2d application. I've searched a lot, even in stack overflow. Then I found the following code:
+(UIImage*) screenshotWithStartNode:(CCNode*)stNode
{
[CCDirector sharedDirector].nextDeltaTimeZero = YES;
CGSize winSize = [[CCDirector sharedDirector] winSize];
CCRenderTexture* renTxture =
[CCRenderTexture renderTextureWithWidth:winSize.width
height:winSize.height];
[renTxture begin];
[stNode visit];
[renTxture end];
return [renTxture getUIImage];
}
Now,
Problem: The above code gives me the entire screenshot. But I am in need of the screenshot of a custom are, such as, within a CGRect(50,50,100,200).
Can anyone please help me..? Thanks...

Answer 1

Wow... found out what I need. I've changed the above method like:
-(UIImage*) screenshotWithStartNode:(CCNode*)startNode
{
[CCDirector sharedDirector].nextDeltaTimeZero = YES;
CGSize winSize = [CCDirector sharedDirector].winSize;
CCRenderTexture* rtx =
[CCRenderTexture renderTextureWithWidth:winSize.width
height:winSize.height];
[rtx begin];
[startNode visit];
[rtx end];
UIImage *tempImage = [rtx getUIImage];
CGRect imageBoundary = CGRectMake(100, 100, 300, 300);
UIGraphicsBeginImageContext(imageBoundary.size);
CGContextRef context = UIGraphicsGetCurrentContext();
// translated rectangle for drawing sub image
CGRect drawRect = CGRectMake(-imageBoundary.origin.x, -imageBoundary.origin.y, tempImage.size.width, tempImage.size.height);
// clip to the bounds of the image context
CGContextClipToRect(context, CGRectMake(0, 0, imageBoundary.size.width, imageBoundary.size.height));
// draw image
[tempImage drawInRect:drawRect];
// grab image
UIImage* subImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return subImage;
}