CGSize size=CGSizeMake(79, 84);//set the width and height
UIGraphicsBeginImageContext(size);
[image drawInRect:CGRectMake(0,0,size.width,size.height)];
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
//here is the scaled image which has been changed to the size specified
UIGraphicsEndImageContext();
Это работает наверняка, и не забудьте импортировать QuartzCore FrameWork ..
Счастливого кодирования (^ _ ^) ....