my image is not getting cropped - ios

Question

i have the following code that i mostly got from SO but my image still is not getting cropped, what am i doing wrong?
#synthesize TopImage;
#synthesize BottomImage;
#synthesize RotaterImage;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
TopImage = [UIImage imageNamed:#"zero.png"];
[TopImage drawAtPoint:CGPointMake(0, 0)];
[self cropImage:TopImage:0];
[self addSubview:[[UIImageView alloc] initWithImage:TopImage]];
// BottomImage = [UIImage imageNamed:#"zero.png"];
// [BottomImage drawAtPoint:CGPointMake(0, 55)];
// [self cropImage:BottomImage:50];
// [self addSubview:[[[UIImageView alloc] initWithImage:BottomImage]retain]];
// RotaterImage = [UIImage imageNamed:#"zero.png"];
// [RotaterImage drawAtPoint:CGPointMake(0, 0) blendMode:kCGBlendModeNormal alpha:0];
// [self addSubview:[[[UIImageView alloc] initWithImage:RotaterImage]retain]];
// [self cropImage:RotaterImage:50];
}
return self;
}
-(void)cropImage:(UIImage *)image:(int)startCroppingPosition{
CGRect tempRect = CGRectMake(0, startCroppingPosition, 23, 40);
CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], tempRect);
// or use the UIImage wherever you like
image = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
}
I am very new to IOS so any help is appreciated

Answer 1

You're creating a new cropped image but not telling the init method about it :)
Try this change :
-(UIImage *)cropImage:(UIImage *)image:(int)startCroppingPosition{
CGRect tempRect = CGRectMake(0, startCroppingPosition, 23, 40);
CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], tempRect);
// or use the UIImage wherever you like
UIImage *newImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
return newImage;
}
and, in init, replace
[TopImage drawAtPoint:CGPointMake(0, 0)];
with
UIImageView* topImageView = [[UIImageView alloc] initWithImage:topImage];
topImageView.frame = CGRectMake(x,y,width,height);
Your crop method now returns the newly cropped image and stores it in TopImage.
Other advice :
Class names begin with a CapitalLetter, variables begin with lowercase. TopImage should really be topImage.
Also, I would always use named parameters in your methods, so
-(void)cropImage:(UIImage *)image:(int)startCroppingPosition
should be something like
-(void)cropImage:(UIImage *)image startPosition:(int)startCroppingPosition
That will make your code much much more readable when you come back to it in a month's time (I've learned that the hard way in the past!)

Answer 2

You are only changing the image and not the image of the UIImageView,
What I would do is replace:
[self addSubview:[[UIImageView alloc] initWithImage:TopImage]];
with
UIImageView *iv = [[UIImageView alloc] initWithImage:TopImage]];
iv.tag = 1000 //number does not matter
[self.view addSubview:iv];
[iv release];
then in crop image you just add:
UIImageView *iv = [self.vief viewWithTag:1000];
iv.image = [UIImage imageWithCGImage:imageRef];
This should then work as expected!