How to zoom in out an UIImage object when user pinches screen

Question

I would like to zoom in out an UIImage object when the user performs the standard pinch action on my application  I m currently using a UIImageView to display my image  if that detail helps in any way   I m trying to figure out how to do this  but no such luck so far   Any clues

User · Accepted Answer

Another easy way to do this is to place your UIImageView within a UIScrollView. As I describe here, you need to set the scroll view's contentSize to be the same as your UIImageView's size. Set your controller instance to be the delegate of the scroll view and implement the viewForZoomingInScrollView: and scrollViewDidEndZooming:withView:atScale: methods to allow for pinch-zooming and image panning. This is effectively what Ben's solution does, only in a slightly more lightweight manner, as you don't have the overhead of a full web view.

One issue you may run into is that the scaling within the scroll view comes in the form of transforms applied to the image. This may lead to blurriness at high zoom factors. For something that can be redrawn, you can follow my suggestions here to provide a crisper display after the pinch gesture is finished. hniels' solution could be used at that point to rescale your image.

User · Answer

As others described  the easiest solution is to put your UIImageView into a UIScrollView  I did this in the Interface Builder  xib file   In viewDidLoad  set the following variables  Set your controller to be a UIScrollViewDelegate   -  void viewDidLoad        super viewDidLoad       self scrollView minimumZoomScale   0 5      self scrollView maximumZoomScale   6 0      self scrollView contentSize   self imageView frame size      self scrollView delegate   self      You are required to implement the following method to return the imageView you want to zoom   -  UIView   viewForZoomingInScrollView  UIScrollView   scrollView       return self imageView      In versions prior to iOS9  you may also need to add this empty delegate method   -  void scrollViewDidEndZooming  UIScrollView   scrollView withView  UIView   view atScale  CGFloat scale       The Apple Documentation does a good job of describing how to do this

User · Answer

Keep in mind that you don t want to zoom in out UIImage  Instead try to zoom in out the View which contains the UIImage View Controller   I have made a solution for this problem  Take a look at my code    IBAction func scaleImage sender  UIPinchGestureRecognizer            self view transform   CGAffineTransformScale self view transform  sender scale  sender scale          sender scale   1           override func viewDidLoad             super viewDidLoad              Do any additional setup after loading the view  typically from a nib          view backgroundColor   UIColor blackColor           N B   Don t forget to hook up the PinchGestureRecognizer

User · Answer

Keep in mind that you re NEVER zooming in on a UIImage  EVER   Instead  you re zooming in and out on the view that displays the UIImage   In this particular case  you chould choose to create a custom UIView with custom drawing to display the image  a UIImageView which displays the image for you  or a UIWebView which will need some additional HTML to back it up   In all cases  you ll need to implement touchesBegan  touchesMoved  and the like to determine what the user is trying to do  zoom  pan  etc

User · Answer

Shefali s solution for UIImageView works great  but it needs a little modification   -  void pinch  UIPinchGestureRecognizer   gesture       if  gesture state    UIGestureRecognizerStateEnded            gesture state    UIGestureRecognizerStateChanged            NSLog   gesture scale    f   gesture scale            CGFloat currentScale   self frame size width   self bounds size width          CGFloat newScale   currentScale   gesture scale           if  newScale  lt  MINIMUM SCALE                newScale   MINIMUM SCALE                    if  newScale  gt  MAXIMUM SCALE                newScale   MAXIMUM SCALE                     CGAffineTransform transform   CGAffineTransformMakeScale newScale  newScale           self transform   transform          gesture scale   1             Shefali s solution had the downside that it did not scale continuously while pinching  Furthermore  when starting a new pinch  the current image scale was reset

User · Answer

Here is a solution I ve used before that does not require you to use the UIWebView     -  UIImage   scaleAndRotateImage UIImage   image       int kMaxResolution   320     Or whatever      CGImageRef imgRef   image CGImage       CGFloat width   CGImageGetWidth imgRef       CGFloat height   CGImageGetHeight imgRef         CGAffineTransform transform   CGAffineTransformIdentity      CGRect bounds   CGRectMake 0  0  width  height       if  width  gt  kMaxResolution    height  gt  kMaxResolution            CGFloat ratio   width height          if  ratio  gt  1                bounds size width   kMaxResolution              bounds size height   bounds size width   ratio                    else               bounds size height   kMaxResolution              bounds size width   bounds size height   ratio                       CGFloat scaleRatio   bounds size width   width      CGSize imageSize   CGSizeMake CGImageGetWidth imgRef   CGImageGetHeight imgRef        CGFloat boundHeight      UIImageOrientation orient   image imageOrientation      switch orient             case UIImageOrientationUp    EXIF   1             transform   CGAffineTransformIdentity              break           case UIImageOrientationUpMirrored    EXIF   2             transform   CGAffineTransformMakeTranslation imageSize width  0 0               transform   CGAffineTransformScale transform  -1 0  1 0               break           case UIImageOrientationDown    EXIF   3             transform   CGAffineTransformMakeTranslation imageSize width  imageSize height               transform   CGAffineTransformRotate transform  M PI               break           case UIImageOrientationDownMirrored    EXIF   4             transform   CGAffineTransformMakeTranslation 0 0  imageSize height               transform   CGAffineTransformScale transform  1 0  -1 0               break           case UIImageOrientationLeftMirrored    EXIF   5             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation imageSize height  imageSize width               transform   CGAffineTransformScale transform  -1 0  1 0               transform   CGAffineTransformRotate transform  3 0   M PI   2 0               break           case UIImageOrientationLeft    EXIF   6             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation 0 0  imageSize width               transform   CGAffineTransformRotate transform  3 0   M PI   2 0               break           case UIImageOrientationRightMirrored    EXIF   7             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeScale -1 0  1 0               transform   CGAffineTransformRotate transform  M PI   2 0               break           case UIImageOrientationRight    EXIF   8             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation imageSize height  0 0               transform   CGAffineTransformRotate transform  M PI   2 0               break           default               NSException raise NSInternalInconsistencyException format   Invalid image orientation                UIGraphicsBeginImageContext bounds size        CGContextRef context   UIGraphicsGetCurrentContext         if  orient    UIImageOrientationRight    orient    UIImageOrientationLeft            CGContextScaleCTM context  -scaleRatio  scaleRatio           CGContextTranslateCTM context  -height  0             else           CGContextScaleCTM context  scaleRatio  -scaleRatio           CGContextTranslateCTM context  0  -height              CGContextConcatCTM context  transform        CGContextDrawImage UIGraphicsGetCurrentContext    CGRectMake 0  0  width  height   imgRef       UIImage  imageCopy   UIGraphicsGetImageFromCurrentImageContext        UIGraphicsEndImageContext         return imageCopy      The article can be found on Apple Support at  http   discussions apple com message jspa messageID 7276709 7276709

User · Answer

Keep in mind that you re NEVER zooming in on a UIImage  EVER   Instead  you re zooming in and out on the view that displays the UIImage   In this particular case  you chould choose to create a custom UIView with custom drawing to display the image  a UIImageView which displays the image for you  or a UIWebView which will need some additional HTML to back it up   In all cases  you ll need to implement touchesBegan  touchesMoved  and the like to determine what the user is trying to do  zoom  pan  etc

User · Answer

Shafali and JRV s answers extended to include panning and pinch to zoom    define MINIMUM SCALE 0 5  define MAXIMUM SCALE 6 0  property CGPoint translation    -  void pan  UIPanGestureRecognizer   gesture       static CGPoint currentTranslation      static CGFloat currentScale   0      if  gesture state    UIGestureRecognizerStateBegan            currentTranslation    translation          currentScale   self view frame size width   self view bounds size width            if  gesture state    UIGestureRecognizerStateEnded    gesture state    UIGestureRecognizerStateChanged             CGPoint translation    gesture translationInView self view             translation x   translation x   currentTranslation x           translation y   translation y   currentTranslation y          CGAffineTransform transform1   CGAffineTransformMakeTranslation  translation x    translation y           CGAffineTransform transform2   CGAffineTransformMakeScale currentScale  currentScale           CGAffineTransform transform   CGAffineTransformConcat transform1  transform2           self view transform   transform            -  void pinch  UIPinchGestureRecognizer   gesture       if  gesture state    UIGestureRecognizerStateEnded    gesture state    UIGestureRecognizerStateChanged              NSLog   gesture scale    f   gesture scale            CGFloat currentScale   self view frame size width   self view bounds size width          CGFloat newScale   currentScale   gesture scale           if  newScale  lt  MINIMUM SCALE                newScale   MINIMUM SCALE                    if  newScale  gt  MAXIMUM SCALE                newScale   MAXIMUM SCALE                     CGAffineTransform transform1   CGAffineTransformMakeTranslation  translation x   translation y           CGAffineTransform transform2   CGAffineTransformMakeScale newScale  newScale           CGAffineTransform transform   CGAffineTransformConcat transform1  transform2           self view transform   transform          gesture scale   1

User · Answer

The simplest way to do this  if all you want is pinch zooming  is to place your image inside a UIWebView  write  small amount of html wrapper code  reference your image  and you re basically done   The more complcated way to do this is to use touchesBegan  touchesMoved  and touchesEnded to keep track of the user s fingers  and adjust your view s transform property appropriately

User · Answer

The simplest way to do this  if all you want is pinch zooming  is to place your image inside a UIWebView  write  small amount of html wrapper code  reference your image  and you re basically done   The more complcated way to do this is to use touchesBegan  touchesMoved  and touchesEnded to keep track of the user s fingers  and adjust your view s transform property appropriately

User · Answer

Below code helps to zoom UIImageView without using UIScrollView    - void HandlePinch  UIPinchGestureRecognizer  recognizer      if   recognizer state     UIGestureRecognizerStateEnded            NSLog            Scale Applied                        if   recognizer scale  lt 1 0f                 recognizer setScale 1 0f                     CGAffineTransform transform   CGAffineTransformMakeScale  recognizer scale     recognizer scale            imgView transform   transform

User · Answer

Below code helps to zoom UIImageView without using UIScrollView    - void HandlePinch  UIPinchGestureRecognizer  recognizer      if   recognizer state     UIGestureRecognizerStateEnded            NSLog            Scale Applied                        if   recognizer scale  lt 1 0f                 recognizer setScale 1 0f                     CGAffineTransform transform   CGAffineTransformMakeScale  recognizer scale     recognizer scale            imgView transform   transform

User · Answer

The simplest way to do this  if all you want is pinch zooming  is to place your image inside a UIWebView  write  small amount of html wrapper code  reference your image  and you re basically done   The more complcated way to do this is to use touchesBegan  touchesMoved  and touchesEnded to keep track of the user s fingers  and adjust your view s transform property appropriately

User · Answer

Shefali s solution for UIImageView works great  but it needs a little modification   -  void pinch  UIPinchGestureRecognizer   gesture       if  gesture state    UIGestureRecognizerStateEnded            gesture state    UIGestureRecognizerStateChanged            NSLog   gesture scale    f   gesture scale            CGFloat currentScale   self frame size width   self bounds size width          CGFloat newScale   currentScale   gesture scale           if  newScale  lt  MINIMUM SCALE                newScale   MINIMUM SCALE                    if  newScale  gt  MAXIMUM SCALE                newScale   MAXIMUM SCALE                     CGAffineTransform transform   CGAffineTransformMakeScale newScale  newScale           self transform   transform          gesture scale   1             Shefali s solution had the downside that it did not scale continuously while pinching  Furthermore  when starting a new pinch  the current image scale was reset

User · Answer

Shafali and JRV s answers extended to include panning and pinch to zoom    define MINIMUM SCALE 0 5  define MAXIMUM SCALE 6 0  property CGPoint translation    -  void pan  UIPanGestureRecognizer   gesture       static CGPoint currentTranslation      static CGFloat currentScale   0      if  gesture state    UIGestureRecognizerStateBegan            currentTranslation    translation          currentScale   self view frame size width   self view bounds size width            if  gesture state    UIGestureRecognizerStateEnded    gesture state    UIGestureRecognizerStateChanged             CGPoint translation    gesture translationInView self view             translation x   translation x   currentTranslation x           translation y   translation y   currentTranslation y          CGAffineTransform transform1   CGAffineTransformMakeTranslation  translation x    translation y           CGAffineTransform transform2   CGAffineTransformMakeScale currentScale  currentScale           CGAffineTransform transform   CGAffineTransformConcat transform1  transform2           self view transform   transform            -  void pinch  UIPinchGestureRecognizer   gesture       if  gesture state    UIGestureRecognizerStateEnded    gesture state    UIGestureRecognizerStateChanged              NSLog   gesture scale    f   gesture scale            CGFloat currentScale   self view frame size width   self view bounds size width          CGFloat newScale   currentScale   gesture scale           if  newScale  lt  MINIMUM SCALE                newScale   MINIMUM SCALE                    if  newScale  gt  MAXIMUM SCALE                newScale   MAXIMUM SCALE                     CGAffineTransform transform1   CGAffineTransformMakeTranslation  translation x   translation y           CGAffineTransform transform2   CGAffineTransformMakeScale newScale  newScale           CGAffineTransform transform   CGAffineTransformConcat transform1  transform2           self view transform   transform          gesture scale   1

User · Answer

Keep in mind that you re NEVER zooming in on a UIImage  EVER   Instead  you re zooming in and out on the view that displays the UIImage   In this particular case  you chould choose to create a custom UIView with custom drawing to display the image  a UIImageView which displays the image for you  or a UIWebView which will need some additional HTML to back it up   In all cases  you ll need to implement touchesBegan  touchesMoved  and the like to determine what the user is trying to do  zoom  pan  etc

User · Answer

Here is a solution I ve used before that does not require you to use the UIWebView     -  UIImage   scaleAndRotateImage UIImage   image       int kMaxResolution   320     Or whatever      CGImageRef imgRef   image CGImage       CGFloat width   CGImageGetWidth imgRef       CGFloat height   CGImageGetHeight imgRef         CGAffineTransform transform   CGAffineTransformIdentity      CGRect bounds   CGRectMake 0  0  width  height       if  width  gt  kMaxResolution    height  gt  kMaxResolution            CGFloat ratio   width height          if  ratio  gt  1                bounds size width   kMaxResolution              bounds size height   bounds size width   ratio                    else               bounds size height   kMaxResolution              bounds size width   bounds size height   ratio                       CGFloat scaleRatio   bounds size width   width      CGSize imageSize   CGSizeMake CGImageGetWidth imgRef   CGImageGetHeight imgRef        CGFloat boundHeight      UIImageOrientation orient   image imageOrientation      switch orient             case UIImageOrientationUp    EXIF   1             transform   CGAffineTransformIdentity              break           case UIImageOrientationUpMirrored    EXIF   2             transform   CGAffineTransformMakeTranslation imageSize width  0 0               transform   CGAffineTransformScale transform  -1 0  1 0               break           case UIImageOrientationDown    EXIF   3             transform   CGAffineTransformMakeTranslation imageSize width  imageSize height               transform   CGAffineTransformRotate transform  M PI               break           case UIImageOrientationDownMirrored    EXIF   4             transform   CGAffineTransformMakeTranslation 0 0  imageSize height               transform   CGAffineTransformScale transform  1 0  -1 0               break           case UIImageOrientationLeftMirrored    EXIF   5             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation imageSize height  imageSize width               transform   CGAffineTransformScale transform  -1 0  1 0               transform   CGAffineTransformRotate transform  3 0   M PI   2 0               break           case UIImageOrientationLeft    EXIF   6             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation 0 0  imageSize width               transform   CGAffineTransformRotate transform  3 0   M PI   2 0               break           case UIImageOrientationRightMirrored    EXIF   7             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeScale -1 0  1 0               transform   CGAffineTransformRotate transform  M PI   2 0               break           case UIImageOrientationRight    EXIF   8             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation imageSize height  0 0               transform   CGAffineTransformRotate transform  M PI   2 0               break           default               NSException raise NSInternalInconsistencyException format   Invalid image orientation                UIGraphicsBeginImageContext bounds size        CGContextRef context   UIGraphicsGetCurrentContext         if  orient    UIImageOrientationRight    orient    UIImageOrientationLeft            CGContextScaleCTM context  -scaleRatio  scaleRatio           CGContextTranslateCTM context  -height  0             else           CGContextScaleCTM context  scaleRatio  -scaleRatio           CGContextTranslateCTM context  0  -height              CGContextConcatCTM context  transform        CGContextDrawImage UIGraphicsGetCurrentContext    CGRectMake 0  0  width  height   imgRef       UIImage  imageCopy   UIGraphicsGetImageFromCurrentImageContext        UIGraphicsEndImageContext         return imageCopy      The article can be found on Apple Support at  http   discussions apple com message jspa messageID 7276709 7276709

User · Answer

Keep in mind that you don t want to zoom in out UIImage  Instead try to zoom in out the View which contains the UIImage View Controller   I have made a solution for this problem  Take a look at my code    IBAction func scaleImage sender  UIPinchGestureRecognizer            self view transform   CGAffineTransformScale self view transform  sender scale  sender scale          sender scale   1           override func viewDidLoad             super viewDidLoad              Do any additional setup after loading the view  typically from a nib          view backgroundColor   UIColor blackColor           N B   Don t forget to hook up the PinchGestureRecognizer

User · Answer

As others described  the easiest solution is to put your UIImageView into a UIScrollView  I did this in the Interface Builder  xib file   In viewDidLoad  set the following variables  Set your controller to be a UIScrollViewDelegate   -  void viewDidLoad        super viewDidLoad       self scrollView minimumZoomScale   0 5      self scrollView maximumZoomScale   6 0      self scrollView contentSize   self imageView frame size      self scrollView delegate   self      You are required to implement the following method to return the imageView you want to zoom   -  UIView   viewForZoomingInScrollView  UIScrollView   scrollView       return self imageView      In versions prior to iOS9  you may also need to add this empty delegate method   -  void scrollViewDidEndZooming  UIScrollView   scrollView withView  UIView   view atScale  CGFloat scale       The Apple Documentation does a good job of describing how to do this

User · Answer

The simplest way to do this  if all you want is pinch zooming  is to place your image inside a UIWebView  write  small amount of html wrapper code  reference your image  and you re basically done   The more complcated way to do this is to use touchesBegan  touchesMoved  and touchesEnded to keep track of the user s fingers  and adjust your view s transform property appropriately

User · Answer

Here is a solution I ve used before that does not require you to use the UIWebView     -  UIImage   scaleAndRotateImage UIImage   image       int kMaxResolution   320     Or whatever      CGImageRef imgRef   image CGImage       CGFloat width   CGImageGetWidth imgRef       CGFloat height   CGImageGetHeight imgRef         CGAffineTransform transform   CGAffineTransformIdentity      CGRect bounds   CGRectMake 0  0  width  height       if  width  gt  kMaxResolution    height  gt  kMaxResolution            CGFloat ratio   width height          if  ratio  gt  1                bounds size width   kMaxResolution              bounds size height   bounds size width   ratio                    else               bounds size height   kMaxResolution              bounds size width   bounds size height   ratio                       CGFloat scaleRatio   bounds size width   width      CGSize imageSize   CGSizeMake CGImageGetWidth imgRef   CGImageGetHeight imgRef        CGFloat boundHeight      UIImageOrientation orient   image imageOrientation      switch orient             case UIImageOrientationUp    EXIF   1             transform   CGAffineTransformIdentity              break           case UIImageOrientationUpMirrored    EXIF   2             transform   CGAffineTransformMakeTranslation imageSize width  0 0               transform   CGAffineTransformScale transform  -1 0  1 0               break           case UIImageOrientationDown    EXIF   3             transform   CGAffineTransformMakeTranslation imageSize width  imageSize height               transform   CGAffineTransformRotate transform  M PI               break           case UIImageOrientationDownMirrored    EXIF   4             transform   CGAffineTransformMakeTranslation 0 0  imageSize height               transform   CGAffineTransformScale transform  1 0  -1 0               break           case UIImageOrientationLeftMirrored    EXIF   5             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation imageSize height  imageSize width               transform   CGAffineTransformScale transform  -1 0  1 0               transform   CGAffineTransformRotate transform  3 0   M PI   2 0               break           case UIImageOrientationLeft    EXIF   6             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation 0 0  imageSize width               transform   CGAffineTransformRotate transform  3 0   M PI   2 0               break           case UIImageOrientationRightMirrored    EXIF   7             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeScale -1 0  1 0               transform   CGAffineTransformRotate transform  M PI   2 0               break           case UIImageOrientationRight    EXIF   8             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation imageSize height  0 0               transform   CGAffineTransformRotate transform  M PI   2 0               break           default               NSException raise NSInternalInconsistencyException format   Invalid image orientation                UIGraphicsBeginImageContext bounds size        CGContextRef context   UIGraphicsGetCurrentContext         if  orient    UIImageOrientationRight    orient    UIImageOrientationLeft            CGContextScaleCTM context  -scaleRatio  scaleRatio           CGContextTranslateCTM context  -height  0             else           CGContextScaleCTM context  scaleRatio  -scaleRatio           CGContextTranslateCTM context  0  -height              CGContextConcatCTM context  transform        CGContextDrawImage UIGraphicsGetCurrentContext    CGRectMake 0  0  width  height   imgRef       UIImage  imageCopy   UIGraphicsGetImageFromCurrentImageContext        UIGraphicsEndImageContext         return imageCopy      The article can be found on Apple Support at  http   discussions apple com message jspa messageID 7276709 7276709

User · Answer

Here is a solution I ve used before that does not require you to use the UIWebView     -  UIImage   scaleAndRotateImage UIImage   image       int kMaxResolution   320     Or whatever      CGImageRef imgRef   image CGImage       CGFloat width   CGImageGetWidth imgRef       CGFloat height   CGImageGetHeight imgRef         CGAffineTransform transform   CGAffineTransformIdentity      CGRect bounds   CGRectMake 0  0  width  height       if  width  gt  kMaxResolution    height  gt  kMaxResolution            CGFloat ratio   width height          if  ratio  gt  1                bounds size width   kMaxResolution              bounds size height   bounds size width   ratio                    else               bounds size height   kMaxResolution              bounds size width   bounds size height   ratio                       CGFloat scaleRatio   bounds size width   width      CGSize imageSize   CGSizeMake CGImageGetWidth imgRef   CGImageGetHeight imgRef        CGFloat boundHeight      UIImageOrientation orient   image imageOrientation      switch orient             case UIImageOrientationUp    EXIF   1             transform   CGAffineTransformIdentity              break           case UIImageOrientationUpMirrored    EXIF   2             transform   CGAffineTransformMakeTranslation imageSize width  0 0               transform   CGAffineTransformScale transform  -1 0  1 0               break           case UIImageOrientationDown    EXIF   3             transform   CGAffineTransformMakeTranslation imageSize width  imageSize height               transform   CGAffineTransformRotate transform  M PI               break           case UIImageOrientationDownMirrored    EXIF   4             transform   CGAffineTransformMakeTranslation 0 0  imageSize height               transform   CGAffineTransformScale transform  1 0  -1 0               break           case UIImageOrientationLeftMirrored    EXIF   5             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation imageSize height  imageSize width               transform   CGAffineTransformScale transform  -1 0  1 0               transform   CGAffineTransformRotate transform  3 0   M PI   2 0               break           case UIImageOrientationLeft    EXIF   6             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation 0 0  imageSize width               transform   CGAffineTransformRotate transform  3 0   M PI   2 0               break           case UIImageOrientationRightMirrored    EXIF   7             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeScale -1 0  1 0               transform   CGAffineTransformRotate transform  M PI   2 0               break           case UIImageOrientationRight    EXIF   8             boundHeight   bounds size height              bounds size height   bounds size width              bounds size width   boundHeight              transform   CGAffineTransformMakeTranslation imageSize height  0 0               transform   CGAffineTransformRotate transform  M PI   2 0               break           default               NSException raise NSInternalInconsistencyException format   Invalid image orientation                UIGraphicsBeginImageContext bounds size        CGContextRef context   UIGraphicsGetCurrentContext         if  orient    UIImageOrientationRight    orient    UIImageOrientationLeft            CGContextScaleCTM context  -scaleRatio  scaleRatio           CGContextTranslateCTM context  -height  0             else           CGContextScaleCTM context  scaleRatio  -scaleRatio           CGContextTranslateCTM context  0  -height              CGContextConcatCTM context  transform        CGContextDrawImage UIGraphicsGetCurrentContext    CGRectMake 0  0  width  height   imgRef       UIImage  imageCopy   UIGraphicsGetImageFromCurrentImageContext        UIGraphicsEndImageContext         return imageCopy      The article can be found on Apple Support at  http   discussions apple com message jspa messageID 7276709 7276709

User · Answer

Keep in mind that you re NEVER zooming in on a UIImage  EVER   Instead  you re zooming in and out on the view that displays the UIImage   In this particular case  you chould choose to create a custom UIView with custom drawing to display the image  a UIImageView which displays the image for you  or a UIWebView which will need some additional HTML to back it up   In all cases  you ll need to implement touchesBegan  touchesMoved  and the like to determine what the user is trying to do  zoom  pan  etc

[cocoa-touch] How to zoom in/out an UIImage object when user pinches screen?

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