UIImage Resize then Crop

Question

I ve been bashing my face into this one for literally days now and even though I feel constantly that I am right on the edge of revelation  I simply cannot achieve my goal   I thought  ahead of time in the conceptual phases of my design  that it would be a trivial matter to grab a image from the iPhone s camera or library  scale it down to a specified height  using a function equivalent to the Aspect Fill option of UIImageView  entirely in code   and then crop off anything that did not fit within a passed CGRect   Getting the original image from camera or library  was trivial  I am shocked at how difficult the other two steps have proved to be   The attached image shows what I am trying to achieve  Would someone please be kind enough to hold my hand  Every code example I have found so far seems to smash the image  be upside down  look like crap  draw out of bounds  or otherwise just not work correctly

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Swift version       static func imageWithImage image UIImage  newSize CGSize  - gt UIImage       UIGraphicsBeginImageContextWithOptions newSize  true  UIScreen mainScreen   scale       image drawInRect CGRectMake 0  0  newSize width  newSize height        let newImage   UIGraphicsGetImageFromCurrentImageContext         UIGraphicsEndImageContext        return newImage

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scrollView     UIScrollView alloc  initWithFrame CGRectMake 0 0 0 0 ScreenWidth ScreenHeigth         scrollView setBackgroundColor  UIColor blackColor         scrollView setDelegate self        scrollView setShowsHorizontalScrollIndicator NO        scrollView setShowsVerticalScrollIndicator NO        scrollView setMaximumZoomScale 2 0       image  image scaleToSize CGSizeMake ScreenWidth  ScreenHeigth        imageView     UIImageView alloc  initWithImage image       UIImageView  imageViewBk     UIImageView alloc  initWithImage  UIImage imageNamed   background png          self view addSubview imageViewBk       CGRect rect      rect origin x 0      rect origin y 0      rect size width   image size width      rect size height   image size height        imageView setFrame rect         scrollView setContentSize  imageView frame  size        scrollView setMinimumZoomScale  scrollView frame  size width    imageView frame  size width        scrollView setZoomScale  scrollView minimumZoomScale         scrollView addSubview imageView          self view  addSubview scrollView     then you can take screen shots to your image by this   float zoomScale   1 0    scrollView zoomScale   CGRect rect  rect origin x    scrollView contentOffset  x   zoomScale  rect origin y    scrollView contentOffset  y   zoomScale  rect size width    scrollView bounds  size width   zoomScale  rect size height    scrollView bounds  size height   zoomScale   CGImageRef cr   CGImageCreateWithImageInRect   imageView image  CGImage   rect    UIImage  cropped    UIImage imageWithCGImage cr    CGImageRelease cr

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I needed the same thing - in my case  to pick the dimension that fits once scaled  and then crop each end to fit the rest to the width   I m working in landscape  so might not have noticed any deficiencies in portrait mode    Here s my code - it s part of a categeory on UIImage  Target size in my code is always set to the full screen size of the device    implementation UIImage  Extras    pragma mark -  pragma mark Scale and crop image  -  UIImage  imageByScalingAndCroppingForSize  CGSize targetSize       UIImage  sourceImage   self      UIImage  newImage   nil          CGSize imageSize   sourceImage size      CGFloat width   imageSize width      CGFloat height   imageSize height      CGFloat targetWidth   targetSize width      CGFloat targetHeight   targetSize height      CGFloat scaleFactor   0 0      CGFloat scaledWidth   targetWidth      CGFloat scaledHeight   targetHeight      CGPoint thumbnailPoint   CGPointMake 0 0 0 0        if  CGSizeEqualToSize imageSize  targetSize     NO                 CGFloat widthFactor   targetWidth   width          CGFloat heightFactor   targetHeight   height           if  widthFactor  gt  heightFactor                         scaleFactor   widthFactor     scale to fit height                   else                       scaleFactor   heightFactor     scale to fit width                    scaledWidth    width   scaleFactor          scaledHeight   height   scaleFactor              center the image         if  widthFactor  gt  heightFactor                        thumbnailPoint y    targetHeight - scaledHeight    0 5                     else                       if  widthFactor  lt  heightFactor                                thumbnailPoint x    targetWidth - scaledWidth    0 5                                        UIGraphicsBeginImageContext targetSize      this will crop      CGRect thumbnailRect   CGRectZero      thumbnailRect origin   thumbnailPoint      thumbnailRect size width    scaledWidth      thumbnailRect size height   scaledHeight        sourceImage drawInRect thumbnailRect        newImage   UIGraphicsGetImageFromCurrentImageContext         if newImage    nil                NSLog   could not scale image                 pop the context to get back to the default     UIGraphicsEndImageContext         return newImage

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The following simple code worked for me    imageView setContentMode UIViewContentModeScaleAspectFill    imageView setClipsToBounds YES

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Here you go  This one is perfect  -   EDIT  see below comment -  Does not work with certain images  fails with  CGContextSetInterpolationQuality  invalid context 0x0 error      Resizes the image according to the given content mode  taking into account the image s orientation -  UIImage   resizedImageWithContentMode  UIViewContentMode contentMode imageToScale  UIImage  imageToScale bounds  CGSize bounds interpolationQuality  CGInterpolationQuality quality         Get the size we want to scale it to     CGFloat horizontalRatio   bounds width   imageToScale size width      CGFloat verticalRatio   bounds height   imageToScale size height      CGFloat ratio       switch  contentMode            case UIViewContentModeScaleAspectFill              ratio   MAX horizontalRatio  verticalRatio               break           case UIViewContentModeScaleAspectFit              ratio   MIN horizontalRatio  verticalRatio               break           default               NSException raise NSInvalidArgumentException format   Unsupported content mode   d   contentMode                   and here it is     CGSize newSize   CGSizeMake imageToScale size width   ratio  imageToScale size height   ratio           start scaling it     CGRect newRect   CGRectIntegral CGRectMake 0  0  newSize width  newSize height        CGImageRef imageRef   imageToScale CGImage      CGContextRef bitmap   CGBitmapContextCreate NULL                                                  newRect size width                                                  newRect size height                                                  CGImageGetBitsPerComponent imageRef                                                   0                                                  CGImageGetColorSpace imageRef                                                   CGImageGetBitmapInfo imageRef         CGContextSetInterpolationQuality bitmap  quality           Draw into the context  this scales the image     CGContextDrawImage bitmap  newRect  imageRef           Get the resized image from the context and a UIImage     CGImageRef newImageRef   CGBitmapContextCreateImage bitmap       UIImage  newImage    UIImage imageWithCGImage newImageRef           Clean up     CGContextRelease bitmap       CGImageRelease newImageRef        return newImage

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Xamarin iOS version for accepted answer on how to resize and then crop UIImage  Aspect Fill  is below      public static UIImage ScaleAndCropImage UIImage sourceImage  SizeF targetSize                var imageSize   sourceImage Size          UIImage newImage   null          var width   imageSize Width          var height   imageSize Height          var targetWidth   targetSize Width          var targetHeight   targetSize Height          var scaleFactor   0 0f          var scaledWidth   targetWidth          var scaledHeight   targetHeight          var thumbnailPoint   PointF Empty          if  imageSize    targetSize                        var widthFactor   targetWidth   width              var heightFactor   targetHeight   height              if  widthFactor  gt  heightFactor                                scaleFactor   widthFactor    scale to fit height                           else                               scaleFactor   heightFactor    scale to fit width                           scaledWidth   width   scaleFactor              scaledHeight   height   scaleFactor                 center the image             if  widthFactor  gt  heightFactor                                thumbnailPoint Y    targetHeight - scaledHeight    0 5f                            else                               if  widthFactor  lt  heightFactor                                        thumbnailPoint X    targetWidth - scaledWidth    0 5f                                                    UIGraphics BeginImageContextWithOptions targetSize  false  0 0f           var thumbnailRect   new RectangleF thumbnailPoint  new SizeF scaledWidth  scaledHeight            sourceImage Draw thumbnailRect           newImage   UIGraphics GetImageFromCurrentImageContext            if  newImage    null                        Console WriteLine  could not scale image                        pop the context to get back to the default         UIGraphics EndImageContext             return newImage

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I converted Sam Wirch s guide to swift and it worked well for me  although there s some very slight  squishing  in the final image that I couldn t resolve   func resizedCroppedImage image  UIImage  newSize CGSize  - gt  UIImage       var ratio  CGFloat   0     var delta  CGFloat   0     var offset   CGPointZero     if image size width  gt  image size height           ratio   newSize width   image size width         delta    ratio   image size width  -  ratio   image size height          offset   CGPointMake delta   2  0        else           ratio   newSize width   image size height         delta    ratio   image size height  -  ratio   image size width          offset   CGPointMake 0  delta   2            let clipRect   CGRectMake -offset x  -offset y   ratio   image size width    delta   ratio   image size height    delta      UIGraphicsBeginImageContextWithOptions newSize  true  0 0      UIRectClip clipRect      image drawInRect clipRect      let newImage   UIGraphicsGetImageFromCurrentImageContext       UIGraphicsEndImageContext       return newImage     If anyone wants the objective c version  it s on his website

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This is a version of Jane Sales  answer in Swift  Cheers       public func resizeImage image  UIImage  size  CGSize  - gt  UIImage        var returnImage  UIImage       var scaleFactor  CGFloat   1 0     var scaledWidth   size width     var scaledHeight   size height     var thumbnailPoint   CGPointMake 0  0       if  CGSizeEqualToSize image size  size            let widthFactor   size width   image size width         let heightFactor   size height   image size height          if widthFactor  gt  heightFactor               scaleFactor   widthFactor           else               scaleFactor   heightFactor                    scaledWidth   image size width   scaleFactor         scaledHeight   image size height   scaleFactor          if widthFactor  gt  heightFactor               thumbnailPoint y    size height - scaledHeight    0 5           else if widthFactor  lt  heightFactor               thumbnailPoint x    size width - scaledWidth    0 5                      UIGraphicsBeginImageContextWithOptions size  true  0       var thumbnailRect   CGRectZero     thumbnailRect origin   thumbnailPoint     thumbnailRect size width   scaledWidth     thumbnailRect size height   scaledHeight      image drawInRect thumbnailRect      returnImage   UIGraphicsGetImageFromCurrentImageContext        UIGraphicsEndImageContext        return returnImage

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This question seems to have been put to rest  but in my quest for a solution that I could more easily understand  and written in Swift   I arrived at this  also posted to  How to crop the UIImage      I wanted to be able to crop from a region based on an aspect ratio  and scale to a size based on a outer bounding extent   Here is my variation   import AVFoundation import ImageIO  class Image        class func crop image UIImage  crop source CGRect  aspect CGSize  outputExtent CGSize  - gt  UIImage            let sourceRect   AVMakeRectWithAspectRatioInsideRect aspect  source          let targetRect   AVMakeRectWithAspectRatioInsideRect aspect  CGRect origin  CGPointZero  size  outputExtent            let opaque   true  deviceScale CGFloat   0 0    use scale of device s main screen         UIGraphicsBeginImageContextWithOptions targetRect size  opaque  deviceScale           let scale   max              targetRect size width   sourceRect size width              targetRect size height   sourceRect size height           let drawRect   CGRect origin  -sourceRect origin   scale  size  image size   scale          image drawInRect drawRect           let scaledImage   UIGraphicsGetImageFromCurrentImageContext           UIGraphicsEndImageContext            return scaledImage           There are a couple things that I found confusing  the separate concerns of cropping and resizing   Cropping is handled with the origin of the rect that you pass to drawInRect  and scaling is handled by the size portion   In my case  I needed to relate the size of the cropping rect on the source  to my output rect of the same aspect ratio   The scale factor is then output   input  and this needs to be applied to the drawRect  passed to drawInRect    One caveat is that this approach effectively assumes that the image you are drawing is larger than the image context   I have not tested this  but I think you can use this code to handle cropping   zooming  but explicitly defining the scale parameter to be the aforementioned scale parameter   By default  UIKit applies a multiplier based on the screen resolution   Finally  it should be noted that this UIKit approach is higher level than CoreGraphics   Quartz and Core Image approaches  and seems to handle image orientation issues   It is also worth mentioning that it is pretty fast  second to ImageIO  according to this post here  http   nshipster com image-resizing

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Here is a Swift 3 version of Sam Wirch s guide to swift posted by William T   extension UIImage        static func resizedCroppedImage image  UIImage  newSize CGSize  - gt  UIImage            var ratio  CGFloat   0         var delta  CGFloat   0         var offset   CGPoint zero          if image size width  gt  image size height               ratio   newSize width   image size width             delta    ratio   image size width  -  ratio   image size height              offset   CGPoint x  delta   2  y  0            else               ratio   newSize width   image size height             delta    ratio   image size height  -  ratio   image size width              offset   CGPoint x  0  y  delta   2                     let clipRect   CGRect x  -offset x  y  -offset y  width   ratio   image size width    delta  height   ratio   image size height    delta          UIGraphicsBeginImageContextWithOptions newSize  true  0 0          UIRectClip clipRect          image draw in  clipRect          let newImage   UIGraphicsGetImageFromCurrentImageContext           UIGraphicsEndImageContext            return newImage

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-  UIImage  imageScale  CGFloat scaleFactor cropForSize  CGSize targetSize       targetSize    targetSize width self size targetSize      UIGraphicsBeginImageContext targetSize      this will crop      CGRect thumbnailRect   CGRectZero       thumbnailRect size width    targetSize width scaleFactor      thumbnailRect size height   targetSize height scaleFactor      CGFloat xOffset    targetSize width- thumbnailRect size width  2      CGFloat yOffset    targetSize height- thumbnailRect size height  2      thumbnailRect origin   CGPointMake xOffset yOffset         self drawInRect thumbnailRect        UIImage  newImage    UIGraphicsGetImageFromCurrentImageContext         if newImage    nil                NSLog   could not scale image               UIGraphicsEndImageContext         return newImage      Below the example of work      Left image -  origin image        Right image with scale x2    If you want to scale image but retain its frame proportions   call method this way    yourImage imageScale 2 0f cropForSize CGSizeZero

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I found that the Swift 3 posted by Evgenii Kanvets does not uniformly scale the image   Here is my Swift 4 version of the function that does not squish the image   static func resizedCroppedImage image  UIImage  newSize CGSize  - gt  UIImage            This function returns a newImage  based on image        - image is scaled uniformaly to fit into a rect of size newSize        - if the newSize rect is of a different aspect ratio from the source image            the new image is cropped to be in the center of the source image             the excess source image is removed       var ratio  CGFloat   0     var delta  CGFloat   0     var drawRect   CGRect        if newSize width  gt  newSize height            ratio   newSize width   image size width         delta    ratio   image size height  - newSize height         drawRect   CGRect x  0  y  -delta   2  width  newSize width  height  newSize height   delta         else            ratio   newSize height   image size height         delta    ratio   image size width  - newSize width         drawRect   CGRect x  -delta   2  y  0  width  newSize width   delta  height  newSize height              UIGraphicsBeginImageContextWithOptions newSize  true  0 0      image draw in  drawRect      let newImage   UIGraphicsGetImageFromCurrentImageContext       UIGraphicsEndImageContext        return newImage

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There s a great piece of code related to the resizing of images   several other operations  I came around this one when trying to figure ou how to resize images    http   vocaro com trevor blog 2009 10 12 resize-a-uiimage-the-right-way

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I modified Brad Larson s Code  It will aspect fill the image in given rect   - UIImage   scaleAndCropToSize  CGSize newSize        float ratio   self size width   self size height       UIGraphicsBeginImageContext newSize        if  ratio  gt  1            CGFloat newWidth   ratio   newSize width          CGFloat newHeight   newSize height          CGFloat leftMargin    newWidth - newHeight    2           self drawInRect CGRectMake -leftMargin  0  newWidth  newHeight              else           CGFloat newWidth   newSize width          CGFloat newHeight   newSize height   ratio          CGFloat topMargin    newHeight - newWidth    2           self drawInRect CGRectMake 0  -topMargin  newSize width  newSize height ratio               UIImage  newImage   UIGraphicsGetImageFromCurrentImageContext        UIGraphicsEndImageContext         return newImage

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An older post contains code for a method to resize your UIImage   The relevant portion is as follows      UIImage  imageWithImage  UIImage  image                 scaledToSize  CGSize newSize       UIGraphicsBeginImageContext  newSize        image drawInRect CGRectMake 0 0 newSize width newSize height       UIImage  newImage   UIGraphicsGetImageFromCurrentImageContext       UIGraphicsEndImageContext        return newImage      As far as cropping goes  I believe that if you alter the method to use a different size for the scaling than for the context  your resulting image should be clipped to the bounds of the context

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UIImage   scaleImage  UIImage   image toSize  CGSize targetSize         If scaleFactor is not touched  no scaling will occur           CGFloat scaleFactor   1 0         Deciding which factor to use to scale the image  factor   targetSize   imageSize      if  image size width  gt  targetSize width    image size height  gt  targetSize height          if     scaleFactor    targetSize width   image size width    gt   targetSize height   image size height      scale to fit width  or             scaleFactor   targetSize height   image size height     scale to fit heigth       UIGraphicsBeginImageContext targetSize           Creating the rect where the scaled image is drawn in     CGRect rect   CGRectMake  targetSize width - image size width   scaleFactor    2                                targetSize height -  image size height   scaleFactor    2                               image size width   scaleFactor  image size height   scaleFactor          Draw the image into the rect      image drawInRect rect          Saving the image  ending image context     UIImage  scaledImage   UIGraphicsGetImageFromCurrentImageContext        UIGraphicsEndImageContext         return scaledImage      I propose this one  Isn t she a beauty

[iphone] UIImage: Resize, then Crop

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