Uiimage Scale



All images associated with a UIImageView object should use the same scale. If you scale an image to 240x240px, then save it to disk, and reload it, you suddenly have an image of 480x480px. Additional UIImage methods let you scale an image into a desired rectangle as you draw, and specify the compositing (blend) mode whereby the image should combine with whatever is already present. scale To Fill value scales the image without regard to the original aspect ratio, which can cause the image to appear distorted. And in the vast majority of cases,. I am using a UIImage captured from the camera and can crop the center square when in landscape. scale Aspect Fit,. Scale UIImage using one method. Since the z-values range and distribution changes between different images, it would be better to automatically scale the axes color-limits based on an analysis of the image. CGImage, scale, orientation) - the missing binding, actually - which did compile (?) and gave me the UIImage I wanted IIRC, but when using the CGImage of the new UIImage, the properties weren't initialized (width and height were 0 for example). Use uiimage to display a picture, icon, or logo in your app. iOS supports high resolution displays via the scale property on UIScreen, UIView, UIImage, and CALayer classes. AIM AIM Linux amazon server API AWS beautifulsoup conversion convert unix timestamp Core Data counting files custom XML date time file count File upload gettext() Image Orientation Image Scale Indicator install Internationalization macos MARC MARC21 MARCXML Network Activity Network Activity Indicator php PHP. Please join us on Visual Studio Developer Community and in the Xamarin and Mono organizations on GitHub to continue tracking issues. To load a UIImage correctly on iOS 4. Below is the code needed to covert back and forth between Mat's and. UIImage* destImage = [[UIImage alloc] initWithCGImage:destRef scale:0. Save UIImage from url; Split file by block size; Export UIImage to file; Get all frame from movie with avfoundation; Using avfoundation framework get movie size; How to rotate & scale uiimage; Iphone sort array. Scale variants offer a way to define the size of the image relative to layout guides in the symbol image's definition file. Scales the image up or down. It is best to specify images whose dimensions match the dimensions of the image view exactly, but image views can scale your images to fit all or some of the available space. These states changes to the different state as per user or system actions. Join GitHub today. There’s a simple way to render a UIView into a UIImage: use the view’s layer, and render it into a bitmap graphic context. Scale (SizeF size, float scaleFactor); this mimics BeginImageContextWithOptions' scale factor, where you can use the scale factor of the device if you pass in 0. A UIImage object is a high-level way to display image data. bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);. Windows Phone, however, lets you place images almost. What you can do is a class giving you back hardware info such as this one, and depending on the aspect ratio modify the file name you pass in the "FromFile" method. In iOS the task of detecting faces in a UIImage is a relatively simple task thanks to the CoreImage framework. Tile Layers are placed overtop of a map tile at a specific zoom level. scale Aspect Fit,. UIImageView - This is an iOS Widget that acts like a container for holding the image. im = uiimage creates an image component in a new figure and returns the Image object. # # newSize - the CGSize of the bounds the image must fit within. Image Buffers In-memory representation of an image Each element describes color of a single pixel Buffer size is proportional to image size. I looked into EdgeInsets but couldn’t get them to work with the image. all code snippets/ popular code snippets/ your code snippets resize UIImage. 0, it would be the size of the imageScrollView's bounds. Use uiimage to display a picture, icon, or logo in your app. You use image objects to represent image data of all kinds, and the UIImage class is capable of managing data for all image formats supported by the underlying platform. Default color is lightGray. Image data may be cached by the SDK. 0, the scale factor is set to the scale factor of the device's main screen. cgImage!, scale: 1. After all, UIImage View automatically scales and crops images according to the behavior specified by its content Mode property. Introduction. Submission failed. A UIImage object is a high-level way to display image data. Questions: I have an UIImageView with an UIImage. UIImage* sourceImage = [UIImage imageNamed:@"whatever. UIImage(Transform) @interface UIImage (Transform) Provide some commen method for UIImage. Basic three of the gestures which we are going to discuss,. I want to add an image and text to a BarButtonItem but can't in IB. Concept of UIImage and UIImageView (container) UIImage - Bitmap with different formats Ex png and jpeg. Easy rounded corners on UITableViewCell image view. Code to convert an Image (UIImage) to Grayscale in Objective-C. Similarly an image with a @3x modifier has a scale of 3. UIImage* destImage = [[UIImage alloc] initWithCGImage:destRef scale:0. size乘以image. Image objects are immutable, so you always create them from existing image data, such as an image file on disk or programmatically created image data. 1) paint image that we are going to use as brush in appropriate color and scale it 2) draw this image along the path we created in 1st part Create extension of UIImage class. 0 results in an image whose size matches the pixel-based dimensions of the image. Can anyone point out to me why when I convert it to a UIImage that I get back a gray scale image? I need it in a UIImage because I am sending it to tesseract, and the gray scale image does not give optimal OCR results. Other content modes place the image at the appropriate location in the image view’s bounds without scaling it. Objective-C +. Also, my concern is since I used latest xCode and iOS versions for development, I might have used features that were not supported with older versions. Howvere I ran into objective-c-only code snippets which are not clear to me. If, however, the file name does not end with "@2x", iOS will scale the image up by the scale factor (2). I recently had the need to take the splash screen and crossfade to the app's content, mainly to prevent rather big (and annoying) change when dealing with dark themes. It automatically handles "@2x" Retina images (although it doesn't currently do "~ipad" versions). I am working on an iOS app and have been researching and seen different approaches of converting video frames from sws_scale() to a UIImage, for. This parameter should be set to the screen scale if you are loading images for display on screen. If no need to scale, return the original image. You can create images from files, from Quartz image objects, or from raw image data you receive. if I use scale 100% with 6plus, then I need to scroll view but if I use 50% then I dont need to scroll Which zoom should I be using to get closer to device. On a device running iOS 4 or later, the behavior is identical if the device's screen has a scale of 1. Side projects, and non-profit work. I haven't tested this on non-retina devices, but this probably means that if I want the same image-size on both retina and non-retina devices, I have to check to see which one I'm currently on before I decide which size I want to. UIImage scale using vImage. UIImage+RoundedCorner. This ensures that the input layout is in the same position as the visual. Each platform requires images to be handled differently. CGImage scale:sourceImage. Image objects are immutable, so you always create them from existing image data, such as an image file on disk or programmatically created image d. Finally, it creates a UIImage from the cropped bitmap with the class factory and passes the bitmap along with a scale factor of 1. iOS - Objective-C | Scale Image Size to Fullscreen You may need to use the following imports (if needed, update your pod file accordingly) #import. I can then zoom / rearrange the image to fit a little better, but i want it to display the WHOLE image, centered and fitting inside. UIImage* destImage = [[UIImage alloc] initWithCGImage:destRef scale:0. Posts about UIImage written by AlexHedley. Find more details, please check Convert UIImage to cv::Mat. Because UIImage also has a scale property which has to have the value 2. Posts about UIImage written by AlexHedley. 0表示什么,表示当前的图片是被缩小了2. When a type isn't specified, Swift will create a String instance out of a string literal when creating a variable or constant, no matter the length. The system chooses the appropriate size variant based on the available space and configuration options. In that case, there is no scheme to identify the image as for retina using the "@2x" convention. For example, I have two images in my app, blue_button. imageOrientation];. Notice (2018-05-24): bugzilla. Scale(SizeF,float) overload that will let you specify the scale factor (and if you specify 0 as the scale factor it will be. Scaling images and creating thumbnails from UIViews Posted on October 1, 2010 by Alexander In this blog post I would like to show how you can do some common image-related tasks, like scaling an UIImage object or creating a thumbnail image from a UIView. rectangle) on UI Image (e. Also keeps the aspect ratio. Every answer on this site that I've found describes creating an UIImageView, then modifying that and displaying it, but you cant set the image of an annotation to an UIImageView, only a UIImage. png as their sprites. The project uses ARC, so you should compile UIImage-Resize. After stepping through the code, I realized that the UIImage object had a scale value of 1. How Can I modify the width and height of RectTransform ? lzt120, Sep 27, 2014 #1. Methods should be pretty self-explanatory. The coordinate space for images in the CoreGraphics and CoreImage frameworks are different. part 1) Wire the writer. To do that, we use the jpegData() method, which takes one parameter: a quality value between 0 and 1, where 1 is “maximum quality”. Concept of UIImage and UIImageView (container) UIImage – Bitmap with different formats Ex png and jpeg. The first problem is that the Scale method isn't using the @2x image for retina displays. In OpenCV all the image processing operations are usually carried out on the Mat structure. The system chooses the appropriate size variant based on the available space and configuration options. I looked into EdgeInsets but couldn’t get them to work with the image. UIImage scale using vImage. I also tried applying a scale transform to the layer, with strangely inconsistent results: Setting scale to, say, 50%, made the image view 40x40px,. It becomes 200% the size and its resolution drops to 1x. Now, if I get the pngData from the UIImage, the size of the image seems to be larger and the dimension is off. If you'd like to discuss a feature request, use our forum on swift. I don't want to use a CGAffineTransform. The project uses ARC, so you should compile UIImage-Resize. bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);. So a scale of 2 will mean that the image is half of its original size. GitHub Gist: instantly share code, notes, and snippets. After all, UIImage View automatically scales and crops images according to the behavior specified by its content Mode property. UIImage(NSData, nfloat) Constructs a UIImage from the provided data, scaled by the scale factor. The width and height values being reported from it's size property, are equal to pixel values reported via CGImageGetWidth CGImageGetHeight functions on the CGImageRef used to create the UIImage. Declaration. Now converting a UIView to a UIImage is nothing new, and there are lots of folks and forums out there that have posted solutions. I am adding a text to the images, and then scale them before placing them in the map. Join GitHub today. im = uiimage creates an image component in a new figure and returns the Image object. In this function, The key here are the two scale values — x and y. It extends the UIImage class to support scaling. Can anyone point out to me why when I convert it to a UIImage that I get back a gray scale image? I need it in a UIImage because I am sending it to tesseract, and the gray scale image does not give optimal OCR results. # # newSize - the CGSize of the bounds the image must fit within. To convert an OpenCV Mat to an UIImage we use the Core Graphics framework available in iOS. I want to assign it as follows: Pages. Join GitHub today. A point is a logical unit which maps to a pixel based on a scale factor. I want to add an image and text to a BarButtonItem but can't in IB. sd_isDecoded A bool value indicating whether the image has already been decoded. iOS but they always turn out much more blurry than in Android. Posts about UIImage written by varunup. Erica Sadun posted a Swift rewrite challenge, and the chosen function is to scale and crop an image. I put the background image on a canvas and then also two UIImages for the two hands. I am using a UIImage captured from the camera and can crop the center square when in landscape. I don't know how to scale content size to fit my png size. I looked into EdgeInsets but couldn’t get them to work with the image. By continuing to use Pastebin, you agree to our use of cookies as described in the Cookies Policy. The only gotcha is you should pass inverse of target ratio as the second argument, as according to the document the second parameter specifies the ratio of original image compared to the new scaled one. image); Swift let imageData: NSData = UIImagePNGRepresentation(self. #FFFFFF or 100x100. Additional methods:. Please try again in a few minutes. Stretching, Redrawing and Positioning with contentMode Apr 4, 2016 · 3 minute read Auto Layout Views The contentMode property of UIView allows you to control how to layout a view when the view's bounds change. Posts about UIImage written by AlexHedley. Core Image is a very powerful framework that's included in iOS and OS X. UImageFromPathScaledToSize. options specify scale of 0, on retina devices it will be set to 2, and I can confirm that on resulting UIImage scale property. Blue print) and save it again. MATLAB ® calls the uifigure function to create the new figure. imageOrientation];. Scale : CoreGraphics. UIView subclass) represents a rectangular area Defines a coordinate space Draws and handles events in that rectangle Hierarchical A view has only one superview - (UIView *)superview. Use uiimage to display a picture, icon, or logo in your app. I've found export [UIImage] as movie, but its all in ObjectiveC and I can't figure it out for Swift. Who likes this? 4. Optimized. Based on what the user is doing the image should be manipulated. "Print screen" and returns the image. TranslateTo(VisualElement, Double, Double, UInt32, Easing) Animates an elements TranslationX and TranslationY properties from their current values to the new values. contain: Scale the image uniformly (maintain the image's aspect ratio) so that both dimensions (width and height) of the image will be equal to or less than the corresponding dimension of the view (minus padding). Now, if I get the pngData from the UIImage, the size of the image seems to be larger and the dimension is off. A MediaLibrary framework in Objective-C for iOS and OS X. OK, I Understand. After stepping through the code, I realized that the UIImage object had a scale value of 1. You can create images from files, from Quartz image objects, or from raw image data you receive. To illustrate, I’ll create an image showing Mars centered in another image of Mars that’s twice as large, using the Multiply blend mode (Figure 15-7):. I have an image like this: and I'd like to resize this image to a specific width: let's say 200px where the height should. Scale(SizeF) was modified to not use the device scale factor (it didn't use to, and when we "fixed" it we broke existing code - see bug #11069 for instance - so it had to be reverted). Try using the UIImage. Key among these is its lack of support for resizing the image, a feature that is normally handled dynamically by its companion, the UIImageView component. # # newSize - the CGSize of the bounds the image must fit within. What iOS4's imageWithContentsOfFile does do is recognise if an image is the '2x' version, and sets the scale accordingly, so it displays correctly. In MyFormsPage I have an Image defined and added as a Child of the Content. Based on what the user is doing the image should be manipulated. Update 2014-05-28: I wrote this when iOS 3 or so was the hot new thing, I'm certain there are better ways to do this by now, possibly built-in. @implementation UIImage (scale) /**. 0 orientation:self. I haven't tested this on non-retina devices, but this probably means that if I want the same image-size on both retina and non-retina devices, I have to check to see which one I'm currently on before I decide which size I want to. com is now in read-only mode. At first I tried using UIImage. Otherwise, it loads the unmodified filename and sets the scale property to 1. 0) for the maximumZoomScale, thus you can scale up the image to 4 times its size, which isn’t so good as the resulting image when scaled up to a size larger than the original will be blurry. UIView subclass) represents a rectangular area Defines a coordinate space Draws and handles events in that rectangle Hierarchical A view has only one superview - (UIView *)superview. I don't want to use a CGAffineTransform. MyImageView. scale The scale factor to apply to the bitmap. Scale(SizeF,float) overload that will let you specify the scale factor (and if you specify 0 as the scale factor it will be. png")) as the above did not scale the image correctly into the UIView's size. In MyFormsPage I have an Image defined and added as a Child of the Content. * Scales an image to fit within a bounds with a size governed by. This can be used from a background thread. The coordinate space for images in the CoreGraphics and CoreImage frameworks are different. Core Image is a very powerful framework that's included in iOS and OS X. m with -fobjc-arc if your project is not using ARC. Questions: I want to cut a UIImage into a circle so that I can then use it as an annotation. Perhaps you. On iOS, which is the focus of this article, Core Image supplies 90+ filters. Image objects are immutable, so you always create them from existing image data, such as an image file on disk or programmatically created image d. FromImage(mypicture. Creates a new UIImage from the provided image data. I want to assign it as follows: Pages. iOS: Converting UIImage to RGBA8 Bitmaps and Back September 22, 2010 by Paul Solt in iPhone Edited 8/24/11: Fixed a bug with alpha transparency not being preserved. 0) for the maximumZoomScale, thus you can scale up the image to 4 times its size, which isn’t so good as the resulting image when scaled up to a size larger than the original will be blurry. Crop and resize UIImage to fit from centre. 1) paint image that we are going to use as brush in appropriate color and scale it 2) draw this image along the path we created in 1st part Create extension of UIImage class. If you load an image from a file whose name includes the @2x modifier, the scale is set to 2. Applying a different scale factor changes the size of the image as reported by the size property. Core Image is a very powerful framework that's included in iOS and OS X. The width and height values being reported from it's size property, are equal to pixel values reported via CGImageGetWidth CGImageGetHeight functions on the CGImageRef used to create the UIImage. This parameter must contain: 100x100, 100x100. If you need help with an AlamofireImage feature, use our forum on swift. Use uiimage to display a picture, icon, or logo in your app. Save UIImage from url; Split file by block size; Export UIImage to file; Get all frame from movie with avfoundation; Using avfoundation framework get movie size; How to rotate & scale uiimage; Iphone sort array. Convert to RGB formats for rendering/effects. - UIImage+Scale. e UIImagePickerController - Some time user wants to select their photo from Album or capture photo and use their photo to. Introduction. Questions: I have a UIImage that is UIImageOrientationUp (portrait) that I would like to rotate counter-clockwise by 90 degrees (to landscape). iOS – Objective-C | Scale Image Size to Fullscreen You may need to use the following imports (if needed, update your pod file accordingly) #import. The first problem is that the Scale method isn't using the @2x image for retina displays. I want to add an image and text to a BarButtonItem but can’t in IB. Perhaps you. Now converting a UIView to a UIImage is nothing new, and there are lots of folks and forums out there that have posted solutions. 0 for photo), and the orientation the data should be interpreted as being in. According to the iOS Developer Library: The content mode specifies how the cached bitmap of the view's layer is adjusted when the view's bounds change. Scale(SizeF) was modified to not use the device scale factor (it didn't use to, and when we "fixed" it we broke existing code - see bug #11069 for instance - so it had to be reverted). Scale to fill for UIColor pattern UIImage Posted on May 26, 2015 May 26, 2015 by serhatsezer Sometimes we need to scale to fill our images to fit in certain image view. If it finds a 2x, it loads that image and sets the scale property of the returned UIImage object to 2. Stretching, Redrawing and Positioning with contentMode Apr 4, 2016 · 3 minute read Auto Layout Views The contentMode property of UIView allows you to control how to layout a view when the view's bounds change. CIImage doesn't support scaled resolutions (1x/2x), so when UIImage(named:) pulls the 2x asset, the scale information is lost in the conversion to CIImage. each phone has high scale factor due to that reason images , display in sharp and clear. scale The scale factor to apply to the bitmap. Now, if I get the pngData from the UIImage, the size of the image seems to be larger and the dimension is off. I am adding a text to the images, and then scale them before placing them in the map. UIImage(String) Creates a UIImage by loading from the provided file name. 0 (from:) which returns an optional UIImage. Also keeps the aspect ratio. Tile Layers are placed overtop of a map tile at a specific zoom level. The Secret of Storing and Loading UIImage(s) The solution couldn't be any simpler: load the stored image with a scale based on the current device screen render factor. And in the vast majority of cases,. This parameter should be set to the screen scale if you are loading images for display on screen. How about if you need to scale, pan and rotate gesture to an image in your native iOS application. Try using the UIImage. Image process is based on Core Graphics and vImage. MATLAB ® calls the uifigure function to create the new figure. If no need to scale, return the original image. Snipplr lets your store and share all of your commonly used pieces of code and HTML with other programmers and designers. if I use scale 100% with 6plus, then I need to scroll view but if I use 50% then I dont need to scroll Which zoom should I be using to get closer to device. This checks to see whether the iOS4 features are present, so this code should work on devices running prior OS versions as well. For example, suppose we press the Home button and a phone call comes in then the currently running app changes its state to the response. It extends the UIImage class to support scaling. Optimized for Neon on Arm. Join GitHub today. After some snooping around in Apple's UIImage reference , I realized the fix was simple: I just had to add "@2x" to my image's filename. Use uiimage to display a picture, icon, or logo in your app. September 25, 2013 varunup align, center, Objective C, UIImage, UIImageView, xCode Leave a comment UITableView update Super View from Its Cell I fought with UITable view and found that there should be some solution to update the Super view according to the selected cell from UITableView. Create and decode a image with the specify image data and scale. This is very easy without a navigation bar, but with one it's a bit more involved so I thought a blog post would be in order. For showing the image in UIImageView to fit in the frame from centre, set two properties of UIImageView. UIImage Apple describes a UIImage object as a high-level way to display image data. 0 orientation:self. We use cookies for various purposes including analytics. You can get the scale factor using:. When we use images in our application then we face different type of scenarios while handling the image. For some reason your suggested change could not be submitted. UIImage的scale及size 博文 来自: yungeIOS的博客 UIImage 的扩展方法——裁剪 图片 和等比列 缩放 图片 -翻转-圆形等 04-16 阅读数 3639. 0; Set this up when you create the cell (make sure you `#import ` at the top, of course). Crop Image from an Image in Objective C Here is the code to cut a piece from an Image or say UIImage + (UIImage *)cropImage:(UIImage *)image withArea:(CGRect)rect andScale:(int) scale{. Render UIView to UIImage. Side projects, and non-profit work. For example, suppose we press the Home button and a phone call comes in then the currently running app changes its state to the response. If the changes to the width and height of an image are not in proportion this can lead to the image looking stretched and distorted. png, UIImage. png as their sprites. 1) paint image that we are going to use as brush in appropriate color and scale it 2) draw this image along the path we created in 1st part Create extension of UIImage class. GitHub Gist: instantly share code, notes, and snippets. It wont let me use a UIImage in the Form. 以下をextensionで追加. Pass it the CGImage, the scale it was taken at (1. I want to assign a copy of these picture to two variables. Ok, good intro, but I'd really just like to see some example code. I have a 2D Sprite and a UIImage objects, both having same. The button UIImage is just that, an Image, and the original needs to be replaced with the tinted image for what ever state of the button you are trying to change. 0; Set this up when you create the cell (make sure you `#import ` at the top, of course). Additional UIImage methods let you scale an image into a desired rectangle as you draw, and specify the compositing (blend) mode whereby the image should combine with whatever is already present. I want to assign it as follows: Pages. @implementation UIImage (scale) /**. 0, the scale factor is set to the scale factor of the device’s main screen. Snipplr lets your store and share all of your commonly used pieces of code and HTML with other programmers and designers. It wont let me use a UIImage in the Form. Generate a UIImage from an SF symbol. Proceed with caution. The code for working with the queued operations (queuedOp) we will look into in a future post. Please try again in a few minutes. The process for generating a dynamically-colored UIImage is pretty simple: draw a grayscale image, mask it with itself (to bound the drawing area to the image itself), then overlay the color you want, with the blend mode set to color burn. Questions: I want to cut a UIImage into a circle so that I can then use it as an annotation. Displaying an image in Xamarin. However I still think it's nice to keep the following snippet of code on hand, be it as an instance or class method, or even by extending UIImage with a category. but i found this useful and applied in my current project as well. UIImage category for convenient image format decoding/encoding. 一、UIImage的size,scale属性 先想一个问题“一个图像的尺寸到底是多大呢?” 第一反应可能就是image. I've tried to google around for a c# sample that could explain how to resize image files to thumbnails (thus keeping aspect ratio). For some reason your suggested change could not be submitted. This parameter should be set to the screen scale if you are loading images for display on screen. UIImage resize (Scale proportion) [duplicate] Possible Duplicate: Resize UIImage with aspect ratio? The following piece of code is resizing the image perfectly, but the problem is that it messes up the aspect ratio (resulting in a skewed image). if I use scale 100% with 6plus, then I need to scroll view but if I use 50% then I dont need to scroll Which zoom should I be using to get closer to device. all code snippets/ popular code snippets/ your code snippets resize UIImage. public UIKit. I could have described my distance from my house to New York as 20 miles, or disregarding traffic, as 18 minutes at 65mph. We set a large number (4. Submission failed. im = uiimage creates an image component in a new figure and returns the Image object. UIImage* destImage = [[UIImage alloc] initWithCGImage:destRef scale:0. I have a UIImageView and the objective is to scale it down proportionally by giving it either a height or width. Suppose we have an UIImageView with name imageView and have to set this in center dynamically then we can follow the below step. When we use images in our application then we face different type of scenarios while handling the image. And this function also preserve the associated value in UIImage+Metadata. I guess you came to this post by searching similar kind of issues in any of the search engine and hope that this resolved your problem. The resolution of a iPhone 5 is 640×1136 pixels. I want to assign a copy of these picture to two variables. If you'd like to discuss AlamofireImage best practices, use our forum on swift. This is very easy without a navigation bar, but with one it's a bit more involved so I thought a blog post would be in order. In Prototyping iOS Animations in Swift I introduced the a range of block-based functions that UIKit provides to create tweened animations and how a simple animation can be programmatically altered with some random variation to create more complex scenes. UIImage resize (Scale proportion) [duplicate] Possible Duplicate: Resize UIImage with aspect ratio? The following piece of code is resizing the image perfectly, but the problem is that it messes up the aspect ratio (resulting in a skewed image). mrballoon · cocoa ios mac scale Save UIImage to Desktop on iOS Simulator. Try using the UIImage. The first problem is that the Scale method isn't using the @2x image for retina displays. I've tried to google around for a c# sample that could explain how to resize image files to thumbnails (thus keeping aspect ratio). MyFormsPage. each phone has high scale factor due to that reason images , display in sharp and clear. Code to convert an Image (UIImage) to Grayscale in Objective-C. 官方文档点蓝色文字:UIImage、CIImage、CGImage。 这篇文章是对官方文档的学习笔记,不是翻译,对文档抽象的地方加了解释和示例,对啰嗦的地方删掉。.