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I am creating a quiz app and having trouble changing the image which is displayed of a specific imageview that is generated in a for loop.
The following code is responsible for generating the imageviews based on the amount of questions in that specific quiz. It is called in the viewDidLoad() method:
var imageView = UIImageView()
func addProgressImages(to view: UIView, count: Int){
let screenSize = UIScreen.main.bounds.size
for i in 0..<count {
let spacing: CGFloat = 2
let tag = i + 888
let width: CGFloat = screenSize.width/CGFloat(count)
let height: CGFloat = width
if let view = view.viewWithTag(tag){
view.removeFromSuperview()
}
let x = spacing + CGFloat(i) * width
imageView = UIImageView(frame: CGRect(x: x, y: 100, width: width - spacing, height: height))
imageView.image = UIImage(named: "question_progress_empty")
imageView.tag = tag
imageView.contentMode = .scaleAspectFit
view.addSubview(imageView)
//print("imageviews displaying")
}
}
I have made an attempt to change some of the images to another image when the user selects an answer to that question with an if statement:
func changeImage() {
if (optA != questionAns){
imageView.image = UIImage(named: "wrong_answer")
print("opta")
}else if(optB == questionAns){
imageView.image = UIImage(named: "wrong_answer")
print("optb")
}else if(optC == questionAns){
print("optc")
imageView.image = UIImage(named: "wrong_answer")
}else{
print("if statement not initialised")
}
}
https://imgur.com/a/zwJ4EVn - This is the output of the above code
Currently, only the last image will be changed when a user clicks a button.
I need help with modifying the imageview which is related to that specific question, e.g. if question 2 is answered, only that imageview will change while the rest remain unmodified.
Hopefully that explanation made any sense, any input would be appreciated,
Thanks.
See you are doing few things wrong.
you have taken UIImageView as instance variable as below, so after
creating all the images its holding the reference to the last
imageView.
var imageView = UIImageView()
Make the var imageView as local variable and in the func
changeImage() get the proper imageView using its tag value then
try to change its image.
If any doubt plz comment.
How to get the imageView back in changeImage() check below code.
let tag = 888 + (questionNumber - 1)
if let imageView = view.viewWithTag(tag) as? UIImageView {
// Change imageView's image here
}
You will probably want to create an array of image views:
var imageViews = [UIImageView]()
And add your UIImagesViews to that array in your loop:
for i in 0..<count {
var imageView = UIImageView()
// additional setup...
imageViews.append(imageView)
}
Then, you can later iterate over your array and change the images:
for imageView in imageViews {
imageView.image = UIImage(named: "wrong_answer")
// etc.
}
I have a UIScrollView, and am using a UIPageControl to present images. The moment the first image appears, the program crashes and indicates a nil value was found.
EDIT: I'm no longer downloading images for the Scroll View, yet I'm still getting the error. The image appears and then the program crashes. Here is the stripped down code. Totally at a loss at this point. FYI, the reason I declare the variable i is I intend to loop and add additional images:
import UIKit
class HistoryViewController: UIViewController {
#IBOutlet weak var scrollView: UIScrollView!
var frame = CGRect(origin: CGPoint(x: 0,y :0), size: CGSize(width: 0, height: 0))
override func viewDidLoad() {
super.viewDidLoad()
self.scrollView.isPagingEnabled = true
let i = 0
frame.origin.x = self.scrollView.frame.size.width * CGFloat(i)
frame.size = self.scrollView.frame.size
let subView = UIImageView(frame: frame)
subView.image = UIImage(named: "maudite")
subView.contentMode = .scaleAspectFit
self.scrollView.addSubview(subView)
self.scrollView.contentSize = CGSize(width: self.scrollView.frame.size.width * CGFloat(1), height: self.scrollView.frame.size.height)
}
}
.....................
I have two theories why this is happening. The first is that The images for the subView that I add to the ScrollView haven't loaded yet. I'm using AlamoFireImage, which downloads images asynchronously.
This is the code that configures the Scroll View:
func configureScrollView() {
self.myScrollView.isPagingEnabled = true
for index in 0..<imageURLS.count {
frame.origin.x = self.myScrollView.frame.size.width * CGFloat(index)
frame.size = self.myScrollView.frame.size
let subView = UIImageView(frame: frame)
if let url = URL(string: imageURLS[index]) {
subView.af_setImage(withURL: (url))
subView.contentMode = .scaleAspectFit
self.myScrollView.addSubview(subView)
}
}
self.myScrollView.contentSize = CGSize(width: self.myScrollView.frame.size.width * CGFloat(imageURLS.count), height: self.myScrollView.frame.size.height)
pageControl.numberOfPages = imageURLS.count
}
The other thing that might be the cause of the issue is that I first have to download the image URL's. I do this and store them in an array. When that is complete, I call the configureScrollView(). I do the call on the Main Thread. Does the function then run on the Main Thread?
for dict in responseArray {
if let url = dict["fileName"] as? String {
let fullURL = "http://www.smarttapp.com" + url
print(fullURL)
self.imageURLS.append(fullURL)
}
}
DispatchQueue.main.async {
self.activityIndicator.stopAnimating()
self.activityIndicator.isHidden = true
self.networkingState = .finishedSearching
self.configureScrollView()
}
}
I have a UIScrollView decendent that implements a takeScreenshot method that looks like this:
-(void)takeScreenshot {
CGRect contextRect = CGRectMake(0, 0, 768, 1004);
UIGraphicsBeginImageContext(contextRect.size);
[self.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// do something with the viewImage here.
}
This basically moves to the top of the scroll view, and takes a screenshot of the visible area. It works fine when the iPad is oriented portrait, but when it's in landscape the bottom of the image is cut off (as the height of the visible area is only 748, not 1004).
Is it possible to get a snapshot of the UIScrollView, including areas not on screen? Or do I need to scroll the view down, take a second photo and stitch them together?
Here is code that works ...
- (IBAction) renderScrollViewToImage
{
UIImage* image = nil;
UIGraphicsBeginImageContext(_scrollView.contentSize);
{
CGPoint savedContentOffset = _scrollView.contentOffset;
CGRect savedFrame = _scrollView.frame;
_scrollView.contentOffset = CGPointZero;
_scrollView.frame = CGRectMake(0, 0, _scrollView.contentSize.width, _scrollView.contentSize.height);
[_scrollView.layer renderInContext: UIGraphicsGetCurrentContext()];
image = UIGraphicsGetImageFromCurrentImageContext();
_scrollView.contentOffset = savedContentOffset;
_scrollView.frame = savedFrame;
}
UIGraphicsEndImageContext();
if (image != nil) {
[UIImagePNGRepresentation(image) writeToFile: #"/tmp/test.png" atomically: YES];
system("open /tmp/test.png");
}
}
The last few lines simply write the image to /tmp/test.png and then opens it in Preview.app. This obviously only works on in the Simulator :-)
Complete project in the ScrollViewScreenShot Github Repository
For me, the currently accepted answer from Stefan Arentz didn't work.
I had to implement this on iOS 8 and above, and tested on the iPhone. The accepted answer just renders the visible part of a scroll view, while the rest of image remains blank.
I tried fixing this using drawViewHierarchyInRect - no luck. Depending on afterScreenUpdates being true or false I got stretched part of image or only part of the contents.
The only way I've found to achieve correct snapshotting of a UIScrollView's entire contents is to add it to another temporary view and then render it.
Sample code is below (scrollview is outlet in my VC)
func getImageOfScrollView() -> UIImage {
var image = UIImage()
UIGraphicsBeginImageContextWithOptions(self.scrollView.contentSize, false, UIScreen.mainScreen().scale)
// save initial values
let savedContentOffset = self.scrollView.contentOffset
let savedFrame = self.scrollView.frame
let savedBackgroundColor = self.scrollView.backgroundColor
// reset offset to top left point
self.scrollView.contentOffset = CGPointZero
// set frame to content size
self.scrollView.frame = CGRectMake(0, 0, self.scrollView.contentSize.width, self.scrollView.contentSize.height)
// remove background
self.scrollView.backgroundColor = UIColor.clearColor()
// make temp view with scroll view content size
// a workaround for issue when image on ipad was drawn incorrectly
let tempView = UIView(frame: CGRectMake(0, 0, self.scrollView.contentSize.width, self.scrollView.contentSize.height))
// save superview
let tempSuperView = self.scrollView.superview
// remove scrollView from old superview
self.scrollView.removeFromSuperview()
// and add to tempView
tempView.addSubview(self.scrollView)
// render view
// drawViewHierarchyInRect not working correctly
tempView.layer.renderInContext(UIGraphicsGetCurrentContext())
// and get image
image = UIGraphicsGetImageFromCurrentImageContext()
// and return everything back
tempView.subviews[0].removeFromSuperview()
tempSuperView?.addSubview(self.scrollView)
// restore saved settings
self.scrollView.contentOffset = savedContentOffset
self.scrollView.frame = savedFrame
self.scrollView.backgroundColor = savedBackgroundColor
UIGraphicsEndImageContext()
return image
}
Working Example of UIView Extension with handling for UIScrollView:
extension UIView {
func screenshot() -> UIImage {
if(self is UIScrollView) {
let scrollView = self as! UIScrollView
let savedContentOffset = scrollView.contentOffset
let savedFrame = scrollView.frame
UIGraphicsBeginImageContext(scrollView.contentSize)
scrollView.contentOffset = .zero
self.frame = CGRect(x: 0, y: 0, width: scrollView.contentSize.width, height: scrollView.contentSize.height)
self.layer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext();
scrollView.contentOffset = savedContentOffset
scrollView.frame = savedFrame
return image!
}
UIGraphicsBeginImageContext(self.bounds.size)
self.layer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image!
}
}
I took this solution from #Roopesh Mittal's answer and made it safer/cleaner.
Swift 5 compatible
fileprivate extension UIScrollView {
func screenshot() -> UIImage? {
let savedContentOffset = contentOffset
let savedFrame = frame
UIGraphicsBeginImageContext(contentSize)
contentOffset = .zero
frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
guard let context = UIGraphicsGetCurrentContext() else { return nil }
layer.render(in: context)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext();
contentOffset = savedContentOffset
frame = savedFrame
return image
}
}
A refined Swift 4.x/5.0 version, based on #RyanG 's answer:
fileprivate extension UIScrollView {
func screenshot() -> UIImage? {
// begin image context
UIGraphicsBeginImageContextWithOptions(contentSize, false, 0.0)
// save the orginal offset & frame
let savedContentOffset = contentOffset
let savedFrame = frame
// end ctx, restore offset & frame before returning
defer {
UIGraphicsEndImageContext()
contentOffset = savedContentOffset
frame = savedFrame
}
// change the offset & frame so as to include all content
contentOffset = .zero
frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
guard let ctx = UIGraphicsGetCurrentContext() else {
return nil
}
layer.render(in: ctx)
let image = UIGraphicsGetImageFromCurrentImageContext()
return image
}
}
In iOS 13 I have ran into issue that this line won't work
frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
to fix the issue, I am removing scrollview from parent and then attaching in after taking the screenshot.
Full Code:
func screenshot() -> UIImage? {
let savedContentOffset = contentOffset
let savedFrame = frame
defer {
contentOffset = savedContentOffset
frame = savedFrame
}
contentOffset = .zero
frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
let image = UIGraphicsImageRenderer(bounds: CGRect(origin: .zero, size: contentSize)).image { renderer in
let context = renderer.cgContext
layer.render(in: context)
}
return image
}
Get Screenshot:
func getScreenshot() -> UIImage? {
scrollView.removeFromSuperview()
let image = scrollView.screenshot()
addScrollView()
return image
}
SWIFT 3 version:
func snapshot() -> UIImage?
{
UIGraphicsBeginImageContext(scrollView.contentSize)
let savedContentOffset = scrollView.contentOffset
let savedFrame = scrollView.frame
scrollView.contentOffset = CGPoint.zero
scrollView.frame = CGRect(x: 0, y: 0, width: scrollView.contentSize.width, height: scrollView.contentSize.height)
scrollView.layer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
scrollView.contentOffset = savedContentOffset
scrollView.frame = savedFrame
UIGraphicsEndImageContext()
return image
}
This worked for me
As many have pointed, current solution doesn't work, and others solutions suggest removing scrollview from superview, which leads into loosing all the constraints.
Here I'm temporarily disabling all constraints related to scroll view and turn them on after screenshot is taken:
extension UIScrollView {
func screenshot() -> UIImage? {
UIGraphicsBeginImageContextWithOptions(contentSize, false, 0.0)
// save the orginal offset, take a ref to all constraints related to the view
let savedContentOffset = contentOffset
let actualConstraints = relatedConstraints()
// deactivate non needed constraints so they won't stop us from resiging scroll view
NSLayoutConstraint.deactivate(actualConstraints)
// enable auth generated constraints based on the frame
translatesAutoresizingMaskIntoConstraints = true
frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
contentOffset = .zero
defer {
UIGraphicsEndImageContext()
// reset original constraints
translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate(actualConstraints)
// layout superview needed before resetting content offset
superview?.layoutIfNeeded()
contentOffset = savedContentOffset
}
guard let ctx = UIGraphicsGetCurrentContext() else {
return nil
}
layer.render(in: ctx)
let image = UIGraphicsGetImageFromCurrentImageContext()
return image
}
}
extension UIView {
func relatedConstraints() -> [NSLayoutConstraint] {
var constraints = self.constraints
var parent = superview
while parent != nil {
constraints.append(contentsOf: parent!.constraints.filter { $0.firstItem === self || $0.secondItem === self })
parent = parent!.superview
}
return constraints
}
}
SWIFT 3 version thanks to #gleb vodovozov:
func getImageOfScrollView()->UIImage{
var image = UIImage();
UIGraphicsBeginImageContextWithOptions(self.scrollView.contentSize, false, UIScreen.main.scale)
// save initial values
let savedContentOffset = self.scrollView.contentOffset;
let savedFrame = self.scrollView.frame;
let savedBackgroundColor = self.scrollView.backgroundColor
// reset offset to top left point
self.scrollView.contentOffset = CGPoint.zero;
// set frame to content size
self.scrollView.frame = CGRect(x: 0, y: 0, width: self.scrollView.contentSize.width, height: self.scrollView.contentSize.height)
// remove background
self.scrollView.backgroundColor = UIColor.clear
// make temp view with scroll view content size
// a workaround for issue when image on ipad was drawn incorrectly
let tempView = UIView(frame: CGRect(x: 0, y: 0, width: self.scrollView.contentSize.width, height: self.scrollView.contentSize.height))
// save superview
let tempSuperView = self.scrollView.superview
// remove scrollView from old superview
self.scrollView.removeFromSuperview()
// and add to tempView
tempView.addSubview(self.scrollView)
// render view
// drawViewHierarchyInRect not working correctly
tempView.layer.render(in: UIGraphicsGetCurrentContext()!)
// and get image
image = UIGraphicsGetImageFromCurrentImageContext()!;
// and return everything back
tempView.subviews[0].removeFromSuperview()
tempSuperView?.addSubview(self.scrollView)
// restore saved settings
self.scrollView.contentOffset = savedContentOffset;
self.scrollView.frame = savedFrame;
self.scrollView.backgroundColor = savedBackgroundColor
UIGraphicsEndImageContext();
return image
}
Here's another way of doing it, which takes the zoom level into account. I have a scrollview with 4 different UIImageView layers in it, and I want to take a screenshot of their current state:
float theScale = 1.0f / theScrollView.zoomScale;
// The viewing rectangle in absolute coordinates
CGRect visibleArea = CGRectMake((int)(theScrollView.contentOffset.x * theScale), (int)(theScrollView.contentOffset.y * theScale),
(int)(theScrollView.bounds.size.width * theScale), (int)(theScrollView.bounds.size.height * theScale));
NSArray *layers = [NSArray arrayWithObjects:imageLayer1, imageLayer2, imageLayer3, imageLayer4, nil];
UIGraphicsBeginImageContext(visibleArea.size);
for (UIImageView *layer in layers) {
CALayer *coreLayer = layer.layer;
coreLayer.bounds = CGRectMake(layer.frame.origin.x - visibleArea.origin.x, layer.frame.origin.y - visibleArea.origin.y, layer.frame.size.width, layer.frame.size.height);
[coreLayer renderInContext:UIGraphicsGetCurrentContext()];
}
UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
This takes the screenshot in absolute coordinates. That is, if you have a 2048*2048 image in the scrollview and you can see about a quarter of it, then regardless of the resolution of your screen it would take a screenshot of 512*512. If you want to take a screenshot at your screen resolution (say, 320*480) then you have to adjust the image as follows, directly after the above code:
UIGraphicsBeginImageContext(theScrollView.frame.size);
[screenshot drawInRect:CGRectMake(0, 0, theScrollView.frame.size.width, theScrollView.frame.size.height)];
UIImage *smallScreenshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
If you don't want to expand your scroll view beyond the entire screen (and it won't work with autolayout anyway) there's a better way.
You can use core graphics transforms in conjunction with the contentOffset of the scroll view to accomplish the same thing.
//
// ScrollViewSnapshotter.swift
// ScrollViewSnapshotter
//
// Created by Moshe Berman on 4/10/16.
// Copyright © 2016 Moshe Berman. All rights reserved.
//
import UIKit
class ScrollViewSnapshotter: NSObject {
func PDFWithScrollView(scrollview: UIScrollView) -> NSData {
/**
* Step 1: The first thing we need is the default origin and size of our pages.
* Since bounds always start at (0, 0) and the scroll view's bounds give us
* the correct size for the visible area, we can just use that.
*
* In the United States, a standard printed page is 8.5 inches by 11 inches,
* but when generating a PDF it's simpler to keep the page size matching the
* visible area of the scroll view. We can let our printer software (such
* as the Preview app on OS X or the Printer app on iOS) do the scaling.
*
* If we wanted to scale ourselves, we could multiply each of those
* numbers by 72, to get the number of points for each dimension.
* We would have to change how we generated the the pages below, so
* for simplicity, we're going to stick to one page per screenful of content.
*/
let pageDimensions = scrollview.bounds
/**
* Step 2: Now we need to know how many pages we will need to fit our content.
* To get this, we divide our scroll views dimensions by the size
* of each page, in either direction.
* We also need to round up, so that the pages don't get clipped.
*/
let pageSize = pageDimensions.size
let totalSize = scrollview.contentSize
let numberOfPagesThatFitHorizontally = Int(ceil(totalSize.width / pageSize.width))
let numberOfPagesThatFitVertically = Int(ceil(totalSize.height / pageSize.height))
/**
* Step 3: Set up a Core Graphics PDF context.
*
* First we create a backing store for the PDF data, then
* pass it and the page dimensions to Core Graphics.
*
* We could pass in some document information here, which mostly cover PDF metadata,
* including author name, creator name (our software) and a password to
* require when viewing the PDF file.
*
* Also note that we can use UIGraphicsBeginPDFContextToFile() instead,
* which writes the PDF to a specified path. I haven't played with it, so
* I don't know if the data is written all at once, or as each page is closed.
*/
let outputData = NSMutableData()
UIGraphicsBeginPDFContextToData(outputData, pageDimensions, nil)
/**
* Step 4: Remember some state for later.
* Then we need to clear the content insets, so that our
* core graphics layer and our content offset match up.
* We don't need to reset the content offset, because that
* happens implicitly, in the loop below.
*/
let savedContentOffset = scrollview.contentOffset
let savedContentInset = scrollview.contentInset
scrollview.contentInset = UIEdgeInsetsZero
/**
* Step 6: Now we loop through the pages and generate the data for each page.
*/
if let context = UIGraphicsGetCurrentContext()
{
for indexHorizontal in 0 ..< numberOfPagesThatFitHorizontally
{
for indexVertical in 0 ..< numberOfPagesThatFitVertically
{
/**
* Step 6a: Start a new page.
*
* This automatically closes the previous page.
* There's a similar method UIGraphicsBeginPDFPageWithInfo,
* which allows you to configure the rectangle of the page and
* other metadata.
*/
UIGraphicsBeginPDFPage()
/**
* Step 6b:The trick here is to move the visible portion of the
* scroll view *and* adjust the core graphics context
* appropriately.
*
* Consider that the viewport of the core graphics context
* is attached to the top of the scroll view's content view
* and we need to push it in the opposite direction as we scroll.
* Further, anything not inside of the visible area of the scroll
* view is clipped, so scrolling will move the core graphics viewport
* out of the rendered area, producing empty pages.
*
* To counter this, we scroll the next screenful into view, and adjust
* the core graphics context. Note that core graphics uses a coordinate
* system which has the y coordinate decreasing as we go from top to bottom.
* This is the opposite of UIKit (although it matches AppKit on OS X.)
*/
let offsetHorizontal = CGFloat(indexHorizontal) * pageSize.width
let offsetVertical = CGFloat(indexVertical) * pageSize.height
scrollview.contentOffset = CGPointMake(offsetHorizontal, offsetVertical)
CGContextTranslateCTM(context, -offsetHorizontal, -offsetVertical) // NOTE: Negative offsets
/**
* Step 6c: Now we are ready to render the page.
*
* There are faster ways to snapshot a view, but this
* is the most straightforward way to render a layer
* into a context.
*/
scrollview.layer.renderInContext(context)
}
}
}
/**
* Step 7: End the document context.
*/
UIGraphicsEndPDFContext()
/**
* Step 8: Restore the scroll view.
*/
scrollview.contentInset = savedContentInset
scrollview.contentOffset = savedContentOffset
/**
* Step 9: Return the data.
* You can write it to a file, or display it the user,
* or even pass it to iOS for sharing.
*/
return outputData
}
}
Here's a blog post I wrote explaining the process.
The process for generating a PDF is very similar to snapshotting an image, except instead of pages, you'd need to make one large canvas that matches the size of the scroll view and then grab the contents in chunks.
I have found below code and its working for me. try this ..
extension UIView {
func capture() -> UIImage {
UIGraphicsBeginImageContextWithOptions(bounds.size, false, UIScreen.main.scale)
drawHierarchy(in: self.bounds, afterScreenUpdates: true)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image
}}
Normally I wouldn't recommend using a library but... Use the SnapshotKit. It works like a charm and The code looks alright too. Using it is straight forward:
Objective-C:
UIImage *tableViewScreenShot = [yourTableView takeSnapshotOfFullContent];
Swift:
let tableViewScreenShot: UIImage = yourTableView.takeSnapshotOfFullContent()
Swift 5 Version
extension UIScrollView {
func takeScrollViewScreenShot() -> UIImage? {
UIGraphicsBeginImageContext(self.contentSize)
let savedContentOffset = self.contentOffset
let savedFrame = self.frame
self.contentOffset = CGPoint.zero
self.layer.frame = CGRect(x: 0, y: 0, width: self.contentSize.width, height: self.contentSize.height)
self.layer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
self.contentOffset = savedContentOffset
self.frame = savedFrame
UIGraphicsEndImageContext()
return image
}
}
It seems to me that the accepted solution can be fixed by updating scrollView.layer.frame rather than scrollView.frame, as pointed out here. I am not sure I actually understand why this works, though!
I don't know much but I can guess that if we set the size of the contextRect like this for landscape, it may work well:
CGRect contextRect = CGRectMake(0, 0, 1004, 768*2);
Because this contextRect will determine the size of the UIGraphicsBeginImageContext so I hope that double the height can solve your problem
I'm trying to add an arrow or like an image to correlate to how many view I have in my UIScrollView in swift. Something in line of this
(UPDATE) - My question is how do you insert an image into your scrollview that will tell it to go forward or backwards depending on how many images you have.
Now I know there is the UIPageControl but I'm looking into an alternative way to show that there is a picture and to the right or right and left. This is the code I have so far. I'll try the best I can to explain what I'm doing.
My picSource.count is data from a website that is carrying pictures
I'm multiplying my number of views by the screenwidth
This is an if else statement that shows if a picture is there post bgImage if not post no photoprovided image.
Let me know if you need more information or if I should revise. Thanks!
// Gallery
if (picSource.count > 1){
var picNum:CGFloat = CGFloat(picSource.count)
// UI News Image Scroller
var scroll = UIScrollView(frame:CGRectMake(-5, 650, screenWidth, 260))
scroll.pagingEnabled = true
scroll.showsHorizontalScrollIndicator = false
scroll.showsVerticalScrollIndicator = false
scroll.contentSize = CGSizeMake(picNum*screenWidth, 220)
// Number of views
var numberOfViews = picSource.count
var imageName = ""
// Loop to add views to scroll view
for (var i = 0; i < numberOfViews; i++){
var myIntValue:Int = Int(screenWidth)
var xOrigin = i * myIntValue
// Creates UIImageView instance using myImage
var scrollImageView = UIImageView(frame: CGRect(origin: CGPoint(x: xOrigin, y: 5), size: CGSize(width: screenWidth, height: 250)))
// Tests which image name needs to be used
imageName = picSource[i]
// Creates image object using specified image name "...jpg"
var url = NSURL(string: "http://www/images/cl/" + adID[adCurrentTag] + "/gallery/" + imageName)
var maybeError: NSError?
if var imageData :NSData = NSData(contentsOfURL: url!,options: NSDataReadingOptions.DataReadingMappedIfSafe, error: &maybeError) {
var bgImage = UIImage(data:imageData)
scrollImageView.contentMode = .ScaleAspectFit
scrollImageView.image = bgImage
// Adds Image to scroll view
scroll.addSubview(scrollImageView)
}else if let error = maybeError {
var photoNotProvided = UIImage(named:"noPhoto800x800.png")
var photoNotProvidedView = UIImageView(frame: CGRectMake(5, 650.0, screenWidth, 300.0))
scrollImageView.image = photoNotProvided
scroll.addSubview(scrollImageView)
}
}
border.addSubview(scroll)
I have a UIScrollView decendent that implements a takeScreenshot method that looks like this:
-(void)takeScreenshot {
CGRect contextRect = CGRectMake(0, 0, 768, 1004);
UIGraphicsBeginImageContext(contextRect.size);
[self.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// do something with the viewImage here.
}
This basically moves to the top of the scroll view, and takes a screenshot of the visible area. It works fine when the iPad is oriented portrait, but when it's in landscape the bottom of the image is cut off (as the height of the visible area is only 748, not 1004).
Is it possible to get a snapshot of the UIScrollView, including areas not on screen? Or do I need to scroll the view down, take a second photo and stitch them together?
Here is code that works ...
- (IBAction) renderScrollViewToImage
{
UIImage* image = nil;
UIGraphicsBeginImageContext(_scrollView.contentSize);
{
CGPoint savedContentOffset = _scrollView.contentOffset;
CGRect savedFrame = _scrollView.frame;
_scrollView.contentOffset = CGPointZero;
_scrollView.frame = CGRectMake(0, 0, _scrollView.contentSize.width, _scrollView.contentSize.height);
[_scrollView.layer renderInContext: UIGraphicsGetCurrentContext()];
image = UIGraphicsGetImageFromCurrentImageContext();
_scrollView.contentOffset = savedContentOffset;
_scrollView.frame = savedFrame;
}
UIGraphicsEndImageContext();
if (image != nil) {
[UIImagePNGRepresentation(image) writeToFile: #"/tmp/test.png" atomically: YES];
system("open /tmp/test.png");
}
}
The last few lines simply write the image to /tmp/test.png and then opens it in Preview.app. This obviously only works on in the Simulator :-)
Complete project in the ScrollViewScreenShot Github Repository
For me, the currently accepted answer from Stefan Arentz didn't work.
I had to implement this on iOS 8 and above, and tested on the iPhone. The accepted answer just renders the visible part of a scroll view, while the rest of image remains blank.
I tried fixing this using drawViewHierarchyInRect - no luck. Depending on afterScreenUpdates being true or false I got stretched part of image or only part of the contents.
The only way I've found to achieve correct snapshotting of a UIScrollView's entire contents is to add it to another temporary view and then render it.
Sample code is below (scrollview is outlet in my VC)
func getImageOfScrollView() -> UIImage {
var image = UIImage()
UIGraphicsBeginImageContextWithOptions(self.scrollView.contentSize, false, UIScreen.mainScreen().scale)
// save initial values
let savedContentOffset = self.scrollView.contentOffset
let savedFrame = self.scrollView.frame
let savedBackgroundColor = self.scrollView.backgroundColor
// reset offset to top left point
self.scrollView.contentOffset = CGPointZero
// set frame to content size
self.scrollView.frame = CGRectMake(0, 0, self.scrollView.contentSize.width, self.scrollView.contentSize.height)
// remove background
self.scrollView.backgroundColor = UIColor.clearColor()
// make temp view with scroll view content size
// a workaround for issue when image on ipad was drawn incorrectly
let tempView = UIView(frame: CGRectMake(0, 0, self.scrollView.contentSize.width, self.scrollView.contentSize.height))
// save superview
let tempSuperView = self.scrollView.superview
// remove scrollView from old superview
self.scrollView.removeFromSuperview()
// and add to tempView
tempView.addSubview(self.scrollView)
// render view
// drawViewHierarchyInRect not working correctly
tempView.layer.renderInContext(UIGraphicsGetCurrentContext())
// and get image
image = UIGraphicsGetImageFromCurrentImageContext()
// and return everything back
tempView.subviews[0].removeFromSuperview()
tempSuperView?.addSubview(self.scrollView)
// restore saved settings
self.scrollView.contentOffset = savedContentOffset
self.scrollView.frame = savedFrame
self.scrollView.backgroundColor = savedBackgroundColor
UIGraphicsEndImageContext()
return image
}
Working Example of UIView Extension with handling for UIScrollView:
extension UIView {
func screenshot() -> UIImage {
if(self is UIScrollView) {
let scrollView = self as! UIScrollView
let savedContentOffset = scrollView.contentOffset
let savedFrame = scrollView.frame
UIGraphicsBeginImageContext(scrollView.contentSize)
scrollView.contentOffset = .zero
self.frame = CGRect(x: 0, y: 0, width: scrollView.contentSize.width, height: scrollView.contentSize.height)
self.layer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext();
scrollView.contentOffset = savedContentOffset
scrollView.frame = savedFrame
return image!
}
UIGraphicsBeginImageContext(self.bounds.size)
self.layer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image!
}
}
I took this solution from #Roopesh Mittal's answer and made it safer/cleaner.
Swift 5 compatible
fileprivate extension UIScrollView {
func screenshot() -> UIImage? {
let savedContentOffset = contentOffset
let savedFrame = frame
UIGraphicsBeginImageContext(contentSize)
contentOffset = .zero
frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
guard let context = UIGraphicsGetCurrentContext() else { return nil }
layer.render(in: context)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext();
contentOffset = savedContentOffset
frame = savedFrame
return image
}
}
A refined Swift 4.x/5.0 version, based on #RyanG 's answer:
fileprivate extension UIScrollView {
func screenshot() -> UIImage? {
// begin image context
UIGraphicsBeginImageContextWithOptions(contentSize, false, 0.0)
// save the orginal offset & frame
let savedContentOffset = contentOffset
let savedFrame = frame
// end ctx, restore offset & frame before returning
defer {
UIGraphicsEndImageContext()
contentOffset = savedContentOffset
frame = savedFrame
}
// change the offset & frame so as to include all content
contentOffset = .zero
frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
guard let ctx = UIGraphicsGetCurrentContext() else {
return nil
}
layer.render(in: ctx)
let image = UIGraphicsGetImageFromCurrentImageContext()
return image
}
}
In iOS 13 I have ran into issue that this line won't work
frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
to fix the issue, I am removing scrollview from parent and then attaching in after taking the screenshot.
Full Code:
func screenshot() -> UIImage? {
let savedContentOffset = contentOffset
let savedFrame = frame
defer {
contentOffset = savedContentOffset
frame = savedFrame
}
contentOffset = .zero
frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
let image = UIGraphicsImageRenderer(bounds: CGRect(origin: .zero, size: contentSize)).image { renderer in
let context = renderer.cgContext
layer.render(in: context)
}
return image
}
Get Screenshot:
func getScreenshot() -> UIImage? {
scrollView.removeFromSuperview()
let image = scrollView.screenshot()
addScrollView()
return image
}
SWIFT 3 version:
func snapshot() -> UIImage?
{
UIGraphicsBeginImageContext(scrollView.contentSize)
let savedContentOffset = scrollView.contentOffset
let savedFrame = scrollView.frame
scrollView.contentOffset = CGPoint.zero
scrollView.frame = CGRect(x: 0, y: 0, width: scrollView.contentSize.width, height: scrollView.contentSize.height)
scrollView.layer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
scrollView.contentOffset = savedContentOffset
scrollView.frame = savedFrame
UIGraphicsEndImageContext()
return image
}
This worked for me
As many have pointed, current solution doesn't work, and others solutions suggest removing scrollview from superview, which leads into loosing all the constraints.
Here I'm temporarily disabling all constraints related to scroll view and turn them on after screenshot is taken:
extension UIScrollView {
func screenshot() -> UIImage? {
UIGraphicsBeginImageContextWithOptions(contentSize, false, 0.0)
// save the orginal offset, take a ref to all constraints related to the view
let savedContentOffset = contentOffset
let actualConstraints = relatedConstraints()
// deactivate non needed constraints so they won't stop us from resiging scroll view
NSLayoutConstraint.deactivate(actualConstraints)
// enable auth generated constraints based on the frame
translatesAutoresizingMaskIntoConstraints = true
frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
contentOffset = .zero
defer {
UIGraphicsEndImageContext()
// reset original constraints
translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate(actualConstraints)
// layout superview needed before resetting content offset
superview?.layoutIfNeeded()
contentOffset = savedContentOffset
}
guard let ctx = UIGraphicsGetCurrentContext() else {
return nil
}
layer.render(in: ctx)
let image = UIGraphicsGetImageFromCurrentImageContext()
return image
}
}
extension UIView {
func relatedConstraints() -> [NSLayoutConstraint] {
var constraints = self.constraints
var parent = superview
while parent != nil {
constraints.append(contentsOf: parent!.constraints.filter { $0.firstItem === self || $0.secondItem === self })
parent = parent!.superview
}
return constraints
}
}
SWIFT 3 version thanks to #gleb vodovozov:
func getImageOfScrollView()->UIImage{
var image = UIImage();
UIGraphicsBeginImageContextWithOptions(self.scrollView.contentSize, false, UIScreen.main.scale)
// save initial values
let savedContentOffset = self.scrollView.contentOffset;
let savedFrame = self.scrollView.frame;
let savedBackgroundColor = self.scrollView.backgroundColor
// reset offset to top left point
self.scrollView.contentOffset = CGPoint.zero;
// set frame to content size
self.scrollView.frame = CGRect(x: 0, y: 0, width: self.scrollView.contentSize.width, height: self.scrollView.contentSize.height)
// remove background
self.scrollView.backgroundColor = UIColor.clear
// make temp view with scroll view content size
// a workaround for issue when image on ipad was drawn incorrectly
let tempView = UIView(frame: CGRect(x: 0, y: 0, width: self.scrollView.contentSize.width, height: self.scrollView.contentSize.height))
// save superview
let tempSuperView = self.scrollView.superview
// remove scrollView from old superview
self.scrollView.removeFromSuperview()
// and add to tempView
tempView.addSubview(self.scrollView)
// render view
// drawViewHierarchyInRect not working correctly
tempView.layer.render(in: UIGraphicsGetCurrentContext()!)
// and get image
image = UIGraphicsGetImageFromCurrentImageContext()!;
// and return everything back
tempView.subviews[0].removeFromSuperview()
tempSuperView?.addSubview(self.scrollView)
// restore saved settings
self.scrollView.contentOffset = savedContentOffset;
self.scrollView.frame = savedFrame;
self.scrollView.backgroundColor = savedBackgroundColor
UIGraphicsEndImageContext();
return image
}
Here's another way of doing it, which takes the zoom level into account. I have a scrollview with 4 different UIImageView layers in it, and I want to take a screenshot of their current state:
float theScale = 1.0f / theScrollView.zoomScale;
// The viewing rectangle in absolute coordinates
CGRect visibleArea = CGRectMake((int)(theScrollView.contentOffset.x * theScale), (int)(theScrollView.contentOffset.y * theScale),
(int)(theScrollView.bounds.size.width * theScale), (int)(theScrollView.bounds.size.height * theScale));
NSArray *layers = [NSArray arrayWithObjects:imageLayer1, imageLayer2, imageLayer3, imageLayer4, nil];
UIGraphicsBeginImageContext(visibleArea.size);
for (UIImageView *layer in layers) {
CALayer *coreLayer = layer.layer;
coreLayer.bounds = CGRectMake(layer.frame.origin.x - visibleArea.origin.x, layer.frame.origin.y - visibleArea.origin.y, layer.frame.size.width, layer.frame.size.height);
[coreLayer renderInContext:UIGraphicsGetCurrentContext()];
}
UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
This takes the screenshot in absolute coordinates. That is, if you have a 2048*2048 image in the scrollview and you can see about a quarter of it, then regardless of the resolution of your screen it would take a screenshot of 512*512. If you want to take a screenshot at your screen resolution (say, 320*480) then you have to adjust the image as follows, directly after the above code:
UIGraphicsBeginImageContext(theScrollView.frame.size);
[screenshot drawInRect:CGRectMake(0, 0, theScrollView.frame.size.width, theScrollView.frame.size.height)];
UIImage *smallScreenshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
If you don't want to expand your scroll view beyond the entire screen (and it won't work with autolayout anyway) there's a better way.
You can use core graphics transforms in conjunction with the contentOffset of the scroll view to accomplish the same thing.
//
// ScrollViewSnapshotter.swift
// ScrollViewSnapshotter
//
// Created by Moshe Berman on 4/10/16.
// Copyright © 2016 Moshe Berman. All rights reserved.
//
import UIKit
class ScrollViewSnapshotter: NSObject {
func PDFWithScrollView(scrollview: UIScrollView) -> NSData {
/**
* Step 1: The first thing we need is the default origin and size of our pages.
* Since bounds always start at (0, 0) and the scroll view's bounds give us
* the correct size for the visible area, we can just use that.
*
* In the United States, a standard printed page is 8.5 inches by 11 inches,
* but when generating a PDF it's simpler to keep the page size matching the
* visible area of the scroll view. We can let our printer software (such
* as the Preview app on OS X or the Printer app on iOS) do the scaling.
*
* If we wanted to scale ourselves, we could multiply each of those
* numbers by 72, to get the number of points for each dimension.
* We would have to change how we generated the the pages below, so
* for simplicity, we're going to stick to one page per screenful of content.
*/
let pageDimensions = scrollview.bounds
/**
* Step 2: Now we need to know how many pages we will need to fit our content.
* To get this, we divide our scroll views dimensions by the size
* of each page, in either direction.
* We also need to round up, so that the pages don't get clipped.
*/
let pageSize = pageDimensions.size
let totalSize = scrollview.contentSize
let numberOfPagesThatFitHorizontally = Int(ceil(totalSize.width / pageSize.width))
let numberOfPagesThatFitVertically = Int(ceil(totalSize.height / pageSize.height))
/**
* Step 3: Set up a Core Graphics PDF context.
*
* First we create a backing store for the PDF data, then
* pass it and the page dimensions to Core Graphics.
*
* We could pass in some document information here, which mostly cover PDF metadata,
* including author name, creator name (our software) and a password to
* require when viewing the PDF file.
*
* Also note that we can use UIGraphicsBeginPDFContextToFile() instead,
* which writes the PDF to a specified path. I haven't played with it, so
* I don't know if the data is written all at once, or as each page is closed.
*/
let outputData = NSMutableData()
UIGraphicsBeginPDFContextToData(outputData, pageDimensions, nil)
/**
* Step 4: Remember some state for later.
* Then we need to clear the content insets, so that our
* core graphics layer and our content offset match up.
* We don't need to reset the content offset, because that
* happens implicitly, in the loop below.
*/
let savedContentOffset = scrollview.contentOffset
let savedContentInset = scrollview.contentInset
scrollview.contentInset = UIEdgeInsetsZero
/**
* Step 6: Now we loop through the pages and generate the data for each page.
*/
if let context = UIGraphicsGetCurrentContext()
{
for indexHorizontal in 0 ..< numberOfPagesThatFitHorizontally
{
for indexVertical in 0 ..< numberOfPagesThatFitVertically
{
/**
* Step 6a: Start a new page.
*
* This automatically closes the previous page.
* There's a similar method UIGraphicsBeginPDFPageWithInfo,
* which allows you to configure the rectangle of the page and
* other metadata.
*/
UIGraphicsBeginPDFPage()
/**
* Step 6b:The trick here is to move the visible portion of the
* scroll view *and* adjust the core graphics context
* appropriately.
*
* Consider that the viewport of the core graphics context
* is attached to the top of the scroll view's content view
* and we need to push it in the opposite direction as we scroll.
* Further, anything not inside of the visible area of the scroll
* view is clipped, so scrolling will move the core graphics viewport
* out of the rendered area, producing empty pages.
*
* To counter this, we scroll the next screenful into view, and adjust
* the core graphics context. Note that core graphics uses a coordinate
* system which has the y coordinate decreasing as we go from top to bottom.
* This is the opposite of UIKit (although it matches AppKit on OS X.)
*/
let offsetHorizontal = CGFloat(indexHorizontal) * pageSize.width
let offsetVertical = CGFloat(indexVertical) * pageSize.height
scrollview.contentOffset = CGPointMake(offsetHorizontal, offsetVertical)
CGContextTranslateCTM(context, -offsetHorizontal, -offsetVertical) // NOTE: Negative offsets
/**
* Step 6c: Now we are ready to render the page.
*
* There are faster ways to snapshot a view, but this
* is the most straightforward way to render a layer
* into a context.
*/
scrollview.layer.renderInContext(context)
}
}
}
/**
* Step 7: End the document context.
*/
UIGraphicsEndPDFContext()
/**
* Step 8: Restore the scroll view.
*/
scrollview.contentInset = savedContentInset
scrollview.contentOffset = savedContentOffset
/**
* Step 9: Return the data.
* You can write it to a file, or display it the user,
* or even pass it to iOS for sharing.
*/
return outputData
}
}
Here's a blog post I wrote explaining the process.
The process for generating a PDF is very similar to snapshotting an image, except instead of pages, you'd need to make one large canvas that matches the size of the scroll view and then grab the contents in chunks.
I have found below code and its working for me. try this ..
extension UIView {
func capture() -> UIImage {
UIGraphicsBeginImageContextWithOptions(bounds.size, false, UIScreen.main.scale)
drawHierarchy(in: self.bounds, afterScreenUpdates: true)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image
}}
Normally I wouldn't recommend using a library but... Use the SnapshotKit. It works like a charm and The code looks alright too. Using it is straight forward:
Objective-C:
UIImage *tableViewScreenShot = [yourTableView takeSnapshotOfFullContent];
Swift:
let tableViewScreenShot: UIImage = yourTableView.takeSnapshotOfFullContent()
Swift 5 Version
extension UIScrollView {
func takeScrollViewScreenShot() -> UIImage? {
UIGraphicsBeginImageContext(self.contentSize)
let savedContentOffset = self.contentOffset
let savedFrame = self.frame
self.contentOffset = CGPoint.zero
self.layer.frame = CGRect(x: 0, y: 0, width: self.contentSize.width, height: self.contentSize.height)
self.layer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
self.contentOffset = savedContentOffset
self.frame = savedFrame
UIGraphicsEndImageContext()
return image
}
}
It seems to me that the accepted solution can be fixed by updating scrollView.layer.frame rather than scrollView.frame, as pointed out here. I am not sure I actually understand why this works, though!
I don't know much but I can guess that if we set the size of the contextRect like this for landscape, it may work well:
CGRect contextRect = CGRectMake(0, 0, 1004, 768*2);
Because this contextRect will determine the size of the UIGraphicsBeginImageContext so I hope that double the height can solve your problem