我有一个UIScrollView后代，它实现了一个看起来像这样的takeScreenshot方法：
-(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.
}
这基本上移动到滚动视图的顶部，并截取可见区域的屏幕截图。当iPad面向人像时，它可以正常工作，但当它处于横向时，图像的底部会被切断（因为可见区域的高度仅为748，而不是1004）。
是否可以获取UIScrollView的快照，包括不在屏幕上的区域？或者我是否需要向下滚动视图，拍摄第二张照片并将它们拼接在一起？
答案 0 :(得分：109)
这是有效的代码......
- (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");
}
}
最后几行只是将图像写入/tmp/test.png，然后在Preview.app中打开它。这显然只适用于模拟器： - ）
中的完整项目答案 1 :(得分：16)
对我来说回答https://stackoverflow.com/a/3539944/4164443没有用。我有一个在iOS 8上实现它的任务。
实际上这种方法适用于iPhone，但iPad（simu和真实设备）是另一种情况。它只是呈现可见部分，其余图像只是空白。
我试过drawViewHierarchyInRect - 没有运气。取决于afterScreenUpdates true或false，我获得了部分图像，或者只是图像的一部分。
因此，我发现实现正确屏幕截图的唯一方法是将scrollview添加到另一个临时视图并进行渲染。
示例代码如下（我的VC中的scrollview是插座）
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
}
答案 2 :(得分：9)
UIView Extension的工作示例，处理UIScrollView：
➜ test node client.js
Connected
Received: Echo server
Hello, server! Love, Client. random data
Connection closed
答案 3 :(得分：6)
我从@Roopesh Mittal采取了上述解决方案，使其更安全/更清洁。
兼容Swift 4
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
}
}
答案 4 :(得分：5)
基于@RyanG的答案的精致的Swift 4.x / 5.0版本：
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
}
}
答案 5 :(得分：3)
SWIFT 3版本：
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
}
这对我有用
答案 6 :(得分：2)
这是另一种方法，它将缩放级别考虑在内。我有一个包含4个不同UIImageView图层的scrollview，我想截取他们当前状态的截图：
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();
这是绝对坐标的截图。也就是说，如果您在滚动视图中有一个2048 * 2048图像，并且您可以看到大约四分之一的图像，那么无论屏幕的分辨率如何，它都需要512 * 512的屏幕截图。如果您想以屏幕分辨率（例如，320 * 480）截取屏幕截图，则必须在上述代码之后直接调整图像，如下所示：
UIGraphicsBeginImageContext(theScrollView.frame.size);
[screenshot drawInRect:CGRectMake(0, 0, theScrollView.frame.size.width, theScrollView.frame.size.height)];
UIImage *smallScreenshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
答案 7 :(得分：2)
如果您不想在整个屏幕之外展开滚动视图（并且无论如何它都无法使用自动布局），那么这是一种更好的方法。
您可以将核心图形变换与滚动视图的contentOffset结合使用来完成相同的操作。
//
// 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
}
}
我写了blog post来解释这个过程。
生成PDF的过程非常类似于快照图像，除了页面之外，您需要制作一个与滚动视图大小相匹配的大画布，然后以块的形式获取内容。
答案 8 :(得分：2)
SWIFT 3版本归功于@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
}
答案 9 :(得分：1)
在iOS 13中，我遇到了这一行不起作用的问题
frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
要解决此问题，我要从父级移除scrollview，然后在截取屏幕截图后附加。
答案 10 :(得分：1)
正如许多人指出的那样，当前的解决方案不起作用，而其他解决方案建议从超级视图中删除滚动视图，这会导致失去所有约束。
在这里，我暂时禁用与滚动视图相关的所有约束，并在截取屏幕截图后将其打开：
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
}
}
答案 11 :(得分：0)
我不太了解但我可以猜测，如果我们为景观设置这样的contextRect的大小，它可能会运作良好：
CGRect contextRect = CGRectMake(0, 0, 1004, 768*2);
因为这个contextRect将确定UIGraphicsBeginImageContext的大小所以我希望高度加倍可以解决你的问题
答案 12 :(得分：0)
这是Stefan Arentz的答案的版本，可在iOS 13中使用。
UIImage* image = nil;
UIScrollView *clonedView = (UIScrollView*) [NSKeyedUnarchiver unarchiveObjectWithData:[NSKeyedArchiver archivedDataWithRootObject:_scrollView]];
UIGraphicsBeginImageContextWithOptions(clonedView.contentSize, NO, 0);
{
clonedView.contentOffset = CGPointZero;
clonedView.frame = CGRectMake(0, 0, clonedView.contentSize.width, clonedView.contentSize.height);
[clonedView.layer renderInContext: UIGraphicsGetCurrentContext()];
image = UIGraphicsGetImageFromCurrentImageContext();
}
UIGraphicsEndImageContext();
答案 13 :(得分：0)
我发现以下代码及其对我有用。试试这个..
extension UIView {
func capture() -> UIImage {
UIGraphicsBeginImageContextWithOptions(bounds.size, false, UIScreen.main.scale)
drawHierarchy(in: self.bounds, afterScreenUpdates: true)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image
}}
答案 14 :(得分：0)
通常我不建议使用库，但是...使用 SnapshotKit。它就像一个魅力，代码看起来也不错。直接使用它：
目标-C：
UIImage *tableViewScreenShot = [yourTableView takeSnapshotOfFullContent];
斯威夫特：
let tableViewScreenShot: UIImage = yourTableView.takeSnapshotOfFullContent()