如何拍摄UIView的屏幕截图？

Question

我想知道我的iPhone应用程序如何利用特定的屏幕截图UIView作为UIImage.

我试过这段代码,但我得到的只是一张空白图片.

UIGraphicsBeginImageContext(CGSizeMake(320,480));
CGContextRef context = UIGraphicsGetCurrentContext();
[myUIView.layer drawInContext:context];
UIImage *screenShot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

myUIView尺寸为320x480,并且有一些子视图.这样做的正确方法是什么？

Answer 1

iOS 7有一个新方法,允许您将视图层次结构绘制到当前图形上下文中.这可以用来非常快速地获得UIImage.

我实现了一个类别方法UIView来获取视图UIImage:

- (UIImage *)pb_takeSnapshot {
    UIGraphicsBeginImageContextWithOptions(self.bounds.size, NO, [UIScreen mainScreen].scale);

    [self drawViewHierarchyInRect:self.bounds afterScreenUpdates:YES];

    // old style [self.layer renderInContext:UIGraphicsGetCurrentContext()];

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

它比现有renderInContext:方法快得多.

参考:https://developer.apple.com/library/content/qa/qa1817/_index.html

SWIFT更新:执行相同的扩展:

extension UIView {

    func pb_takeSnapshot() -> UIImage {
        UIGraphicsBeginImageContextWithOptions(bounds.size, false, UIScreen.mainScreen().scale)

        drawViewHierarchyInRect(self.bounds, afterScreenUpdates: true)

        // old style: layer.renderInContext(UIGraphicsGetCurrentContext())

        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }
}

SWIFT更新3

    UIGraphicsBeginImageContextWithOptions(bounds.size, false, UIScreen.main.scale)

    drawHierarchy(in: self.bounds, afterScreenUpdates: true)

    let image = UIGraphicsGetImageFromCurrentImageContext()!
    UIGraphicsEndImageContext()
    return image

Answer 2

我想你可能想要renderInContext,而不是drawInContext.drawInContext更像是一个覆盖的方法......

请注意,它可能无法在所有视图中工作,特别是大约一年前,当我尝试将其与实时摄像头视图一起使用时,它不起作用.

Answer 3

您需要捕获屏幕截图或UIView 的关键窗口.您可以使用UIGraphicsBeginImageContextWithOptions 在Retina Resolution中执行此操作,并将其缩放参数设置为0.0f.它始终以原始分辨率(iPhone 4及更高版本的视网膜)捕获.

这个做全屏截图(关键窗口)

UIWindow *keyWindow = [[UIApplication sharedApplication] keyWindow];
CGRect rect = [keyWindow bounds];
UIGraphicsBeginImageContextWithOptions(rect.size,YES,0.0f);
CGContextRef context = UIGraphicsGetCurrentContext();
[keyWindow.layer renderInContext:context];   
UIImage *capturedScreen = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

此代码以原始分辨率捕获UIView

CGRect rect = [captureView bounds];
UIGraphicsBeginImageContextWithOptions(rect.size,YES,0.0f);
CGContextRef context = UIGraphicsGetCurrentContext();
[captureView.layer renderInContext:context];   
UIImage *capturedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

如果您需要,可以在应用程序的文档文件夹中以99%的质量保存Upg图像.

NSString  *imagePath = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"Documents/capturedImage.jpg"]];    
[UIImageJPEGRepresentation(capturedImage, 0.95) writeToFile:imagePath atomically:YES];

Answer 4

从iOS7开始,我们有以下默认方法:

- (UIView *)snapshotViewAfterScreenUpdates:(BOOL)afterUpdates

调用上面的方法比尝试自己将当前视图的内容呈现为位图图像更快.

如果要将图形效果(如模糊)应用于快照,请改用该drawViewHierarchyInRect:afterScreenUpdates:方法.

https://developer.apple.com/library/ios/documentation/uikit/reference/uiview_class/uiview/uiview.html

Answer 5

我为UIView创建了可用的扩展,以便在Swift中截取屏幕截图:

extension UIView{

var screenshot: UIImage{

    UIGraphicsBeginImageContext(self.bounds.size);
    let context = UIGraphicsGetCurrentContext();
    self.layer.renderInContext(context)
    let screenShot = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return screenShot
}
}

要使用它只需键入:

let screenshot = view.screenshot

Answer 6

有来自iOS 10的新API

extension UIView {
    func makeScreenshot() -> UIImage {
        let renderer = UIGraphicsImageRenderer(bounds: self.bounds)
        return renderer.image { (context) in
            self.layer.render(in: context.cgContext)
        }
    }
}

Answer 7

- (void)drawRect:(CGRect)rect {
  UIGraphicsBeginImageContext(self.bounds.size);    
  [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
  UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);  
}

此方法可能会放入您的Controller类.

Answer 8

细节

• Xcode 版本 10.3 (10G8)，Swift 5

解决方案

import UIKit

extension CALayer {
    func makeSnapshot() -> UIImage? {
        let scale = UIScreen.main.scale
        UIGraphicsBeginImageContextWithOptions(frame.size, false, scale)
        defer { UIGraphicsEndImageContext() }
        guard let context = UIGraphicsGetCurrentContext() else { return nil }
        render(in: context)
        let screenshot = UIGraphicsGetImageFromCurrentImageContext()
        return screenshot
    }
}

extension UIView {
    func makeSnapshot() -> UIImage? {
        if #available(iOS 10.0, *) {
            let renderer = UIGraphicsImageRenderer(size: frame.size)
            return renderer.image { _ in drawHierarchy(in: bounds, afterScreenUpdates: true) }
        } else {
            return layer.makeSnapshot()
        }
    }
}

用法

let image = view.makeSnapshot()

完整样品

不要忘记在此处添加解决方案代码

import UIKit

class ViewController: UIViewController {

    @IBOutlet var viewForScreenShot: UIView!
    @IBOutlet var screenShotRenderer: UIImageView!

    @IBAction func makeViewScreenShotButtonTapped2(_ sender: UIButton) {
        screenShotRenderer.image = viewForScreenShot.makeSnapshot()
    }
}

主故事板

<?xml version="1.0" encoding="UTF-8"?>
<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="11762" systemVersion="16C67" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" colorMatched="YES" initialViewController="BYZ-38-t0r">
    <device id="retina4_7" orientation="portrait">
        <adaptation id="fullscreen"/>
    </device>
    <dependencies>
        <deployment identifier="iOS"/>
        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="11757"/>
        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
    </dependencies>
    <scenes>
        <!--View Controller-->
        <scene sceneID="tne-QT-ifu">
            <objects>
                <viewController id="BYZ-38-t0r" customClass="ViewController" customModule="stackoverflow_2214957" customModuleProvider="target" sceneMemberID="viewController">
                    <layoutGuides>
                        <viewControllerLayoutGuide type="top" id="y3c-jy-aDJ"/>
                        <viewControllerLayoutGuide type="bottom" id="wfy-db-euE"/>
                    </layoutGuides>
                    <view key="view" contentMode="scaleToFill" id="8bC-Xf-vdC">
                        <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
                        <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                        <subviews>
                            <view contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="Acg-GO-mMN">
                                <rect key="frame" x="67" y="28" width="240" height="128"/>
                                <subviews>
                                    <textField opaque="NO" clipsSubviews="YES" contentMode="scaleToFill" contentHorizontalAlignment="left" contentVerticalAlignment="center" borderStyle="roundedRect" textAlignment="natural" minimumFontSize="17" translatesAutoresizingMaskIntoConstraints="NO" id="4Fr-O3-56t">
                                        <rect key="frame" x="72" y="49" width="96" height="30"/>
                                        <constraints>
                                            <constraint firstAttribute="height" constant="30" id="cLv-es-h7Q"/>
                                            <constraint firstAttribute="width" constant="96" id="ytF-FH-gdm"/>
                                        </constraints>
                                        <nil key="textColor"/>
                                        <fontDescription key="fontDescription" type="system" pointSize="14"/>
                                        <textInputTraits key="textInputTraits"/>
                                    </textField>
                                </subviews>
                                <color key="backgroundColor" red="0.0" green="0.47843137250000001" blue="1" alpha="0.49277611300000002" colorSpace="custom" customColorSpace="sRGB"/>
                                <color key="tintColor" white="0.66666666666666663" alpha="1" colorSpace="calibratedWhite"/>
                                <constraints>
                                    <constraint firstItem="4Fr-O3-56t" firstAttribute="centerX" secondItem="Acg-GO-mMN" secondAttribute="centerX" id="egj-rT-Gz5"/>
                                    <constraint firstItem="4Fr-O3-56t" firstAttribute="centerY" secondItem="Acg-GO-mMN" secondAttribute="centerY" id="ymi-Ll-WIV"/>
                                </constraints>
                            </view>
                            <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="SQq-IE-pvj">
                                <rect key="frame" x="109" y="214" width="157" height="30"/>
                                <state key="normal" title="make view screen shot"/>
                                <connections>
                                    <action selector="makeViewScreenShotButtonTapped2:" destination="BYZ-38-t0r" eventType="touchUpInside" id="KSY-ec-uvA"/>
                                </connections>
                            </button>
                            <imageView userInteractionEnabled="NO" contentMode="scaleAspectFit" horizontalHuggingPriority="251" verticalHuggingPriority="251" translatesAutoresizingMaskIntoConstraints="NO" id="CEZ-Ju-Tpq">
                                <rect key="frame" x="67" y="269" width="240" height="128"/>
                                <constraints>
                                    <constraint firstAttribute="width" constant="240" id="STo-iJ-rM4"/>
                                    <constraint firstAttribute="height" constant="128" id="tfi-zF-zdn"/>
                                </constraints>
                            </imageView>
                        </subviews>
                        <color key="backgroundColor" red="0.95941069162436543" green="0.95941069162436543" blue="0.95941069162436543" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                        <constraints>
                            <constraint firstItem="CEZ-Ju-Tpq" firstAttribute="top" secondItem="SQq-IE-pvj" secondAttribute="bottom" constant="25" id="6x1-iB-gKF"/>
                            <constraint firstItem="Acg-GO-mMN" firstAttribute="leading" secondItem="CEZ-Ju-Tpq" secondAttribute="leading" id="LUp-Be-FiC"/>
                            <constraint firstItem="SQq-IE-pvj" firstAttribute="top" secondItem="Acg-GO-mMN" secondAttribute="bottom" constant="58" id="Qu0-YT-k9O"/>
                            <constraint firstItem="Acg-GO-mMN" firstAttribute="centerX" secondItem="8bC-Xf-vdC" secondAttribute="centerX" id="Qze-zd-ajY"/>
                            <constraint firstItem="Acg-GO-mMN" firstAttribute="trailing" secondItem="CEZ-Ju-Tpq" secondAttribute="trailing" id="b1d-sp-GHD"/>
                            <constraint firstItem="SQq-IE-pvj" firstAttribute="centerX" secondItem="CEZ-Ju-Tpq" secondAttribute="centerX" id="qCL-AF-Cro"/>
                            <constraint firstItem="Acg-GO-mMN" firstAttribute="top" secondItem="y3c-jy-aDJ" secondAttribute="bottom" constant="8" symbolic="YES" id="u5Y-eh-oSG"/>
                            <constraint firstItem="CEZ-Ju-Tpq" firstAttribute="centerY" secondItem="8bC-Xf-vdC" secondAttribute="centerY" id="vkx-JQ-pOF"/>
                        </constraints>
                    </view>
                    <connections>
                        <outlet property="screenShotRenderer" destination="CEZ-Ju-Tpq" id="8QB-OE-ib6"/>
                        <outlet property="viewForScreenShot" destination="Acg-GO-mMN" id="jgL-yn-8kk"/>
                    </connections>
                </viewController>
                <placeholder placeholderIdentifier="IBFirstResponder" id="dkx-z0-nzr" sceneMemberID="firstResponder"/>
            </objects>
            <point key="canvasLocation" x="32.799999999999997" y="37.331334332833585"/>
        </scene>
    </scenes>
</document>

结果

Answer 9

CGImageRef UIGetScreenImage();

Apple现在允许我们在公共应用程序中使用它,即使它是私有API