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我需要对整个 iPhone 屏幕进行实时屏幕截图。屏幕嵌入了三个容器视图。这些容器之一是 UIImagePickerController。屏幕上的所有东西都捕捉得很漂亮，但是拥有 UIImagePickerController 的容器是黑色的。我需要整个屏幕截图，因此操作的连续性看起来是无缝的。有没有办法从 UIImagePickerController 捕获屏幕上当前显示的内容？下面是我用来捕获屏幕图像的代码。

我也尝试过Apple 的 Technical Q&A QA1703。

UIGraphicsBeginImageContextWithOptions(myView.bounds.size, YES, 0.0f);
[myView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

提前感谢您的帮助！

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1 回答 1

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在尝试捕获包含 GLKView 和 UIImagePickerController 的屏幕截图之前，我遇到了类似的问题。有时我会出现黑屏，有时我会收到有关无效上下文的投诉（使用与您类似的代码时）。我找不到解决方案，所以我实现了一个 AVFoundation 摄像头，此后再也没有回头。这里有一些快速的源代码可以帮助你。

视图控制器.h

// Frameworks
#import <CoreVideo/CoreVideo.h>
#import <CoreMedia/CoreMedia.h>
#import <AVFoundation/AVFoundation.h>
#import <UIKit/UIKit.h>

@interface CameraViewController : UIViewController <AVCaptureVideoDataOutputSampleBufferDelegate>

// Camera
@property (strong, nonatomic) AVCaptureSession* captureSession;
@property (strong, nonatomic) AVCaptureVideoPreviewLayer* previewLayer;
@property (strong, nonatomic) UIImage* cameraImage;

@end

视图控制器.m

#import "CameraViewController.h"

@implementation CameraViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self setupCamera];
}

- (void)setupCamera
{    
    AVCaptureDeviceInput* input = [AVCaptureDeviceInput deviceInputWithDevice:[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo] error:nil];
    AVCaptureVideoDataOutput* output = [[AVCaptureVideoDataOutput alloc] init];
    output.alwaysDiscardsLateVideoFrames = YES;

    dispatch_queue_t queue;
    queue = dispatch_queue_create("cameraQueue", NULL);
    [output setSampleBufferDelegate:self queue:queue];

    NSString* key = (NSString *) kCVPixelBufferPixelFormatTypeKey;
    NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA];
    NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:value forKey:key];
    [output setVideoSettings:videoSettings];

    self.captureSession = [[AVCaptureSession alloc] init];
    [self.captureSession addInput:input];
    [self.captureSession addOutput:output];
    [self.captureSession setSessionPreset:AVCaptureSessionPresetPhoto];

    self.previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.captureSession];
    self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;

    // CHECK FOR YOUR APP
    self.previewLayer.frame = CGRectMake(0, 0, self.view.frame.size.height, self.view.frame.size.width);
    self.previewLayer.orientation = AVCaptureVideoOrientationLandscapeRight;
    // CHECK FOR YOUR APP

    [self.view.layer insertSublayer:self.previewLayer atIndex:0];

    [self.captureSession startRunning];
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    CVPixelBufferLockBaseAddress(imageBuffer,0);
    uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer);
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef newContext = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    CGImageRef newImage = CGBitmapContextCreateImage(newContext);

    CGContextRelease(newContext);
    CGColorSpaceRelease(colorSpace);

    self.cameraImage = [UIImage imageWithCGImage:newImage];

    CGImageRelease(newImage);

    CVPixelBufferUnlockBaseAddress(imageBuffer,0);
}

// Call whenever you need a snapshot
- (UIImage *)snapshot
{
    NSLog(@"SNAPSHOT");
    return self.cameraImage;
}

@end

此代码根据所选预设（在本例中为照片：852x640）捕获输入图像，因此如果您想将其与视图一起捕获，我建议使用以下选项：

  1. 捕捉后缩放、裁剪和转换图像。优点：相机仍然运行流畅。缺点：更多代码
  2. 添加一个 UIImageView 而不是，它会在委托previewLayer中更新其图像。captureOutput优点：所见即所得。缺点：可能会导致您的相机运行速度变慢。

在上述两种情况下，您都需要在截屏后将生成的捕获与其他图像合并（不像听起来那么难）。

AVFoundation 及其相关框架非常令人生畏，因此这是一个非常精简的实现，可以满足您的需求。如果您想了解更多详细信息，请查看以下示例：

希望有帮助！

于 2012-12-30T09:50:07.083 回答