Question

有没有办法在捕获ios设备屏幕时捕获CAEmitterCells（使用CAEmitterLayer生成）？
UIGetScreenImage（）有效，但由于它是私有方法，我不允许使用它。
UIGraphicsBeginImageContext 似乎不起作用，只是从结果图像中省略了粒子。

修改这是我目前用于捕获视图的代码。我实际上正在使用here的aroth提供的代码录制一个长达30秒的屏幕视频。它的工作原理是每秒记录25个自身的图像（它的UIView子类）及其子视图（在我们的例子中包括UIView，其层是CAEmitterLayer），并使用AVAssetWriter组成记录。

这是相当满口的，所以我只是将相关的行放在这里：我在XCode中使用ARC工具对代码进行了编程，因此代码可能与内存管理有点不同。

- (CGContextRef) createBitmapContextOfSize:(CGSize) size {
    CGContextRef    context = NULL;
    CGColorSpaceRef colorSpace;
    int             bitmapByteCount;
    int             bitmapBytesPerRow;

    bitmapBytesPerRow   = (size.width * 4);
    bitmapByteCount     = (bitmapBytesPerRow * size.height);
    colorSpace = CGColorSpaceCreateDeviceRGB();
    if (bitmapData != NULL) {
        free(bitmapData);
    }
    bitmapData = malloc( bitmapByteCount );
    if (bitmapData == NULL) {
        fprintf (stderr, "Memory not allocated!");
        return NULL;
    }

    context = CGBitmapContextCreate (bitmapData,
                                     size.width,
                                     size.height,
                                     8,      // bits per component
                                     bitmapBytesPerRow,
                                     colorSpace,
                                     kCGImageAlphaNoneSkipFirst);

    CGContextSetAllowsAntialiasing(context,NO);
    if (context== NULL) {
        free (bitmapData);
        fprintf (stderr, "Context not created!");
        return NULL;
    }
    CGColorSpaceRelease( colorSpace );

    return context;
}

//static int frameCount = 0;            //debugging
- (void) drawRect:(CGRect)rect {
    NSDate* start = [NSDate date];
    CGContextRef context = [self createBitmapContextOfSize:self.frame.size];

    //not sure why this is necessary...image renders upside-down and mirrored
    CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, self.frame.size.height);
    CGContextConcatCTM(context, flipVertical);

    [self.layer renderInContext:context];

    CGImageRef cgImage = CGBitmapContextCreateImage(context);
    UIImage* background = [UIImage imageWithCGImage: cgImage];
    CGImageRelease(cgImage);

    self.currentScreen = background;

    //debugging
    //if (frameCount < 40) {
    //      NSString* filename = [NSString stringWithFormat:@"Documents/frame_%d.png", frameCount];
    //      NSString* pngPath = [NSHomeDirectory() stringByAppendingPathComponent:filename];
    //      [UIImagePNGRepresentation(self.currentScreen) writeToFile: pngPath atomically: YES];
    //      frameCount++;
    //}

    //NOTE:  to record a scrollview while it is scrolling you need to implement your UIScrollViewDelegate such that it calls
    //       'setNeedsDisplay' on the ScreenCaptureView.
    if (_recording) {
        float millisElapsed = [[NSDate date] timeIntervalSinceDate:startedAt] * 1000.0;
        [self writeVideoFrameAtTime:CMTimeMake((int)millisElapsed, 1000)];
    }

    float processingSeconds = [[NSDate date] timeIntervalSinceDate:start];
    float delayRemaining = (1.0 / self.frameRate) - processingSeconds;

    CGContextRelease(context);

    //redraw at the specified framerate
    [self performSelector:@selector(setNeedsDisplay) withObject:nil afterDelay:delayRemaining > 0.0 ? delayRemaining : 0.01];
}

真的希望这会有所帮助。感谢您的支持！

Answer 1

您是否尝试使用-[CALayer renderInContext:]？

iOS：在屏幕上捕获CAEmitterLayer粒子

1 个答案: