Taking a screenshot when camera is on -iOS [closed

2019-02-18 19:06发布

问题:

I am working on an AR app where I am using apple's AVCam Example code in my project. I am trying to take a screenshot using the following methods that I have found on here but they are not working for me. Any suggestions? Thanks.

    - (UIImage *) screenshot {
        UIWindow *window = [UIApplication sharedApplication].keyWindow;

        if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)])
            UIGraphicsBeginImageContextWithOptions(window.bounds.size, NO, [UIScreen mainScreen].scale);
        else
            UIGraphicsBeginImageContext(window.bounds.size);
        [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        NSData * data = UIImageJPEGRepresentation(image, 1.0);

        return [UIImage imageWithData:data];
    }

    - (UI

Image*)screenshot2
{
    // On iOS prior to 4, fall back to use UIGraphicsBeginImageContext
    CGSize imageSize = [[UIScreen mainScreen] bounds].size;
    if (NULL != UIGraphicsBeginImageContextWithOptions)
        UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0);
    else
        UIGraphicsBeginImageContext(imageSize);

    CGContextRef context = UIGraphicsGetCurrentContext();

    // Iterate over every window from back to front
    for (UIWindow *window in [[UIApplication sharedApplication] windows])
    {
        if (![window respondsToSelector:@selector(screen)] || [window screen] == [UIScreen mainScreen])
        {
            // -renderInContext: renders in the coordinate space of the layer,
            // so we must first apply the layer's geometry to the graphics context
            CGContextSaveGState(context);
            // Center the context around the window's anchor point
            CGContextTranslateCTM(context, [window center].x, [window center].y);
            // Apply the window's transform about the anchor point
            CGContextConcatCTM(context, [window transform]);
            // Offset by the portion of the bounds left of and above the anchor point
            CGContextTranslateCTM(context,
                                  -[window bounds].size.width * [[window layer] anchorPoint].x,
                                  -[window bounds].size.height * [[window layer] anchorPoint].y);

            // Render the layer hierarchy to the current context
            [[window layer] renderInContext:context];

            // Restore the context
            CGContextRestoreGState(context);
        }
    }

    // Retrieve the screenshot image
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return image;
}

回答1:

The code does not work because CALayer's renderInContext does not render content from the camera.

See the following reference: https://developer.apple.com/library/ios/qa/qa1714/_index.html

As described in the link above, you can:
1) capture the contents of the camera using the related AVFoundation APIs (https://developer.apple.com/library/ios/qa/qa1702/_index.html#//apple_ref/doc/uid/DTS40010192)
2) and then draw the captured image to the graphics context where you rendered your UIKit elements.