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在UIView后面捕获(动画)屏幕

[英]Capturing (animated) screen behind UIView

最近我问了一个类似的问题,关于如何向UIView添加半透明效果,并获得了很好的答复。

但是,它使用了大量的CPU能力进行处理,因此我使用了答案背后的一些想法,但是使用了效率更高的GPUImage进行了过滤。

它适用于静态屏幕,但是我想用动画更改背景UIImageView的图像。 但是,当我将UIView设置为在过渡期间对背景进行采样时,似乎会忽略过渡并在动画开始之前显示新的Image。
相关代码如下(如果需要更多,请询问!):

包含自定义UIViewUIImageView背景的超级视图:

//The Transition
[contentView setScheduled:YES]; //Starts the sampling every 0.2 seconds

//bg is the UIImageView and contentView is the 'translucent' UIView subclass
[UIView transitionWithView:bg duration:1.0 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
    [bg setImage:newImage];
}completion:^(BOOL finished){
    [contentView setScheduled:NO];
}];

然后在UIView子类中:

- (UIImage *)snapshotOfSuperview:(UIView *)superview
{
CGFloat scale = 0.5;
if (([UIScreen mainScreen].scale > 1 || self.contentMode == UIViewContentModeScaleAspectFill))
{
    CGFloat blockSize = 12.0f/5;
    scale = blockSize/MAX(blockSize * 2, floor(self.blurRadius));
}
UIGraphicsBeginImageContextWithOptions(self.bounds.size, YES, scale);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, -self.frame.origin.x, -self.frame.origin.y);
self.hidden=YES; //Don't take a snapshot of the view
[superview.layer renderInContext:context];
self.hidden=NO;
UIImage *snapshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return snapshot;
}

-(void)updateViewBG{
UIImage *superviewImage = [self snapshotOfSuperview:self.superview];

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    GPUImageGaussianBlurFilter* filter = [[GPUImageGaussianBlurFilter alloc] init];
    filter.blurSize = 0.8f;
    UIImage* newBG = [self applyTint:self.tintColour image:[filter imageByFilteringImage:superviewImage]];

    dispatch_async(dispatch_get_main_queue(), ^{
        self.layer.contents = (id)newBG.CGImage;
        self.layer.contentsScale = newBG.scale;
    });
});
}

-(UIImage*)applyTint:(UIColor*)colour image:(UIImage*)inImage{
UIImage *newImage;
if (colour) {
    UIGraphicsBeginImageContext(inImage.size);

    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGRect area = CGRectMake(0, 0, inImage.size.width, inImage.size.height);

    CGContextScaleCTM(ctx, 1, -1);
    CGContextTranslateCTM(ctx, 0, -area.size.height);
    CGContextSaveGState(ctx);
    CGContextClipToMask(ctx, area, inImage.CGImage);
    [colour set];
    CGContextFillRect(ctx, area);
    CGContextRestoreGState(ctx);
    CGContextSetBlendMode(ctx, kCGBlendModeLighten);
    CGContextDrawImage(ctx, area, inImage.CGImage);
    newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
}else{
    newImage = inImage;
}
return newImage;
}

-(void)displayLayer:(CALayer *)layer{
[self updateViewBG];
}

如何获得背景以跟随动画?

我认为问题在于,一旦更改图像,就会调用displayLayer(不考虑进行中的过渡),因此新图像将用于半透明。

您应该修改updateViewBG以便它不会在过渡完成之前更新图层内容。 例如,您可以将标记添加到类中,在开始转换时进行设置,并在转换完成时将其重置。 设置标志后,请勿调用updateViewBG

[UIView transitionWithView:bg duration:1.0 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{

    self.isTransitionInProgress = YES;
    [bg setImage:newImage];

}completion:^(BOOL finished){

    [contentView setScheduled:NO];

    self.isTransitionInProgress = NO;
    [contentView.layer setNeedsDisplay];

}];



-(void)displayLayer:(CALayer *)layer{
    if (!self.isTransitionInProgress)
        [self updateViewBG];
}

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