[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UIView
和UIImageView
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];
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.