objective-c - 如何加快图像模糊？

Question

我在模态 uiviewcontroller 中的 viewWillAppear 中有以下代码。

在这个例子中，我包括 UIImage+ImageEffects.h 来做背景图像的模糊。

-(void) viewWillAppear:(BOOL)animated
{
[super viewWillAppear:NO];

// grab an image of our parent view
UIView *parentView = self.presentingViewController.view;

UIImage *parentViewImage = [self takeSnapshotOfView:parentView];

UIImage *blurredImage = nil;

//BLUR THE IMAGE
blurredImage = [self blurWithImageEffects:parentViewImage];

// insert an image view with a picture of the parent view at the back of our view's subview stack...
UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.view.bounds];
imageView.image = blurredImage;
[self.view insertSubview:imageView atIndex:0];

}

[编辑] 添加模糊方法

- (UIImage *)takeSnapshotOfView:(UIView *)view
{
    CGFloat reductionFactor = 1.5;
    UIGraphicsBeginImageContext(CGSizeMake(view.frame.size.width/reductionFactor, view.frame.size.height/reductionFactor));
    [view drawViewHierarchyInRect:CGRectMake(0, 0, view.frame.size.width/reductionFactor, view.frame.size.height/reductionFactor) afterScreenUpdates:YES];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;
}

- (UIImage *)blurWithImageEffects:(UIImage *)image
{
    return [image applyBlurWithRadius:10 tintColor:[UIColor colorWithWhite:1 alpha:0.2] saturationDeltaFactor:1.5 maskImage:nil];
}

代码工作正常，背景显示模糊，但在装有 iOS 8 的 iPad 3 上确实很慢。当点击显示此视图控制器的按钮时，在视图控制器从底部向上滑动之前会有一个暂停。如果我删除模糊，视图控制器会更快地向上滑动。

我尝试将代码放在 viewDidAppear 中，但是在出现模糊之前会显示几秒钟的明显白色背景。但是当在 viewDidAppear 中时，视图控制器会立即向上滑动。

如果我减少 applyWithBlurRadius 值，这似乎不会减少应用模糊所需的时间。

有什么办法可以让它跑得更快吗？

Answer 1

GPUImage 可能会解决您的问题，它的速度很快，并且不会给处理带来太多负担。

链接到框架：https ://github.com/BradLarson/GPUImage

使用 GPUImage Blur 的链接

• http://blog.bubbly.net/tag/gpu-image/
• http://www.raywenderlich.com/60968/ios-7-blur-effects-gpuimage

但是，下面显示了一个参考，它将为您提供基本概念：

首先准备要模糊的视图：

- (NSData *)PhotoForBlurring:(UIView *)view{
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, NO, 1.0);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    NSData * data = UIImagePNGRepresentation(image);
    [data writeToFile:@"aName.png" atomically:YES];
    return data; }

-(void)sharingScrapPage{
     GPUImageiOSBlurFilter *blur = [[GPUImageiOSBlurFilter alloc]init];
     blur.blurRadiusInPixels=2.0;
     blur.downsampling=6.0;

     [blurview removeFromSuperview];
     blurview = [[UIImageView alloc]initWithFrame:getRectDisplay(0, 0, 480, 320)]; // Landscape Iphone 4S
     UIImage *imageForBlurring=[UIImage imageWithData:[self PhotoForBlurring:self.view]];
     NSData* pngdataForBlurring = UIImagePNGRepresentation (imageForBlurring);
     UIImage* blurImage = [UIImage imageWithData:pngdataForBlurring];
     blurImage=[blur imageByFilteringImage:blurImage];
     blurview.image=blurImage;
     [self.view addSubview:blurview];

     [progressHUD removeFromSuperview];
     progressHUD = [[ProgressHUD alloc]initWithFrame:getRectDisplay(190, 110, 100, 90)];
     [blurview addSubview:progressHUD]; }