ios - UIImage+ImageEffects 在设备上不起作用

Question

我有一个模态视图，我想在其中显示计算结果。为了使它看起来像 iOS7，我想要一个带有模糊背景的弹出 View 的有色背景。

我设法使用来自苹果的“UIImage+ImageEffects .h/m”文件让那个东西工作。

这是模态视图的 viewDidLoad:

- (void)viewDidLoad {

    [super viewDidLoad];

    /* How it works

     self.image is a screenshot of the VC presenting the modal view

     1- we set the background as the screenshot of the previous viewControler
     2- we hide the popup view
     3- we set the background of the popup as a blured snapshot of its container view    (self.view)
     4- we unhide the popup view and set its radius
     5- we create a tinted version of the background image (what we got from the previous view controller
     6- we set the background of self.view to the tinted version


     */

    // ***  1  ***

    self.view.backgroundColor=[UIColor colorWithPatternImage:self.image];


     // ***  2  ***

    self.containerView.hidden=YES;


    // ***  3  ***

    UIImage *pepe=[self bluredImageFromView:self.containerView withBackground:self.view withBackgroundTintColor:[UIColor colorWithWhite:1 alpha:0.75]];
    self.containerView.backgroundColor=[UIColor colorWithPatternImage:pepe];

    // ***  4  ***

    self.containerView.hidden=NO;
    self.containerView.layer.cornerRadius=4.5f;

    // ***  5  ***

    UIImage *tintedBackground =[self.image applyBlurWithRadius:0
                                                      tintColor:[UIColor colorWithRed:0.85 green:0.85 blue:0.85 alpha:0.35]
                                          saturationDeltaFactor:1.8
                                                      maskImage:nil];
    // ***  6  ***

    self.view.backgroundColor=[UIColor colorWithPatternImage:tintedBackground];


}

它在模拟器上运行良好，但是当我在我的 iPhone (4S) 上尝试时，当显示模态视图时，我遇到了黑屏。没有错误，没有来自控制台的提示，什么都没有。

有什么想法吗？

编辑

我添加代码:

if (!self.image) NSLog (@"self.image is empty");

在viewDidLoad的最开始

似乎在模拟器上 self.image 不是 nil 而在设备上是。我试图在父 VC 上从 prepareForSegue 实例化 self.image 但没有用。

Answer 1

我不知道你的 bluredImageFromView 是如何工作的，但是模拟器和实际的 iOS 设备之间存在安全(沙盒)差异(特别是 resizableSnapshotViewFromRect: 和drawViewHierarchyInRect:) 这可能解释了它为什么有效(但在设备上不起作用。)
看看这个 thread在 raywenderlich.com 上，有人从 Apple Developer 技术支持那里得到了建议。此示例代码显然来自 Apple。

- (IBAction)doBlurAndCrop:(id)sender {

UIImage *snapshotImage;

    /* draw the image of all the views below our view */
UIGraphicsBeginImageContextWithOptions(self.sourceImageView.bounds.size, NO, 0);
BOOL successfulDrawHierarchy = [self.sourceImageView drawViewHierarchyInRect:self.sourceImageView.bounds afterScreenUpdates:YES];
if ( successfulDrawHierarchy ) {
    snapshotImage = UIGraphicsGetImageFromCurrentImageContext();
} else {
    NSLog(@"drawViewHierarchyInRect:afterScreenUpdates: failed - there's nothing to draw...");
}
UIGraphicsEndImageContext();

if ( successfulDrawHierarchy ) {

        /* calculate the coordinates of the rectangle we're interested in within the returned image */
    CGRect cropRect = CGRectOffset(self.targetImageView.frame, - self.sourceImageView.frame.origin.x, - self.sourceImageView.frame.origin.y);

        /* draw the cropped section with a clipping region */
    UIGraphicsBeginImageContextWithOptions(cropRect.size, YES, 0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextClipToRect(context, CGRectMake(0, 0, cropRect.size.width, cropRect.size.height));
    CGRect targetRectangeForCrop = CGRectMake(-cropRect.origin.x, -cropRect.origin.y, snapshotImage.size.width, snapshotImage.size.height);
    [snapshotImage drawInRect:targetRectangeForCrop];
    UIImage *croppedSnapshotImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

        /* apply a special effect to the resulting image and copy it into place on screen */
    UIColor *tintColor = [UIColor colorWithWhite:1.0 alpha:0.3];
    self.targetImageView.image = [croppedSnapshotImage applyBlurWithRadius:5 tintColor:tintColor saturationDeltaFactor:1.8 maskImage:nil];
}
}