无法在iOS7上使用GPUImage缩放UIImage

我有一年多的代码成功地缩放、旋转并将UIImage转换为1bpp(黑白)。它在我的iPhone 5s、我测试过的iPad等上运行良好。然而,运行iOS 7.1.2的iPhone 4崩溃了。

我的代码(UIImage上的一个类别)是:

- (void) prepareImageForOCRWithCompletionHandler:(void (^) (UIImage *image))completion {

    if (!completion) return; // no sense in doing anything if nobody listens for the completion

    int width = self.size.width;
    int height = self.size.height;

    DLog(@"width=%d, height=%d", width, height);

    if (width > height) {
        int temp = width;
        width = height;
        height = temp;
    }

    int scaledWidth = 1728; // class F tiffs should be 1728, 2048 or 2483 pixels wide http://www.libtiff.org/support.html
    int scaledHeight = scaledWidth * height / width;

    DLog(@"width=%d, height=%d, scaledWidth=%d, scaledHeight=%d", width, height, scaledWidth, scaledHeight);

    GPUImagePicture *source = [[GPUImagePicture alloc] initWithImage:self];

    GPUImageFilter *rotateFilter = [[GPUImageFilter alloc] init];
    [rotateFilter setInputRotation:kGPUImageRotateRight atIndex:0];

    GPUImageTransformFilter *scaleFilter = [[GPUImageTransformFilter alloc] init];
    [scaleFilter forceProcessingAtSizeRespectingAspectRatio:CGSizeMake(scaledWidth, scaledHeight)];

    GPUImageAdaptiveThresholdFilter *thresholdFilter = [[GPUImageAdaptiveThresholdFilter alloc] init];

    [source addTarget:rotateFilter];
    [rotateFilter addTarget:scaleFilter];
    [scaleFilter addTarget:thresholdFilter];

    [source processImageWithCompletionHandler:^{
        UIImage *result = [thresholdFilter imageFromCurrentlyProcessedOutput];
        completion(result);
    }];
}

在Xcode控制台中使用以下消息调用GPUImage完成处理程序之前,应用程序崩溃:

2015-02-05 13:39:10.131 MyApp[345:60b] -[UIImage(BJM) prepareImageForOCRWithCompletionHandler:] [Line 54] width=1936, height=2592
2015-02-05 13:39:10.133 MyApp[345:60b] -[UIImage(BJM) prepareImageForOCRWithCompletionHandler:] [Line 65] width=1936, height=2592, scaledWidth=1728, scaledHeight=2313
2015-02-05 13:39:12.328 MyApp[345:7273] *** Assertion failure in -[GPUImageTransformFilter createFilterFBOofSize:], /Users/brian/repos/GPUImage/framework/Source/GPUImageFilter.m:380
2015-02-05 13:39:12.364 MyApp[345:7273] void uncaughtExceptionHandler(NSException *__strong) [Line 75] uncaught exception: Incomplete filter FBO: 36054
2015-02-05 13:39:12.366 MyApp[345:7273] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Incomplete filter FBO: 36054'
*** First throw call stack:
(0x30560f83 0x3ad11ccf 0x30560e5d 0x30f0ed5b 0x2a7adf 0x2aa82d 0x2a73a7 0x2a7c77 0x2a7daf 0x2b0265 0x2a80d5 0x2a9285 0x2acd49 0x3b1f9833 0x3b1f9ded 0x3b1fa297 0x3b20c88d 0x3b20cb21 0x3b33bbd3 0x3b33ba98)
libc++abi.dylib: terminating with uncaught exception of type NSException

如果我从管道中删除GPUImageTransformFilter,它就会工作。如果我恢复了变换过滤器,但将1728更改为1000,它也会起作用。这似乎是原始图像太小的问题。然而,原件是1936x2592。我还将宽度和高度int改为CGFloats,认为舍入错误导致了问题。没有运气。

这确实是一个令人羞愧的问题。谢谢你抽出时间。