在后台线程中读取CGImageRef使应用程序崩溃

Question

我有一个很大的jpeg图像，我想在我的opengl引擎中异步加载tile。 如果它在主线程上完成但一切都很好，但速度很慢。

当我尝试将加载在NSOperationBlock上的图块加载时，它总是在尝试访问我以前在主线程中加载的共享图像数据指针时崩溃。

必须有一些我不能与后台操作，因为我假设我可以访问我在主线程上创建的内存部分。

我尝试做的是以下几点：

@interface MyViewer 
{ 
} 
@property (atomic, assign) CGImageRef imageRef; 
@property (atomic, assign) CGDataProviderRef dataProvider; 
@property (atomic, assign) int loadedTextures; 
@end 

... 

- (void) loadAllTiles:(NSData*) imgData 
{ 
    queue = [[NSOperationQueue alloc] init]; 
    //Loop for Total Number of Textures 

    self.dataProvider = CGDataProviderCreateWithData(NULL,[imgData bytes],[imgData length],0); 
    self.imageRef = CGImageCreateWithJPEGDataProvider(self.dataProvider, NULL, NO, kCGRenderingIntentDefault); 

    for (int i=0; i<tileCount; i++) 
    { 

     // I also tried this but without luck 
     //CGImageRetain(self.imageRef); 
     //CGDataProviderRetain(self.dataProvider); 

     NSBlockOperation *partsLoading = [[NSBlockOperation alloc] init]; 
     __weak NSBlockOperation *weakpartsLoadingOp = partsLoading; 
     [partsLoading addExecutionBlock:^{ 

      TamTexture2D& pTex2D = viewer->getTile(i); 

      CGImageRef subImgRef = CGImageCreateWithImageInRect(self.imageRef, CGRectMake(pTex2D.left, pTex2D.top, pTex2D.width, pTex2D.height)); 

      //!!!Its crashing here!!! 
      CFDataRef cgSubImgDataRef = CGDataProviderCopyData(CGImageGetDataProvider(subImgRef)); 
      CGImageRelease(subImgRef); 

      ... 
      }]; 

     //Adding Parts loading on low priority thread. Is it all right ???? 
     [partsLoading setThreadPriority:0.0]; 
     [queue addOperation:partsLoading]; 

} 

Answer 1

我终于找到了我的问题......

我已阅读Quartz2D doc和我们似乎不应该使用CGDataProviderCreateWithData和CGImageCreateWithJPEGDataProvider了。我想那里的用法不是线程安全的。

正如所建议的医生，我现在用的CGImageSource API这样的：

self.imageSrcRef = CGImageSourceCreateWithData((__bridge CFDataRef)imgData, NULL); 

// get imagePropertiesDictionary 
CFDictionaryRef imagePropertiesDictionary = CGImageSourceCopyPropertiesAtIndex(m_imageSrcRef,0, NULL); 

self.imageRef = CGImageSourceCreateImageAtIndex(m_imageSrcRef, 0, imagePropertiesDictionary);