我的iPad系统包含大量PDF文件。对于每个PDF文件，我生成第一页的图像（以支持UI中的可视索引）。
我用来生成图像的代码已经成功地用于数千种不同的PDF文件。但是，我现在遇到了一个PDF文件，可以在Adobe Reader中打开，但是当我尝试在iOS中生成图像时会导致错误的访问异常。导致问题的实际文档位于：PDF document
我用来生成图像的代码如下：
+(void)createLiteratureImageWithMeta:(HPSLiteratureMeta*)literatureMeta andData:(NSData*)literatureData
{
// Used to create a .png image file of the first page of a pdf document.
// The image is written to the file system, and has a name of the literatureId for the corresponding literature coredata record.
CFDataRef myPDFData = (__bridge CFDataRef)literatureData;
CGDataProviderRef provider = CGDataProviderCreateWithCFData(myPDFData);
CGPDFDocumentRef pdf = CGPDFDocumentCreateWithProvider(provider);
if (pdf)
{
CGPDFPageRef PDFPage = CGPDFDocumentGetPage(pdf, 1);
if (PDFPage)
{
UIView* view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 210, 297)]; // A4 = 210mm x 297mm
// Determine the size of the PDF page.
CGRect pageRect = CGPDFPageGetBoxRect(PDFPage, kCGPDFMediaBox);
CGFloat PDFScale = view.frame.size.width/pageRect.size.width;
pageRect.size = CGSizeMake(pageRect.size.width*PDFScale, pageRect.size.height*PDFScale);
/*
Create a low resolution image representation of the PDF page to display before the TiledPDFView renders its content.
*/
UIGraphicsBeginImageContext(pageRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
// First fill the background with white.
CGContextSetRGBFillColor(context, 1.0,1.0,1.0,1.0);
CGContextFillRect(context,pageRect);
CGContextSaveGState(context);
// Flip the context so that the PDF page is rendered right side up.
CGContextTranslateCTM(context, 0.0, pageRect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// Scale the context so that the PDF page is rendered at the correct size for the zoom level.
CGContextScaleCTM(context, PDFScale,PDFScale);
CGContextDrawPDFPage(context, PDFPage);
CGContextRestoreGState(context);
UIImage *backgroundImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageView *backgroundImageView = [[UIImageView alloc] initWithImage:backgroundImage];
backgroundImageView.frame = pageRect;
backgroundImageView.contentMode = UIViewContentModeScaleAspectFit;
[view addSubview:backgroundImageView];
[view sendSubviewToBack:backgroundImageView];
NSData* imageData = UIImagePNGRepresentation(backgroundImageView.image);
NSString* filename = [NSString stringWithFormat:@"%@.png",literatureMeta.id];
filename = [HPSFileHelper encodeFilename:filename];
[HPSFileHelper writeDataToFileWithData:imageData andFilename:filename];
}
CGPDFDocumentRelease (pdf);
CGDataProviderRelease (provider);
}
pdf = nil;
provider = nil;
}
对于以下行抛出异常（从开始大约下降47行）：
CGContextDrawPDFPage(context, PDFPage);
它在这条线上一直崩溃。
崩溃看起来像这样：
Thread : Crashed: NSOperationQueue 0x1562f060
0 ImageIO 0x2e254032 transfer_fixed_point(kdu_line_buf*, int, int, unsigned char*, int, bool) + 477
1 ??? 0x00001010
2 ImageIO 0x2e2537d3 kdu_region_decompressor::process_generic(int, int, kdu_coords, int, int, int, kdu_dims&, kdu_dims&, int, bool) + 8570
3 ImageIO 0x2e251651 kdu_region_decompressor::process(unsigned char**, bool, int, kdu_coords, int, int, int, kdu_dims&, kdu_dims&, int, bool) + 208
4 ImageIO 0x2e247365 kdrc_stream::process(int, kdu_dims&, int&) + 588
5 ImageIO 0x2e24db69 kdu_region_compositor::process(int, kdu_dims&) + 268
6 ImageIO 0x2e2b5ef3 _cg_JP2DecompressBlock + 374
7 ImageIO 0x2e2b76b9 copyImageBlockSetJP2 + 1016
8 ImageIO 0x2e17f71f ImageProviderCopyImageBlockSetCallback + 542
9 CoreGraphics 0x2d4c545d CGImageProviderCopyImageBlockSetWithOptions + 136
10 CoreGraphics 0x2d4e817b CGImageProviderCopyImageBlockSet + 26
11 CoreGraphics 0x2d4c512b img_blocks_create + 406
12 CoreGraphics 0x2d4e814b img_blocks_extent + 62
13 CoreGraphics 0x2d4e8105 img_interpolate_extent + 108
14 CoreGraphics 0x2d4b9179 img_data_lock + 4408
15 CoreGraphics 0x2d4b783d CGSImageDataLock + 88
16 libRIP.A.dylib 0x2d803e67 ripc_AcquireImage + 98
17 libRIP.A.dylib 0x2d80320d ripc_DrawImage + 588
18 CoreGraphics 0x2d4b7753 CGContextDelegateDrawImage + 50
19 CoreGraphics 0x2d4b75e9 CGContextDrawImage + 284
20 CoreGraphics 0x2d5776b3 draw_image + 82
21 CoreGraphics 0x2d57764b CGPDFDrawingContextDrawImage + 218
22 CoreGraphics 0x2d537831 op_Do + 96
23 CoreGraphics 0x2d551419 pdf_scanner_handle_xname + 76
24 CoreGraphics 0x2d550fa7 CGPDFScannerScan + 202
25 CoreGraphics 0x2d54bbc3 CGPDFDrawingContextDrawGroupStream + 194
26 CoreGraphics 0x2d59df4d CGPDFDrawingContextDrawGroup + 284
27 CoreGraphics 0x2d53781f op_Do + 78
28 CoreGraphics 0x2d551419 pdf_scanner_handle_xname + 76
29 CoreGraphics 0x2d550fa7 CGPDFScannerScan + 202
30 CoreGraphics 0x2d54b7e7 CGPDFDrawingContextDrawPage + 358
31 CoreGraphics 0x2d59d7c1 pdf_page_draw_in_context + 88
32 CoreGraphics 0x2d57e541 CGContextDrawPDFPage + 36
33 HPS 0x00060737 +[HPSImageHelper createLiteratureImageWithMeta:andData:] (HPSImageHelper.m:690)
34 HPS 0x00092d0d -[HPSDbOperationFileDownload doTheWorkWithMOC:] (HPSDbOperationFileDownload.m:63)
35 HPS 0x00070eb1 -[HPSDbOperationBase main] (HPSDbOperationBase.m:80)
36 Foundation 0x2dd6c7db -[__NSOperationInternal _start:] + 770
37 Foundation 0x2de10995 __NSOQSchedule_f + 60
38 libdispatch.dylib 0x380bd68f _dispatch_async_redirect_invoke$VARIANT$mp + 110
39 libdispatch.dylib 0x380bed71 _dispatch_root_queue_drain + 220
40 libdispatch.dylib 0x380bef59 _dispatch_worker_thread2 + 56
41 libsystem_pthread.dylib 0x381f9dbf _pthread_wqthread + 298
任何人都可以看到代码的问题（到目前为止已经有数千个其他文档运行良好）？有人能够检测到实际PDF的问题吗？
非常感谢。
答案 0 :(得分：0)
PSPDFKit的开发人员似乎遇到了类似的问题，似乎可以追溯到iOS 7.1 Beta 1版本修复过的一些Apple代码。
以下是讨论此问题的机票链接：https://github.com/PSPDFKit/PSPDFKit-Demo/wiki/Help!-This-PDF-is-crashing-PSPDFKit
我建议在iOS 7.1 Beta 1或更高版本上运行它，看看问题是否仍然存在。或者，尝试他们在故障单上的建议，并通过预览重新保存pdf以查看是否可以修复它。