我将新收到的PDF文档的缩略图呈现到Documents-Directory。

我正在使用以下代码:

CFURLRef pdfURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), CFSTR("thedoc.pdf"), NULL, NULL);
        CGPDFDocumentRef bookPDF = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL);
        UIGraphicsBeginImageContext(CGSizeMake(100, 130));
        NSUInteger totalNum = CGPDFDocumentGetNumberOfPages(bookPDF);
        CGContextRef context = UIGraphicsGetCurrentContext();

        for(int i = 0; i < totalNum; i++ ) {
            CGRect arect = CGRectMake(0,0,200,282);
            CGContextSaveGState(context);
            CGContextTranslateCTM(context, 0.0, 141);
            CGContextScaleCTM(context, 1.0, -1.0);
            CGContextSetGrayFillColor(context, 1.0, 1.0);
            CGContextFillRect(context, arect);
            // Grab the first PDF page
            CGPDFPageRef page = CGPDFDocumentGetPage(bookPDF, i + 1);
            CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFMediaBox, arect, 0, true);
            // And apply the transform.
            CGContextConcatCTM(context, pdfTransform);
            CGContextDrawPDFPage(context, page);
            // Create the new UIImage from the context
            UIImage* thumbnailImage = UIGraphicsGetImageFromCurrentImageContext();
            if (thumbnailImage == nil) {
                NSLog(@"ERROR during creation of PNG");
            }
            // SAVE THE IMAGE TO DOCUMENTS-DIRECTORY
            NSString  *pngPath = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"%@/thumbPage%i.png",theLocalFolder ,i]];
            // Write image to PNG
            BOOL writtenBool = [UIImagePNGRepresentation(thumbnailImage) writeToFile:pngPath atomically:YES];
            // END SAVE THE IMAGE TO DOCUMENT-DIRECTORY
            CGContextRestoreGState(context);
            NSLog(@"Rendering PDF-Thumbnail %i (%i): %@", i, writtenBool, [NSString stringWithFormat:@"%@/thumbPage%i.png",theLocalFolder ,i]);
        }

控制台中没有错误,但是PNG不会存储到document-Directory。布尔
writtenBool

为“0”,表示写操作不成功。我不知道为什么我写的路径
png路径
到控制台,路径也是正确的。如果我打开终端并写
open <<copyed path from console>>

它会在finder中打开正确的路径。

是什么原因导致它不起作用?我看了一下api,但似乎没有
error:

对于UIImagePNGRepresentation:writeToFile:

谢谢你的帮助!

最佳答案

UIImagePNGRepresentation(thumbnailImage)返回一个NSData对象

对于NSData对象,可以使用以下方法:
writeToFile:atomically:
writeToFile:options:error:
writeToURL:atomically:
writeToURL:options:error:

因此,您可以尝试使用BOOL writtenBool = [UIImagePNGRepresentation(thumbnailImage) writeToFile:pngPath options:NSDataWritingAtomic error:&error];之类的代码来查看发生了什么。

关于ios - UIImagePNGRepresentation writeToFile可以捕获错误吗?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/8360273/

10-09 01:39