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/