iphone - 将pdf文件转换为文本文件

Question

大家好，我正在研究 Objective-C。我之前的问题是 How can I edit PDF files in an iOS application?经过大量谷歌搜索后，我发现了以下内容。在 UIWebView 中显示 pdf，使用 C/javascript 提取数据并进行编辑。我仍然不确定这个程序。现在我的计划是

1) 显示pdf

2) 当用户想要编辑 pdf 时，我将 pdf 转换为文本并允许他编辑

3) 尝试保存将内容转换回 pdf。

这是一个很好的方法吗？？我知道第 1 步。现在我如何转换 pdf--> 文本和文本-->pdf。

提前致谢

Answer 1

当您将自定义文档类型(doc、ppt、pdf 等)加载到 UIWebView 时，webview 返回一个 nil HTML 字符串，即使是通过 javascript。有一些提取 PDF 文本的建议 here .

但是将字符串转回 PDF 是不同的。如果您想保留原始 PDF 的格式，我敢肯定这是不可能的，因为 NSAttributedString 在 iOS 上的作用不大。但这将适用于纯文本或 NSAttributedString，如果可能的话:

NSData *PDFDataFromString(NSString *str) {
    NSMutableData *data = [NSMutableData data];

    //Create an NSAttributedString for CoreText. If you find a way to translate
    //PDF into an NSAttributedString, you can skip this step and simply use an
    //NSAttributedString for this method's argument.

    NSAttributedString* string = [[[NSAttributedString alloc] initWithString:str] autorelease];

    //612 and 792 are the dimensions of the paper in pixels. (8.5" x 11")
    CGRect paperRect = CGRectMake(0.0, 0.0, 612, 792);

    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef) string);
    CGSize requiredSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetter, CFRangeMake(0, [string length]), NULL, CGSizeMake(paperRect.size.width - 144, 1e40), NULL);

    //Subtract the top and bottom margins (72 and 72), so they aren't factored in page count calculations.
    NSUInteger pageCount = ceill(requiredSize.height / (paperRect.size.height - 144));
    CFIndex resumePageIndex = 0;
    UIGraphicsBeginPDFContextToData(data, paperRect, nil);

    for(NSUInteger i = 0; i < pageCount; i++) 
    {

    //After calculating the required number of pages, break up the string and
    //draw them into sequential pages.

        UIGraphicsBeginPDFPage();
        CGContextRef currentContext = UIGraphicsGetCurrentContext();
        CGContextSaveGState (currentContext);
        CGContextSetTextMatrix(currentContext, CGAffineTransformIdentity);
        CGMutablePathRef framePath = CGPathCreateMutable();

        //72 and 72 are the X and Y margins of the page in pixels.
        CGPathAddRect(framePath, NULL, CGRectInset(paperRect, 72.0, 72.0));

        CTFrameRef frameRef = CTFramesetterCreateFrame(framesetter, CFRangeMake(resumePageIndex, 0), framePath, NULL);
        resumePageIndex += CTFrameGetVisibleStringRange(frameRef).length;
        CGPathRelease(framePath);
        CGContextTranslateCTM(currentContext, 0, paperRect.size.height);
        CGContextScaleCTM(currentContext, 1.0, -1.0);
        CTFrameDraw(frameRef, currentContext);
        CFRelease(frameRef);    
        CGContextRestoreGState (currentContext);
    }
    CFRelease(framesetter);
    UIGraphicsEndPDFContext();
    return data;
}