将pdf文件转换为文本文件

Question

大家好我正在研究Objective-C.我以前的问题是如何在iOS应用程序中编辑PDF文件？ 经过大量的谷歌搜索后,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它

3)试着保存将内容转换回pdf.

这是一种继续进行的方式吗？im k with step 1.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 中时，即使通过 javascript，webview 也会返回 nil HTML 字符串。关于提取 PDF 文本的一些建议这里。

但将字符串转回 PDF 是不同的。如果你想保留原始 PDF 的格式，我确信这是不可能的，因为 iOS 上的 NSAttributedString 没有做太多事情。但这适用于纯文本或 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;
}