ios 標示pdf中URL字串。

有一需求要把pdf中的url字串標示出來。原理是解析pdf結構，相似 xml結構。查找「Annots」的key。代碼以下。 

- (void) renderPageAtIndex:(NSUInteger)index inContext:(CGContextRef)ctx inPage:(CGPDFPageRef)page{
        
        //CGPDFPageRef page = CGPDFDocumentGetPage(pdf, i+1);
        CGPDFDictionaryRef pageDictionary = CGPDFPageGetDictionary(page);
        CGPDFArrayRef outputArray;
        if(!CGPDFDictionaryGetArray(pageDictionary,"Annots", &outputArray)) {
            return;
        }
        int arrayCount = CGPDFArrayGetCount( outputArray );
        if(!arrayCount) {
            continue;
        }
        for( int j = 0; j <arrayCount; ++j ) {
            CGPDFObjectRef aDictObj;
            if(!CGPDFArrayGetObject(outputArray, j, &aDictObj)) {
                return;
            }
            CGPDFDictionaryRef annotDict;
            if(!CGPDFObjectGetValue(aDictObj, kCGPDFObjectTypeDictionary, &annotDict)) {
                return;
            }
            CGPDFDictionaryRef aDict;
            if(!CGPDFDictionaryGetDictionary(annotDict,"A", &aDict)) {
                return;
            }
            CGPDFStringRef uriStringRef;
            if(!CGPDFDictionaryGetString(aDict,"URI", &uriStringRef)) {
                return;
            }
            CGPDFArrayRef rectArray;
            if(!CGPDFDictionaryGetArray(annotDict,"Rect", &rectArray)) {
                return;
            }
            int arrayCount = CGPDFArrayGetCount( rectArray );
            CGPDFReal coords[4];
            for( int k = 0; k <arrayCount; ++k ) {
                CGPDFObjectRef rectObj;
                if(!CGPDFArrayGetObject(rectArray, k, &rectObj)) {
                    return;
                }
                CGPDFReal coord;
                if(!CGPDFObjectGetValue(rectObj, kCGPDFObjectTypeReal, &coord)) {
                    return;
                }
                coords[k] = coord;
            }
            char *uriString = (char *)CGPDFStringGetBytePtr(uriStringRef);
            NSString *uri = [NSString stringWithCString:uriString encoding:NSUTF8StringEncoding];
            CGRect rect = CGRectMake(coords[0],coords[1],coords[2],coords[3]);
            CGPDFInteger pageRotate = 0;
            CGPDFDictionaryGetInteger( pageDictionary,"Rotate", &pageRotate );
            CGRect pageRect = CGRectIntegral( CGPDFPageGetBoxRect( page, kCGPDFMediaBox ));
            if( pageRotate == 90 || pageRotate == 270 ) {
                CGFloat temp = pageRect.size.width;
                pageRect.size.width = pageRect.size.height;
                pageRect.size.height = temp;
            }
            rect.size.width -= rect.origin.x;
            rect.size.height -= rect.origin.y;
            CGAffineTransform trans = CGAffineTransformIdentity;
            trans = CGAffineTransformTranslate(trans, 0, pageRect.size.height);
            trans = CGAffineTransformScale(trans, 1.0, -1.0);
            rect = CGRectApplyAffineTransform(rect, trans);
            //do whatever you need with the coordinates.
            //e.g. you could create a button and put it on top of your page
            //and use it to open the URL with UIApplication's openURL
            NSURL *url = [NSURL URLWithString:uri];
            NSLog(@"URL: %@", url);
            CGPDFContextSetURLForRect(ctx, (CFURLRef)url, rect);
            //CFRelease(url);
            CGContextSetFillColorWithColor(ctx, [[UIColor yellowColor] CGColor]);
            CGContextSetBlendMode(ctx, kCGBlendModeMultiply);
            
            CGContextSaveGState(ctx);
            CGContextConcatCTM(ctx, trans);
            CGContextFillRect(ctx, rect);
            CGContextRestoreGState(ctx);
            
        }
    
}

效果以下

另外，代碼只是處理了當前一頁。可自行修改處理整個pdf的查找標示。參考：https://ask.helplib.com/iphone/post_562254