从目标C中的PDF中提取可编辑字段

Question

我已经研究了一段时间，在我的iOS应用程序中使用PDF。我已经找出了一些拼图，比如扫描操作符和在UIWebView中显示PDF。但是，我真正需要做的是在文档中识别可编辑的字段。

理想情况下，我希望能够直接与字段交互，但这听起来非常困难，并不是显而易见的第一步。我已经与一个Windows服务进行了接口，该服务可以以这种方式操作PDF，并满足于识别可编辑字段、在窗体视图中从用户收集字段数据以及将数据返回到服务器的POSTing。问题是我看不出如何识别这些字段。我正在与政府发布的PDF进行交互，比如I-9s和W-4s，因此我无法控制PDF的创建或字段的命名。这就是我需要动态提取它们的原因。如能提供任何帮助和/或参考资料，将不胜感激。

我使用苹果Quatrz2D编程指南中的this reference在扫描PDF时触发操作符回调，但这并不能帮助我找到可编辑的字段。

我还简单地加载了一个UIWebView，其中包含要显示给用户的PDF数据。

[_webView loadData:decodedData MIMEType:@"application/pdf" textEncodingName:@"utf-8" baseURL:nil];

更新：

我构建了一个PDF帮助类(如下图所示)，以遍历目录中所有可能的对象类型。最初，我没有处理数组中的嵌套字典，所以我没有看到表单字段。一旦我修正了，我就意识到，为了避免循环递归调用，会启动无限循环，必须考虑父引用。下面的代码显示了文档目录中的大量信息。现在我只需要解析它来隔离我需要的表单字段。

PDFHelper.h

#import <Foundation/Foundation.h>

id selfClass;

@interface PDFHelper : NSObject

@property (nonatomic, strong) NSData *pdfData;
@property (nonatomic, strong) NSMutableDictionary *pdfDict;
@property (nonatomic) int catalogLevel;


-(NSArray *) copyPDFArray:(CGPDFArrayRef)arr referencingDictionary:(CGPDFDictionaryRef)dict referencingKey:(const char *)key;
-(NSArray *) getFormFields;
-(CGPDFDictionaryRef) getDocumentCatalog;

@end

PDFHelper.m

#import "PDFHelper.h"
#import "FileHelpers.h"
#import "Log.h"

@implementation PDFHelper

@synthesize pdfData = _pdfData;
@synthesize pdfDict = _pdfDict;
@synthesize catalogLevel = _catalogLevel;

-(id)init
{
    self = [super init];
    if(self)
    {
        selfClass = self;
        _pdfDict = [[NSMutableDictionary alloc] init];
        _catalogLevel = 1;
    }

    return self;
}

-(NSArray *) getFormFields
{
    CGPDFDictionaryRef acroForm = NULL;
    if (CGPDFDictionaryGetDictionary([self getPdfDocDictionary], "AcroForm", &acroForm))
        CGPDFDictionaryApplyFunction(acroForm, getDictionaryObjects, acroForm);
    return [_pdfDict objectForKey:@"XFA"];
}

-(CGPDFDictionaryRef) getDocumentCatalog
{
    CGPDFDictionaryRef docCatalog = [self getPdfDocDictionary];
    CGPDFDictionaryApplyFunction(docCatalog, getDictionaryObjects, docCatalog);
    return docCatalog;
}

-(CGPDFDictionaryRef) getPdfDocDictionary
{
    NSURL *pdf = [[NSURL alloc] initFileURLWithPath:[FileHelpers pathInLibraryDirectory:@"file.pdf"]];

    [_pdfData writeToFile:[pdf path] atomically:YES];

    CGPDFDocumentRef pdfDocument = CGPDFDocumentCreateWithURL((__bridge CFURLRef)pdf);
    CGPDFDictionaryRef returnDict = CGPDFDocumentGetCatalog(pdfDocument);
    return returnDict;
}

void getDictionaryObjects (const char *key, CGPDFObjectRef object, void *info) {

    NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"key: %s", key]];
    for (int i = 0; i < [selfClass catalogLevel]; i++)
        logString = [NSString stringWithFormat:@"-%@", logString];
    [Log LogDebug:logString];

    CGPDFDictionaryRef contentDict = (CGPDFDictionaryRef)info;

    CGPDFObjectType type = CGPDFObjectGetType(object);
    switch (type) {
        case kCGPDFObjectTypeNull: {            
                [Log LogDebug:[NSString stringWithFormat:@"*****pdf null value"]];
            break;
        }
        case kCGPDFObjectTypeBoolean: {
            CGPDFBoolean objectBoolean;
            if (CGPDFObjectGetValue(object, kCGPDFObjectTypeBoolean, &objectBoolean)) {
                NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf boolean value: %@", [NSNumber numberWithBool:objectBoolean]]];
                for (int i = 0; i < [selfClass catalogLevel]; i++)
                    logString = [NSString stringWithFormat:@"-%@", logString];
                [Log LogDebug:logString];
                [[selfClass pdfDict] setObject:[NSNumber numberWithBool:objectBoolean]
                                        forKey:[NSString stringWithCString:key encoding:NSUTF8StringEncoding]];
            }
            break;
        }
        case kCGPDFObjectTypeInteger: {
            CGPDFInteger objectInteger;
            if (CGPDFObjectGetValue(object, kCGPDFObjectTypeInteger, &objectInteger)) {
                NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf integer value: %ld", (long int)objectInteger]];
                for (int i = 0; i < [selfClass catalogLevel]; i++)
                    logString = [NSString stringWithFormat:@"-%@", logString];
                [Log LogDebug:logString];
                [[selfClass pdfDict] setObject:[NSNumber numberWithInt:objectInteger]
                                        forKey:[NSString stringWithCString:key encoding:NSUTF8StringEncoding]];
            }
            break;
        }
        case kCGPDFObjectTypeReal: {
            CGPDFReal objectReal;
            if (CGPDFObjectGetValue(object, kCGPDFObjectTypeReal, &objectReal)) {
                NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf real value: %ld", (long int)objectReal]];
                for (int i = 0; i < [selfClass catalogLevel]; i++)
                    logString = [NSString stringWithFormat:@"-%@", logString];
                [Log LogDebug:logString];
                [[selfClass pdfDict] setObject:[NSNumber numberWithInt:objectReal]
                                        forKey:[NSString stringWithCString:key encoding:NSUTF8StringEncoding]];
            }
            break;
        }
        case kCGPDFObjectTypeName: {
            const char *name;
            if (CGPDFDictionaryGetName(contentDict, key, &name))
            {
                NSString *dictName = [[NSString alloc] initWithCString:name encoding:NSUTF8StringEncoding];
                if (dictName)
                {
                    NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf name value: %@", dictName]];
                    for (int i = 0; i < [selfClass catalogLevel]; i++)
                        logString = [NSString stringWithFormat:@"-%@", logString];
                    [Log LogDebug:logString];
                    [[selfClass pdfDict] setObject:dictName
                                            forKey:[NSString stringWithCString:key encoding:NSUTF8StringEncoding]];
                }
            }
            break;
        }
        case kCGPDFObjectTypeString: {
            CGPDFStringRef objectString;
            if (CGPDFObjectGetValue(object, kCGPDFObjectTypeString, &objectString)) {
                NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf string value: %@", (__bridge NSString *)CGPDFStringCopyTextString(objectString)]];
                for (int i = 0; i < [selfClass catalogLevel]; i++)
                    logString = [NSString stringWithFormat:@"-%@", logString];
                [Log LogDebug:logString];
                [[selfClass pdfDict] setObject:(__bridge NSString *)CGPDFStringCopyTextString(objectString)
                                        forKey:[NSString stringWithCString:key encoding:NSUTF8StringEncoding]];
            }
            break;
        }
        case kCGPDFObjectTypeArray: {
            CGPDFArrayRef objectArray;
            if (CGPDFObjectGetValue(object, kCGPDFObjectTypeArray, &objectArray)) {
                NSArray *myArray=[selfClass copyPDFArray:objectArray referencingDictionary:contentDict referencingKey:key];
                [[selfClass pdfDict] setObject:myArray
                                        forKey:[NSString stringWithCString:key encoding:NSUTF8StringEncoding]];

            }
            break;
        }
        case kCGPDFObjectTypeDictionary: {
            CGPDFDictionaryRef objectDictionary;
            if (CGPDFObjectGetValue(object, kCGPDFObjectTypeDictionary, &objectDictionary)) {
                NSString *logString = @"Found dictionary";
                for (int i = 0; i < [selfClass catalogLevel]; i++)
                    logString = [NSString stringWithFormat:@"-%@", logString];
                //[Log LogDebug:logString];
                NSString *keyCheck = [[NSString alloc] initWithUTF8String:key];
                if (![keyCheck isEqualToString:@"Parent"] && ![keyCheck isEqualToString:@"P"])
                {
                    [selfClass setCatalogLevel:[selfClass catalogLevel] + 1];
                    CGPDFDictionaryApplyFunction(objectDictionary, getDictionaryObjects, objectDictionary);
                    [selfClass setCatalogLevel:[selfClass catalogLevel] - 1];
                }
            }
            break;
        }
        case kCGPDFObjectTypeStream: {
            CGPDFStreamRef objectStream;
            if (CGPDFObjectGetValue(object, kCGPDFObjectTypeStream, &objectStream)) {

                CGPDFDictionaryRef dict = CGPDFStreamGetDictionary( objectStream );

                CGPDFDataFormat fmt = CGPDFDataFormatRaw;
                CFDataRef streamData = CGPDFStreamCopyData(objectStream, &fmt);
                NSData *data = [[NSData alloc] initWithData:(__bridge NSData *)(streamData)];
                [data writeToFile:[FileHelpers pathInDocumentDirectory:@"data.dat"] atomically:YES];
                NSString *dataString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
                //if (!dataString) {
                //    dataString = [[NSString alloc] initWithData:(__bridge NSData *)(streamData) encoding:NSUTF16StringEncoding];
               // }

                NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf stream length: %ld - %@", (long int)CFDataGetLength( streamData ), dataString]];

                for (int i = 0; i < [selfClass catalogLevel]; i++)
                    logString = [NSString stringWithFormat:@"-%@", logString];
                [Log LogDebug:logString];

                NSString *keyCheck = [[NSString alloc] initWithUTF8String:key];
                if( dict && ![keyCheck isEqualToString:@"Parent"] && ![keyCheck isEqualToString:@"P"])
                {
                    [selfClass setCatalogLevel:[selfClass catalogLevel] + 1];
                    CGPDFDictionaryApplyFunction(dict, getDictionaryObjects, dict);
                    [selfClass setCatalogLevel:[selfClass catalogLevel] - 1];
                }
            }
        }
    }
}

- (NSArray *)copyPDFArray:(CGPDFArrayRef)arr referencingDictionary:(CGPDFDictionaryRef)dict referencingKey:(const char *)key
{
    int i = 0;
    NSMutableArray *temp = [[NSMutableArray alloc] init];

    NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf array count: %zu", CGPDFArrayGetCount(arr)]];
    for (int i = 0; i < [selfClass catalogLevel]; i++)
        logString = [NSString stringWithFormat:@"-%@", logString];
    [Log LogDebug:logString];

    for(i=0; i<CGPDFArrayGetCount(arr); i++){
        CGPDFObjectRef object;
        CGPDFArrayGetObject(arr, i, &object);
        CGPDFObjectType type = CGPDFObjectGetType(object);
        switch(type){
            case kCGPDFObjectTypeNull: {
                NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf array null(%d)", i]];
                for (int i = 0; i < [selfClass catalogLevel]; i++)
                    logString = [NSString stringWithFormat:@"-%@", logString];
                [Log LogDebug:logString];
                break;
            }
            case kCGPDFObjectTypeBoolean: {
                CGPDFBoolean objectBool;
                if (CGPDFObjectGetValue(object, kCGPDFObjectTypeBoolean, &objectBool)) {
                    NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf array boolean value(%d): %@", i, [NSNumber numberWithBool:objectBool]]];
                    for (int i = 0; i < [selfClass catalogLevel]; i++)
                        logString = [NSString stringWithFormat:@"-%@", logString];
                    [Log LogDebug:logString];
                    [temp addObject:[NSNumber numberWithBool:objectBool]];
                }
                break;
            }
            case kCGPDFObjectTypeInteger: {
                CGPDFInteger objectInteger;
                if (CGPDFObjectGetValue(object, kCGPDFObjectTypeInteger, &objectInteger)) {
                    NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf array integer value(%d): %ld", i, (long int)objectInteger]];
                    for (int i = 0; i < [selfClass catalogLevel]; i++)
                        logString = [NSString stringWithFormat:@"-%@", logString];
                    [Log LogDebug:logString];
                    [temp addObject:[NSNumber numberWithInt:objectInteger]];
                }
                break;
            }
            case kCGPDFObjectTypeReal:
            {
                CGPDFReal objectReal;
                if (CGPDFObjectGetValue(object, kCGPDFObjectTypeReal, &objectReal))
                {
                    NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf array real(%d): %ld", i, (long int)objectReal]];
                    for (int i = 0; i < [selfClass catalogLevel]; i++)
                        logString = [NSString stringWithFormat:@"-%@", logString];
                    [Log LogDebug:logString];
                    [temp addObject:[NSNumber numberWithInt:objectReal]];
                }
                break;
            }
            case kCGPDFObjectTypeName:
            {
                const char *name;
                if (CGPDFDictionaryGetName(dict, key, &name))
                {
                    NSString *dictName = [[NSString alloc] initWithCString:name encoding:NSUTF8StringEncoding];

                    if (dictName)
                    {
                        NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf array name value(%d): %@", i, dictName]];
                        for (int i = 0; i < [selfClass catalogLevel]; i++)
                            logString = [NSString stringWithFormat:@"-%@", logString];
                        [Log LogDebug:logString];
                        [[selfClass pdfDict] setObject:dictName
                                                forKey:[NSString stringWithCString:key encoding:NSUTF8StringEncoding]];
                    }
                }
                break;
            }
            case kCGPDFObjectTypeString:
            {
                CGPDFStringRef objectString;
                if (CGPDFObjectGetValue(object, kCGPDFObjectTypeString, &objectString))
                {
                    NSString *tempStr = (__bridge NSString *)CGPDFStringCopyTextString(objectString);
                    NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf array string(%d): %@", i, tempStr]];
                    for (int i = 0; i < [selfClass catalogLevel]; i++)
                        logString = [NSString stringWithFormat:@"-%@", logString];
                    [Log LogDebug:logString];
                    [temp addObject:tempStr];
                }
                break;
            }
            case kCGPDFObjectTypeArray :
            {
                CGPDFArrayRef objectArray;
                if (CGPDFObjectGetValue(object, kCGPDFObjectTypeArray, &objectArray))
                {
                    NSArray *tempArr = [selfClass copyPDFArray:objectArray referencingDictionary:dict referencingKey:key];
                    [temp addObject:tempArr];
                }
                break;
            }
            case kCGPDFObjectTypeDictionary :
            {
                CGPDFDictionaryRef objectDict;
                NSString *keyCheck = [[NSString alloc] initWithUTF8String:key];
                if (CGPDFObjectGetValue(object, kCGPDFObjectTypeDictionary, &objectDict) && ![keyCheck isEqualToString:@"Parent"] && ![keyCheck isEqualToString:@"P"])
                {
                    [selfClass setCatalogLevel:[selfClass catalogLevel] + 1];
                    CGPDFDictionaryApplyFunction( objectDict, getDictionaryObjects,  objectDict);
                    [selfClass setCatalogLevel:[selfClass catalogLevel] - 1];
                }
                break;
            }
            case kCGPDFObjectTypeStream :
            {
                CGPDFStreamRef objectStream;
                if (CGPDFObjectGetValue(object, kCGPDFObjectTypeStream, &objectStream))
                {
                    CGPDFDictionaryRef streamDict = CGPDFStreamGetDictionary( objectStream );
                    CGPDFDataFormat fmt = CGPDFDataFormatRaw;
                    CFDataRef streamData = CGPDFStreamCopyData(objectStream, &fmt);
                    NSString *dataString = [[NSString alloc] initWithData:(__bridge NSData *)(streamData) encoding:NSUTF8StringEncoding];

                    NSString *logString = [[NSString alloc] initWithString:[NSString stringWithFormat:@"pdf array stream length: (%d): %ld - %@", i, (long int)CFDataGetLength( streamData ), dataString]];

                    for (int i = 0; i < [selfClass catalogLevel]; i++)
                        logString = [NSString stringWithFormat:@"-%@", logString];
                    [Log LogDebug:logString];


                    NSString *keyCheck = [[NSString alloc] initWithUTF8String:key];
                    if( streamDict && ![keyCheck isEqualToString:@"Parent"] && ![keyCheck isEqualToString:@"P"])
                    {
                        [selfClass setCatalogLevel:[selfClass catalogLevel] + 1];
                        CGPDFDictionaryApplyFunction( streamDict, getDictionaryObjects, streamDict );
                        [selfClass setCatalogLevel:[selfClass catalogLevel] - 1];
                    }
                }
            }

        }
    }
    return temp;
}

@end

Answer 1

使用“可编辑字段”，是指在使用Acrobat或Adobe时可以填充的表单元素的类型？

这些字段不是实际页面描述的一部分。如果您查看PDF规范文档，您将在第12.7章中找到对“交互式表单”的描述，说明文档的字段字典是从文档目录中名为"AcroForm“的元素开始存储的。

据我所知，iOS确实允许您访问文档目录，因此您必须在目录字典中找到"AcroForm“字段，然后下降到字段字典结构中来收集您想要的信息。整个文档中的所有字段都以分层的方式存储在这里。