Exiv2

I'm going to mark this as 80% done as something might come up in the next few weeks.

The code to read the command files is in src/exiv2.cpp/parseCmdFiles(). I was a little surprised to see that it doesn't use basicio, so it's not possible to use -mhttp://this/that. The parsing of the command files uses std::getline(). getline is not part of the basicio API. The code could be modified to "suck up" the data using basicio into a temporary file and parsed with std::getline().

It's possible to argue at the -PV option should also imply -Pk as a convenience.

Ah, that's interesting, Phil. If you've thought of this, I don't have a stupid idea! Mind you, to give credit for the idea, it's Nick who asked if we could do something like this.

I'll say this is 50% done and bump the estimate from 3 to 6 hours. Something to think about on a wet afternoon in England (shouldn't need to wait long for that in November).

The syntax of the exiv2 command is:

$ exiv2 [options] [action] file

We generally say "do abc ...." to one or more files and our insert/extract/preview/sidecar files are usually paired by name with the file. The pipe idea fits nicely into that model as we are typically reading, or writing. A command-option such as -tagsfromfile is a departure from our usual semantics as we are reading from one source and writing to one or more outputs. Maybe the syntax could be:

$ exiv2 -PkV1 --grep GPSL http://dev.exiv2.org/attachments/download/805/DSC_7154.jpg robin.jpg

The purpose of the '1' is to say read from the first, and apply to the rest. Without the '1', the command:

$ exiv2 -PkV --grep GPSL http://dev.exiv2.org/attachments/download/805/DSC_7154.jpg robin.jpg

Would say "Report by reading both DSC_7154.jpg AND robin.jpg". Oh, I'm getting excited. The command:

$ exiv2 -PkV+ --grep GPSL http://dev.exiv2.org/attachments/download/805/DSC_7154.jpg robin.jpg foo.jpg man.jpg

Would be to pair the files, so copy from DSC... into robin.jpg, copy from foo.jpg to man.jpg.

I have implemented this and attach a patch. I'm not going to submit this to trunk at the time, for a variety of reasons:

1. There is an alternative to this using the pipe design.
2. Let's wait for feedback concerning the 'set a.b.c value' commands. Life may be more complicated than this!
3. The -P1 and -P+ options are new semantics for the exiv2 application. I'd like to pause and think before jumping into a major semantic change.
4. We should avoid adding complicated stuff to the exiv2 application as its purpose is to be our test harness and "more complex" sample application.

So Phil: As always, I appreciate your input and encouragement. And I want you to know that I have spent a rainy afternoon implementing this. For the moment, I prefer to leave things as they are.

Demo:

$ curl -O --silent http://clanmills.com/robin.jpg ; exiv2 -pa robin.jpg ; exiv2 -P1V --grep GPSL ~/temp/Stonehenge.jpg  robin.jpg ; exiv2 -pa robin.jpg
Exif.Image.GPSTag                            Long        1  26
Exif.GPSInfo.GPSLatitudeRef                  Ascii       2  North
Exif.GPSInfo.GPSLatitude                     Rational    3  51deg 10.69690' 
Exif.GPSInfo.GPSLongitudeRef                 Ascii       2  West
Exif.GPSInfo.GPSLongitude                    Rational    3  1deg 49.59840' 
779 rmills@rmillsmbp:~/gnu/exiv2/trunk $ 

Implementing the -P+ option is a mod to the code in exiv2.cpp around line 930.

    // #1137
    // when -P1 is set (prFirst), pop the first file, print the metadata to stream and parse
    // set the action to modify to read the generated commands
    //
    // implementing the -P+ (prPair) feature is a simple variation of this code
    // to read (and subsequently remove) every other file in params->files_ to stream
    //
    if (rc == 0 && Params::instance().printItems_ & Params::prFirst ) {
        Params& params = Params::instance();
        // Cancel prFirst
        params.printItems_ |= !Params::prFirst;

        // Read and pop the first file
        std::string           file  = params.files_[0];
        Exiv2::Image::AutoPtr image = Exiv2::ImageFactory::open(file);
        assert(image.get() != 0);
        image->readMetadata();
        params.files_.erase (Params::instance().files_.begin());

        // Write the 'set' commands and read them into modifyCmds_
        Action::Print* printAction = new Action::Print();
        std::ostringstream    os ;
        printAction->printMetadata(image.get(),os);
        delete printAction;
        std::istringstream is(os.str());
        parseCmdStream(modifyCmds_,is,file);

        // Change action to modify
        params.action_ = Action::modify;
    }