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androidgpsexif

Correct Value(s) to store in TAG_GPS_PROCESSING_METHOD

Thanks for reading this question. I am sure the experts on this site will be able to provide the help I need.

I am trying to write an app which allows users to edit the exif information of the photos on their Android Phone.

As a part of improved user experience, I want to apply data validation where ever possible.

For the Exif Tag - TAG_GPS_PROCESSING_METHOD I am not able to apply the validation correctly.

Here is the part of code that I have applied :

String strGPSProc = etGPSProc.getText().toString();

if(strGPSProc.equalsIgnoreCase("GPS") || strGPSProc.equalsIgnoreCase("CELLID") || strGPSProc.equalsIgnoreCase("WLAN") || strGPSProc.equalsIgnoreCase("MANUAL") ) {
        returnValue = true;
}else {
        returnValue=false;
        showToast("Incorrect value for GPS Processing Method. Correct value options are GPS, CELLID, WLAN or MANUAL.");
        etGPSProc.requestFocus();
}

This code checks if the value entered in the EditText meant for GPSProcessingMethod, has any one of the four prescribed value as described in the documentation of EXIF.

But when I try to save this using setAttribute() and saveAttributes() functions, a non catch-able exception appears in logcat.

Unsupported encoding for GPSProcessingMethod

I understand from Exif Documentation that values for GPSProcessingMethod needs to be stored with some header information.

I need some expert advise on how to implement this correctly, with out using any other 3rd part classes.

Solution

  • Accoridng to the Exif specification:

    GPSProcessingMethod

    A character string recording the name of the method used for location finding. The first byte indicates the character code used (Table 6､Table 7), and this is followed by the name of the method. Since the Type is not ASCII, NULL termination is not necessary

    Atually, Table 6 lists the character codes as 8 byte sequences, so the above should probably read "The first bytes indicate...". Anyway, the character code designation for ASCII is defined as 41.H, 53.H, 43.H, 49.H, 49.H, 00.H, 00.H, 00.H., Unicode is (unsurprisingly) 55.H, 4E.H, 49.H, 43.H, 4F.H, 44.H, 45.H, 00.H. I guess these should be all you need.

    Hope that helps.

    EDIT: Just discovered that ExifInterface.setAttribute() only supports String values... You could try encoding the value at the beginning of your string, but I doubt that would work. Sounds like the encoding should be handled by the setAttribute() or saveAttributes() method. Could it be a bug in the API? I had a look at the source code, but the actual writing of values is done by native code so I stopped digging further.