B4A Library JpegUtils library gives access to Exif data

agraham · Sep 21, 2011

This library contains an ExifData object that allows you to read and write the EXIF data in a Jpeg file. It is a very thin wrapper over the Android ExifInterface class.

Erel · Jun 24, 2013

Here (make sure to test the results):

B4X:

Sub Activity_Create(FirstTime As Boolean)
   Dim s As String = "56/1,16973828/65539,393216/1795N "
   Dim m As Matcher = Regex.Matcher("(\d+/\d+),(\d+/\d+),(\d+/\d+)", s)
   If m.Find Then
      Dim lat As Double
      lat = FractionToDouble(m.Group(1))
      lat = lat + FractionToDouble(m.Group(2)) / 60
      lat = lat + FractionToDouble(m.Group(3)) / 3600
      Log(lat)
   End If
End Sub

Private Sub FractionToDouble(frac As String) As Double
   Dim n() As String = Regex.Split("/", frac)
   Return n(0) / n(1)
End Sub

Please start a new thread for the second question.

corvo · Jun 24, 2013

Thank you Erel, but it don't works, the result of your code is 60.377(and more), but the correct latitude is 38.22741586714989, and your code don't work also whit longitude (but the format of the longitude is different from exiftag "858861618/976629818.939537202/1E"). I put the pics in this post, maibe you can find some problem in the image or in the code (the pic is in a .rar cause the siza was too big for the forum limit)

corvo · Jun 24, 2013

Sorry i forget the pic in the previous post

this is the pic

Erel · Jun 24, 2013

The degrees portion is 56 (56/1). Maybe the latitude was not written correctly.

corvo · Jun 24, 2013

Erel, if i use the function of the phone "find the place of the pic" google maps put a marker on my home.....

Erel · Jun 24, 2013

I've downloaded a program that shows the image on a map: Download Photo GPS Extract

corvo · Jun 24, 2013

i don't know Erele, try whit your phone and you will see my home

Erel · Jun 24, 2013

Maybe Google Maps use a different method to extract the location. I'm not familiar more than you with the EXIF format. I'm just following the documentation.

agraham · Jun 24, 2013

Those strings certainly look odd. Have you tried to see what exif.getLatLong returns?

corvo · Jun 24, 2013

i don't now how to use it, every time i got a error

agraham · Jun 24, 2013

getLatLong

Method

Stores the latitude and longitude value in a float array. The first element is the latitude,
and the second element is the longitude.
Returns false if the Exif tags are not available.

Returns : Boolean

getLatLong(output As Float())

B4X:

Dim LL(2) As Float
exif.getLatLong(LL)
Msgbox("Latitude = " & LL(0), "Latitude")

agraham · Jun 24, 2013

There seems to be something odd about the format that the camera is writing.

An online EXIF viewer gives this

Camera
SAMSUNG GT-I8190N

GPS Position
60.316476 degrees N, 1.813130 degrees E

Opening the image in Google Earth shows

Lat: 60.3166727, Lon: 1.9337032

gadgetmonster · Jul 2, 2013

Saving Exif Latitude and Longitude

Hi,

I am using this wonderful library to get lat and long data from photos. This works a treat. My problem is saving it back out. I can save the date and time fine, its just saving latitude and longitude.

If I have two variables lat = 51.329444 and lon = 1.1839 for example, I do the following:

B4X:

exif.Initialize(File.DirRootExternal & "/app/", "photo.jpg")
exif.setAttribute(exif.TAG_GPS_LATITUDE, lat)
exif.setAttribute(exif.TAG_GPS_LONGITUDE, lon)
exif.setAttribute(exif.TAG_DATETIME,  exifDTM)
exif.saveAttributes

The date is fine but how should the latitude and longitude be formatted?

The above does not work as I can't load the coordinates back in. I have also tried hard coding to something like 59; 19; 46 but that doesn't work either.

Any ideas?

agraham · Jul 2, 2013

See my post #20 in this thread. Looks like you need a string of three rational numbers separated by commas.

gadgetmonster · Jul 3, 2013

agraham said:
See my post #20 in this thread. Looks like you need a string of three rational numbers separated by commas.

I have tried a test using:

B4X:

exif.setAttribute(exif.TAG_GPS_LATITUDE, "51/1,19/1,46/1")
exif.setAttribute(exif.TAG_GPS_LONGITUDE, "1/1,5/5,5/5")

and

B4X:

exif.setAttribute(exif.TAG_GPS_LATITUDE, "51,19,46")
exif.setAttribute(exif.TAG_GPS_LONGITUDE, "1,5,5")

but this still doesn't work.

Am I missing something here?

agraham · Jul 3, 2013

If you Google "android exif save latitude" you will find a couple of Stack Overflow threads that indicate that your first example above should work. I'm afraid that I have no idea why it doesn't in your case.

gadgetmonster · Jul 3, 2013

A little bit of a development.

I have tested the photo I am saving out and the exif data is saved. I used a desktop app that positions photos on a map and it is spot on. This proves that the exif data is being written out and correctly.

The problem therefore is when I read it back in. I am using:

B4X:

exif.Initialize(File.DirRootExternal & "/app/", "photo.jpg")
Dim output(2) as Float
if exif.getLatLong(output) = True Then
    lat = output(0)
    lon = output(1)
else
    lat = ""
    lon = ""
end if

exif.getLatLong(output) always = false

agraham · Jul 3, 2013

The Android docs say getlatLong "Returns false if the Exif tags are not available." so it looks like your device doesn't support it for some reason.

Have you tried GetAttribute(exif.TAG_GPS_LATITUDE)?

gadgetmonster · Jul 3, 2013

Ok now i'm getting somewhere

If I use exif.getAttribute(exif.TAG_GPS_LATITUDE) this will return what I saved i.e. 51/1,19/1,46/1

so the problem seems to be with exif.getlanglong

daemon · Sep 26, 2014

Hi,

Can this library work on Byte() instead of a file?
I want to use this library on a picture taken from camera, without storing the data to a file. I want to store after updating EXIF data.

Thanks!

B4A Library JpegUtils library gives access to Exif data

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