exif.js doesn't read orientation tags properly

[jywarren]

http://mapknitter.org/maps/gps-test shows several which seem to be off by increments of 90 degrees;

See how this is done in the backend: https://github.com/publiclab/mapknitter/blob/master/app/models/warpable.rb#L231-L242

EXIF orientation values:

Value	0th Row	0th Column
1	top	left side
2	top	right side
3	bottom	right side
4	bottom	left side
5	left side	top
6	right side	top
7	right side	bottom
8	left side	bottom

[jywarren]

Specifically RIM0342.JPG is wrong, and RIM0352.JPG is right, in the CUAS example.

[jywarren]

So, this is now implemented (a67ff2a) but is not working properly. exif and exifprobe on Ubuntu correctly identifies the two images above as "3" and "8" -- but exif.js reads both as "1".

$:~/Desktop/gps$ exifprobe RIMG0352.JPG | grep Orientation
@0x000003a=58      :        <0x0112=  274> Orientation                 [3 =SHORT         1]  = 3 = '0,0 is bottom right'
$:~/Desktop/gps$ exifprobe RIMG0342.JPG | grep Orientation
@0x000003a=58      :        <0x0112=  274> Orientation                 [3 =SHORT         1]  = 8 = '0,0 is left bottom'

[jywarren]

Filed an issue here: exif-js/exif-js#45

[grvsachdeva]

@jywarren I noticed there was a update in issue exif-js/exif-js#45. Would you like to update here too? Thanks!

[jywarren]

Hmm do you think it was fixed?

[grvsachdeva]

No @jywarren, the issue is still open.

[jywarren]

I think we'll have to try to help solve it upstream in exif.js. Thanks!

[sashadev-sky]

@jywarren @gauravano I started working looking at the exif data today when looking at your modularization of exporter code PR. Will definitely look into this more.

Just wondering what API are we using exactly? There wasn't much documentation to guide me

[jywarren]

We're probably going to start doing this in Leaflet.DistortableImage as part of @rexagod's new GPS placement API -- see publiclab/Leaflet.DistortableImage#169 -- although it's still in progress. But It basically uses the Exif.js library to dig GPS tags out of the images, and to auto-place them accordingly!