Steps to reproduce :

Browse photo directories in external storage in Owncloud official app 1.9.0
    Only placeholder is shown
    Not Thumbnails in external storage on official android app - Works fine directly from web browser (Like Firefox)
    Thumbnails work fine out of the external storage on official android app
    Thumbnails work fine in external storage with Web browser

My external storage is just another local folder in the same owncloud's server

Expected behaviour :

There is a thumbnail.

Actual behaviour :

Placeholder icon is shown

Operating system:

Debian Jessie (8.0)

Web server:
Apache

Database:
MySQL

PHP version:
5.6.14

ownCloud version: 8.2.1(stable)

Owncloud log :
{"reqId":"qvwmBaQX\/gQVUzWPBpx5","remoteAddr":"192.168.0.254","app":"core","message":"Generating preview for \"files\/DonneesReseaux\/DessinsPerso\/Euro2008.png\" with \"OC\\Preview\\PNG\"","level":0,"time":"2015-12-13T21:43:27+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/Euro2008.png"} {"reqId":"qvwmBaQX\/gQVUzWPBpx5","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Image is not a JPEG.","level":0,"time":"2015-12-13T21:43:27+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/Euro2008.png"} {"reqId":"qvwmBaQX\/gQVUzWPBpx5","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Orientation: -1","level":0,"time":"2015-12-13T21:43:27+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/Euro2008.png"} {"reqId":"KxfNYjDs5j8L7qHjhX8D","remoteAddr":"192.168.0.254","app":"core","message":"Generating preview for \"files\/DonneesReseaux\/DessinsPerso\/FondEcranCroixSmartphoneSansPhoto.png\" with \"OC\\Preview\\PNG\"","level":0,"time":"2015-12-13T21:43:28+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/FondEcranCroixSmartphoneSansPhoto.png"} {"reqId":"KxfNYjDs5j8L7qHjhX8D","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Image is not a JPEG.","level":0,"time":"2015-12-13T21:43:28+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/FondEcranCroixSmartphoneSansPhoto.png"} {"reqId":"KxfNYjDs5j8L7qHjhX8D","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Orientation: -1","level":0,"time":"2015-12-13T21:43:28+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/FondEcranCroixSmartphoneSansPhoto.png"} {"reqId":"PfoWr48VV4NyRVJCDyhv","remoteAddr":"192.168.0.254","app":"core","message":"Generating preview for \"files\/DonneesReseaux\/DessinsPerso\/logo.png\" with \"OC\\Preview\\PNG\"","level":0,"time":"2015-12-13T21:43:28+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/logo.png"} {"reqId":"PfoWr48VV4NyRVJCDyhv","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Image is not a JPEG.","level":0,"time":"2015-12-13T21:43:28+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/logo.png"} {"reqId":"PfoWr48VV4NyRVJCDyhv","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Orientation: -1","level":0,"time":"2015-12-13T21:43:28+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/logo.png"} {"reqId":"CUZ+fj5crMxsSrxA6kG7","remoteAddr":"192.168.0.254","app":"core","message":"Generating preview for \"files\/DonneesReseaux\/DessinsPerso\/PtitCoeur.png\" with \"OC\\Preview\\PNG\"","level":0,"time":"2015-12-13T21:43:29+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/PtitCoeur.png"} {"reqId":"CUZ+fj5crMxsSrxA6kG7","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Image is not a JPEG.","level":0,"time":"2015-12-13T21:43:29+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/PtitCoeur.png"} {"reqId":"CUZ+fj5crMxsSrxA6kG7","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Orientation: -1","level":0,"time":"2015-12-13T21:43:29+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/PtitCoeur.png"} {"reqId":"C3fC8nRYyW+OxJYqPNd7","remoteAddr":"192.168.0.254","app":"core","message":"Generating preview for \"files\/DonneesReseaux\/DessinsPerso\/SmileyCoeur2.png\" with \"OC\\Preview\\PNG\"","level":0,"time":"2015-12-13T21:43:30+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/SmileyCoeur2.png"} {"reqId":"C3fC8nRYyW+OxJYqPNd7","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Image is not a JPEG.","level":0,"time":"2015-12-13T21:43:30+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/SmileyCoeur2.png"} {"reqId":"C3fC8nRYyW+OxJYqPNd7","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Orientation: -1","level":0,"time":"2015-12-13T21:43:30+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/SmileyCoeur2.png"} {"reqId":"0h45oTMfydQVuZWYy+32","remoteAddr":"192.168.0.254","app":"core","message":"Generating preview for \"files\/DonneesReseaux\/DessinsPerso\/WorldCup2010.png\" with \"OC\\Preview\\PNG\"","level":0,"time":"2015-12-13T21:43:30+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/WorldCup2010.png"} {"reqId":"0h45oTMfydQVuZWYy+32","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Image is not a JPEG.","level":0,"time":"2015-12-13T21:43:30+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/WorldCup2010.png"} {"reqId":"0h45oTMfydQVuZWYy+32","remoteAddr":"192.168.0.254","app":"core","message":"OC_Image->fixOrientation() Orientation: -1","level":0,"time":"2015-12-13T21:43:30+00:00","method":"GET","url":"\/owncloud\/index.php\/apps\/files\/api\/v1\/thumbnail\/448\/448\/DonneesReseaux\/DessinsPerso\/WorldCup2010.png"}