Fix gallery preview

Hi,

my Gallery is facing a weird issue with the preview of photos by showing them partitially for some files but others just have a grey document icon. How can I fix this issue?

Did you check that these are supported file types? These can be adjusted via config.php: https://docs.nextcloud.com/server/13/admin_manual/configuration_server/config_sample_php_parameters.html#previews
Some might need additional php modules.

@flux84 I recommend to install the Preview Generator app and follow the recommendation concerning the preview sizes to be generated as described here: https://github.com/rullzer/previewgenerator/blob/master/README.md . Since I’ve set the mentioned parameters and
used the following preview configuration settings, photos are loaded much faster and without
any display problems:

  'enable_previews' => true,
  'preview_max_x'   => 1024,
  'preview_max_y'   => 1024,
  'preview_max_scale_factor'   => 10,
  'preview_max_filesize_image' => 50,