For a writer document Thumbnails/Thumbnail.png makes 17,9 Ko.
When it is converted to gif it makes only 6,9 Ko.
Created attachment 90358 [details]
ODTs, JPEG graphic, and some thumbnails showing size difference.
The main graphic in the attached testkit uses this source image:
ODT file names indicate the version of LO used to create the document under Ubuntu 10.04 running:
- v188.8.131.52 OOO330m19 Build: 6
- v184.108.40.206 OOO340m1 Build: 602
- v220.127.116.11 Build ID: 3215f89-f603614-ab984f2-7348103-1225a5b
- v18.104.22.168 Build ID: 70feb7d99726f064edab4605a8ab840c50ec57a
Thumbnail generation under v3.3 and v3.4 series is flawed - the original image inserted into the document is not scaled correctly. The thumbnails generated by v22.214.171.124 and v126.96.36.199 are included separately for comparison. The "palette" version of each is created via ImageMagick:
$ convert thumbnail_v3572.png -type Palette thumbnail_v3572_palette.png
This is equivalent to converting to PNG8 (the 256 colour GIF equivalent) and results in a thumbnail ~40% the size of the original thumbnail PNG. This is slightly smaller than the corresponding PNG -> GIF conversion using the same tool.
Confirmed as per comment #1. Status set to NEW. Version left at v188.8.131.52 for the reasons indicated however it may need to have Severity set to enhancement as this functionality has never been available in LO before.
TomaÅ¾ Vajngerl committed a patch related to this issue.
It has been pushed to "master":
fdo#62104 Optimize thumbnail size by using PNG8 and other tricks
The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.
This bug fix comes with LibreOffice 4.4 and is mentioned in the release notes (https://wiki.documentfoundation.org/ReleaseNotes/4.4)