Automatic image compression produces huge PDF files (corverts JPG to bitmap)

[Benjamin Drung]

I am using scribus 1.4.6+dfsg-4build1 on Ubuntu 17.10 (artful). Create a new Scribus document and just insert one JPG compressed picture (Sleeping_hedgehog.jpg in my example). Then export this document as PDF. Use following settings in Image Compression Method:

Compression Method: Automatic
Compression Quality: Maximum
Unticked Maximum Image Resolution

The resulting PDF is multiple times bigger than the original JPG picture:

$ du -sh *
23M Example_automatic_high.pdf
23M Example_automatic_maximum.pdf
23M Example_automatic_medium.pdf
2,9M Example_jpeg_maximum.pdf
23M Example_lossless_maximum.pdf
12K Example.sla
2,2M Sleeping hedgehog.jpg

I expected that the resulting PDF just embeds the JPG picture without modifying it, but this is not the case. I don't see a way to let Scribus embed all JPG/PNG images unmodified in the PDF.

[Benjamin Drung (bdrung)]

From https://bugs.scribus.net/view.php?id=10505:

"A(nother) user recently noted on irc that progressive mode JPEG induced huge PDFs, when not-progressive type just did fine PDFs (i'm not sure but i seem to remember that this user said it was a new behaviour)."

This is exactly my problem. When I convert the picture and remove the progressive mode, the resulting PDF is small.