"cover.jpg" generated with additional white space (for small cover jpgs)
This issue is with the regeneration of cover.jpg of an epub on Calibre 2.40.0 (Portable version) running on Windows 7.
It with an epub with a rather small embedded cover jpg of 313x499 pixels. When dragged into Calibre 2.5.0, the cover.jpg in the library remains as 313x499 and the Calibre display stretches to full height. See attached "Image 2.5.0.png".
However, when the same epub is dragged into Calibre 2.40.0, cover.jpg is generated to 590x750 pixels, but the image is not stretched from 313x499 to 590x750. Instead the image remains as 313x499 and white space is added on the left, right and bottom of the image to make it to 590x750. This regenerated image (with the three white sides) appears on the Calibre display. See attached "Image 2.40.0.png".
I include the epub used, but I have tried this with several other epubs with small cover jpgs and the effect is the same. On reinstalling some older versions, I believe this change happened between versions 2.5.0 and 2.10.0.
I cannot find any settings or tweaks in Preferences to change this back to the 2.5.0 treatment. I also tried to compare the settings between 2.5.0 and 2.40.0 but could not find where to make the change.
Thank you for your attention on this matter.