[TYPO3] imgResource returns jpg

[Stano Paška]

Hi,

I use imgResource in TypoScript to produce small thumbnails from jpegs.
Thumbnail has a jpg extension but it is gif file (with ugly dither).

... {
  file.width = 120c
  file.height = 120c
  file.maxH = 120
  file.maxW = 120
}

When  use this
... {
//  file.width = 120c
//  file.height = 120c
  file.maxH = 120
  file.maxW = 120
}

thumbnails are correct jpgs and looks nicer, but does not have square
dimensions.

I tried combinations of this
file.ext = jpg
file.type = jpg
file.format = jpg
file.params = -format jpg -quality 75 -type TrueColor
but with no luck.

Can you help me?

Thanks.

Stano Paska.