Optimum image size in pixels to fit Kobo Libre 2 screen

[porphyry5]

I have .jpg images I can convert to a pdf to read on Kobo Libre 2.

There is an extensive white border around all the images, so I can use imagemagick to crop them to the ideal size to fit Libre's screen.

What is that ideal size in pixels?

[DNSB]

The Libra 2 screen is 1264 x 1680 pixels. You may want to use a few pixels per side for a margin so say, 1254 x 1672 for the actual image.

Though personally, I would prefer a CBZ or an ePub format to store those images.

[porphyry5]

Originally Posted by DNSB

The Libra 2 screen is 1264 x 1680 pixels. You may want to use a few pixels per side for a margin so say, 1254 x 1672 for the actual image.

Though personally, I would prefer a CBZ or an ePub format to store those images.

Thanks much.

[rashkae]

You'll definitely want cbz format for viewing image collection on Libra Colour. Epub format would by very slow (unless converting to kepub, another topic), not allow zoom/resize, and will not dither properly leaving lots of banding, (*very* noticeable on greyscale images.)

[porphyry5]

Originally Posted by rashkae

You'll definitely want cbz format for viewing image collection on Libra Colour. Epub format would by very slow (unless converting to kepub, another topic), not allow zoom/resize, and will not dither properly leaving lots of banding, (*very* noticeable on greyscale images.)

The original file is a pdf of text with such a large margin of blank space that the actual text is hard to read when viewed in a reader. But I've not been able to find an app that will crop the pages in a pdf. The closest I could get is pdftoppm which coverts each page to a .ppm image and will crop them to any size you specify. One can then convert these images back to a pdf with img2pdf, and create a text layer in that pdf with ocrmypdf, re-enabling instant dictionary lookup for the text.

Instant dictionary access is by far my major reason for preferring ereaders to paper volumes, and far outweighs any objection to the size of the output pdf (usually 10-20 times the size of the original).

I don't know, but I doubt that .epub or .cbz would provide that facility, or am I wrong about that?