[CavemanJoe]

Hey all, vintage ereader user here, intensely appreciative of Calibre's handling of .cbz files and hoping that similar functionality can be applied to non-cbz inputs.

When you use Calibre's built-in PRS-505 profile to import a .cbz (such as a comic) and convert to .epub, Calibre will automatically resize every image to perfectly fit the PRS-505's screen, and also turn the image greyscale to an appropriate number of shades to further reduce file size, with optional sharpening. I believe this feature was originally a plugin that was impressive enough to be merged with the main Calibre project.

I have a stack of ex-display-model PRS-505 ereaders that I'm replacing batteries and handing out to friends, and I'm in the process of writing a guide on how to make new ebook files play nicely with vintage ereaders, to try to keep these machines in use and out of the e-waste stream. Even after removing DRM, these lovely old 600x800 machines frequently choke on the gargantuan chapter heading images inside modern .epub files.

I've had success using a combination of Polish Books (to subset fonts and compress images) and Bulk Image Resizer plugins, but Bulk Image Resizer can't be run on multiple books at once (it requires you to enter the ebook editor window and run on books one at a time), nor does it greyscale any images.

The process I've come up with is a far cry from the excellent one-click .cbz to .epub workflow, and I was initially thinking of writing a plugin that would automatically shrink all images to screen-appropriate sizes and colour depth, but quickly realised this would be a massive duplication of effort given that Calibre already has the ability to resize-and-greyscale all images when converting .cbz to .epub, but doesn't have the same behaviour when importing books in other formats.

Is there a way to do this that I'm missing, should I submit this as a feature request, or am I diving into plugin writing?

Cheers!