How to use the free desktop version of ComicRack to shrink .CBR digital comic book files in size, for reading on an older under-powered Android tablet:
1. Install the free ComicRack for Windows. It’s mature software, and the desktop version is genuinely free.
2. Load ComicRack. Get yourself all the way out of whatever ‘minimal interface’ / ‘full-screen’ view you’re in. In the corner, click on ‘Folders’, and navigate to the folder containing the .CBR comics that you want to reduce in size.
3. Shift-click to select all the folder’s comics. Click on “Export Books”.
4. Now set up your Export preset. Tell ComicRack where the save the new files, the size reduction, compression, and more.
Erm… now, what size to shrink them to? You’re not told what the page width is (although you can use CbxConverter if you really want to know) but let’s assume that a HD .CBR page is 1988px, with double-page spreads at 3975px.
Let’s imagine that you have a Archos 70 Android tablet from four or five years ago, which had the benefit of an excellent and crisp screen at 800 x 480px. A preset that gives each page 1000px, in .JPG at 60% compression, should be very lightweight. Here I’ve also set it up for that, and to split double-page spreads into two pages…
5. Save your configuration as a preset, and test your preset. If don’t get it right the first time, delete it and start over. If 60% JPG compression is too strong, try 85%. If you have a slightly more powerful tablet than otherwise, you might try a 1400px width.
6. Once you’re happy that you have the right mix on your preset, from now on you can use this custom master preset for “Export Books”. Simply click on “Export Books”, select your preset from the dropdown, and the conversion starts. There’s no progress bar, but if you look in your chosen export folder you’ll see the new files being created one by one.
7. That’s it. As a .CBR and .CBZ reader I use the excellent free Comitton (aka ComittoNxN — scroll down the Google Play page a little, to see the link to the free version) (Also on Kindle Fire). Its only disadvantage is that on layered PDF files it only displays the artwork, not the lettering laid on top of the art.
In past years many have suggested the free CbxConverter as a .CBR size shrinker. It’s effective, but it can only save using the .webp graphics format. Which means you can’t use ComittoNxN as a reader because it doesn’t yet support .webp, which means that on an older tablet you have to use Perfect Viewer instead — and Perfect Viewer has an awfully clunky magnifier compared to ComittoN, even when you pay the donation.