Image resolution/size in BloomPUBs

I’ve noticed that the image quality in BloomPUBs is lower than in the corresponding PDFs. It seems clear that the BloomPUB creation process downsamples images. What is the standard size or resolution that images are downsampled to?

Currently, images in BloomPUBs and online READing are downsampled to a max dimension of 600 pixels.

This is to better serve users who have poor internet and/or limited memory on their devices.

The PDF, as you note, utilizes the full image quality.

Recently, some Bloom users have asked for an option to increase the quality of images in their BloomPUBs and we provided a “back door” way to change this:

In the publish-settings.json file for the Bloom book, change




Then re-upload the book to Bloom Library.

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@ColinSuggett Thanks for this!
Is 1200x900 an absolute maximum, or can the image sizes be greater?

1200 x 900 is our proposal for a higher tier of resolution, but this can be increased.