I have epub books that are about 99.9% images (eg: Diary of a Wimpy Kid) and when viewed as mobi on my Kindle Voyage, the images don't fill the screen and thus are too small to comfortably view. I suspect the images would look fine on a lower-resolution kindle but not on the voyage. I could long-press the image, click the magnifier to expand the image to fill the screen, but I have to do this for every page.
When testing converting comics files using different apps (mangai or kcc), I've noticed that the kindle's mobi viewer will automatically crop out white margins and upscale images to fill the screen. I'm not sure if this only works for white margins in the actual image or if it would work with the white margins in the html page (which is the situation with the epubs), but this feature may help resolve my issue if there is a way to enable it. I think this is a feature of the mobi reader in the paperwhite as well.
I don't know what special setting needs to be set in the mobi to enable this feature. When this is happening, the menu has these options:
* Animation On/Off
* Fit to Screen On/Off
Note that I'm not aware of a way to DISABLE the automatic margin trimming/image upscaling for these documents.
Otherwise, are there any other options in the conversion process to upscale these images, either by actually upscaling the images or some sort of width=100% html setting? In calibre, when I edit the epub, I see the html simply has each image in a separate <p> tag:
Code:
<p class="image"><a id="page_124"/><img alt="Image" src="../images/f0124-01.jpg"/></p>
<p class="image"><a id="page_125"/><img alt="Image" src="../images/f0125-01.jpg"/></p>
<p class="image"><a id="page_126"/><img alt="Image" src="../images/f0126-01.jpg"/></p>
<p class="image"><a id="page_127"/><img alt="Image" src="../images/f0127-01.jpg"/></p>