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Tex2002ans · 04-19-2018, 05:09 PM

Hmmmm, could it be the PNGs are lower than 8-bit?

I remember years ago, GrannyGrump's post about 4-bit PNGs being buggy in ADE:

https://www.mobileread.com/forums/sh....php?p=2633151

and I know I ran across some oddities with Kindlegen with my Formulas to PNG (mostly with transparent backgrounds):

https://www.mobileread.com/forums/sh...d.php?t=223254

I detailed my method of saving as 17 colors, so it forced any sort of PNG compression/optimizers to treat it as 8-bit PNGs.

And from what I remember... MAAAANY YEARS ago, Kindlegen didn't support PNGs. Many years back, Kindlegen added PNG support, and sometimes did Color->JPG + Grayscale/Indexed->GIF... and when I last tested a few years back, my PNGs were not converted to JPG or GIF by Kindlegen.

Thought 1: Hmmmm could it also be a regression in Kindlegen recently? I must admit, I haven't done a lot of conversions with images lately (~the past year and a half).

Thought 2: I haven't poked around in these images specifically... do you have an Alpha channel or a strange Indexed PNG with transparency in it?

Thought 3: Taking another stab in the dark here... but could it also be PNGs over a certain filesize get compressed by Kindlegen? See if there's a limit of something like 256 KB where the PNG won't get converted.

04-19-2018, 05:09 PM	#7
Tex2002ans Wizard Posts: 2,306 Karma: 13057279 Join Date: Jul 2012 Device: Kobo Forma, Nook	Hmmmm, could it be the PNGs are lower than 8-bit? I remember years ago, GrannyGrump's post about 4-bit PNGs being buggy in ADE: https://www.mobileread.com/forums/sh....php?p=2633151 and I know I ran across some oddities with Kindlegen with my Formulas to PNG (mostly with transparent backgrounds): https://www.mobileread.com/forums/sh...d.php?t=223254 I detailed my method of saving as 17 colors, so it forced any sort of PNG compression/optimizers to treat it as 8-bit PNGs. And from what I remember... MAAAANY YEARS ago, Kindlegen didn't support PNGs. Many years back, Kindlegen added PNG support, and sometimes did Color->JPG + Grayscale/Indexed->GIF... and when I last tested a few years back, my PNGs were not converted to JPG or GIF by Kindlegen. Thought 1: Hmmmm could it also be a regression in Kindlegen recently? I must admit, I haven't done a lot of conversions with images lately (~the past year and a half). Thought 2: I haven't poked around in these images specifically... do you have an Alpha channel or a strange Indexed PNG with transparency in it? Thought 3: Taking another stab in the dark here... but could it also be PNGs over a certain filesize get compressed by Kindlegen? See if there's a limit of something like 256 KB where the PNG won't get converted. Last edited by Tex2002ans; 04-19-2018 at 05:23 PM.