Need to know Kindle Keyboard supported greyscale values.

[Nivos]

Hello everyone,

First off, I had also posted this question in the kindle main forum, however seeing as how you're developers and the content you create will have to display properly on the Kindle you probably know the answer so I'm also asking it here.

My question is, which color values exactly does the kindle keyboard support?

I bought a kindle keyboard wifi on ebay, and decided I want to put custom screensavers on it. I spent the past few days creating many photos, all 600x800, all greyscale, and all with as much contrast as I'm comfortable with. Today my kindle arrived and I immediately installed the jailbreak and screensaver hack. Now that I've got my custom images on the kindle I see a huge problem.
I had followed these two tutorials here to create the images:
http://www.ebookworm.us/creating-kin...ges-with-gimp/
http://blog.grapii.com/2011/09/how-t...-screensavers/

Those two tutorials both used the same color palette for dithering, however when I used the same palette on my images they didn't display correctly at all on my kindle. So does anyone know the exact colors of the kindle keyboard's palette?




Edit: I noticed in the posting rules that duplicate posting is forbidden, so I apologize for this. Unfortunately I don't know how to remove threads.

[knc1]

Originally Posted by Nivos

- - - - - -
Edit: I noticed in the posting rules that duplicate posting is forbidden, so I apologize for this. Unfortunately I don't know how to remove threads.

Not a problem, we will just double our support fees.

[NiLuJe]

@Nivos: There's a palette gif in the ScreenSavers hack . (linkss/etc/kindle_colors.gif)

EDIT: Which definitely is correct, and the same one mentioned in your second link. So, define 'huge problem', and your methodology, because it's definitely not the palette itself that's the issue .

[eschwartz]

Originally Posted by Nivos

Edit: I noticed in the posting rules that duplicate posting is forbidden, so I apologize for this. Unfortunately I don't know how to remove threads.

Moderator Notice

Deleted extraneous thread.

[Nivos]

Thank you for the replies.

@knc1: I'll make sure to pay my due

@eshcwartz: Thank you for helping me out, I'm still new around here.

@NiLuJe: I'll try and describe my process and show some examples of what's wrong.
Here's what I did to get the photo ready:
1. Rescale to 3:4 ratio.
2. Use a compositing software to turn the image to greyscale and rescale to 600x800. (also changed file to .png)
3. Open greyscale image in GIMP and change contrast and brightness.
4. Select image -> Mode -> Indexed.
5. In dialog that comes up select "Use-custom palette", and select the palette for kindle. I also deselected "Remove unused colors from colormap".
6. In Dithering select Floyd-Steinberg.
7. Export as .png at maximum compression (since it's a lossless format).

Then I just moved the file to the screensavers folder on my Kindle and rebooted. Here are the results of my work. I uploaded the same photos to the Kindle photo viewer so that I could take a screenshot of what it looks like on the kindle.

Original:


Image violates guidelines for size - MODERATOR]

Original on Kindle:

Image violates guidelines for size - MODERATOR]

Optimized (The one with Indexing and Dithering):

Image violates guidelines for size - MODERATOR]

Optimized on Kindle:


Image violates guidelines for size - MODERATOR]

[knc1]

Try using your graphics tools on a copy of an Amazon screensaver file.

What you are looking for is the (4) bit into (8 bit) byte packing (and any inversions).

[Dr. Drib]

Moderator Notice

Please take a few moments to read our Posting Guidelines, in particular the part about the maximum image size allowed (600x600 pixels).

Thanks.

[NiLuJe]

Please post links (or just attach them) to your results instead of inlining them, Drib's moderating broom swiped your images before I could take a look at them .

Not sure why you're using a few different softwares, so let's say if you were using GIMP all along:

* Crop/Compose/Scale
* Greyscale
* Remap to eInk palette w/ FS dithering
* Re-Greyscale [by which I mean Image > Mode > Greyscale] (might be important, otherwise the PNG is saved as a 16c, not 8-bit, which upsets some FW versions).
* Save as PNG

Also, unless you have some very specific needs, I'd recommend playing with the levels in a real colorspace, *before* greyscaling everything.

[Nivos]

Original:

http://i.imgur.com/nPrHX8d.png

Original on Kindle:

http://i.imgur.com/90GFNwB.gif

Optimized (The one with Indexing and Dithering):

http://i.imgur.com/PNhOkd7.png

Optimized on Kindle:

http://i.imgur.com/9KcKXlO.gif


I now reread the posting rules in their entirety without skipping anything so I hope there won't be any need for more modding

@NiLuJe: I didn't re-greyscale so that may be the issue. I'll try it out and let you know if it succeeds. And using different software is simply a matter of convenience for me.

[NiLuJe]

@Nivos: Yep, most likely the issue. That usually ends up looking like a polarized mess like that.

identify ~/Downloads/PNhOkd7.png
~/Downloads/PNhOkd7.png PNG 600x800 600x800+0+0 8-bit sRGB 16c 103KB 0.000u 0:00.000

vs.

identify ~/Kindle/Hacks/ScreenSavers/src/linkss/screensavers/00_you_can_delete_me.png
~/Kindle/Hacks/ScreenSavers/src/linkss/screensavers/00_you_can_delete_me.png PNG 600x800 600x800+0+0 8-bit sRGB 256c 71.2KB 0.000u 0:00.000

Keep in mind that the reader, image viewer, eips, and the screensavers don't necessarily handle everything the same way, but making sure the resulting file is a true PNG8, even if it only contains 16 actual colors, is the best way to make everyone happy .

[Nivos]

Perfection!
Thank you very much NiLuJe, that solved my problem.