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Old 03-30-2015, 08:09 AM   #1
ikeabord
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Strange eips behaviour

Hi everyone,

This is my first post here, but I've used the forum extensively so thank you for providing such a great resource!

I have a jailbroken Kindle 4 NT with USBNet installed. Everything works as expected except for one thing I can't figure out. I haven't been able to find the same problem on these forums.

I am using the Kindle to display 8bit PNG images at regular intervals using eips. To display an image I do:

Code:
eips -g image.png
The problem is that some images display correctly while others, for lack of a better word, get kind of 'skewed'/distorted. Even the Kindle's default screensaver images.

I've attached two images, one that works and one that doesn't. Attached is also pictures of how they look on the Kindle.

I hope someone has an idea why this happens. Thanks in advance!
Attached Thumbnails
Click image for larger version

Name:	Orca.png
Views:	638
Size:	29.2 KB
ID:	136570   Click image for larger version

Name:	scr.png
Views:	185
Size:	92.2 KB
ID:	136571   Click image for larger version

Name:	orca_kindle.jpg
Views:	164
Size:	247.6 KB
ID:	136574   Click image for larger version

Name:	scr_kindle.jpg
Views:	150
Size:	258.2 KB
ID:	136575  
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Old 03-30-2015, 08:27 AM   #2
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They need to be saved as true PNG-8, even if they're dithered down to 16 colors.

The first one is, the second isn't, it's saved as a paletted PNG, which eips can't deal with.

Code:
Orca.png PNG 600x800 600x800+0+0 8-bit sRGB 256c 29.9KB 0.000u 0:00.000
scr.png PNG 600x800 600x800+0+0 8-bit sRGB 16c 94.5KB 0.000u 0:00.000
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Old 03-30-2015, 08:35 AM   #3
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Quote:
Originally Posted by NiLuJe View Post
They need to be saved as true PNG-8, even if they're dithered down to 16 colors.

The first one is, the second isn't, it's saved as a paletted PNG, which eips can't deal with.

Code:
Orca.png PNG 600x800 600x800+0+0 8-bit sRGB 256c 29.9KB 0.000u 0:00.000
scr.png PNG 600x800 600x800+0+0 8-bit sRGB 16c 94.5KB 0.000u 0:00.000
Oh, I see. Thank you very much! Can you recommend any tools for converting PNG images to true PNG-8?
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Old 03-30-2015, 08:50 AM   #4
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Anything does the job really, as long as you make sure not to leave them paletted after dithering.

I usually go the CLI-way with ImageMagick, I have posted my usual one-liner a couple of times before .
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Old 03-30-2015, 08:58 AM   #5
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Thank you, I'll take a look at that. I can't believe it took less than 20 minutes for you to provide an answer. Your help is much appreciated!
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Old 03-30-2015, 09:23 AM   #6
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I can't recall if the Kindles have the 'file' command pre-installed in the system files or not ...
But if they do, a quick check:
Code:
core2quad Downloads $ file *.png
Orca.png: PNG image data, 600 x 800, 8-bit grayscale, non-interlaced
scr.png:  PNG image data, 600 x 800, 8-bit colormap, non-interlaced
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Old 03-30-2015, 12:13 PM   #7
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I just checked and it doesn't seem to have it pre-installed. But it's installed on my laptop and I didn't know I could use it for this purpose, so thanks!
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Old 06-07-2017, 01:12 AM   #8
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Interesting case!
I wanted to put some useful information on 'battery dead' screen (where I think it would be the most useful). Took the original pictures from /opt/amazon/low_level_screens/600x800/ and added info through GIMP.
Then I did all by the suggestion given here to convert my png's to required format using ImageMagick:
Code:
convert {input_image} -type GrayScale -depth 8 -colors 256 gray.png
I tested this new image by both methods.
Imagemagick's identify call gives me:
Code:
$cd$>magick identify critbatt.png
critbatt.png PNG 600x800 600x800+0+0 8-bit Gray 256c 9894B 0.000u 0:00.000
which looks exactly as NiLuJe suggested.

Also I run 'eips -g critbatt.png' from Putty and it showed up correctly!
Finally, I put my images to /opt/amazon/low_level_screens/ru/600x800/ (where my localization folder is).

However, the last test always fails - the real experiment. So I wait until the battery drains (Kindle is a real die hard survivor, I would say!) - and it shows up all screwed up, the same as in the OP's second case. The image is squeezed.

Interestingly enough, all other replaced images works perfectly! The more vibrant splash screen, update screens, USB charging screens (from different folder and in .gif fromat, but nevertheless) etc.
I didn't try shipping mode image though since I don't know how to summon this mode (probably some search bar commands IRC)

So, the question is, what is the reason of such strange exclusion?
I would appreciate if anyone knows. Thank you!

P.S. Yes, the original image works. When I received my Kindle it was showing this 'battery dead' screen correctly.

Last edited by mergen3107; 06-07-2017 at 01:15 AM.
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Old 06-10-2017, 04:57 PM   #9
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Tried a bit more.

I put completely different image instead of critbatt.png and it turns out that the first squeezed one is 'stuck' somewhere in cache - is still shows up in the same way instead of the new one, only the fist half is visible, but it is squeezed to the whole screen real estate.

I also tried to put a tricky image which has all the necessary information 'squeezed' only to the first half in width, so I thought when Kindle squeeze it again it will look normal. However it didn't work probably due to the suspicion in the previous paragraph.

Any clues where I should look for this 'low power cache' and the reasons why it stuck?

P.S.
Also I am thinking about the case that these folders of 'opt/amazon/low_level_screens/$locale$/600x800/' serve a container which Kindle grabs boot pictures but only for the first time.
A contrary argument is that iterative replacement of 'reboot.png' was always working - I got it working after some trials. So now I am a bit confused.

Would appreciate any help.
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Old 06-10-2017, 05:37 PM   #10
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Quote:
Originally Posted by mergen3107 View Post
- - - - -
P.S. Yes, the original image works. When I received my Kindle it was showing this 'battery dead' screen correctly.
In what language?

Ah....


That screen can show before a locale (language) is selected at first start-up. Yours was.

So maybe it is kept somewhere other than the localized versions.

I.E: You might be changing en_Universal while looking at en_GB (or some such sort of combination).
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