K5 FW 5.x ScreenSavers Hack

[Machinus]

The mod comes with a default screensaver image which says that no screensaver image has been set yet. I'm pretty sure somewhere in the documentation it says to replace that image. That's what I want to do.

[NiLuJe]

Then you are looking in the wrong place, and @0x6c616d70 is correct, the only place you ought to be looking in is the screensavers/ folder, where the default file is named 00_you_can_delete_me-*.png.

[Machinus]

Originally Posted by NiLuJe

Then you are looking in the wrong place, and @0x6c616d70 is correct, the only place you ought to be looking in is the screensavers/ folder, where the default file is named 00_you_can_delete_me-*.png.

I also replaced the files in the screensavers folder. The trouble I'm having is with image processing. I don't know how to get the kindle to accept grayscaled images.

[mergen3107]

@Machinus
Try to convert the image with Image Magick (credit goes to NiLuJe from a an old post from Kobo forum, I believe):

convert input.png -filter LanczosSharp -resize 1072x1448 -background black -gravity center -extent '1072x1448!' -colorspace Gray -dither Riemersma -remap eink_cmap.gif -quality 75 -define png:color-type=3 png:out.png

First copy the attached file to the directory where you will be using the command prompt. Replace input.png with your image filename.

I converted all my screensavers this way and never had an issue since.

[NiLuJe]

That's not actually the right magic trickery necessary on Kindle (although it *may* work just fine in most cases).

(That one builds a 16c paletted PNG, i.e., decent for FBInk, although for better performance, no palette is still better).

What the Cover Mode does is instead this:

-define png:color-type=0 -define png:bit-depth=8

e.g., a 256c PNG8 w/o a palette; which ensures greater compatibility with all the weird Kindle bits involved.

[NiLuJe]

@Machinus: Also note that, while I'm no longer super familiar with the code, I'm pretty sure it won't take too kindly to you having broken the default files *outside* of the screensavers folder, so, I'd do a clean reinstall just to be safe, too.

[mergen3107]

@NiLuJe
Lol, Ok thank you!

[Machinus]

Originally Posted by NiLuJe

@Machinus: Also note that, while I'm no longer super familiar with the code, I'm pretty sure it won't take too kindly to you having broken the default files *outside* of the screensavers folder, so, I'd do a clean reinstall just to be safe, too.

I was able to get an image to work by setting it to 8-bit linear lighting in grayscale mode, using GIMP, and then saving it as an 8-bit GRAY PNG. This one displays properly when I power off the device. Interesting that it can interpolate for 8-bit images even though the screen is 4-bit. I noticed that it renamed the first image to "bg_ss00.png" when it finally worked.

I made a second image the same way, using the same steps, named it "bg_ss01.png," and saved it to the screensavers directory. However, when this image comes up in the shuffle, it is not displayed. The device instead just shows a black screen. I have restarted the framework, and the kindle, and it still does not display. The image returns the same properties with your preferred tool:

D:\linkss\screensavers>magick identify bg_ss00.png
bg_ss00.png PNG 1072x1448 1072x1448+0+0 8-bit Gray 256c 502614B 0.000u 0:00.007

D:\linkss\screensavers>magick identify bg_ss01.png
bg_ss01.png PNG 1072x1448 1072x1448+0+0 8-bit Gray 256c 686324B 0.000u 0:00.007

The first one works, but the second one doesn't.

[0x6c616d70]

Originally Posted by Machinus

. Interesting that it can interpolate for 8-bit images even though the screen is 4-bit.

Probably a minor detail at this point, it seems to me that the app can detect which kindle you have and automagically quantize and remap the bits for your screen type.

Interestingly, all it did was rename the original files without converting it. I tried dumping full color png and its still intact. Dropping in a grayscale image would probably just save processing time.

[NiLuJe]

@Machinus: You *really* need to just read the documentation.

Do *not* manually insert files and/or rename files in the *active* pool yourself. And take heed of the "needs a restart" warnings.

----

Anything >= K4 actually runs an 8bpp framebuffer, with the quantization happening inside the EPDC.
Not that you should even have cared about that even on earlier devices actually running @ 4bpp. That's an implementation detail nobody outside of people talking directly to the fb (e.g., FBInk, KOReader) have to deal with (see earlier link).

That said, regardless of the target device, knowing the actual eInk palette is interesting when you want to dither your images properly first, like the cover mode does, because that hasn't changed since the K2. But it's not a hard requirement, it's just in order to achieve better (psycho) fidelity.

[Hundebub]

Hi!
I've installed the Update_python_0.15.N_install_pw2_kt2_kv_pw3_koa_kt 3_koa2_pw4_kt4.bin on my Kindle Oasis 3.
After my Kindle restarted, only the standard screensavers where shown on sleep mode.
So I uninstalled it agian with: Update_python_0.15.N_uninstall.bin and installed the Update_python3_0.15.N_install_pw2_kt2_kv_pw3_koa_k t3_koa2_pw4_kt4 to try if that helps.
But it is still showing only the normal amazon screensavers.
What did go wrong?

[NiLuJe]

Define "Normal amazon screensavers". (I smell SO).

[Hundebub]

penciles, letters,... the usual stuff.
I don't have amazon ads on my kindle, if you meant that.

[NiLuJe]

Then check the MRPI logs .

[Hundebub]

The last line says "Success! " after installing the "Update_python3_0.15.N_install_pw2_kt2_kv_pw3_koa_ kt3_koa2_pw4_kt4.bin"

I really don't know what I did wrong?