Alright. I was waiting until a dedicated forum for COOL-ER talk opened up before posting this, but I guess that hasn't happened yet.

So here we go. A bit of a technical look at the COOL-ER.

First off, I should say this is my first e-book reader, so I have no prior frame of reference. However I do know a bit about graphics, specifically putting pictures on an LCD or CRT.

The COOL-ER hardware is pretty good. It has a nice 6" 600x800 screen with 8 shades of grey (yes 8, not 4). As people have suggested, the buttons are stiff and clicky. If you used an original Aspire One netbook, you'll know exactly what it's like.

The problem however is the software. It's very much an Alpha release, as in feature complete, but buggy. In my tests, I found it extremely easy to crash the device. On the other hand, where it crashes is pretty easy to find, so you can learn to avoid it until we get a firmware update.

First of all, my needs for a device, I wanted a reader I could use like a USB stick or simple MP3 player. I.e. drop my files I want on it, and it's good to go. As far as this is concerned, the COOL-ER works. I can freely drop whatever the heck I want on the device through Windows. All is good here.

Viewing files however, needs some work. I wanted a device I could view PDF's and images on. For image formats, currently the COOL-ER only does JPG's. PNG's would be nice, since we only have 8 colors anyways.

By setting the font size to "1", PDF's will render exactly as they would on Windows... with one exception. They don't resample. Or specifically, it does pixel resampling instead of subpixel or multisampling. JPG's exhibit the same problem, and likely any images supported in other formats. If you don't know what I mean, here's an example:

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In the ZTST column, the word "NEVER" has the bottom of the E's cut off. Proper resampling (subpixel or multisampling) wouldn't do that.

That's my main complaint about the device. It's a software problem though, so if Interead is on ball, they can fix that in a firmware update.

My other issue is how the internal dithering works. However as is, you can be a little creative and pull off some good results.

So what you can do (as I've done) you can prepare images specifically for the device. Merely grayscaling an image isn't enough. You need to compensate for the system's bad dithering, and visible region.

The screen is 600x800... however, the UI only lets you fit an image that's 600x736. So with that number there, you can resize and image and get a 1:1 picture.

As for the colors themselves, I did a bunch of experiments to find the ideal luminance (i.e. gray) values to use. I put a gradient on the screen, marked where the banding artifacts showed up, and picked a value in the middle. What that means, if you take an image and make it use the following 8 color palette (with dithering), it'll look good.

The 8 luminance (i.e. gray) values for tricking the system dithering I came up with are as follows.

0, 50, 82, 112, 137, 163, 188, 255.

You'll note those colors aren't evenly spaced. Also the first and last values are clamped to the edges. If you're up for experimenting, you could try 17 and 230 instead of 0 and 255, but it shouldn't make too much difference.

Doing this to an image will look a little weird, nearly blown out on a PC. However, they will look good on the device.

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Alright! So the point of this is get around the current limits of the software. It's inability to resample, and it's choppy dithering algorithm. Ultimately, so we can use the COOL-ER to read comics.

So what I've done is taken a bunch of images, resized them to 736 pixels tall, reduced them to the 8 color greyscale palette mentioned above (WITH DITHERING!), converted them back to greyscale (for the next step), and saved them as JPG's. I used a compression quality setting of 95%, so the files were a little large, but mostly correct. In practice, you could use a far lower setting, since JPEG artifacts will likely get rounded up/down to the right colors by the dithering algorithm.

It's kinda hard to photograph an e-reader. At least, my camera isn't high enough resolution to get all the pixel details in one shot. I tried scanning the e-reader too, but the 3 mm recession of the screen wouldn't let it focus. Still, here's what I was able to get.

First things first, a color page of a manga with a good blend of sky and edge tones. (Eureka Seven)

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Next, a webcomic featuring some colored outline vector art. Only one shot of this though, sorry. (Something from Sugary Serials)

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A page of manga with heavy black usage and no grays (except for antialiasing). (Lucu Lucu)

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Finally, a heavy sketchy webcomic. (Megatokyo)

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Again, I want to stress these aren't stock images. To get them to look like this, it involved some image processing. I should really take some unprocessed snaps so you can better tell how this improves things, but heh... I have to admit I'm a little lazy.

Anyways, that was my little experiment with the COOL-ER. I did the research, so I figured I may as well share.

Hope you found this interesting.
The reason we think the COOL-ER hardware has 4 grey scales is that it is a Netronix EB-600 which includes a display controller that definitely only supports 4 grey levels. However dithering could easily increase this to 8 effective grey levels. Does your count of 8 grey levels include dithering on the device?

Since this is a Netronix EB-600 with Netronix firmware, your results should also apply to other similar devices like the Astak Mentor Lite (not out yet), Inves-Book 600 and Elonex 600EB.
OK, I'll bite. To test that out, I made 2 images that it should effectively be unable to display. I'm including the originals this time so other people with similar devices can do the same tests.

The first is a 1 pixel spaced stipple pattern.

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With this, you technically shouldn't be able to see 8 bands in the middle of the image. Here's the best detail photo I could get of it, looking at it from the left side.

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Next, I created 16 shade dither pattern from the palette.

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If it's really an 8, it should be able to display this perfectly.

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Ooh! Almost! The 3 colors near the middle seem to blend together. That's not good.

Oh well, I guess it's a 4 after all, since it'd be pretty absurd to think it's a 6.
For comics with simpler strokes, 800x600 and 8 shade is enough, but for most comic with compilcated strokes (such as "One Piece"), it's a pain to read those comics on such device.
IHMO, iLiad is the merely acceptable device to read comics.
and recent versions of the CyBook Gen3.
Great work! I'm currently studying anatomy and wanted to know what a direct pdf of an anatomy book would look like on the cool-er device? The comics you showed looks pretty good and would be similar to what I'm doing. But to image correct all the pages would be too time consuming. Can you post something un touched and post? Like a scanned illustation with small text and large text to see how the details display.

Thanks!
My guess is that it would look better on a Sony Reader, all of which (starting with the PRS-505) have 8 grey shades in hardware and good dithering. For screenshots, see More display issues on the DR.
Thanks for the link!! Settled my decision to the Sony then. My anatomy pdfs will convert nicely...

Thanks!