After getting a number of emails from folks in various forums, I thought I would post this for those of you interested in transferring photos to you e-ink readers.
I only have a Kindle, and don't know if or how you can put photos on any other readers, and this post isn't about how to do the transfer, that's already been covered in other posts by other people.
This is about how and why to do prep work on your photos before you transfer them.
First, before you do anything else, resize and crop your photo to the proper dimensions for your device. On most or all e-ink readers at this time, that is 600 wide by 800 high. Not 639 x 845, not 596 x 801 .... 600 by 800.
I've got two methods for cropping and resizing that have always worked well for me.
For portrait photos (taller than wide), I generally first set the height to 800. Most graphics programs will automatically calcuate the width (assuming that you intend to keep the original proportions). If the width comes up as a value less than 600, then I set the width as 600 and let the computer calcuate a height something greater than 800.
Then, I crop the image ... either the height or the width, so that my resulting image is exactly 600 x 800.
Another method I sometimes use when I'm just not certain how I'm going to want to crop or resize is to create a blank image that is 600 x 800. I then copy and paste the image I am working with into that blank frame ... and move it around until I get an image I like.
The next thing that you need to understand is ... e-ink can't display any more than 4 levels of gray. That's it ... that is your palette. Yes, you can copy a color image onto your e-ink device ... it just won't display very well. That's because the screen takes all the colors within a certain range of contrast ... and makes them all the same shade of gray. What you get is murk.
In addition, just making a color image "black and white" does not solve the problem. This is because most "black and white" images on a computer are 256 levels of gray. So, put it on your e-ink screen, and you have the same problem .... the screen has to reduce 256 levels down to four and you have murk again.
It's not enough just to increase the contrast ... in the end you will lose much of the detail you want ... especially in a photo.
So, how to solve the problem? Depending on your graphics program, it can be quite easy. Others make it harder than it needs to be. My program of choice to do this is Paintshop Pro version 8. Yes, I've got Photoshop ... but I always use the easiest and fasted tool to do the job. And, in this case it is PSP 8 .... which is a dirt cheap buy on eBay.
Step one is to reduce the color photo down to 256 shades of gray. In PSP this is image/grayscale. In PS it is image/adjustments/black and white. You can also use image/mode/grayscale.
http://www.geocities.com/ricky1750/Graphics/A62Egs.jpg
OK ... so now we need to check the contrast. If at all possible, you want to have an image that has a good range of dark to light. If everything is nearly the same shade of gray ... reducing it to four shades isn't going to make it a better image ... but worse.
So, in both programs you play with what are called "curves". In PSP the command is adjust/brightness and contrast/curves and in PS it is image/adjustments/curves.
The idea is to drag the curve around until you get an image that gives to a good range of dark to light, but still allows you to see detail.
Once you get the contrast set the way you like it, then we get to the meat of the problem .... reducing the levels of gray. With line art, it's fairly simple ... you can just "posterize" to four levels. Most graphics programs have a posterize command.
HOWEVER .... posterize works horribly on most photos. It will wipe out most or all of your detail.
What you should do in order to preserve your detail is something called "dithering" ... essentially it makes you photo look more like something out of a newspaper. What you are doing is creating the illusion of more gray scales using just the four you have.
In PSP, the command is image/decrease color depth/x colors/number of colors = 4/optimized median cut/error diffusion
You can still see the boy's eyes under the shadow of his cap. Much better than posterized.
In PS, use the command file/save/save for web & devices. Set the dither to 100%, colors to 4, palette to perceptual, and diffusion.
I have found that, when using Photoshop, it is necessary to play with the curves to adjust the contrast more often than it is with PSP.
In any event, it does not take long to prepare a photo for e-ink, especially not once you are used to doing it. And, a little bit of prep work makes for a much better display.
