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Old 06-12-2010, 01:04 AM   #1
Pranananda
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Posts: 97
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Join Date: Apr 2010
Location: Humboldt County, California
Device: ipad, iPod touch, JetBook Lite
Better pictures on your JetBook Lite

If you are putting pictures on your Jetbook, either as standalone pictures or in an ebook, you may notice that your picture looks a bit splotchy. And sometimes they look great just as they are.

To help with the splotchy pictures, you can use Photoshop or Gimp or another photo editing program to smooth out the splotchiness.

The JB has 16 shades of gray. But a good black and white photo on a computer will have 256 shades of gray. When you put a color or black in white picture on your Jetbook, the software reduces the colors or the 256 shades of gray down to 16 grays in a somewhat simplistic fashion. What happens is a range of 16 grays are reduced down to 1 gray.

You can sometimes get a better picture if you create more grays in your photo via a technique called dithering. Dithering takes 2 grays, and blends them together to get a shade of gray that is in between those two grays.

Dithering requires having a color table (or color palette or color lookup table) to use as the base colors in the photographs. I've attached a Photoshop color table and a Gimp color palette to this message you can used for your dithering experiments.

In both Photoshop Elements and Gimp, the technique is somewhat similar.
  • open a color picture
  • resize the picture to match the 3 inch X 4 inch display
  • go to Image->Mode->Index Color… on Photoshop, or Image->Mode->Indexed… on Gimp
  • choose the custom palette. In Photoshop, for Palette choose Custom…, and on the new dialog click Open and select Grays-16.act attached to this message. In Gimp, you have to copy Grays-16.gpl into the .gimp-2.6/palettes directory located in your Home Folder. This will show up in the Indexed… panel as the first element in the Use Custom Palette popup as Grays16.
  • choose your dithering option. On Photoshop, there is Diffusion, Pattern, and Noise. On Gimp there is Floyd-Steinberg (normal), Floyd-Steinberg (reduced Color Bleeding), and Positioned. Try them out, see how they look on the Jetbook, to see which one works best for your picture. And it may be that the dithering is no better than the default behavior.
  • click the OK or the Convert button.
With Gimp, to install the Grays-16.gpl, run gimp and quit. Go to ~/.gimp-2.6/palettes, and copy Grays-16.gpl there. Then restart gimp and load an image and do the Image->Mode->Indexed… operation.

Save your image as a .png file when you are finished.

I've attached an example of how some of the different dithers look.

If you are using a photo editor other than Photoshop or Gimp, and need to create your own color table, create a table with 16 color in them. Each color will have the same red, green, and blue value, the first having all 0s, the last having all 255s (that is red=255, green=255, and blue=255). The rgb (red, blue, green) values for the 16 shades of gray are 0 17 34 51 68 85 102 119 136 153 170 187 204 221 238 255.
Attached Thumbnails
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Attached Files
File Type: zip Grays-16.zip (540 Bytes, 136 views)

Last edited by Pranananda; 06-12-2010 at 01:16 AM.
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