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About Rocket eBook
   Technical Details
   A History of Publishing
   Using the Rocket eBook
   Maintaining Your eBook

   About the RocketWriter
   Creating From a File
   Creating From a Website
   Image Design
   Reading a RocketEdition
   Getting Comfortable
   Using Reference Features
   Building Up Your Library
   Managing Your Library

   User's Guide

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Image Design for the Rocket eBook

There are several issues to be considered when formatting titles for the Rocket eBook. The ability to accurately represent graphical information is key to some titles and may dictate if the title is even appropriate for use on a Rocket eBook.

The purpose of this document is to help identify what types of images will convert easily and look good as well as provide a few examples of how more complicated images can be managed.

General Observations

The Rocket eBook screen is very high resolution and ideal for reading text.  However, making good-looking images can sometimes be difficult because of the 1-bit per pixel, monochrome screen.  With some work, most images look quite good on the Rocket-eBook.

  • Line art generally looks good and requires little modification.
  • Graphs, charts, tables etc. can all look good but almost always require some amount of hand processing.
  • Multi-page artwork and photographs should be avoided if possible.
  • Newspaper clippings and maps often look fine however some have very small text that may be illegible one the artwork has been resized.
  • Using mainstream tools such as Adobe's PhotoShop images that would otherwise look poor can be manipulated to look much better by using the anti-alias control, filters, brightness/contrast, black/white level control etc.
  • Each image may need individual consideration. Simply converting artwork to .png format without any modifications will display less then optimal results.
Technical Information
  • Images that are 312x312 pixels or less will fit on the display in any orientation. Images larger than the screen size can be "panned" on the horizontal and/or vertical axis as needed. This feature works very well for graphs, charts, tables, maps etc.
  • The Rocket eBook supports Portable Network Graphics PNG (pronounced "ping") files. Most graphic programs easily convert or export in PNG format however some applications may not allow for 1bit conversion.
  • Images that are in a non-bitmap format (EPS, etc.) will scale much better since they are not resolution-dependent. Bitmapped images may scale better if first converted to vector images via applications such as Adobe's Streamline. In many cases converting to grayscale and then resizing will also result in better images since the operator has tools available to manipulate the image that are not available in bitmap mode.
  • Scanned images are discouraged since it is difficult to get acceptable results. Screen shots provide much better results and generally require less conversion time. There are many "screen snap" utilities available via the Web.
  • Default settings (Interlace, Filter, etc.) for Photoshop produce reasonable results. Users experienced with these applications may be able to "tune" them for better results. In our testing Diffusion Dither produced the best images.
  • Images are linked to the HTML body via the <img> tag. Images must reside in the same directory level as the HTML since the Rocket eBook currently has no understanding of sub-directories. See Designing RocketEditions for more information.
Sample Images

This example shows a graph in its original .eps format and then a bitmap .png conversion of the same graph. A simple conversion in this case results in a very bad looking image.

In this example a much better representation of the graph was developed using the original .eps file with the anti-aliasing feature turned off. While this might normally produces a less desired effect it actually helps with bitmap conversion. The Photoshop Sharpen filter, Adjust Level and Brightness/Contrast controls we're also used.

Sample Bitmap Image Conversion Process

While there are many possible scenarios this is an example of a typical image conversion process:

  • Convert the artwork to Grayscale if the file is already a bitmap.
  • Resize the artwork to the appropriate size. When working with small print and/or large images that require panning, try to get the overall image size as small as possible with the smallest text as legible as possible.
  • Once the image is the right size start working with the Adjust Levels and the Brightness/Contrast controls. The idea here is to get the Grey’s out and as much black/white separation as possible. Using PhotoShop you can preview the work as you go along. Determining what ultimately looks good requires some experience and testing.
  • When the image has reached a point that seems like it might be ready, convert it back to a bitmap. If the image looks good then it can be converted to a .png and saved. If the image looks bad, undo the bitmap conversion and try again. Repeat this process until the image looks good in bitmap format.
  • Save to a 1bit .png and preview on the Rocket-eBook.
  • Verify the size is correct and that image looks nice.
  • Repeat these steps if anything needs to be changed.
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