Making Better Black and White Overlays and Page Segments

Resolving The Problem

This document assumes that the IBM® AFP driver has been installed on the PC. You will not be able to create AFP source files without it.

For more information about installing the AFP driver, please refer to the section entitled Installing the IBM AFP Printer Driver in the following document:

N1018625: Creating AFP Resources Using the IBM AFP Printer Drivers


You Might Not Need This Document

If your company has an Art or Graphic Design department that can provide you with high quality images, you can ask them for a 300 x 300 pel graphic of the image you wish to make into an overlay or a page segment. When requesting images from co-workers, request high quality black and white images in TIFF or BMP format if possible. JPEG images, while typically the most commonly used, are lossy image formats, meaning that they do not store an image precisely, but rather try to save space by grouping similarly colored areas of the image. This makes the file smaller, but of low quality when printed. TIFF or BMP (and some other) image formats are lossless, meaning that each pixel of the image will actually be printed as shown. These image types create much better print output.

Note: This document does not apply to full color overlays and page segments used by Infoprint Server.


How to Clean Up Your Images

Most poor quality overlays and page segments start with poor quality images, but often the difference between a high quality image and a low quality image is hard to see, as in the following images:



If we look closely, the original image from the right is pure black and white, which makes a crisp and clean overlay or page segment:



If the same image is saved as a JPEG (as on the left) the images look very similar, but if you zoom in, the edges have become fuzzy. While this looks good on a screen, these fuzzy edges will not make a good overlay or page segment:



Because a printed overlay or page segment cannot contain any color (including shades of grey), all that color must be dithered out, which results in very jagged edges:




How Do I Clean Up My Images?

As previously stated, the best overlays and page segments are made when the original image file is created at a high pel density; however, there are ways to make existing images look better. The following example shows how to change a graphic file with Microsoft® Paint, which comes free with Microsoft Windows. If you have a high power graphic application, you will have access to many more editing options, including direct control of the dithering process.

1.	If the original image is not the right size, scale it to the correct size before making any other changes to it. The Stretch/Skew option can be found under the Image menu. Most printing from IBM® i5/OS® is 300 pel, which is 300 dots per inch (dpi). A 2"x1" printout would need a 600x300 pixel source graphic.
2.	With the image at the correct size, you can now make any desired cosmetic changes to it.
3.	After editing is complete, from the File menu select File > Save As and change the Save As Type to Monochrome Bitmap format: