|[ Main index | Thoughts on various 8 bit machines, collecting, etc. | Wouter's pages: Making and editing scans||]|
1. Contrast-quantize 0.2: a non-linear contrast enhancing program. Used up to now in almost all black & white (or rather: black + 1 colour) scans currently on this website.
2. Contrast-quantize 0.8: a linear contrast enhancing program with edge calculations, edge-of-scan is taken into account too and image intensity can be kept the same as in the original (rescaling the intensities). Also works only for black + 1 colour.
The front cover of Beebug v1n1: original, some contrast enhancement with xv, enhanced with V0.8:
File sizes: 530 KB (GIF, 240 KB for a JPEG), 240 KB (JPEG), 74 KB.
The results of 0.2 on this image were too poor to use (either too many artefacts or the filesize was way too large, about 500KB for a 1600x1200 GIF). Both the original and xv-edited images were saved with jpeg quality=90 giving file sizes of about 240K. The GIF from V0.8 is just 74K and has no paper texture any more... (I've kept image intensity the same as the original image)
Image from the PCW June 1980, page 90: original, enhanced with V0.2 (original CD2 version), enhanced with 0.2 (high compression, final CD2 version), enhanced with V0.8:
File sizes: 350 KB, 230 KB, 132 KB, 218 KB.
The V0.8 image was actually made from a 600dpi scan which was then reduced in size after enhancement. Also, although the V0.8 image is a lot bigger in its filesize than the final CD2 version (high compression), it has no patterns from the enhancement which the CD2 version does have. The earlier CD 2 image was also made using V0.2 but using less compression, so it is even bigger, but it still has patterns in the tape drive image. All enhanced images have their intensity maximised.
Note: All these images were all reduced in size to fit on a 1600x1200 screen. The scans were done at 300dpi unless otherwise noted, and enhancements were made to that original image, then also reduced in size (no enhancements using the results of another enhanced image, so a V0.8 enhanced image did not use previously enhanced images for example).
An interesting effect of version 0.8 is that it removes almost all traces of ghost images... This is due to its limitation of not handling real gray surfaces. This does not mean using a black background is no longer useful as edge pixels are still affected (although the extra contrast from the reflected light might actually improve the final result. I'll have to do some experiments).
For multi-colour images I'm working on another program...
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Last modified: Thu Nov 1 23:55:49 CET 2012