In the Compose section (Modify Data) of this loader you will find three options: Subtract, Difference and Multiply. To be short, Subtract just subtracts the gray values of the picture to be loaded from the gray values currently in memory by the ratio previously set (gadget Select where the percentage can be seen). If there are large color areas in the picture to be loaded, then there will result differently strong darkened spots in the picture being composed.
|Difference creates a picture where there will be computed
the interval between the gray value currently loaded and the appropriate
value already in memory (in BASIC: result= ABS(old gray value - new gray
value), producing some kind of punching out.
Finally, Multiply can be comprehended as easily. The appropriate values of either picture will be multiplied, then delimited to their extremes (zero is lowest and 15 is highest), and stored back to memory. Multiply can be further affected by its Select gadget (pos/neg). This process will strongly enhance the picture's contrast, and can be taken to easily create masks for ldr.4Bit&Mask (yet another method is described at mod..PatternEd).
Common to all 4Bit operations is them not dealing colors but instead grays. They always result in gray values which at best will be represented by colors. In spite, these pictures may quite well look esthetical, but above all they are considered for black&white printout or for exporting to Amigas or PCs.
Displayed in "Image Information":
Copyright © 1996, A. Dettke, Last Updated - 05/24/98