HSV rev. 0.99

    	      (C) Copyright Frank Ederveen, Dec. 1992.
    	      
         Postwarez (i.e. send me a card if you like this)


INTRODUCTION

	Hi.
	Have you ever tried to mix colors with RGB-Sliders? I bet you have,
	and did you like it? I didn't.. so I wrote this small utility to
	help me out. In it's current state it's able to rewrite your palette
	-prefs, so you don't have to use Commodores pallete program anymore :*]

	It's based on the HSV color model, as described in 'Computer Graphics',
	Principles and Practice, Foley, van Dam, Feiner and Hughes, pages 590-592.

	It goes something like this: 
	(if you don't understand what is't all about either, take a look at
	the picture 'HSV.iff'.)

13.3.4 The HSV Color Model

The RGB,CMY, and YIQ models are hardware-oriented. By contrast, Smith's HSV
(hue, saturation, value) model (also called the HSB model, with B
for brightness) is user-oriented, being based on the intuitive appeal of
the artist's tint, shade and tone. The coordinate system is cylindrical,
and the subset of the space within wich the model is defined is a hexcone,
or six-sided pyramid, as in Fig. 13.30. The top of the hexcone corresponds
to V=1, which contains the relatively bright colors. The colors of the V=1
plane are not all of the same perceived brightness, however.

 Hue, or H, is measured by the angle around the vertical axis, with red at
0°, green at 120°, and so on. Complementary colors in the
HSV hexcone are 180° opposite one another. The value of S is a ratio
ranging from 0 on the centre line (V axis) to 1 on the triangular sides of
the hexcone. Saturation is measured relative to the color gamut represented
by the model, which is, of course, a subset of the entire CIE chromaticity
diagram. Therefor, saturation of 100 percent in the model is less than 100
percent excitation purity.

 The hexcone is one unit high in V, with apex at the origin. The point at
the apex is black and has a V coordinate of 0. at this point, the values of
H and S are irrelevant. The point S=0, V=1 is white. Intermediate values of
V for S=0 (on the center line) are the grays. When S=0,the value of H is
irrelevant (called by convention UNDEFINED). When S is not zero, H is
relevant . For example, pure red is at H=0,S=1,V=1. Indeed, any color with
V=1,S=1 is akin to an artist's pure pigment used as the starting point in
mixing colors. Adding white pigment corresponds to decreasing S (without
changing V). shades are created by keeping S=1 and decreasing V. Tones are
created by decreasing both S and V. Of course, changing H corresponds to
selecting the pure pigment with which to start. Thus, H,Sand V corrrespond
to concepts from the artist's color system, and are not exactly the same as
the similar terms introduced in Section 13.2.

 The top of the HSV hexcone corresponds to the projection seen by looking
along the principal diagonal of the RGB color cube from white toward black.
The RGB cube has subcubes. Each subcube, when viewed along its main diagonal,
is like the hexcone, except smaller. Each plane constant V in HSV space
corresponds to such a view of a subcube in RGB space. The main diagonal of
RGB space becomes the V axis of HSV space. Thus, we can see intuitively the
correspondence between RGB and HSV.
to the other.

USAGE
	Sorry but this one's WB 2.0 only.
	
	Usage shouldn't be any problem, Just start the 'HSV' program and 
	play with the sliders for a while, things should become much clearer
	then. H is Hue and is displayed in degrees (0..359), S is Saturation,
	displayed in percent (0..100) and V stands for Value which is
	displayed in percent (0..100) also. The HSV and the RGB sliders
	slide both, so if you're adjusting the HSV model, you can
	immediately see it's RGB equivalent. If you select the 'save' button,
	the current palette is saved as 'ENVARC:palette.prefs'.
	If you are one of those lucky few using an Amiga 1200 or 4000 and 
	have your WB screen opened with more than 4 bit-planes, the 'save'
	button is disabled 'cause it currently can't write Hi-Color pref-files.
	You can still adjust your colors, then select the 'use' button and save
	the palette using Commodores palette program.

AUTHOR

	Frank Ederveen
	Mathaak 5
	6581 VK Malden
	The Netherlands, EUROPE
	Fax. +31-80-556737 (mention my name somewhere, it's not mine)


DISTRIBUTION

	Anyone may distribute and/or use this package for privite use.
	If you might want to include it in a commercial package, please let
	me know so we can sort things out.
	If you use it more often than once, please send me a post-card from 
	wherever you live (I just like getting mail, that's all).
	
BUGS AND FUTURE DEVELOPMENTS

	If you find there's anything wrong with this program (and I'm quite
	sure GNUmerous things are) please send me a letter or Fax.

	It's working fine on the machine with which it has been made, a good
	old A2000C, A2630, Kickstart 37.175, WB 38.30.
	
	I doubt whether anyone will use this program for very long since
	Commodore has included something like this in their WB 3.0 Palette
	Prefs Program which everybody will be using shortly.