colorspace_doc.txt

本程序根据用户不同的需求设计窗口的背景

Ever wanted one of those fancy color picking dialogs that apps
like Corel PhotoHouse have ? If you did, here it is !!

IMPORTANT : Please copy the 2 bitmap files 
		CCRGB.BMP and CCHSB.BMP into your C:\temp directory.
		The demo depends on those files. You can change 
		these values from the OnInitDialog member function
		in CColorPickerDlg .


First, some general stuff about how I got this stuff together.

   The most important part, obviously , is the color space
   conversion from RGB to HSB. I got some help ( lots actually)
   on this from one of the discussion boards on Codeguru ( Thanks !)

   Once you have this piece of code, you have the next problem,
   which is to create proper bitmaps which are required for displaying
   the color spaces. 
   
	Creating the Hue bitmap is quite easy as you just have to 
	go through each of the hue values (0-360) and iterate 
	through each of the saturation values (0-255). I used a 
	standard brightness value of 255 for the bitmap as 
	other values give pretty dull results. 

	Next , and this is the difficult part - comes the part 
	where you create the RGB bitmap. This is a little tough
	as you have to not only create gradients but also fit
	them together seamlessly . I accomplished this by first
	creating rectangular gradients and then using some 
	texture mapping code ( courtesy Micheal Abrash - Zen )
	to fit them together . 


	Now the next part is to give the whole thing a user 
	interface. Again the HSB part is easy as finding
	the angle of a point as well as its distance from 
	another are pretty straightforward. And to those
	math gurus who are fuming at the code - please forgive
	me - I took the simplest approach I knew of -
		x2 + y2 = a2 . 

	Then we come to the RGB space. Again, this requires a 
	lot of 3d math -  I again took the easiest route - As
	I knew which bitmap I was using as well as the coordinates
	of the vertices, I used some 2d math to map points
	from the 3d space to 2d and vice versa. It`s not
	terribly elegant , but it works , and thats what I get
	paid for.

	If you look at the contructor of the CColorPickerDlg, 
	you`ll notice that I set up certain values for the
	vertices and centre. This I got from the bitmap I`m 
	using. You could quite easily use a different bitmap
	if you don`t like the one I provide ( can`t imagine why
	though ) , by just setting differnt values here . The
	code which actually does the math should adjust accordingly.


	Now - for the important stuff - how do you use it ?
	Simple - Copy the Dialog resource - IDD_DIALOG_COLORS from
	the resource file of the demo project into your project.
	Then, include ColorPickerDlg.h in the file you want to 
	call it from ( the view in the demo ) and use the following
	bit of code :
		CColorPickerDlg dlg(m_color) // where m_color is the
									// color you want to inialize
									// with.
		if(dlg.DoModal() == IDOK)
		{
			// User pressed ok 
			m_color = dlg.GetColor();
		}
	That is it. And yes, please include 
			ColorPickerDlg.cpp 
			Dib.cpp
			Common.cpp
		in your project. 
	The latter two are support files which provide some
	DIB manipulation routines as well as some of the
	math stuff.
	
	

	The demo app which I have provided uses red as the default
	background. Choose View | Color Space to invoke the color 
	picker . When you choose a different color, it is
	used as the background.