Color
ColorMix.gif (1017 bytes) Color Mix  Lab Report
Demonstrate Additive and Subtractive Color Primaries
ScreenColorMix.gif (31208 bytes)

Purpose
The purpose of ColorMix is to provide an interactive laboratory for mixing "additive" or "subtractive" colors.

Background
RGB (Red-Green-Blue) is an "additive" color system used in color display monitors where light is mixed.  CMY (Cyan-Magenta-Yellow) and CMYK (Cyan-Magenta-Yellow-blacK) are "subtractive" color systems used in printing where inks or pigments are mixed.

This project is an interactive version of Plate III (after p. 240), "Primary and secondary colors of light and pigments," in Digital Image Processing, but note that the CMY plate has been rotated in the book's version.

Materials and Equipment

Software Requirements
Windows 95/98/NT
Delphi 3/4  (to recompile)
ColorMix.EXE

Hardware Requirements
800-by-600 display in High Color or True Color Mode

Procedure

  1. Double click on the ColorMix.Exe icon to start the program.
  2. With Additive Primaries selected in the Combobox, select any or all of the colors (Red, Green, Blue) to "add" to the black background. 
  3. With Subtractive Primaries selected in the Combobox, select any or all of the colors (Red, Green, Blue) to "subtract" from the white background.
    ScreenColorMixCMY.gif (10189 bytes)
  4. If desired, select the Print button to print the additive or subtractive color mix.
  5. If desired, select the Save to File button to write a 512-by-512 bitmap with the additive or subtractive color mix to the specified disk file.

Discussion

Additive Colors (Mixtures of Light)

Black + Red = Red
Black + Green = Green
Black + Blue = Blue

Black + Red + Green = Yellow
Black + Red + Blue = Magenta
Black + Blue + Green = Cyan

Black + Red + Green + Blue = White

Subtractive Colors (Mixtures of Pigments)

White - Red = Cyan
White - Green = Magenta
White - Blue = Yellow

White - Red - Green = Blue
White - Red - Blue = Green
White - Blue - Green = Red

White - Red - Green - Blue = Black

Links
Synthèse additive et soustractive (French).  Similar but interesting example:
http://telesun.insa-lyon.fr/~telesun/Couleur/L02/titre.html

Conclusion
The next time you see a yellow flower, such as a tulip or a dandelion, think of the flower as being "NOT Blue" instead of "Yellow".

Keywords
RGB, CMY, CMYK, Additive Color, Subtractive Color, Scanline

Files
Delphi 3/4 Source and EXE (146 KB):  ColorMix.ZIP

Updated 26 Feb 2005


since 22 Jan 1999