|Display Color Chart for Comparison with GretagMacbeth ColorChecker®
Display NetScape Colors in Hue Order
|"NetScape" Colors in Hue Order|
The purpose of this program is to display color charts on the screen or print a copy of the charts. The Gretag Macbeth chart can be compared with the color patches on a GretagMacbeth ColorChecker chart. The "Netscape" chart can be used for selection of color by hue.
Materials and Equipment
Delphi 3/4 (to recompile)
800-by-600 display in high or true color
The following chart assigns a number to each color patch of the ColorChecker:
Here is technical information about each of these color patches from the ColorChecker jacket:
|CIE (1931)||Munsell Notation|
|1||dark skin||0.400||0.350||10.1||3 YR||3.70||3.2||moderate brown|
|2||light skin||0.377||0.345||35.8||2.2 YR||6.47||4.1||light reddish brown|
|3||blue sky||0.247||0.251||19.3||4.3 PB||4.95||5.5||moderate blue|
|4||foliage||0.337||0.422||13.3||6.7 GY||4.20||4.1||moderate olive green|
|5||blue flower||0.265||0.240||24.3||9.7 PB||5.47||6.7||light violet|
|6||bluish green||0.261||0.343||43.1||2.5 BG||7.00||6.0||light bluish green|
|7||orange||0.506||0.407||30.1||5 YR||6.00||11.0||strong orange|
|8||purplish blue||0.211||0.175||12.0||7.5 PB||4.00||10.7||strong purplish blue|
|9||moderate red||0.453||0.306||19.8||2.5 R||5.00||10.0||moderate red|
|10||purple||0.285||0.202||6.6||5 P||3.00||7.0||deep purple|
|11||yellow green||0.380||0.489||44.3||5 GY||7.10||9.1||strong yellow green|
|12||orange yellow||0.473||0.438||43.1||10 YR||7.00||10.5||strong orange yellow|
|13||blue||0.187||0.129||6.1||7.5 PB||2.90||12.7||vivid purplish blue|
|14||green||0.305||0.478||23.4||0.25 G||5.40||8.65||strong yellowish green|
|15||red||0.539||0.313||12.0||5 R||4.00||12.0||strong red|
|16||yellow||0.448||0.470||59.1||5 Y||8.00||11.1||vivid yellow|
|17||magenta||0.364||0.233||19.8||2.5 RP||5.00||12.0||strong reddish green|
|18||cyan||0.196||0.252||19.8||5 B||5.00||8.0||strong greenish blue|
|20||neutral 8||0.310||0.316||59.1||N||8.00||-||light gray|
|21||neutral 6.5||0.310||0.316||36.2||N||6.50||-||light-medium gray|
|22||neutral 5||0.310||0.316||19.8||N||5.00||-||medium gray|
|23||neutral 3.5||0.310||0.316||9.0||N||3.50||-||dark gray|
Two sets of RGB values are given below for the ColorChecker.
The color values in Munsell Notation were converted to RGB values using the Munsell Conversion Program (Version 1.5 Beta), which was available for free testing in late 1997. See www.gretagmacbeth.com and www.munsell.com/munsell1.htm. (I still have a screen capture for each color patch.) These RGB values are used in the ColorChart program. I do not know where to obtain that program today.
The RGB values from the Munsell Conversion Program do not seem to be very accurate when displayed using the program ColorChart. When scanned with a Paperport Scanner, the RGB values appear to be more "correct.". The scanner RGB values are from a 60-by-45 pixel area within each color patch.
Here's what the scanned (and reduced) ColorChecker looks like:
RGB Values for ColorChecker
Also see Bruce Lindbloom's RGB Values for the ColorChart.
I do not have any color calibration equipment, so I cannot experimentally derive these values from the ColorChecker and a specified lighting source.
See the file ColorNameLibrary.PAS for all the color names, RGB values (in hex and decimal) as well as the HSV values.
The color gamut of a CRT can match a real ColorChecker fairly well with reduced intensity. The Color gamut of printed chart is not nearly as good as the real chart.
Black is especially difficult to reproduce on a color display monitor, since there is no practical way to force absorption of light that may already be reflecting from the screen. Mike McGuire, in a post to sci.engr.color, suggests we need a new DASAR technology: Darkness Amplification by Stimulated Absorption of Radiation!
Two different approaches were used to display the color names. For the GretagMacbeth chart, with only 24 colors, the OnMouseMove event handler did a simple linear search to find the pixel color from the list defined in the ColorNameLibrary.PAS unit. A search would have been too slow for the Netscape color list, which has 455 entries. So the (X,Y) mouse coordinates were converted to "color patch" indices, (iPatch, jPatch). The color index was determined using information about how the patches were drawn and was used as an index into the array of names.
Information about the ColorChecker from GretagMacbeth:
"The ColorChecker is a checkerboard array of 24 scientifically prepared colored squares in a wide range of colors. Many of these squares represent natural objects of special interest, such as human skin, foliage, and blue sky. These squares are not only the same color as their counterparts, but also reflect light the same way in all parts of the visible spectrum. Because of this unique feature, the squares will match the colors of natural objects under any illumination and with any color reproduction process."
According to Alan Roberts, BBC Research and Development, matching Munsell colors and RGB values is difficult because "the linear RGB values depend on the precise chromaticities of the display, and the non-linear correction you must apply to the RGB values depends on the power law of the actual display." All of the assumptions used by Munsell in their color conversion program are not known. (See other discussions in the sci.engr.color newsgroup starting with a 6 April 1998 post, "Munsell colours and RGB," by Christine Rigden.)
See comments from Bob Cunningham about perceptual differences between the GretagMacbeth ColorChecker RGB values and what appears on a monitor. (Nov 2002)
Maintaining color fidelity is very difficult. Matching colors seen on the screen with those printed by a color printer is very difficult since they have a different color gamuts.
Color names, Macbeth ColorChecker, Netscape colors, Color Calibration, RGB, Munsell Notation, color gamut, RGB, HSV, OnMouseMove
GretagMacbeth is a trademark and ColorChecker® is a registered trademark of GretagMacbeth, New Windsor, NY.
Delphi 3/4 Source and EXE (153 KB): ColorCharts.ZIP
Updated 26 Feb 2005
since 13 Nov 1998