Color
ColorCharts  Lab Report
Display Color Chart for Comparison with GretagMacbeth™ ColorChecker ;
Display NetScape Colors in Hue Order
ScreenColorChartA.jpg (31908 bytes)
"NetScape" Colors in Hue Order
ScreenColorChartB.jpg (64115 bytes)

Purpose
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

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

Hardware Requirements
800-by-600 display in high or true color

Other
GretagMacbeth™ ColorChecker

Procedure

  1. Double click on the ColorChart.Exe icon to start the program.  Select either color chart tab, Gretag MacBeth or Netscape.
  2. With the Gretag tab selected, adjust the brightness of screen and compare with a real GretagMacbeth ColorChecker. (In my opinion, "black" is the color that doesn't match very well. On the screen it looks dark gray, but on a real ColorChecker chart it looks very black.)
  3. Move the mouse over any of the color patches to observe the color name below the image.   In addition to the name, the RGB values are shown in hex (as $00bbggrr -- or the appropriate Delphi color name, e.g., clNavy), as well as in decimal.  In addition, the HSV color coordinates are displayed.
  4. Press the Print button to print the chart. Obviously, a color printer is a good idea here.
  5. Press the Write BMP button to create an 800 x 600 x 24-bit color bitmap, Gretag.BMP, or a 750 x 570 x 24-bit color bitmap, Netscape.BMP.

Data

The following chart assigns a number to each color patch of the ColorChecker:

1 2 3 4 5 6
7 8 9 10 11 12
13 14 15 16 17 18
19 20 21 22 23 24

Here is technical information about each of these color patches from the ColorChecker jacket:

    CIE (1931) Munsell Notation  
No. Name x y Y Hue Value Chroma ISCC/NBS Name
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
19 white 0.310 0.316 90.0 N 9.50 - white
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
24 black 0.310 0.316 3.1 N 2.00 - black

 

Two sets of RGB values are given below for the ColorChecker.

  1. 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.

  2. 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:

ColorChecker.jpg (4066 bytes)

 

RGB Values for ColorChecker

    Munsell Conversion
Program
Paperport
5300
Scanner
No. Name R G B R G B
1 dark skin 129 96 82 92 67 52
2 light skin 205 163 144    190    147    127
3 blue sky 112 135 169 93 117 143
4 foliage 103 121 81 76 103 64
5 blue flower 146 142 188 127 127 162
6 bluish green 120 198 182 120 186 174
7 orange 223 141 57 200 120 58
8 purplish blue 91 106 178 72 90 148
9 moderate red 203 106 114 191 89 90
10 purple 107 74 122 75 43 82
11 yellow green 173 197 78 154 188 96
12 orange yellow 233 175 61 208 164 77
13 blue 65 75 163 32 55 127
14 green 88 160 87 78 138 86
15 red 186 70 73 172 44 39
16 yellow 240 208 47 230 209 95
17 magenta 197 103 162 185 92 128
18 cyan 0 146 178 67 122 157
19 white 249 248 248 254 254 253
20 neutral 8 211 209 210 203 206 201
21 neutral 6.5 173 172 173 151 156 152
22 neutral 5 136 135 135 106 114 111
23 neutral 3.5 99 99 99 62 71 70
24 black 65 65 65 16 20 21

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.

Discussion
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)

Conclusions
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.


Keywords
Color names, Macbeth ColorChecker, Netscape colors, Color Calibration, RGB, Munsell Notation, color gamut, RGB, HSV, OnMouseMove

Note
GretagMacbeth™ is a trademark and ColorChecker is a registered trademark of GretagMacbeth, New Windsor, NY.

Files
Delphi 3/4 Source and EXE (153 KB):   ColorCharts.ZIP


Updated 26 Feb 2005


since 13 Nov 1998