Information on the Matching Game for color spaces

The Game:

The idea is rather simple -- generate a pseudo-random color, and let the user try to match it with their choice of color space. The user can choose any of the color space applets to run alongside the matching game applet, and use the color space applet as normal.

When you think you are close enough to the desired color to possibly have a match, all you have to do is press the button labelled "Click here to see if your chosen color is close enough." If it really is "close enough", fireworks will shoot off, and a message will tell you how far away you were. If you were not "close enough", then you will get a message telling you so, and telling you how far off you were.

The Applet:

At the top of the applet is a button labelled "Press here to generate a new color to match." If you press the button, the applet resets itself with a new color for you to try to match.

Below that is a pop-up list that looks something like the picture to the left. It has the same purpose as in the CIE LUV color space applet, which is as follows:
There is a list of different monitor choices to choose from. This is because the CIE LUV space is device-independent, and colors with the same LUV components are to look the same on all monitors. The technically correct way to run a model of the CIE LUV color space is to run a calibration test on the monitor the viewer is using, and then transform the chosen LUV coordinates into RGB space dependent on the results of that calibration test. However, most monitors conform to some standard, so I chose what appear to be the most popular 3 computer monitor standards, and allow the user to choose which one his/her monitor most closely matches. These different standards were developed by the CCIR (Comite Consultatif International des Radiocommunications). They are:
  • CCIR Rec [for Recommendation] 601-1: This is the old NTSC (National Television System Committee) standard. Its white point is called "C Illuminant", with CIE (xn;yn) values of (0.310063; 0.316158).
  • CCIR Rec [for Recommendation] 709: Its white point is D65, with CIE (xn;yn) values of (0.312713; 0.329016).
  • ITU D65: CCIR and CCITT were absorbed into their parent body, the International Telecommunications Union (ITU), which made its new recommendation also with a white point of D65 and CIE (xn;yn) values of (0.312713; 0.329016). This is probably the monitor standard that most monitors adhere to, so it is the default one chosen.

    The reason that you are given a choice of a monitor standard to use, as in the CIE LUV color space, is that in order to measure the distance between two colors, it is useful to have those colors expressed in a perceptually uniform color space (such as the CIE LUV color space), so that two colors that have the same cartesian distance from the color to match theoretically also have the same perceptual distance (i.e. appear to be the same "color distance" away from the desired color). The matching game transforms all the colors from the chosen color space applet into CIE LUV space, and uses these to measure the distance between two colors. Because the CIE LUV color space is device-independent, as mentioned above, these choices are given of what monitor standard to use.

    Below this pop-up list is a label and a splatch of color that inform you of the color you should be trying to match.

    Below this is a button labelled "Click here to see if your chosen color is close enough." When you think you have matched the color in the applet, then click this button, and you will find out if the matching game thought you were close enough. You have as many tries to match each color as you desire. Simply press the button at the top labelled "Press here to generate a new color to match" when you want to try a different color.

    I chose the "close enough" distance in the CIE LUV color space to be 5.0 both from my own "feel" of how close was close enough, as well as from recommendation from the book Computer Generated Color (by Jackson, MacDonald, and Freeman, published by John Wiley & Sons, 1994), which relates that the Draft International Standard ISO 9241 specifies that colors should be interpreted as identical if they are within 5.0 units of distance in the CIE LUV space. I.E. the coordinates of the color you have generated with the color space applet must transform into CIE LUV coordinates that are within a cartesian distance of 5.0 of the CIE LUV coordinates of the color to match, in order to be an official match. I chose 5.0 because it seemed, rather arbitrarily, to me that that was reasonably close enough perceptually.

    Credit: I got the original fireworks applet from here, and modified it to suit my purposes.



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