Mesoscale & Microscale Meteorology Division
National Center for Atmospheric Research

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Monitor Calibration Programs

10 July 2001

There are five Java programs used to visually calibrate a computer monitor. These programs are located in the directory: 

/users/boyd/java/cal

>ls *.java
-rw-r--r--    1 boyd     users       3066 Jun 28 14:54 blkcal.java
-rw-r--r--    1 boyd     users       3267 Jun 22 10:39 cntcal.java
-rw-r--r--    1 boyd     users       3479 Jun 29 08:48 gamcal.java
-rw-r--r--    1 boyd     users       3422 Jun 28 15:19 vhltst.java
-rw-r--r--    1 boyd     users       3951 Jun 22 13:19 whtcal.java

The program blkcal.java is used to calibrate a monitor's black level. It displays a black square with the xysize dimensions. A gray square is nested within the black square, the monitor brightness and/or contrast is set so that the interior square is just visible. 
>java blkcal
Usage: java blkcal xysize

>java blkcal 400

The program cntcal.java is used to calibrate check a monitor's contrast. It displays a gray rectangle with 11 vertical bars ranging from black to white. If a monitor's contrast if properly adjusted all the bar should be visable. 
>java cntcal
Usage: java cntcal xsize

>java cntcal 800

The program whtcal.java is used to calibrate a monitor's RGB baises. It displays a matrix of color squares with 11 horizontal values similar to cntcal.java, and 9 vertical color variations, the middle row being gray, the specified color increasing above and decreasing below. The specified color is adjusted to make the middle row appear gray. Being a 2D display the program must be run 3 times, adjusting red, green, and blue. Selecting color patches with the mouse will ouput the RGB values of the color. 
>java whtcal
Usage: java whtcal cflag xsize

>java whtcal r 800
>java whtcal g 800
>java whtcal b 800

The program gamcal.java is used to determine the gamma of a computer's display system. It displays a vertical bar of horizontals lines, half black and half white which visually mix to a mid point value. Along side of this bar is another vertical bar with 12 horizontal gray bars. These bars range in value corresponding to a gamma of 0.6 to 2.8 in 0.2 increments. From a distance one of these gray bars should match the tone of the adjacent vertical bar. Selecting the matching gray bar with the mouse will output the gray bar's value and the gamma it indicates. Color biases may be present, the program vhltst.java may be used to illustrate such biases. 
>java gamcal
Usage: java gamcal

>java gamcal

The program vhltst.java is used to see if a monitor has density or color biases when displaying closely spaced vertical and horizontal lines. It displays two squares of alternate black and white lines, one square with vertical lines and another with horizontal lines. The dimensions of the squares are specified with the xysize argument and the line width is specified with the linesize argument. This this program provides information about a monitor, color and density biases usually cannot be corrected. 
>java vhltst
Usage: java vhltst linesize, xysize

>java vhltst 1 300

None interactive images of these programs have been captured and placed on our Web site, they may be accessed with the following URL. It is best to use the programs if possible, the Web versions accuracy is changed by saving them to a file at a given gamma and how a given browser displays them. 
http://www.mmm.ucar.edu/smg/test/test.html