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PLOT /SCALING
[GREG2\]PLOT /SCALING Type [Low_cut High_cut]
Defines the type of transfer function to be used. Type can be LINear,
natural LOGarithmic, or EQUalization. The Low_cut and High_cut are the
lowest and highest represented values respectively. The default "cuts"
are the image extrema. The current cuts are stored in the variable array
CURIMA%SCALE. The current scaling (as an integer code) is stored in the
variable CURIMA%SCALING.
The LOG transfer function computes the logarithm of the pixel values.
There can be negative pixel values as long as the low and high cuts re-
main positive. If one or two cuts are negative or null, they will be im-
plicitly replaced with a better suited positive value (lowest positive
or highest positive value depending on the cut).
The EQUalization scaling tries its best to put the same number of pixels
in each slot of the color table, thus increasing immensely the visibili-
ty of low-contrast images. This scaling mode has problem (and warns us-
er) when a large number of pixels have exactly the same value (i.e., no
contrast at all). Beware that most "real" images are obtained with re-
ceivers working with a small number (11 to 16) of bits, thus restricting
the range of available Real numbers in the data.
The SIC variables CURIMA%EQUAL%NLEV, CURIMA%EQUAL%LEV and CURI-
MA%EQUAL%HIST contain the number of different levels computed in EQUAL-
IZATION mode, the values of these levels, and the number of pixels in
each level, respectively. Useful to know which contour levels to draw,
and necessary for the WEDGE command.
Gildas manager
2024-03-29