Colorbox granularity (number of rectangles)

[Juhász P. <pet...@gm...>]

Dear.all;

Consider the result of the following script (on full screen if
possible):

#####################
cutoff = 300
set palette defined \
 (0 'white', cutoff-1 'pink',\
 cutoff '#7f0000', cutoff+5 '#ff0000',\
 cutoff+10 '#ff007f', cutoff+15 '#ff7f00',\
 cutoff+20 '#ffff00')

set isosa 1000
set xr [0:10]
set yr [0:cutoff+20]
set cbr [0:cutoff+20]

plot '++' w image
######################

This is actually a minimal version of a real script.
The contrived looking palette is intended to show that variation in the
data is only interesting as long as it's above the cutoff. The palette
is rapidly changing above the cutoff, however, and this emphasizes the
effect of the limited resolution of the colorbox.


The culprit is apparently this line in
draw_inside_color_smooth_box_bitmap in color.c:

    int steps = 128; /* I think that nobody can distinguish more colours
drawn in the palette */

Apparently this assumption is false, especially on large resolution
bitmap terminals.

Would it be sensible to adjust the number of steps based on the space
available (yes, I guess, on bitmap terminals, but what about
vector-based ones)? Or perhaps to make it user-settable?

Péter Juhász