Gnuplot/palette
< Gnuplot
Palette or color gradient[1]
Palette is a color storage for use by:
- `pm3d`
- filled color contours or polygons
- color histograms
- color gradient background
- and whatever it is or it will be implemented...
Here it stands for a palette of smooth "continuous" colors or grays, but let's call it just a palette. Color palettes require terminal entries for filled color polygons and palettes of smooth colors, are currently available for terminals listed in help for `set pm3d`.
The range of color values are adjustable independently by:
- `set cbrange`
- `set log cb`.
The whole color palette is visualized in the `colorbox`.
show palette edit
Syntax:
show palette
show palette palette <n> {{float | int}}
show palette gradient
show palette fit2rgbformulae
show palette rgbformulae
Command:
- `show palette` shows the current palette properties.
- `show palette gradient` displays the gradient defining the palette (if appropriate)
- `show palette rgbformulae` prints the available fixed gray --> color transformation formulae.
- `show palette palette <n>` prints to the screen or to the file given by `set print` a table of RGB triplets calculated for the current palette settings and a palette having <n> discrete colors. The default wide table can be limited to 3 columns of r,g,b float values [0..1] or integer values [0..255] by options float or int, respectively. This way, the current gnuplot color palette can be loaded into other imaging applications, for example Octave. Alternatively, the `test palette` command will plot the R,G,B profiles for the current palette and leave the profile values in a datablock $PALETTE.
Check the standard color gradient (traditional pm3d is black-blue-red-yellow):
show palette
Output:
palette is COLOR rgb color mapping by rgbformulae are 7,5,15 figure is POSITIVE all color formulae ARE NOT written into output postscript file allocating ALL remaining color positions for discrete palette terminals Color-Model: RGB gamma is 1.5
Help:
help show palette
test palette edit
Command `test palette` plots profiles of R(z),G(z),B(z), where 0<=z<=1. These are the RGB components of the current color `palette`. It also plots the apparent net intensity as calculated using NTSC coefficients to map RGB onto a grayscale. The profile values are also loaded into a datablock named $PALETTE.
test palette[2]
It can be saved to the graphic file :
set terminal png set output 'p.png' test palette
where
- NTSC
//from function test_palette_subcommand from command.c
ntsc = 0.299 * rgb.r + 0.587 * rgb.g + 0.114 * rgb.b;
Code :
// command.c
/*
* process the 'test palette' command
* 1) Write a sequence of plot commands + set commands into a temp file
* 2) Create a datablock with palette values
* 3) Load the temp file to plot from the datablock
* The set commands then act to restore the initial state
*/
static void
test_palette_subcommand()
{
enum {test_palette_colors = 256};
struct udvt_entry *datablock;
char *save_replot_line;
TBOOLEAN save_is_3d_plot;
int i;
static const char pre1[] = "\
reset;\
uns border; se tics scale 0;\
se cbtic 0,0.1,1 mirr format '' scale 1;\
se xr[0:1];se yr[0:1];se zr[0:1];se cbr[0:1];\
set colorbox hor user orig 0.05,0.02 size 0.925,0.12;";
static const char pre2[] = "\
se lmarg scre 0.05;se rmarg scre 0.975; se bmarg scre 0.22; se tmarg scre 0.86;\
se grid; se xtics 0,0.1;se ytics 0,0.1;\
se key top right at scre 0.975,0.975 horizontal \
title 'R,G,B profiles of the current color palette';";
static const char pre3[] = "\
p NaN lc palette notit,\
$PALETTE u 1:2 t 'red' w l lt 1 lc rgb 'red',\
'' u 1:3 t 'green' w l lt 1 lc rgb 'green',\
'' u 1:4 t 'blue' w l lt 1 lc rgb 'blue',\
'' u 1:5 t 'NTSC' w l lt 1 lc rgb 'black'\
\n";
FILE *f = tmpfile();
#if defined(_MSC_VER) || defined(__MINGW32__)
/* On Vista/Windows 7 tmpfile() fails. */
if (!f) {
char buf[PATH_MAX];
/* We really want the "ANSI" version */
GetTempPathA(sizeof(buf), buf);
strcat(buf, "gnuplot-pal.tmp");
f = fopen(buf, "w+");
}
#endif
while (!END_OF_COMMAND)
c_token++;
if (!f)
int_error(NO_CARET, "cannot write temporary file");
/* Store R/G/B/Int curves in a datablock */
datablock = add_udv_by_name("$PALETTE");
if (datablock->udv_value.type != NOTDEFINED)
gpfree_datablock(&datablock->udv_value);
datablock->udv_value.type = DATABLOCK;
datablock->udv_value.v.data_array = NULL;
/* Part of the purpose for writing these values into a datablock */
/* is so that the user can read them back if desired. But data */
/* will be read back using the current numeric locale, so for */
/* consistency we must also use the locale when creating it. */
set_numeric_locale();
for (i = 0; i < test_palette_colors; i++) {
char dataline[64];
rgb_color rgb;
double ntsc;
double z = (double)i / (test_palette_colors - 1);
double gray = (sm_palette.positive == SMPAL_NEGATIVE) ? 1. - z : z;
rgb1_from_gray(gray, &rgb);
ntsc = 0.299 * rgb.r + 0.587 * rgb.g + 0.114 * rgb.b;
sprintf(dataline, "%0.4f %0.4f %0.4f %0.4f %0.4f %c",
z, rgb.r, rgb.g, rgb.b, ntsc, '\0');
append_to_datablock(&datablock->udv_value, strdup(dataline));
}
reset_numeric_locale();
/* commands to setup the test palette plot */
enable_reset_palette = 0;
save_replot_line = gp_strdup(replot_line);
save_is_3d_plot = is_3d_plot;
fputs(pre1, f);
fputs(pre2, f);
fputs(pre3, f);
/* save current gnuplot 'set' status because of the tricky sets
* for our temporary testing plot.
*/
save_set(f);
/* execute all commands from the temporary file */
rewind(f);
load_file(f, NULL, 1); /* note: it does fclose(f) */
/* enable reset_palette() and restore replot line */
enable_reset_palette = 1;
free(replot_line);
replot_line = save_replot_line;
is_3d_plot = save_is_3d_plot;
}
set palette edit
Command `set palette` without options
set palette
sets up the default values
Code:
// color.c
void
init_color()
{
/* initialize global palette */
sm_palette.colorFormulae = 37; /* const */
sm_palette.formulaR = 7;
sm_palette.formulaG = 5;
sm_palette.formulaB = 15;
sm_palette.positive = SMPAL_POSITIVE;
sm_palette.use_maxcolors = 0;
sm_palette.colors = 0;
sm_palette.color = NULL;
sm_palette.ps_allcF = FALSE;
sm_palette.gradient_num = 0;
sm_palette.gradient = NULL;
sm_palette.cmodel = C_MODEL_RGB;
sm_palette.Afunc.at = sm_palette.Bfunc.at = sm_palette.Cfunc.at = NULL;
sm_palette.colorMode = SMPAL_COLOR_MODE_RGB;
sm_palette.gamma = 1.5;
}
file edit
Syntax:
set palette file '<filename>' {datafile-modifiers}
Where:
- filename jest to nazwa pliku palety zawierającego kolumny z danymi. Nie jest to plik z rozszerzeniem pal zawierajacy polecenia gnuplota
- data-modifiers jest to opcjonalny składnik służacy do wybierania elementów z palety( tabeli). Przykład: 'using ($1/255):($2/255):($3/255)'
Polecenie `set palette file` odpowiada poleceniu set palette defined a dane są wczytywane z pliku filename.
Sprawdzamy zawartość pomocy:
help set palette file
Przypadki użycia
- plik tekstowy ( gpf nie pal, który wczytujemy za pomocą polecenia load)
- plik binarny
- dane wczytywane z linii poleceń
Text file edit
Syntax:
set palette file 'palette.txt' using ($1/255):($2/255):($3/255) # Read in a palette of RGB triples each in range [0,255]
W pliku mogą być:
- 4 kolumny: gray, R, G, B
- trzy kolumny: R, G, B
# http://soliton.vm.bytemark.co.uk/pub/cpt-city/arendal/arctic.gpf
set palette file "arctic.gpf"
set terminal png
set output "arctic.png"
test palette
Zbiory plików tekstowych gpf
- cpt-city : "Gnuplot Palette File (with gpf extension) in the RGB colour-space" ( 4 kolumny)
- pliki map programu Fractint ( 3 kolumny )
set palette file "Skydye07.map" using ($1/255):($2/255):($3/255) # Read in a palette of RGB triples each in range [0,255]
Binary file edit
Syntax
set palette file "palette.bin" binary record=64 using 1:2:3 # put 64 triplets of R,G,B doubles into file palette.bin and load
CLI edit
Możemy użyć tego polecenia do wprowadzenie tabeli kolorów w linii komend:
- zamiast nazwy pliku podajemy "-"[6]
- wprowadzmy tabelę
- kończymy literą e
# Equidistant rainbow (blue-green-yellow-red) palette
set palette model RGB file "-"
0 0 1
0 1 0
1 1 0
1 0 0
e
# cpt-city/ma/gray/grayscale01a 0 … 100, continuous, RGB, 3 segments
set palette file "-"
0.00000 0.00000 0.00000 0.00000
0.35010 0.93333 0.93333 0.93333
0.75000 0.80000 0.80000 0.80000
1.00000 0.66667 0.66667 0.66667
e
cubehelix edit
- Cubehelix gradient
-
2D RGB profile -
3D RGB profile
Rodzina palet kolorów opracowana przez D A Green (2011)[7] w której kolor (odcień) zmienia się wzdłuż standardowego koła kolorów, a jednocześnie intensywność rośnie monotonicznie, gdy wartość szarości zmienia się od 0 do 1.
Zalety:
- drukuje równie dobrze w kolorze i czerni/bieli[8]
gnuplot> set palette cubehelix
gnuplot> show palette
palette is COLOR
Cubehelix color palette: start 0.5 cycles -1.5 saturation 1
figure is POSITIVE
all color formulae ARE NOT written into output postscript file
allocating ALL remaining color positions for discrete palette terminals
Color-Model: RGB
gamma is 1.5
W kodzie:
// color.h: t_sm_palette typedef struct (Declaration of smooth palette, i.e. palette for smooth colours)
/* control parameters for the cubehelix palette scheme */
double cubehelix_start; /* offset (radians) from colorwheel 0 */
double cubehelix_cycles; /* number of times round the colorwheel */
double cubehelix_saturation; /* color saturation */
the cubehelix palette can be modified by gamma. E.g.
set palette cubehelix gamma 2.0
C function using gnuplot code :
/*
GNUPLOT - stdfn.h
Copyright 1986 - 1993, 1998, 2004 Thomas Williams, Colin Kelley
*/
#ifndef clip_to_01
#define clip_to_01(val) \
((val) < 0 ? 0 : (val) > 1 ? 1 : (val))
#endif
/*
input : position
output : c array ( rgb color)
the colour scheme spirals (as a squashed helix) around the diagonal of the RGB colour cube
https://arxiv.org/abs/1108.5083
A colour scheme for the display of astronomical intensity images by D. A. Green
*/
void GiveCubehelixColor(double position, unsigned char c[]){
/* GNUPLOT - color.h
* Petr Mikulik, December 1998 -- June 1999
* Copyright: open source as much as possible
*/
// t_sm_palette
/* gamma for gray scale and cubehelix palettes only */
double gamma = 1.5;
/* control parameters for the cubehelix palette scheme */
//set palette cubehelix start 0.5 cycles -1.5 saturation 1
//set palette gamma 1.5
double cubehelix_start = 0.5; /* offset (radians) from colorwheel 0 */
double cubehelix_cycles = -1.5; /* number of times round the colorwheel */
double cubehelix_saturation = 1.0; /* color saturation */
double r,g,b;
double gray = position;
/*
Petr Mikulik, December 1998 -- June 1999
* Copyright: open source as much as possible
*/
// /* Map gray in [0,1] to color components according to colorMode */
// function color_components_from_gray
// from gnuplot/src/getcolor.c
double phi, a;
phi = 2. * M_PI * (cubehelix_start/3. + gray * cubehelix_cycles);
// gamma correction
if (gamma != 1.0) gray = pow(gray, 1./gamma);
a = cubehelix_saturation * gray * (1.-gray) / 2.;
// compute
r = gray + a * (-0.14861 * cos(phi) + 1.78277 * sin(phi));
g = gray + a * (-0.29227 * cos(phi) - 0.90649 * sin(phi));
b = gray + a * ( 1.97294 * cos(phi));
// normalize to [9,1] range
r = clip_to_01(r);
g = clip_to_01(g);
b = clip_to_01(b);
// change range to [0,255]
c[0] = (unsigned char) 255*r; //R
c[1] = (unsigned char) 255*g; // G
c[2] = (unsigned char) 255*b; // B
}
Examples:
gamma edit
Składnia:
set palette gamma <gamma>
Ustawia współczynnik gamma na wartość <gamma>
Standardowa wartość współczynnika gamma = 1.5
Przykłady:[9]
set palette gamma 1.25
Gamma korekcja innymi metodami:[10]
set palette model RGB set palette functions gray**0.64, gray**0.67, gray**0.70
lub:
gamma = 2.2
color(gray) = gray**(1./gamma)
set palette model RGB functions color(gray), color(gray), color(gray) # A gamma-corrected black and white palette
W stosunku do palet szarych zamiast
set palette defined ( 0 0 0 0, 1 1 1 1 )
możemy użyć :
set palette defined ( 0 0 0 0, 0.5 .73 .73 .73, 1 1 1 1 )
Zobacz w kodzie:
// color.h
/* gamma for gray scale and cubehelix palettes only */
double gamma;
gray/color edit
Ustawienie szarej palety kolorów
set palette gray
przy standarowych ustawieniach odpowiada to :
set palette gray positive gamma 1.5 # nieliniowa
Jeśli chcemy otrzymać liniową palete to ustawiamy gamma na 1.0:
set palette gray gamma 1.0 # liniowa plaeta
Powrót do kolorowej palety:
set palette color
Zobacz też color modes:
//color.h
/*
* color modes
*/
typedef enum {
SMPAL_COLOR_MODE_NONE = '0',
SMPAL_COLOR_MODE_GRAY = 'g', /* grayscale only */
SMPAL_COLOR_MODE_RGB = 'r', /* one of several fixed transforms */
SMPAL_COLOR_MODE_FUNCTIONS = 'f', /* user defined transforms */
SMPAL_COLOR_MODE_GRADIENT = 'd', /* interpolated table:
* explicitly defined or read from file */
SMPAL_COLOR_MODE_CUBEHELIX = 'c'
} palette_color_mode;
model/functions edit
Składnia:
set palette functions <R>,<G>,<B>
set palette model { RGB | HSV | CMY | YIQ | XYZ }
może być łączone:[11]
set palette model HSV functions gray, 1, 1 # full color hsv = rainbow set palette model XYZ functions gray**0.35, gray**0.5, gray**0.8 # black to gold
gamma = 2.2
color(gray) = gray**(1./gamma)
set palette model RGB functions color(gray), color(gray), color(gray) # A gamma-corrected black and white palette
Definicje
- gray jest zmienną przyjmującą wartości od 0 do 1
rgbformulae edit
Składnia:
set palette rgbformulae <r>,<g>,<b>skrócona postać :
set palette rgb r,g,b
r, g i b są to funkcje odpowiadające za obliczenie każdej ze składowej koloru. (mimo że nazwy składowych są R,G oraz B to ich znaczenie jest zależne od modelu koloru, tzn. w modelu HSV R będzie oznaczało H). Mamy do dyspozycji 37 wbudowanych funkcji ponumerowanych od 0 do 36 (liczby ujemne dają odwrócony gradient). Możemy je wyświetlić:
show palette rgbformulae
Otrzymamy:
* there are 37 available rgb color mapping formulae: 0: 0 1: 0.5 2: 1 3: x 4: x^2 5: x^3 6: x^4 7: sqrt(x) 8: sqrt(sqrt(x)) 9: sin(90x) 10: cos(90x) 11: |x-0.5| 12: (2x-1)^2 13: sin(180x) 14: |cos(180x)| 15: sin(360x) 16: cos(360x) 17: |sin(360x)| 18: |cos(360x)| 19: |sin(720x)| 20: |cos(720x)| 21: 3x 22: 3x-1 23: 3x-2 24: |3x-1| 25: |3x-2| 26: (3x-1)/2 27: (3x-2)/2 28: |(3x-1)/2| 29: |(3x-2)/2| 30: x/0.32-0.78125 31: 2*x-0.84 32: 4x;1;-2x+1.84;x/0.08-11.5 33: |2*x - 0.5| 34: 2*x 35: 2*x - 0.5 36: 2*x - 1 * negative numbers mean inverted=negative colour component * thus the ranges in `set pm3d rgbformulae' are -36..36
Kod znajdziemy w: gnuplot/src/getcolor.c/GetColorValueFromFormula
Standardowo są wybrane funkcje nr 7 dla składowej czerwonej, 5 dla składowej zielonej i 15 dla niebieskiej. Możemy wybrać inny zestaw, na przykład proponowany w dokumentacji zestaw "gorący" ( ang. hot =black-red-yellow-white):
set palette rgbformulae 21,22,23
albo odwrócony gorący gradient:
set palette rgbformulae -21,-22,-23
lub odwrócony liniowy gradient szarości
set palette rgbformulae -3,-3,-3 # 1-x, 1-x, 1-x
Przykłady przestrzenie RGB:[12]
7,5,15 ... traditional pm3d (black-blue-red-yellow)
3,11,6 ... green-red-violet
23,28,3 ... ocean (green-blue-white); try also all other permutations
30,31,32 ... color printable on gray (black-blue-violet-yellow-white)
33,13,10 ... rainbow (blue-green-yellow-red)
34,35,36 ... AFM hot (black-red-yellow-white)
Pełna paleta HSV
3,2,2 ... red-yellow-green-cyan-blue-magenta-red
defined edit
Składnia:
set palette defined { ( <gray1> <color1> {, <grayN> <colorN>}... ) }
gdzie
<color> := { <r> <g> <b> | ’<color-name>’ | ’#rrggbb’ }
Paleta jest zbudowana poprzez liniową interpolację między wartościami określonymi w definicji.
Przykłady:
set palette defined (0 "dark-green", 1 "green", 1 "yellow", 4 "red")
test palette
Otrzymujemy nieciągły gradient.
Za pomocą 2 kolorów otrzymujemy ciągły gradient ( liniowy) pomiędzy bielą ( 1 1 1) a czernią ( 0 0 0 )
set palette model RGB
set output "gray.png"
set palette defined (0 1 1 1, 1 0 0 0) # <r> <g> <b>
test palette
Inna równowazna składnie polecena set palette:
set palette defined ( 0 "white", 1 "black") # ’<color-name>’
set palette defined ( 0 "#ffffff", 1 "#000000") # ’#rrggbb’
# Approximate the default palette used by MATLAB:
set pal defined (1 '#00008f', 8 '#0000ff', 24 '#00ffff', 40 '#ffff00', 56 '#ff0000', 64 '#800000')
Dane możemy wprowadzić z
- linii poleceń
- z pliku palety pal
load 'a.pal'
Przykład pliku tekstowego pal:
# jet.pal with 4 columns
set palette defined (0 0.0 0.0 0.5, \
1 0.0 0.0 1.0, \
2 0.0 0.5 1.0, \
3 0.0 1.0 1.0, \
4 0.5 1.0 0.5, \
5 1.0 1.0 0.0, \
6 1.0 0.5 0.0, \
7 1.0 0.0 0.0, \
8 0.5 0.0 0.0 )
# ColorBrewer Accent
# https://github.com/Gnuplotting/gnuplot-palettes/blob/master/accent.pal
# for use with qualitative/categorical data
# provides 8 colors, 4 pale and 4 saturated
# compatible with gnuplot >=4.2
# author: Anna Schneider
# pale green - pale purple - pale orange - pale yellow - blue - magenta - brown - grey
# palette
set palette maxcolors 8
set palette defined (
0 '#7FC97F',\
1 '#BEAED4',\
2 '#FDC086',\
3 '#FFFF99',\
4 '#386CB0',\
5 '#F0027F',\
6 '#BF5B17',\
7 '#666666' )
Zbiory palet:
Sprawdzamy jaki gradient ma aktualna paleta:
show palette gradient
Otrzymujemy:
0. gray=0.0000, (r,g,b)=(1.0000,1.0000,1.0000), #ffffff = 255 255 255 1. gray=1.0000, (r,g,b)=(0.0000,0.0000,0.0000), #000000 = 0 0 0
References edit
- ↑ Color_gradient in wikipedia
- ↑ /src/command.c
- ↑ Poynton's Color FAQ by Charles Poynton
- ↑ https://livebook gnuplot-in-action-second-edition by P K Janert
- ↑ Luma_(video) w ang wikipedii
- ↑ gnuplot 5.0.4 : Special-filenames
- ↑ A colour scheme for the display of astronomical intensity images by D. A. Green
- ↑ cubehelix-or-how-i-learned-to-love by James Davenport
- ↑ gnuplot 5.5 demo pm3dgamma
- ↑ gnuplot 5.0.4 : gamma
- ↑ gnuplot 4.2 docs: Palette/Functions
- ↑ gnuplot-doc : rgbformulae