File:0 3d 60 75 v.png
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Summary
Description0 3d 60 75 v.png |
English: 3D RGB profile of the rainbow color map[1] |
Date | |
Source | Own work |
Author | Adam majewski |
Other versions |
|
Licensing
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This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.
- You are free:
- to share – to copy, distribute and transmit the work
- to remix – to adapt the work
- Under the following conditions:
- attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
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C source code
/*
https://gitlab.com/adammajewski/color_gradient
c console program for testing color gradient
uses a code from gnuplot
gcc h.c -lm -Wall
a@zelman:~/c/varia/outor/gradient/hsv$ ./a.out
===========================
h= 360.000000 s=0.000000 v=1.000000
r= 1.000000 g=1.000000 b=1.000000
-----------------------------------
h= 0.000000 s=1.000000 v=1.000000
r= 1.000000 g=0.000000 b=0.000000
*/
#include <stdio.h>
#include <string.h> // strncat
#include <stdlib.h> // malloc
#include <math.h> // floor; needs -lm also
// size of virtual 2D array of pixels
// each piexel has a RGB color
int iWidth = 600;
int iHeight ; //
// size of the dynamic 1D array
unsigned char * data;
size_t ColorSize = 3; // RGB = number of color components = channels
size_t ArrayLength; // number of 1D array's elements = ENumber = iWidth*iHeight*ColorSize
size_t ElementSize; // size of array's element in bytes
size_t ArraySize; // size of array in bytes = ElementSize*ArrayLength
// ppm P6 file
size_t HeaderSize ; // size of the P6 file header in bytes
size_t FileSize; // = HeaderSize +ArraySize [bytes]
// gives position of 2D point (ix,iy) in 1D array ; uses also global variables: iWidth , ColorSize
int Give_i ( int iX, int iY)
{
return (iX + iY * iWidth) * ColorSize;
}
/*
GNUPLOT : http://gnuplot.sourceforge.net/
file : getoutor.c
* Petr Mikulik, December 1998 -- June 1999
* Copyright: open source as much as possible
*
*/
// from colour.h
/* Contains a colour in RGB scheme.
Values of r, g and b are all in range [0;1] */
typedef struct {
double r, g, b;
} rgb;
/* hsv :
h : deg [0,360]
s : % [0.0,100.0]
v : % [0.0,100]
*/
typedef struct {
double h, s, v;
} hsv;
/*
* outor Conversion Algorithms
* taken from http://www.cs.rit.edu/~ncs/outor/t_convert.html
* each outor model should provide a conversion to RGB.
* RGB values are clipped to [0,1] as some outors in some
* models have no RGB value.
*/
static void
HSV_2_RGB(hsv in, rgb *out)
{
double h,s,v, f,p,q,t;
int i;
h = in.h;
s = in.s;
v = in.v;
if (s == 0) { /* achromatic (gray) */
out->r = out->g = out->b = v;
return;
}
h *= 6.; /* h range in gnuplot is [0,1] and not the usual [0,360] */
i = floor(h);
f = h - i;
p = v * (1.0 - s);
q = v * (1.0 - s*f);
t = v * (1.0 - s*(1.0-f));
switch(i % 6) {
case 0:
out->r = v;
out->g = t;
out->b = p;
break;
case 1:
out->r = q;
out->g = v;
out->b = p;
break;
case 2:
out->r = p;
out->g = v;
out->b = t;
break;
case 3:
out->r = p;
out->g = q;
out->b = v;
break;
case 4:
out->r = t;
out->g = p;
out->b = v;
break;
default:
out->r = v;
out->g = p;
out->b = q;
break;
}
}
void PrintColor( FILE *fp, double position, hsv in, rgb out){
// normalized to [0.0, 1.0] range RGB color channels
double R = out.r;
double G = out.g;
double B = out.b;
// [Relative luminance is formed as a weighted sum of linear RGB components](https://en.wikipedia.org/wiki/Luma_(video))
//
//from function test_palette_subcommand from file gnuplot/src/command.c test_palette_subcommand
//ntsc = 0.299 * rgb.r + 0.587 * rgb.g + 0.114 * rgb.b;
double Y = 0.299*R + 0.587*G + 0.114*B;
//print
fprintf(fp, "%f\t", position);
fprintf(fp, "%f\t %f\t%f\t%f\t", R, G, B, Y);
fprintf(fp, "%f\t %f\t %f\n", in.h, in.s, in.v);
}
/* position -> hsv -> rgb
input position double [0.0, 1.0]
output rgb = unsigned char c array
rainbow gradient = Rainbow colormap or sawtooth rainbow or hsv
*/
void ComputeAndPrintColor( FILE *fp, double position, unsigned char c[]){
// "cyclic colormap traversing HSV color space. The map is obtained by linearly varying the hue through all possible values while keeping constant maximum saturation and value."
hsv in = {position, 1.0, 1.0}; // set palette model HSV functions gray,1,1
rgb out;
// compute hsv from position
HSV_2_RGB(in, &out); // convert hsv to rgb
//
PrintColor( fp, position, in, out);
// change range
c[0] = 255*out.r; //R
c[1] = 255*out.g; // G
c[2] = 255*out.b; // B
}
int PlotPoint(unsigned char A[], int i, unsigned char color[]){
A[i] = color[0]; /* Red*/
A[i+1] = color[1]; /* Green */
A[i+2] = color[2]; /* Blue */
return 0;
}
// --------------------
int FillArray (unsigned char A[] , int n){
int iX;
int iXmax = iWidth;
int iY;
int iYmax = iHeight;
int i; // index of 1D array
double position; // number form 0.0 to 1.0 used for color gradient
unsigned char color[3]; //
// text file used by the gnuplot for creating images
char name [100]; /* name of file */
snprintf(name, sizeof name, "%d", n); /* */
char *filename =strncat(name,".txt", 4);
FILE *fp = fopen(filename, "w");
if (fp==NULL) {
printf("Error opening text file!\n");
return 1;
}
fprintf(fp, "# position \t\t R \t\t G \t\tB \t\tY \t h\ts\tv\n"); // header of the text file
//
for(iX=0; iX<iXmax; ++iX){
position = (double) iX / iXmax;
ComputeAndPrintColor(fp, position, color);
// vertical
for(iY=0; iY<iYmax; ++iY){
i = Give_i(iX, iY);
PlotPoint(A, i , color);
}
}
fclose(fp);
return 0;
}
// --------------- save dynamic "A" array of uinsigned char to the binary ppm file ( P6 ) --------------------------------
int SaveArray2PPM (unsigned char A[], size_t ASize, int k)
{
FILE *fp;
const unsigned char MaxColorComponentValue = 255; /* color component is coded from 0 to 255 ; it is 8 bit color file */
char name [100]; /* name of file */
snprintf(name, sizeof name, "%d", k); /* */
char *filename =strncat(name,".ppm", 4);
/* save image to the pgm file */
fp = fopen (filename, "wb"); /*create new file,give it a name and open it in binary mode */
if (fp == NULL)
{ printf("File open error");
return 1;}
else {
fprintf (fp, "P6\n%u %u\n%u\n", iWidth, iHeight, MaxColorComponentValue); /*write header to the file */
fwrite (A, ASize, 1, fp); // write dynamic A array to the binary file in one step
printf ("File %s saved. \n", filename);
fclose (fp);
return 0;}
}
// n = nummber of the gradient function
int MakeGradientImage(unsigned char A[], int n){
FillArray(data, n);
SaveArray2PPM(data, ArraySize, n+iWidth);
return 0;
}
int setup(){
iHeight = iWidth/3;
// 1D array
ArrayLength = iWidth*iHeight*ColorSize;
ElementSize = sizeof(unsigned char);
ArraySize = ElementSize*ArrayLength ;
HeaderSize = 11 + (size_t) (log10(iHeight) +log10(iWidth));
FileSize = HeaderSize + ArraySize;
/* create dynamic 1D array for RGB colors */
data = malloc (ArraySize);
if (data == NULL ){
printf ( "Could not allocate memory for the array\n");
return 1;}
return 0;
}
void info(){
printf("ppm (P6) header size = %zu bytes\n", HeaderSize);
printf("Array Size = %zu bytes\n", ArraySize);
printf("PPM file size = %zu bytes\n", FileSize);
}
int end(){
printf (" allways free memory (deallocate ) to avoid memory leaks \n"); // https://en.wikipedia.org/wiki/C_dynamic_memory_allocation
free (data);
info();
return 0;
}
int main(){
setup();
MakeGradientImage(data, 0);
end();
return 0;
}
Gnuplot source code
set xlabel "R"
set ylabel "G"
set zlabel "B"
unset yrange
set nokey
unset tics
set xrange [0.0:1.0]
set yrange [0.0:1.0]
set zrange [0.0:1.0]
set grid
set border 4095 ls 1 lc rgb "black" # Draw a complete box around a `splot`:
set xzeroaxis
set yzeroaxis
# set view <rot_x>{,{<rot_z>}{,{<scale>}{,<scale_z>}}}
# view is 60 rot_x, 30 rot_z, 1 scale, 1 scale_z
set view 60,75
set view equal xyz # to get an orthographic projection with all of the axes scaled equally
set xyplane at 0 # adjusts the position at which the xy plane is drawn in a 3D plot
# Set the output file name
outfile = sprintf('%d_3d_60_75_v.png',n)
set output outfile
# title of the image for the array of strings
sTitle = sprintf("3D %s profile of the rainbow colormap", word(spaces,n+1) )
set title sTitle
# http://www.bersch.net/gnuplot-doc/linetypes,-colors,-and-styles.html
# There are several ways to specify color when one plots using gnuplot.
# Among them hex-string (like "#0000ff") and rgbvalue (like "256")
# specification is very important.
# here rgb value is computed
rgb(r,g,b) = 65536*int(255*r) + 256*int(255*g) + int(255*b)
# http://gnuplot-surprising.blogspot.com/2012/10/
#convert dec color value to its hex string
dec2hex(dec)=gprintf("%02x",dec)
#convert rgb color value to its hex string
rgb2hex(r,g,b)="#".\
dec2hex(255*r).\
dec2hex(255*g).\
dec2hex(255*b)
# Now plot the data with lines and points
set label "(0,0,0)" at -0.1,0,0 right
#set label "0" at 1,-0.1,0 right
#set label "1" at 1,+1.1,0 right
#set label "2" at 0,1.1,0 right
#set label "3" at 0,1,1 left
#set label "4" at 0,0,1 left
# set label "5" at 1,0,1 left
#set label "6" at 1,0,0 left
set label "(1,1,1)" at 1.1,1,1 left
splot infile using 1:1:1 with lines lw 3 lc rgb 'gray',\
infile using 2:3:4:(rgb($2,$3,$4)) with points pt 7 ps 2 lc rgb variable ,\
'-' w p pt 7 ps 2 lc rgb 'black'
0 0 0
1 1 1
e
Captions
3D RGB profile of the rainbow color map
Items portrayed in this file
depicts
some value
31 January 2020
image/png
8cb6d933f67359bcc34179e511931734a6036b14
31,779 byte
480 pixel
640 pixel
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