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Fix and improve fl_contrast() calculations

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- src/fl_contrast.cxx:
  - FL_CONTRAST_LEGACY: reset black/white threshold from 55 to 50
  - FL_CONTRAST_CIELAB: change default contrast level from 55 to 39

- test/contrast.cxx:
  - set default contrast mode to CIELAB
  - add "random color" button to test random foreground colors (text)
  - slightly increase terminal size
  - make the Fl_Terminal widget the resizable() of the window
This commit is contained in:
Albrecht Schlosser 2024-05-16 18:55:30 +02:00
parent 9df6dc2aeb
commit 9820d9f555
2 changed files with 79 additions and 19 deletions
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24
src/fl_contrast.cxx
View File

@ -24,6 +24,10 @@
#include <FL/Fl.H>
#include <math.h>
#ifndef DEBUG_CONTRAST_LEGACY
#define DEBUG_CONTRAST_LEGACY 0
#endif // DEBUG_CONTRAST_LEGACY
// Initial values of global/static variables defined by fl_contrast_* functions.
// This defines the default contrast mode since FLTK 1.4.0
@ -31,7 +35,11 @@ static int fl_contrast_mode_ = FL_CONTRAST_CIELAB;
// This defines the default contrast level per contrast mode
static int fl_contrast_level_[10] = {
0, 50, 55, 0, 0, 0, 0, 0, 0, 0
0, // 0 = FL_CONTRAST_NONE
50, // 1 = FL_CONTRAST_LEGACY
39, // 2 = FL_CONTRAST_CIELAB
0, // 3 = FL_CONTRAST_CUSTOM
0 // 4-9 = not yet defined
};
// There is no default custom contrast function
@ -338,6 +346,18 @@ static Fl_Color fl_contrast_legacy(Fl_Color fg, Fl_Color bg, Fl_Fontsize fs, int
int lc = lfg - lbg; // calculated contrast (-255 .. 255)
#if DEBUG_CONTRAST_LEGACY
const char *rv = "?"; // return value as text (init)
if (lc > tc || lc < -tc) rv = "fg"; // sufficient contrast
else if (lbg > tbw) rv = "BLACK"; // light background
else rv = "WHITE"; // dark background
printf("fl_contrast_legacy: lfg %4d (%7.2f) lbg %4d (%7.2f) lc %4d (%7.2f) => %s\n",
lfg, lfg/255.*100, lbg, lbg/255.*100, lc, lc/255.*100, rv);
#endif // DEBUG_CONTRAST_LEGACY
// Compare and return the contrasting color...
if (lc > tc || lc < -tc) return fg; // sufficient contrast
@ -364,7 +384,7 @@ static Fl_Color fl_contrast_cielab(Fl_Color fg, Fl_Color bg, Fl_Fontsize fs, int
(void) context; // currently ignored
double tc = (double)fl_contrast_level(); // sufficient contrast threshold
double tbw = 55.; // black/white threshold
double tbw = 50.; // black/white threshold
// Compute the perceived lightness L* (Lstar) and the contrast

74
test/contrast.cxx
View File

@ -1,7 +1,7 @@
//
// Contrast function test program for the Fast Light Tool Kit (FLTK).
//
// Copyright 2022 by Bill Spitzak and others.
// Copyright 2022-2024 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file. If this
@ -35,7 +35,7 @@
// program version
const char *version = "0.9.0";
const char *version = "0.9.1";
// prototypes and forward declarations
@ -103,8 +103,8 @@ int g_selected = -1; // selected button: -1 = none, 0 - 255 = valid b
Fl_Fontsize g_fs = 15; // fontsize for button labels
int g_level = 0; // *init* fl_contrast_level (sensitivity)
int g_algo = FL_CONTRAST_LEGACY;// contrast algorithm: 0 = none, 1 = legacy (1.3.x), 2 = CIELAB, 3 = custom
const char *alch = ""; // algorithm as char: "LEGACY", "CIELAB" , or "CUSTOM"
int g_algo = FL_CONTRAST_CIELAB; // contrast algorithm: 0 = none, 1 = legacy (1.3.x), 2 = CIELAB, 3 = custom
const char *alch = ""; // algorithm as char: "LEGACY", "CIELAB" , or "CUSTOM"
Fl_Color lcolor = FL_BLACK; // label color, set by slider callback
Button *buttons[256]; // array of color buttons
@ -224,6 +224,38 @@ void slider_cb(Fl_Widget *w, void *v) {
w->window()->redraw();
}
// callback for the "random color" button
void rc_cb(Fl_Widget *w, void *v) {
static bool first = true;
unsigned int r, g, b;
if (first) {
// Seed the random number generator...
srand((unsigned int)time(NULL));
first = false;
r = g = b = 0; // initialize with black
} else {
r = rand() % 256;
g = rand() % 256;
b = rand() % 256;
}
sliders[1] -> value(r);
sliders[2] -> value(g);
sliders[3] -> value(b);
// update button label colors
lcolor = fl_rgb_color(r, g, b); // set color value
update_labels();
// output label color
char color_buf[10];
sprintf(color_buf, "%02X %02X %02X", r, g, b);
color_out->value(color_buf);
w->window()->redraw();
}
// callback for contrast algorithm (radio buttons)
void algo_cb(Fl_Widget *w, void *v) {
@ -275,7 +307,7 @@ int main(int argc, char **argv) {
int cw = 16 * bw + 10;
int ch = 16 * bh + 10;
int ww = cw + 10;
int wh = 16 * bh + 135 + 10 + 150 /* terminal */ + 10;
int wh = 16 * bh + 135 + 10 + 170 /* terminal */ + 10;
Fl_Double_Window window(ww, wh, "fl_contrast test");
int n = 0;
@ -358,7 +390,7 @@ int main(int argc, char **argv) {
Fl_Radio_Round_Button *aleg = new Fl_Radio_Round_Button(cgx, cgy + 25, cgw, abh, "LEGACY");
Fl_Radio_Round_Button *acie = new Fl_Radio_Round_Button(cgx, cgy + 50, cgw, abh, "CIELAB");
Fl_Radio_Round_Button *aapc = new Fl_Radio_Round_Button(cgx, cgy + 75, cgw, abh, "CUSTOM");
aleg->value(1);
acie->value(1);
anon->callback(algo_cb, (void *)0);
aleg->callback(algo_cb, (void *)1);
acie->callback(algo_cb, (void *)2);
@ -407,6 +439,12 @@ int main(int argc, char **argv) {
lf->tooltip("Click to output a linefeed to the log.");
lf->callback(lf_cb);
// random color (R) button
Fl_Button *rc = new Fl_Button(10 + 8 * bw + lf->w() + 2, blue->y(), bw*3/4, sh, "&RC");
rc->tooltip("Click to select a random text color.");
rc->callback(rc_cb);
// color chooser for field #255
int ccx = 10 + 12 * bw;
@ -421,7 +459,13 @@ int main(int argc, char **argv) {
color_chooser->mode(1); // byte mode
color_chooser->align(FL_ALIGN_LEFT_BOTTOM);
// simple terminal for output (FLTK 1.4 only)
// set contrast mode and level, update button label colors
fl_contrast_mode(g_algo);
fl_contrast_function(custom_contrast); // dummy contrast function
algo_cb(acie, fl_voidptr(2));
// Fl_Terminal for output
int ttx = 10;
int tty = color_chooser->y() + cch + 10;
@ -433,22 +477,18 @@ int main(int argc, char **argv) {
term->textfgcolor(FL_BLACK);
term->textsize(13);
term->printf("FLTK fl_contrast() test program with different contrast algorithms, version %s\n", version);
term->printf("FLTK version %d.%d.%d\n", FL_MAJOR_VERSION, FL_MINOR_VERSION, FL_PATCH_VERSION);
term->printf("FLTK %d.%d.%d fl_contrast() test program with different contrast algorithms, version %s\n",
FL_MAJOR_VERSION, FL_MINOR_VERSION, FL_PATCH_VERSION, version);
term->printf(" - Select a foreground (text) color with the gray or red/green/blue sliders (displayed inside each field).\n");
term->printf(" - Select an arbitrary background color for field #255 with the color chooser.\n");
term->printf(" - Select a colored field (by clicking on it) to display its attributes.\n");
term->printf(" - Select the contrast algorithm by clicking on the radio buttons.\n");
term->printf(" - Tune the contrast algorithm with the light blue \"level\" slider (default: 50).\n");
term->printf(" - Tune the contrast algorithm with the light blue \"level\" slider (default: %d).\n", fl_contrast_level());
term->printf(" - Select a random foreground (text) color by clicking the RC button\n");
// set contrast mode and level, update button label colors
fl_contrast_mode(g_algo);
fl_contrast_function(custom_contrast); // dummy function
algo_cb(NULL, fl_voidptr(g_algo)); // updates button labels
window.resizable(window);
window.resizable(term);
window.end();
window.show(argc, argv);
rc_cb(rc, 0); // update button labels - must be called after show()
return Fl::run();
}