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fl_contrast() now compares the luminosity of each color (STR

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#837)



git-svn-id: file:///fltk/svn/fltk/branches/branch-1.1@4339 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
This commit is contained in:
Michael R Sweet 2005-05-12 17:08:35 +00:00
parent 2d1eade9bf
commit f88e7b23af
2 changed files with 15 additions and 7 deletions
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2
CHANGES
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@ -2,6 +2,8 @@ CHANGES IN FLTK 1.1.7
- Documentation fixes (STR #648, STR #692, STR #730, STR
#744, STR #745)
- fl_contrast() now compares the luminosity of each color
(STR #837)
- Fl_Input_ crashed on some platforms when wrapping
international text characters (STR #836)
- Fixed some BMP images loading bugs (STR #825)

20
src/fl_color.cxx
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@ -362,20 +362,26 @@ Fl_Color fl_inactive(Fl_Color c) {
}
Fl_Color fl_contrast(Fl_Color fg, Fl_Color bg) {
unsigned c1, c2;
unsigned c1, c2; // RGB colors
int l1, l2; // Luminosities
// Get the RGB values for each color...
if (fg & 0xffffff00) c1 = (unsigned)fg;
else c1 = fl_cmap[fg];
if (bg & 0xffffff00) c2 = (unsigned)bg;
else c2 = fl_cmap[bg];
if ((c1^c2)&0x80800000)
return fg;
else if (c2&0x80800000)
return FL_BLACK;
else
return FL_WHITE;
// Compute the luminosity...
l1 = ((c1 >> 24) * 31 + ((c1 >> 16) & 255) * 61 + ((c1 >> 8) & 255) * 8) / 100;
l2 = ((c2 >> 24) * 31 + ((c2 >> 16) & 255) * 61 + ((c2 >> 8) & 255) * 8) / 100;
// Compare and return the contrasting color...
if ((l1 - l2) > 127) return fg;
else if ((l2 - l1) > 127) return fg;
else if (l2 > 127) return FL_BLACK;
else return FL_WHITE;
}
//