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move contrasting_text_color() into ArdourCanvas

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This commit is contained in:
Paul Davis 2014-06-30 10:38:45 -04:00
parent 4c1f4011fd
commit 471570705d
6 changed files with 37 additions and 35 deletions
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32
libs/canvas/utils.cc
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@ -220,3 +220,35 @@ ArdourCanvas::distance_to_segment_squared (Duple const & p, Duple const & p1, Du
return ((dpqx * dpqx) + (dpqy * dpqy));
}
uint32_t
ArdourCanvas::contrasting_text_color (uint32_t c)
{
double r, g, b, a;
ArdourCanvas::color_to_rgba (c, r, g, b, a);
const double black_r = 0.0;
const double black_g = 0.0;
const double black_b = 0.0;
const double white_r = 1.0;
const double white_g = 1.0;
const double white_b = 1.0;
/* Use W3C contrast guideline calculation */
double white_contrast = (max (r, white_r) - min (r, white_r)) +
(max (g, white_g) - min (g, white_g)) +
(max (b, white_b) - min (b, white_b));
double black_contrast = (max (r, black_r) - min (r, black_r)) +
(max (g, black_g) - min (g, black_g)) +
(max (b, black_b) - min (b, black_b));
if (white_contrast > black_contrast) {
/* use white */
return ArdourCanvas::rgba_to_color (1.0, 1.0, 1.0, 1.0);
} else {
/* use black */
return ArdourCanvas::rgba_to_color (0.0, 0.0, 0.0, 1.0);
}
}