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fix the brightness/contrast --> levels step by doing proper math (TM). 

2008-09-18  Simon Budig  <simon@gimp.org>

	* app/gegl/gimpbrightnesscontrastconfig.c: fix the
	brightness/contrast --> levels step by doing proper math (TM).


svn path=/trunk/; revision=26984
This commit is contained in:
Simon Budig 2008-09-17 22:55:55 +00:00 committed by Simon Budig
parent cd4dd6c5b6
commit 53385418fb
2 changed files with 56 additions and 21 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
2008-09-18 Simon Budig <simon@gimp.org>
* app/gegl/gimpbrightnesscontrastconfig.c: fix the
brightness/contrast --> levels step by doing proper math (TM).
2008-09-18 Sven Neumann <sven@gimp.org>
* tools/pdbgen/pdb/drawable.pdb: gimp_drawable_mask_intersect()

72
app/gegl/gimpbrightnesscontrastconfig.c
View File

@ -162,7 +162,7 @@ gimp_brightness_contrast_config_to_levels_config (GimpBrightnessContrastConfig *
{
GimpLevelsConfig *levels;
gdouble brightness;
gdouble contrast;
gdouble slant;
gdouble value;
g_return_val_if_fail (GIMP_IS_BRIGHTNESS_CONTRAST_CONFIG (config), NULL);
@ -170,33 +170,63 @@ gimp_brightness_contrast_config_to_levels_config (GimpBrightnessContrastConfig *
levels = g_object_new (GIMP_TYPE_LEVELS_CONFIG, NULL);
brightness = config->brightness / 2.0;
contrast = (config->contrast < 0 ?
(config->contrast + 1.0) :
config->contrast * 4.0 + 1.0);
slant = tan ((config->contrast + 1) * G_PI_4);
value = -0.5 * contrast + brightness + 0.5;
if (value < 0.0)
if (config->brightness >= 0)
{
value = 0.0;
value = -0.5 * slant + brightness * slant + 0.5;
levels->low_input[GIMP_HISTOGRAM_VALUE] =
(-0.5 - brightness) / contrast + 0.5;
if (value < 0.0)
{
value = 0.0;
/* this slightly convoluted math follows by inverting the
* calculation of the brightness/contrast LUT in base/lut-funcs.h */
levels->low_input[GIMP_HISTOGRAM_VALUE] =
(brightness * slant + 0.5 * slant - 0.5) / (slant - brightness * slant);
}
levels->low_output[GIMP_HISTOGRAM_VALUE] = value;
value = 0.5 * slant + 0.5;
if (value > 1.0)
{
value = 1.0;
levels->high_input[GIMP_HISTOGRAM_VALUE] =
(brightness * slant + 0.5 * slant + 0.5) / (slant - brightness * slant);
}
levels->high_output[GIMP_HISTOGRAM_VALUE] = value;
}
levels->low_output[GIMP_HISTOGRAM_VALUE] = value;
value = 0.5 * contrast + brightness + 0.5;
if (value > 1.0)
else
{
value = 1.0;
value = 0.5 - 0.5 * slant;
levels->high_input[GIMP_HISTOGRAM_VALUE] =
(0.5 - brightness) / contrast + 0.5;
if (value < 0.0)
{
value = 0.0;
levels->low_input[GIMP_HISTOGRAM_VALUE] =
(0.5 * slant - 0.5) / (slant + brightness * slant);
}
levels->low_output[GIMP_HISTOGRAM_VALUE] = value;
value = slant * brightness + slant * 0.5 + 0.5;
if (value > 1.0)
{
value = 1.0;
levels->high_input[GIMP_HISTOGRAM_VALUE] =
(0.5 * slant + 0.5) / (slant + brightness * slant);
}
levels->high_output[GIMP_HISTOGRAM_VALUE] = value;
}
levels->high_output[GIMP_HISTOGRAM_VALUE] = value;
return levels;
}