void
gimp_brightness_contrast_config_set_node (GimpBrightnessContrastConfig *config,
GeglNode *node)
{
gdouble brightness;
gdouble contrast;
g_return_if_fail (GIMP_IS_BRIGHTNESS_CONTRAST_CONFIG (config));
g_return_if_fail (GEGL_IS_NODE (node));
brightness = config->brightness / 2.0;
contrast = (config->contrast < 0 ?
(config->contrast + 1.0) :
config->contrast * 4.0 + 1.0);
gegl_node_set (node,
"brightness", brightness,
"contrast", contrast,
NULL);
}
GimpLevelsConfig *
gimp_brightness_contrast_config_to_levels_config (GimpBrightnessContrastConfig *config)
{
GimpLevelsConfig *levels;
gdouble brightness;
gdouble slant;
gdouble value;
g_return_val_if_fail (GIMP_IS_BRIGHTNESS_CONTRAST_CONFIG (config), NULL);
levels = g_object_new (GIMP_TYPE_LEVELS_CONFIG, NULL);
brightness = config->brightness / 2.0;
slant = tan ((config->contrast + 1) * G_PI_4);
if (config->brightness >= 0)
{
value = -0.5 * slant + brightness * slant + 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;
}
else
{
value = 0.5 - 0.5 * slant;
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;
}
return levels;
}
