libclut_rgb_contrast + libclut_cie_contrast

Signed-off-by: Mattias Andrée <maandree@member.fsf.org>

2 files changed, 160 insertions, 2 deletions

diff --git a/README b/README
index 5a5c9f1..0402112 100644
--- a/README
+++ b/README
@@ -2,8 +2,7 @@ NAME
 	libclut - A C colour lookup table library
 
 DESCRIPTION
-	libclut is header-only C library for manipulating
-	colour lookup tables.
+	libclut is C library for manipulating colour lookup tables.
 
 SEE ALSO
 	libred(7), redshift(1), blueshift(1), libgamma(7)
diff --git a/src/libclut.h b/src/libclut.h
new file mode 100644
index 0000000..6ef81eb
--- /dev/null
+++ b/src/libclut.h
@@ -0,0 +1,159 @@
+/**
+ * Copyright © 2016  Mattias Andrée <maandree@member.fsf.org>
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef LIBCLUT_H
+#define LIBCLUT_H
+
+#include <stddef.h>
+
+
+
+/**
+ * Modify a ramp.
+ * 
+ * None of the parameter may have side-effects.
+ * 
+ * This is intended for internal use.
+ * 
+ * @param  ramp     Pointer to the gamma ramps, must have and array
+ *                  named `channel` and a scalar named `channel` followed
+ *                  by "_size".
+ * @param  channel  The channel, must be either "red", "green", or "blue".
+ * @param  type     The data type used for each stop in the ramps.
+ * @param  expr     Expression that evalutes the value a stop should have.
+ *                  It can use the variable `LIBCLUT_VALUE` to get the
+ *                  current value of the stop.
+ */
+#define libclut__(ramp, channel, type, expr)		\
+  do							\
+    {							\
+      size_t i__, n__ = (ramp)->channel##_size;		\
+      type LIBCLUT_VALUE;				\
+      for (i__ = 0; i__ < n__; i__++)			\
+	{						\
+	  LIBCLUT_VALUE = (ramp)->channel[i__];		\
+	  (ramp)->channel[i__] = (type)(expr);		\
+	}						\
+    }							\
+  while (0)
+
+
+
+/**
+ * Apply contrast correction on the colour curves using sRGB.
+ * 
+ * In this context, contrast is a measure of difference between
+ * the whitepoint and blackpoint, if the difference is 0 than
+ * they are both grey.
+ * 
+ * None of the parameter may have side-effects.
+ * 
+ * @param  ramp  Pointer to the gamma ramps, must have the arrays
+ *               `red`, `green`, and `blue`, and the scalars
+ *               `red_size`, `green_size`, and `blue_size`. Ramp
+ *               structures from libgamma can be used.
+ * @param  max   The maximum value on each stop in the ramps.
+ * @param  type  The data type used for each stop in the ramps.
+ * @param  r     The contrast parameter for the red curve.
+ * @param  g     The contrast parameter for the green curve.
+ * @param  b     The contrast parameter for the blue curve.
+ */
+#define libclut_rgb_contrast(ramp, max, type, r, g, b)							\
+  do													\
+    {													\
+      if (r != 1.0)  libclut__(ramp, red,   type, LIBCLUT_VALUE - (max) / 2.0 * r + (max) / 2.0);	\
+      if (g != 1.0)  libclut__(ramp, green, type, LIBCLUT_VALUE - (max) / 2.0 * g + (max) / 2.0);	\
+      if (b != 1.0)  libclut__(ramp, blue,  type, LIBCLUT_VALUE - (max) / 2.0 * b + (max) / 2.0);	\
+    }													\
+  while (0)
+
+
+/**
+ * Apply contrast correction on the colour curves using CIE xyY.
+ * 
+ * In this context, contrast is a measure of difference between
+ * the whitepoint and blackpoint, if the difference is 0 than
+ * they are both grey.
+ * 
+ * None of the parameter may have side-effects.
+ * 
+ * @param  ramp  Pointer to the gamma ramps, must have the arrays
+ *               `red`, `green`, and `blue`, and the scalars
+ *               `red_size`, `green_size`, and `blue_size`. Ramp
+ *               structures from libgamma can be used.
+ * @param  max   The maximum value on each stop in the ramps.
+ * @param  type  The data type used for each stop in the ramps.
+ * @param  r     The contrast parameter for the red curve.
+ * @param  g     The contrast parameter for the green curve.
+ * @param  b     The contrast parameter for the blue curve.
+ */
+#define libclut_cie_contrast(ramp, max, type, r, g, b)							\
+  do													\
+    {													\
+      size_t rn__ = (ramp)->red_size;									\
+      size_t gn__ = (ramp)->green_size;									\
+      size_t bn__ = (ramp)->blue_size;									\
+      size_t i__;											\
+      double x__, y__, Y__, r__, g__, b__;								\
+      type* rs__ = (ramp)->red;										\
+      type* gs__ = (ramp)->green;									\
+      type* bs__ = (ramp)->blue;									\
+      if ((r == g) && (g == b) && (rn__ == gn__) && (gn__ == bn__))					\
+	{												\
+	  if (r == 1.0)											\
+	    break;											\
+	  for (i__ = 0; i__ < rn__; i__)								\
+	    {												\
+	      libclut_model_srgb_to_ciexyy(rs__[i__] / ((double)(max)), gs__[i__] / ((double)(max)),	\
+					   bs__[i__] / ((double)(max)), &x__, &y__, &Y__);		\
+	      libclut_model_ciexyy_to_srgb(x__, y__, (Y__ - 0.5) * r * 0.5, &r__, &g__, &b__);		\
+	      rs__[i__] = (type)(r__ * (double)(max));							\
+	      gs__[i__] = (type)(g__ * (double)(max));							\
+	      bs__[i__] = (type)(b__ * (double)(max));							\
+	    }												\
+	}												\
+      else												\
+	{												\
+	  if ((r == 1.0) && (g == 1.0) && (b == 1.0))							\
+	    break;											\
+	  libclut_model_srgb_to_ciexyy(rs__[i__] / ((double)(max)), gs__[i__] / ((double)(max)),	\
+				       bs__[i__] / ((double)(max)), &x__, &y__, &Y__);			\
+	  for (i__ = 0; i__ < rn__; i__)								\
+	    {												\
+	      if (r != 1.0)										\
+		{											\
+		  libclut_model_ciexyy_to_srgb(x__, y__, (Y__ - 0.5) * r * 0.5, &r__, &g__, &b__);	\
+		  rs__[i__] = (type)(r__ * (double)(max));						\
+		}											\
+	      if (g != 1.0)										\
+		{											\
+		  libclut_model_ciexyy_to_srgb(x__, y__, (Y__ - 0.5) * g * 0.5, &r__, &g__, &b__);	\
+		  gs__[i__] = (type)(g__ * (double)(max));						\
+		}											\
+	      if (b != 1.0)										\
+		{											\
+		  libclut_model_ciexyy_to_srgb(x__, y__, (Y__ - 0.5) * b * 0.5, &r__, &g__, &b__);	\
+		  bs__[i__] = (type)(b__ * (double)(max));						\
+		}											\
+	    }												\
+	}												\
+    }													\
+  while (0)
+
+
+
+#endif
+