Add libglitter_desaturate_{double,float}

Signed-off-by: Mattias Andrée <maandree@kth.se>

7 files changed, 97 insertions, 4 deletions

diff --git a/Makefile b/Makefile
index b0f2b07..e36b3fb 100644
--- a/Makefile
+++ b/Makefile
@@ -23,6 +23,8 @@ OBJ =\
 	libglitter_compose_uint32.o\
 	libglitter_compose_uint64.o\
 	libglitter_compose_uint8.o\
+	libglitter_desaturate_double.o\
+	libglitter_desaturate_float.o\
 	libglitter_create_render_context.o\
 	libglitter_free_render_context.o\
 	libglitter_update_render_context.o
@@ -42,6 +44,7 @@ libglitter_compose_uint16.o: libglitter_compose_uint64.c libglitter_compose_doub
 libglitter_compose_uint32.o: libglitter_compose_uint64.c libglitter_compose_double.c
 libglitter_compose_uint64.o: libglitter_compose_double.c
 libglitter_compose_uint8.o: libglitter_compose_uint64.c libglitter_compose_double.c
+libglitter_desaturate_float.o: libglitter_desaturate_double.c
 
 .c.o:
 	$(CC) -c -o $@ $< $(CFLAGS) $(CPPFLAGS)
diff --git a/TODO b/TODO
index 65602ac..743943b 100644
--- a/TODO
+++ b/TODO
@@ -1,4 +1,5 @@
-Add colour space conversion and saturation
+Add colour space conversion
+Add function to output primary chromas from an EDID
 Add support for GPU-acceleration
 Add man pages
 Add tests
diff --git a/common.h b/common.h
index b3a287b..6566fd0 100644
--- a/common.h
+++ b/common.h
@@ -4,6 +4,7 @@
 
 #include "libglitter.h"
 #include <alloca.h>
+#include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdlib.h>
diff --git a/config.mk b/config.mk
index 9b16e1d..64c9979 100644
--- a/config.mk
+++ b/config.mk
@@ -5,4 +5,4 @@ CC = cc
 
 CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700 -D_GNU_SOURCE
 CFLAGS   = -std=c99 -Wall -g
-LDFLAGS  =
+LDFLAGS  = -lm
diff --git a/libglitter.h b/libglitter.h
index 68a7b0e..0fc5888 100644
--- a/libglitter.h
+++ b/libglitter.h
@@ -70,7 +70,7 @@ void libglitter_free_render_context(LIBGLITTER_RENDER_CONTEXT *);
  * model's transfer function: it does not directly give
  * you appropriate sRGB values
  * 
- * @param  outputs          Array of output rasters, on for each subpixel colour.
+ * @param  outputs          Array of output rasters, one for each subpixel colour.
  *                          The function may change the offset for each raster,
  *                          as such, the given pointer shall not be used anywhere
  *                          else during the execution of the function and the
@@ -105,7 +105,7 @@ void libglitter_compose_float(float **, const float *restrict, size_t, size_t,
  * model's transfer function: it does not directly give
  * you appropriate sRGB values
  * 
- * @param  outputs          Array of output rasters, on for each subpixel colour.
+ * @param  outputs          Array of output rasters, one for each subpixel colour.
  *                          The function may change the offset for each raster,
  *                          as such, the given pointer shall not be used anywhere
  *                          else during the execution of the function and the
@@ -149,4 +149,38 @@ void libglitter_compose_uint8(uint8_t **, const uint8_t *restrict, size_t, size_
                               size_t, size_t, const LIBGLITTER_RENDER_CONTEXT *);
 
 
+/**
+ * Transform rasters from fully using subpixel rendering to
+ * balance between subpixel rendering and greyscale antialiasing
+ * 
+ * @param  rasters     Array of rasters, one for each subpixel colour.
+ *                     The function may change the offset for each raster,
+ *                     as such, the given pointer shall not be used anywhere
+ *                     else during the execution of the function and the
+ *                     inner pointers shall be considered undefined after
+ *                     the execution of the function
+ * @param  nrasters    The number of rasters
+ * @param  rowsize     The number of cells in a row in each raster
+ * @param  cellsize    The number of values stored in each raster,
+ *                     between each cell, plus 1 (that is, the number of
+ *                     values per cell)
+ * @param  width       The horizontal number of pixels in the rasters
+ * @param  height      The vertical number of pixels in the rasters
+ * @param  saturation  The subpixel rendering saturation, 1 for regular
+ *                     subpixel rendering, 0 for greyscale, values
+ *                     inbetween for a compromise
+ * @param  primary_ys  The CIE Y value (in e.g. CIE xyY or CIE XYZ) for
+ *                     each subpixel colour; or `NULL` for the sRGB values
+ *                     (this is only allowed if there are exactly 3 rasters)
+ */
+void libglitter_desaturate_double(double **, size_t, size_t, size_t, size_t, size_t, double, const double *);
+
+/**
+ * This value is identical to `libglitter_desaturate_double`,
+ * apart from it parameter types, see `libglitter_desaturate_double`
+ * for details about this function
+ */
+void libglitter_desaturate_float(float **, size_t, size_t, size_t, size_t, size_t, float, const float *);
+
+
 #endif
diff --git a/libglitter_desaturate_double.c b/libglitter_desaturate_double.c
new file mode 100644
index 0000000..62eaa3a
--- /dev/null
+++ b/libglitter_desaturate_double.c
@@ -0,0 +1,48 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+#if defined(__GNUC__) && !defined(__clang__)
+# pragma GCC diagnostic ignored "-Wunsuffixed-float-constants"
+#endif
+
+
+void
+libglitter_desaturate_double(double **rasters, size_t nrasters, size_t rowsize, size_t cellsize,
+                             size_t width, size_t height, double saturation, const double *primary_ys)
+{
+	size_t y, x, ch, raster_y, raster_i;
+	double intensity;
+
+	rowsize *= cellsize;
+
+	if (nrasters == 3) {
+		double *raster1 = rasters[0];
+		double *raster2 = rasters[1];
+		double *raster3 = rasters[2];
+		double primary1_y = primary_ys ? primary_ys[0] : (double)0.212673370378408277403536885686;
+		double primary2_y = primary_ys ? primary_ys[1] : (double)0.715151730491031756287156895269;
+		double primary3_y = primary_ys ? primary_ys[2] : (double)0.072174899130559869164791564344;
+		for (y = 0, raster_y = 0; y < height; y++, raster_y += rowsize) {
+			for (x = 0, raster_i = raster_y; x < width; x++, raster_i += cellsize) {
+				intensity  = raster1[raster_i] * primary1_y;
+				intensity += raster2[raster_i] * primary2_y;
+				intensity += raster3[raster_i] * primary3_y;
+				raster1[raster_i] = fma(raster1[raster_i] - intensity, saturation, intensity);
+				raster2[raster_i] = fma(raster2[raster_i] - intensity, saturation, intensity);
+				raster3[raster_i] = fma(raster3[raster_i] - intensity, saturation, intensity);
+			}
+		}
+
+	} else {
+		for (y = 0, raster_y = 0; y < height; y++, raster_y += rowsize) {
+			for (x = 0, raster_i = raster_y; x < width; x++, raster_i += cellsize) {
+				intensity = 0;
+				for (ch = 0; ch < nrasters; ch++)
+					intensity += rasters[ch][raster_i] * primary_ys[ch];
+				for (ch = 0; ch < nrasters; ch++)
+					rasters[ch][raster_i] = fma(rasters[ch][raster_i] - intensity, saturation, intensity);
+			}
+		}
+	}
+}
diff --git a/libglitter_desaturate_float.c b/libglitter_desaturate_float.c
new file mode 100644
index 0000000..54488a3
--- /dev/null
+++ b/libglitter_desaturate_float.c
@@ -0,0 +1,6 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#define libglitter_desaturate_double libglitter_desaturate_float
+#define double float
+#define fma fmaf
+#include "libglitter_desaturate_double.c"