[babl] Add extension with HCY color model, and pixel formats

[Øyvind Kolås <ok src gnome org>]

commit b71dcaaf22b5e36529d8430cb78dcdee49643770
Author: SBP <vorstar mac com>
Date:   Fri Nov 11 17:14:38 2016 -0600

    Add extension with HCY color model, and pixel formats

 extensions/HCY.c |  369 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 369 insertions(+), 0 deletions(-)
---
diff --git a/extensions/HCY.c b/extensions/HCY.c
new file mode 100644
index 0000000..51382ef
--- /dev/null
+++ b/extensions/HCY.c
@@ -0,0 +1,369 @@
+/* babl - dynamically extendable universal pixel conversion library.
+ * Copyright (C) 2016,  Sirio Bolaños Puchet <vorstar mac com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+ /*
+ * Adding support for HCY colorspace, based on the reference implementation by
+ * Kuzma Shapran (https://code.google.com/archive/p/colour-space-viewer)
+ */
+
+#include "config.h"
+
+#include <math.h>
+#include <string.h>
+
+#include "babl.h"
+#include "base/util.h"
+
+/* Rec. 601 as in original code //Rec. 709 */
+#define RGB_LUMA_RED 0.299 //0.2126
+#define RGB_LUMA_GREEN 0.587 //0.7152
+#define RGB_LUMA_BLUE 0.114 //0.0722
+#define EPSILON 1e-10
+
+static long rgba_to_hcya     (char *src,
+                              char *dst,
+                              long  samples);
+
+static long hcya_to_rgba     (char *src,
+                              char *dst,
+                              long  samples);
+
+static long rgba_to_hcy      (char *src,
+                              char *dst,
+                              long  samples);
+
+static long hcy_to_rgba      (char *src,
+                              char *dst,
+                              long  samples);
+
+static void rgba_to_hcy_step (char *src,
+                              char *dst);
+
+static void hcy_to_rgba_step (char *src,
+                              char *dst);
+
+static void components       (void);
+static void models           (void);
+static void conversions      (void);
+static void formats          (void);
+
+int init (void);
+
+int
+init (void)
+{
+  components  ();
+  models      ();
+  conversions ();
+  formats     ();
+
+  return 0;
+}
+
+
+static void
+components (void)
+{
+  babl_component_new ("hue", NULL);
+  babl_component_new ("HCY chroma", "chroma", NULL);
+  babl_component_new ("HCY luma", "luma", NULL);
+  babl_component_new ("alpha", NULL);
+}
+
+static void
+models (void)
+{
+  babl_model_new (
+    "name", "HCYA",
+    babl_component ("hue"),
+    babl_component ("HCY chroma"),
+    babl_component ("HCY luma"),
+    babl_component ("alpha"),
+    NULL
+  );
+
+  babl_model_new (
+    "name", "HCY",
+    babl_component ("hue"),
+    babl_component ("HCY chroma"),
+    babl_component ("HCY luma"),
+    NULL
+  );
+}
+
+static void
+conversions (void)
+{
+  babl_conversion_new (
+    babl_model ("RGBA"),
+    babl_model ("HCYA"),
+    "linear", rgba_to_hcya,
+    NULL
+  );
+
+  babl_conversion_new (
+    babl_model ("RGBA"),
+    babl_model ("HCY"),
+    "linear", rgba_to_hcy,
+    NULL
+  );
+
+  babl_conversion_new (
+    babl_model ("HCYA"),
+    babl_model ("RGBA"),
+    "linear", hcya_to_rgba,
+    NULL
+  );
+
+  babl_conversion_new (
+    babl_model ("HCY"),
+    babl_model ("RGBA"),
+    "linear", hcy_to_rgba,
+    NULL
+  );
+}
+
+static void
+formats (void)
+{
+  babl_format_new (
+    "name", "HCYA float",
+    babl_model ("HCYA"),
+    babl_type ("float"),
+    babl_component ("hue"),
+    babl_component ("HCY chroma"),
+    babl_component ("HCY luma"),
+    babl_component ("alpha"),
+    NULL
+  );
+
+  babl_format_new (
+    "name", "HCY float",
+    babl_model ("HCY"),
+    babl_type ("float"),
+    babl_component ("hue"),
+    babl_component ("HCY chroma"),
+    babl_component ("HCY luma"),
+    NULL
+  );
+}
+
+static void
+rgba_to_hcy_step (char *src,
+                  char *dst)
+{
+  static const double weights[3] = {RGB_LUMA_RED,RGB_LUMA_GREEN,RGB_LUMA_BLUE};
+  double hue, chroma, luma;
+  double X, Y_peak = 0.;
+  int H_sec = 4, t = -1;
+
+  double rgb[3] = {linear_to_gamma_2_2 (((double *) src)[0]),
+    linear_to_gamma_2_2 (((double *) src)[1]),
+    linear_to_gamma_2_2 (((double *) src)[2])};
+  int ix[3] = {0,1,2};
+
+  if (rgb[0] < rgb[1]) {
+    if (rgb[1] > rgb[2]) {
+      if (rgb[0] < rgb[2]) { ix[1] = 2; ix[2] = 1; H_sec = 2; t = 1; }
+      else { ix[0] = 2; ix[1] = 0; ix[2] = 1; H_sec = 2; }
+    }
+  } else {
+    if (rgb[1] < rgb[2]) {
+      if (rgb[0] < rgb[2]) { ix[0] = 1; ix[1] = 0; H_sec = 4; t = 1; }
+      else { ix[0] = 1; ix[1] = 2; ix[2] = 0; H_sec = 6; }
+    } else { ix[0] = 2; ix[2] = 0; H_sec = 0; t = 1; }
+  }
+
+  luma = weights[0] * rgb[0] + weights[1] * rgb[1] + weights[2] * rgb[2];
+  chroma = rgb[ix[2]] - rgb[ix[0]];
+
+  if (chroma >= EPSILON)
+  {
+    X = (rgb[ix[1]] - rgb[ix[0]]) / chroma;
+
+    Y_peak = weights[ix[2]] + X * weights[ix[1]];
+    if (luma > 0. && luma < 1.)
+      chroma /= luma < Y_peak ? luma/Y_peak : (1. - luma)/(1. - Y_peak);
+
+    hue = (H_sec + t * X) / 6.;
+  }
+  else
+    chroma = hue = 0.0;
+
+  ((double *) dst)[0] = hue;
+  ((double *) dst)[1] = chroma;
+  ((double *) dst)[2] = luma;
+}
+
+static void
+hcy_to_rgba_step (char *src,
+                  char *dst)
+{
+  double red, green, blue;
+  double Y_peak = 0., H_insec, X, m;
+  int H_sec;
+
+  double hue    = ((double *) src)[0];
+  double chroma = ((double *) src)[1];
+  double luma   = ((double *) src)[2];
+
+  if(chroma < EPSILON) {
+    red = green = blue = luma;
+  } else {
+    hue *= 6.;
+    H_sec = (int)hue;
+
+    switch (H_sec)
+    {
+      case 0:
+        H_insec = hue - H_sec;
+        Y_peak = RGB_LUMA_RED + H_insec * RGB_LUMA_GREEN;
+        chroma *= luma < Y_peak ? luma/Y_peak : (1. - luma)/(1. - Y_peak);
+        X = chroma * H_insec;
+        m = luma - (RGB_LUMA_RED * chroma + RGB_LUMA_GREEN * X);
+        red = m + chroma; green = m + X; blue = m;
+        break;
+      case 1:
+        H_insec = 1. - (hue - H_sec);
+        Y_peak = RGB_LUMA_GREEN + H_insec * RGB_LUMA_RED;
+        chroma *= luma < Y_peak ? luma/Y_peak : (1. - luma)/(1. - Y_peak);
+        X = chroma * H_insec;
+        m = luma - (RGB_LUMA_RED * X + RGB_LUMA_GREEN * chroma);
+        red = m + X; green = m + chroma; blue = m;
+        break;
+      case 2:
+        H_insec = hue - H_sec;
+        Y_peak = RGB_LUMA_GREEN + H_insec * RGB_LUMA_BLUE;
+        chroma *= luma < Y_peak ? luma/Y_peak : (1. - luma)/(1. - Y_peak);
+        X = chroma * H_insec;
+        m = luma - (RGB_LUMA_GREEN * chroma + RGB_LUMA_BLUE * X);
+        red = m; green = m + chroma; blue = m + X;
+        break;
+      case 3:
+        H_insec = 1. - (hue - H_sec);
+        Y_peak = RGB_LUMA_BLUE + H_insec * RGB_LUMA_GREEN;
+        chroma *= luma < Y_peak ? luma/Y_peak : (1. - luma)/(1. - Y_peak);
+        X = chroma * H_insec;
+        m = luma - (RGB_LUMA_GREEN * X + RGB_LUMA_BLUE * chroma);
+        red = m; green = m + X; blue = m + chroma;
+        break;
+      case 4:
+        H_insec = hue - H_sec;
+        Y_peak = RGB_LUMA_BLUE + H_insec * RGB_LUMA_RED;
+        chroma *= luma < Y_peak ? luma/Y_peak : (1. - luma)/(1. - Y_peak);
+        X = chroma * H_insec;
+        m = luma - (RGB_LUMA_RED * X + RGB_LUMA_BLUE * chroma);
+        red = m + X; green = m; blue = m + chroma;
+        break;
+      default:
+        H_insec = 1. - (hue - H_sec);
+        Y_peak = RGB_LUMA_RED + H_insec * RGB_LUMA_BLUE;
+        chroma *= luma < Y_peak ? luma/Y_peak : (1. - luma)/(1. - Y_peak);
+        X = chroma * H_insec;
+        m = luma - (RGB_LUMA_RED * chroma + RGB_LUMA_BLUE * X);
+        red = m + chroma; green = m; blue = m + X;
+        break;
+    }
+  }
+
+  ((double *) dst)[0] = gamma_2_2_to_linear (red);
+  ((double *) dst)[1] = gamma_2_2_to_linear (green);
+  ((double *) dst)[2] = gamma_2_2_to_linear (blue);
+}
+
+static long
+rgba_to_hcya (char *src,
+              char *dst,
+              long  samples)
+{
+  long n = samples;
+
+  while (n--)
+  {
+    double alpha = ((double *) src)[3];
+
+    rgba_to_hcy_step (src, dst);
+
+    ((double *) dst)[3] = alpha;
+
+    src += 4 * sizeof (double);
+    dst += 4 * sizeof (double);
+  }
+
+  return samples;
+}
+
+static long
+hcya_to_rgba (char *src,
+              char *dst,
+              long  samples)
+{
+  long n = samples;
+
+  while (n--)
+  {
+    double alpha = ((double *) src)[3];
+
+    hcy_to_rgba_step (src, dst);
+
+    ((double *) dst)[3] = alpha;
+
+    src += 4 * sizeof (double);
+    dst += 4 * sizeof (double);
+  }
+
+  return samples;
+}
+
+static long
+rgba_to_hcy (char *src,
+             char *dst,
+             long  samples)
+{
+  long n = samples;
+
+  while (n--)
+  {
+    rgba_to_hcy_step (src, dst);
+
+    src += 4 * sizeof (double);
+    dst += 3 * sizeof (double);
+  }
+
+  return samples;
+}
+
+static long
+hcy_to_rgba (char *src,
+             char *dst,
+             long  samples)
+{
+  long n = samples;
+
+  while (n--)
+  {
+    hcy_to_rgba_step (src, dst);
+
+    ((double *) dst)[3] = 1.0;
+
+    src += 3 * sizeof (double);
+    dst += 4 * sizeof (double);
+  }
+
+  return samples;
+}