[babl] Add some float conversions for grey

[Daniel Sabo <daniels src gnome org>]

commit d7e1ab2b9fcc57143e32fe84af110cfba01e2ca3
Author: Daniel Sabo <DanielSabo gmail com>
Date:   Fri May 31 13:25:28 2013 -0700

    Add some float conversions for grey

 extensions/Makefile.am |    2 +
 extensions/grey.c      |  137 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 139 insertions(+), 0 deletions(-)
---
diff --git a/extensions/Makefile.am b/extensions/Makefile.am
index 30ac8c5..ea5d89e 100644
--- a/extensions/Makefile.am
+++ b/extensions/Makefile.am
@@ -21,6 +21,7 @@ ext_LTLIBRARIES = \
        gggl-lies.la    \
        gggl.la         \
        gimp-8bit.la    \
+       grey.la         \
        float.la        \
        fast-float.la   \
        naive-CMYK.la   \
@@ -37,6 +38,7 @@ gegl_fixups_la_SOURCES = gegl-fixups.c
 gggl_lies_la_SOURCES = gggl-lies.c
 gggl_la_SOURCES = gggl.c
 gimp_8bit_la_SOURCES = gimp-8bit.c
+grey_la_SOURCES = grey.c
 naive_CMYK_la_SOURCES = naive-CMYK.c
 HSV_la_SOURCES = HSV.c
 sse_fixups_la_SOURCES = sse-fixups.c
diff --git a/extensions/grey.c b/extensions/grey.c
new file mode 100644
index 0000000..a6fef28
--- /dev/null
+++ b/extensions/grey.c
@@ -0,0 +1,137 @@
+/* babl - dynamically extendable universal pixel conversion library.
+ * Copyright (C) 2013, Daniel Sabo
+ *
+ * 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/>.
+ */
+
+#include "config.h"
+#include <stdio.h>
+
+#include "babl.h"
+
+#include "base/util.h"
+#include "base/rgb-constants.h"
+#include "extensions/util.h"
+
+/* There was some debate on #gimp about whether these constants
+ * are accurate, for now I've elected to just follow whatever
+ * babl/base does.
+ *   - Daniel
+ */
+
+/* Float versions of the double constants in rgb-constants.h */
+static const float RGB_LUMINANCE_RED_FLOAT = RGB_LUMINANCE_RED;
+static const float RGB_LUMINANCE_GREEN_FLOAT = RGB_LUMINANCE_GREEN;
+static const float RGB_LUMINANCE_BLUE_FLOAT = RGB_LUMINANCE_BLUE;
+
+static long
+conv_rgbaF_linear_y8_linear (unsigned char *src,
+                             unsigned char *dst,
+                             long           samples)
+{
+  static const float RGB_LUMINANCE_RED_FLOAT = RGB_LUMINANCE_RED;
+  static const float RGB_LUMINANCE_GREEN_FLOAT = RGB_LUMINANCE_GREEN;
+  static const float RGB_LUMINANCE_BLUE_FLOAT = RGB_LUMINANCE_BLUE;
+
+  float *s = (float *) src;
+  long   n = samples;
+
+  while (n--)
+    {
+      float value;
+      long int v;
+      value  = *s++ * RGB_LUMINANCE_RED_FLOAT;
+      value += *s++ * RGB_LUMINANCE_GREEN_FLOAT;
+      value += *s++ * RGB_LUMINANCE_BLUE_FLOAT;
+      s++;
+
+      v = rint (value * 255.0);
+      *dst++ = (v < 0) ? 0 : ((v > 255) ? 255 : v);
+    }
+
+  return samples;
+}
+
+static long
+conv_rgbaF_linear_yF_linear (unsigned char *src,
+                             unsigned char *dst,
+                             long           samples)
+{
+
+  float *s = (float *) src;
+  float *d = (float *) dst;
+  long   n = samples;
+
+  while (n--)
+    {
+      float value;
+      value  = *s++ * RGB_LUMINANCE_RED_FLOAT;
+      value += *s++ * RGB_LUMINANCE_GREEN_FLOAT;
+      value += *s++ * RGB_LUMINANCE_BLUE_FLOAT;
+      s++;
+      *d++ = value;
+    }
+
+  return samples;
+}
+
+static long
+conv_rgbaF_linear_yaF_linear (unsigned char *src,
+                              unsigned char *dst,
+                              long           samples)
+{
+
+  float *s = (float *) src;
+  float *d = (float *) dst;
+  long   n = samples;
+
+  while (n--)
+    {
+      float value;
+      value  = *s++ * RGB_LUMINANCE_RED_FLOAT;
+      value += *s++ * RGB_LUMINANCE_GREEN_FLOAT;
+      value += *s++ * RGB_LUMINANCE_BLUE_FLOAT;
+      *d++ = value;
+      *d++ = *s++;  /* alpha */
+    }
+
+  return samples;
+}
+
+int init (void);
+
+int
+init (void)
+{
+  babl_conversion_new (babl_format ("RGBA float"),
+                       babl_format ("Y u8"),
+                       "linear",
+                       conv_rgbaF_linear_y8_linear,
+                       NULL);
+
+  babl_conversion_new (babl_format ("RGBA float"),
+                       babl_format ("Y float"),
+                       "linear",
+                       conv_rgbaF_linear_yF_linear,
+                       NULL);
+
+  babl_conversion_new (babl_format ("RGBA float"),
+                       babl_format ("YA float"),
+                       "linear",
+                       conv_rgbaF_linear_yaF_linear,
+                       NULL);
+
+  return 0;
+}