[babl/daniel-tolerance-hacks] Add some float<->int16 conversions.

[Daniel Sabo <daniels src gnome org>]

commit b4c18771042a7d79cb9eabba5c331d9f90267a84
Author: Daniel Sabo <DanielSabo gmail com>
Date:   Thu Feb 28 13:28:19 2013 -0800

    Add some float<->int16 conversions.

 extensions/Makefile.am |    2 +
 extensions/int16.c     |   78 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+), 0 deletions(-)
---
diff --git a/extensions/Makefile.am b/extensions/Makefile.am
index 58465f3..456e30e 100644
--- a/extensions/Makefile.am
+++ b/extensions/Makefile.am
@@ -24,6 +24,7 @@ ext_LTLIBRARIES = \
        gimp-8bit.la    \
        float.la    \
        fast-float.la    \
+       int16.la    \
        naive-CMYK.la   \
        HSV.la   \
        sse-fixups.la
@@ -35,6 +36,7 @@ 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
+int16_la_SOURCES = int16.c
 naive_CMYK_la_SOURCES = naive-CMYK.c
 HSV_la_SOURCES = HSV.c
 sse_fixups_la_SOURCES = sse-fixups.c
diff --git a/extensions/int16.c b/extensions/int16.c
new file mode 100644
index 0000000..af17af5
--- /dev/null
+++ b/extensions/int16.c
@@ -0,0 +1,78 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include "babl.h"
+
+#include "base/util.h"
+
+int init (void);
+
+static long
+float_pre_to_u16 (unsigned char *src_char, unsigned char *dst_char, long samples)
+{
+  float *src    = (float *)src_char;
+  uint16_t *dst = (uint16_t *)dst_char;
+  long n = samples;
+  while (n--)
+    {
+      if (src[3] < BABL_ALPHA_THRESHOLD)
+        {
+          dst[0] = 0;
+          dst[1] = 0;
+          dst[2] = 0;
+          dst[3] = 0;
+        }
+      else
+        {
+          float a_recip = 65535.0f * (1.0f / src[3]);
+          float r = src[0] * a_recip + 0.5;
+          float g = src[1] * a_recip + 0.5;
+          float b = src[2] * a_recip + 0.5;
+          float a = 65535.0f * src[3] + 0.5;
+          dst[0] = r >= 65535.0f ? 0xFFFF : r;
+          dst[1] = g >= 65535.0f ? 0xFFFF : g;
+          dst[2] = b >= 65535.0f ? 0xFFFF : b;
+          dst[3] = a >= 65535.0f ? 0xFFFF : a;
+        }
+      
+      src += 4;
+      dst += 4;
+    }
+  return samples;
+}
+
+static long
+u16_to_float_pre (unsigned char *src_char, unsigned char *dst_char, long samples)
+{
+  uint16_t *src = (uint16_t *)src_char;
+  float *dst    = (float *)dst_char;
+  long n = samples;
+  while (n--)
+    {
+      float a_term = src[3] / (65535.0f * 65535.0f);
+      dst[0] = src[0] * a_term;
+      dst[1] = src[1] * a_term;
+      dst[2] = src[2] * a_term;
+      dst[3] = src[3] / 65535.0;
+      
+      src += 4;
+      dst += 4;
+    }
+  return samples;
+}
+
+int
+init (void)
+{
+  babl_conversion_new (babl_format ("RaGaBaA float"),
+                       babl_format ("RGBA u16"),
+                      "linear", 
+                       float_pre_to_u16,
+                       NULL);
+  babl_conversion_new (babl_format ("RGBA u16"),
+                       babl_format ("RaGaBaA float"),
+                      "linear", 
+                       u16_to_float_pre,
+                       NULL);
+
+  return 0;
+}