gallium: Move sRGB <-> RGB handling to libmesautil

Signed-off-by: Jason Ekstrand <[email protected]>
Reviewed-by: Marek Olšák <[email protected]>

1 files changed, 133 insertions, 0 deletions

diff --git a/src/util/format_srgb.h b/src/util/format_srgb.h
new file mode 100644
index 00000000000..8e92c38f461
--- /dev/null
+++ b/src/util/format_srgb.h
@@ -0,0 +1,133 @@
+/**************************************************************************
+ *
+ * Copyright 2010 VMware, Inc.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ **************************************************************************/
+
+/**
+ * @file
+ * SRGB translation.
+ *
+ * @author Brian Paul <[email protected]>
+ * @author Michal Krol <[email protected]>
+ * @author Jose Fonseca <[email protected]>
+ */
+
+#ifndef U_FORMAT_SRGB_H_
+#define U_FORMAT_SRGB_H_
+
+#include <stdint.h>
+
+extern const float
+util_format_srgb_8unorm_to_linear_float_table[256];
+
+extern const uint8_t
+util_format_srgb_to_linear_8unorm_table[256];
+
+extern const uint8_t
+util_format_linear_to_srgb_8unorm_table[256];
+
+extern const unsigned
+util_format_linear_to_srgb_helper_table[104];
+
+
+/**
+ * Convert a unclamped linear float to srgb value in the [0,255].
+ */
+static inline uint8_t
+util_format_linear_float_to_srgb_8unorm(float x)
+{
+   /*
+    * This is taken from https://gist.github.com/rygorous/2203834
+    * Use LUT and do linear interpolation.
+    */
+   union {
+      uint32_t ui;
+      float f;
+   } almostone, minval, f;
+   unsigned tab, bias, scale, t;
+
+   almostone.ui = 0x3f7fffff;
+   minval.ui = (127-13) << 23;
+
+   /*
+    * Clamp to [2^(-13), 1-eps]; these two values map to 0 and 1, respectively.
+    * The tests are carefully written so that NaNs map to 0, same as in the
+    * reference implementation.
+    */
+   if (!(x > minval.f))
+      x = minval.f;
+   if (x > almostone.f)
+      x = almostone.f;
+
+   /* Do the table lookup and unpack bias, scale */
+   f.f = x;
+   tab = util_format_linear_to_srgb_helper_table[(f.ui - minval.ui) >> 20];
+   bias = (tab >> 16) << 9;
+   scale = tab & 0xffff;
+
+   /* Grab next-highest mantissa bits and perform linear interpolation */
+   t = (f.ui >> 12) & 0xff;
+   return (uint8_t) ((bias + scale*t) >> 16);
+}
+
+
+/**
+ * Convert an 8-bit sRGB value from non-linear space to a
+ * linear RGB value in [0, 1].
+ * Implemented with a 256-entry lookup table.
+ */
+static inline float
+util_format_srgb_8unorm_to_linear_float(uint8_t x)
+{
+   return util_format_srgb_8unorm_to_linear_float_table[x];
+}
+
+
+/*
+ * XXX These 2 functions probably don't make a lot of sense (but lots
+ * of potential callers which most likely all don't make sense neither)
+ */
+
+/**
+ * Convert a 8bit normalized value from linear to srgb.
+ */
+static inline uint8_t
+util_format_linear_to_srgb_8unorm(uint8_t x)
+{
+   return util_format_linear_to_srgb_8unorm_table[x];
+}
+
+
+/**
+ * Convert a 8bit normalized value from srgb to linear.
+ */
+static inline uint8_t
+util_format_srgb_to_linear_8unorm(uint8_t x)
+{
+   return util_format_srgb_to_linear_8unorm_table[x];
+}
+
+
+#endif /* U_FORMAT_SRGB_H_ */