--- /dev/null
+/*
+ * Copyright (C) 2011 Marek Olšák <maraeo@gmail.com>
+ *
+ * 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, sublicense,
+ * 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 above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * 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 NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS 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.
+ */
+
+/* Copied from EXT_texture_shared_exponent and edited, getting rid of
+ * expensive float math bits too. */
+
+#ifndef RGB9E5_H
+#define RGB9E5_H
+
+#include <assert.h>
+
+#include "c99_math.h"
+
+#define RGB9E5_EXPONENT_BITS 5
+#define RGB9E5_MANTISSA_BITS 9
+#define RGB9E5_EXP_BIAS 15
+#define RGB9E5_MAX_VALID_BIASED_EXP 31
+
+#define MAX_RGB9E5_EXP (RGB9E5_MAX_VALID_BIASED_EXP - RGB9E5_EXP_BIAS)
+#define RGB9E5_MANTISSA_VALUES (1<<RGB9E5_MANTISSA_BITS)
+#define MAX_RGB9E5_MANTISSA (RGB9E5_MANTISSA_VALUES-1)
+#define MAX_RGB9E5 (((float)MAX_RGB9E5_MANTISSA)/RGB9E5_MANTISSA_VALUES * (1<<MAX_RGB9E5_EXP))
+
+typedef union {
+ unsigned int raw;
+ float value;
+ struct {
+#if defined(MESA_BIG_ENDIAN) || defined(PIPE_ARCH_BIG_ENDIAN)
+ unsigned int negative:1;
+ unsigned int biasedexponent:8;
+ unsigned int mantissa:23;
+#else
+ unsigned int mantissa:23;
+ unsigned int biasedexponent:8;
+ unsigned int negative:1;
+#endif
+ } field;
+} float754;
+
+typedef union {
+ unsigned int raw;
+ struct {
+#if defined(MESA_BIG_ENDIAN) || defined(PIPE_ARCH_BIG_ENDIAN)
+ unsigned int biasedexponent:RGB9E5_EXPONENT_BITS;
+ unsigned int b:RGB9E5_MANTISSA_BITS;
+ unsigned int g:RGB9E5_MANTISSA_BITS;
+ unsigned int r:RGB9E5_MANTISSA_BITS;
+#else
+ unsigned int r:RGB9E5_MANTISSA_BITS;
+ unsigned int g:RGB9E5_MANTISSA_BITS;
+ unsigned int b:RGB9E5_MANTISSA_BITS;
+ unsigned int biasedexponent:RGB9E5_EXPONENT_BITS;
+#endif
+ } field;
+} rgb9e5;
+
+
+static inline int rgb9e5_ClampRange(float x)
+{
+ float754 f;
+ float754 max;
+ f.value = x;
+ max.value = MAX_RGB9E5;
+
+ if (f.raw > 0x7f800000)
+ /* catches neg, NaNs */
+ return 0;
+ else if (f.raw >= max.raw)
+ return max.raw;
+ else
+ return f.raw;
+}
+
+static inline unsigned float3_to_rgb9e5(const float rgb[3])
+{
+ rgb9e5 retval;
+ int rm, gm, bm, exp_shared;
+ float754 revdenom = {0};
+ float754 rc, bc, gc, maxrgb;
+
+ rc.raw = rgb9e5_ClampRange(rgb[0]);
+ gc.raw = rgb9e5_ClampRange(rgb[1]);
+ bc.raw = rgb9e5_ClampRange(rgb[2]);
+ maxrgb.raw = MAX3(rc.raw, gc.raw, bc.raw);
+
+ /*
+ * Compared to what the spec suggests, instead of conditionally adjusting
+ * the exponent after the fact do it here by doing the equivalent of +0.5 -
+ * the int add will spill over into the exponent in this case.
+ */
+ maxrgb.raw += maxrgb.raw & (1 << (23-9));
+ exp_shared = MAX2((maxrgb.raw >> 23), -RGB9E5_EXP_BIAS - 1 + 127) +
+ 1 + RGB9E5_EXP_BIAS - 127;
+ revdenom.field.biasedexponent = 127 - (exp_shared - RGB9E5_EXP_BIAS -
+ RGB9E5_MANTISSA_BITS) + 1;
+ assert(exp_shared <= RGB9E5_MAX_VALID_BIASED_EXP);
+
+ /*
+ * The spec uses strict round-up behavior (d3d10 disagrees, but in any case
+ * must match what is done above for figuring out exponent).
+ * We avoid the doubles ((int) rc * revdenom + 0.5) by doing the rounding
+ * ourselves (revdenom was adjusted by +1, above).
+ */
+ rm = (int) (rc.value * revdenom.value);
+ gm = (int) (gc.value * revdenom.value);
+ bm = (int) (bc.value * revdenom.value);
+ rm = (rm & 1) + (rm >> 1);
+ gm = (gm & 1) + (gm >> 1);
+ bm = (bm & 1) + (bm >> 1);
+
+ assert(rm <= MAX_RGB9E5_MANTISSA);
+ assert(gm <= MAX_RGB9E5_MANTISSA);
+ assert(bm <= MAX_RGB9E5_MANTISSA);
+ assert(rm >= 0);
+ assert(gm >= 0);
+ assert(bm >= 0);
+
+ retval.field.r = rm;
+ retval.field.g = gm;
+ retval.field.b = bm;
+ retval.field.biasedexponent = exp_shared;
+
+ return retval.raw;
+}
+
+static inline void rgb9e5_to_float3(unsigned rgb, float retval[3])
+{
+ rgb9e5 v;
+ int exponent;
+ float754 scale = {0};
+
+ v.raw = rgb;
+ exponent = v.field.biasedexponent - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS;
+ scale.field.biasedexponent = exponent + 127;
+
+ retval[0] = v.field.r * scale.value;
+ retval[1] = v.field.g * scale.value;
+ retval[2] = v.field.b * scale.value;
+}
+
+#endif
projects / mesa.git / blobdiff