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Diffstat (limited to 'src/util/format_rgb9e5.h')
| -rw-r--r-- | src/util/format_rgb9e5.h | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/src/util/format_rgb9e5.h b/src/util/format_rgb9e5.h new file mode 100644 index 00000000000..21feba7b710 --- /dev/null +++ b/src/util/format_rgb9e5.h @@ -0,0 +1,161 @@ +/* + * Copyright (C) 2011 Marek Olšák <[email protected]> + * + * 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 |