src/util/format_r11g11b10f.h - third_party/mesa - Git at Google

 /*
  * 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.
  */

 /* Based on code from The OpenGL Programming Guide / 7th Edition, Appendix J.
  * Available here: http://www.opengl-redbook.com/appendices/
  * The algorithm in the book contains a bug though, which is fixed in the code
  * below.
  */

 #ifndef FORMAT_R11G11B10F_H
 #define FORMAT_R11G11B10F_H

 #include <stdint.h>

 #include "rounding.h"

 #define UF11(e, m)           ((e << 6) | (m))
 #define UF11_EXPONENT_BIAS   15
 #define UF11_EXPONENT_BITS   0x1F
 #define UF11_EXPONENT_SHIFT  6
 #define UF11_MANTISSA_BITS   0x3F
 #define UF11_MANTISSA_SHIFT  (23 - UF11_EXPONENT_SHIFT)
 #define UF11_MAX_EXPONENT    (UF11_EXPONENT_BITS << UF11_EXPONENT_SHIFT)

 #define UF10(e, m)           ((e << 5) | (m))
 #define UF10_EXPONENT_BIAS   15
 #define UF10_EXPONENT_BITS   0x1F
 #define UF10_EXPONENT_SHIFT  5
 #define UF10_MANTISSA_BITS   0x1F
 #define UF10_MANTISSA_SHIFT  (23 - UF10_EXPONENT_SHIFT)
 #define UF10_MAX_EXPONENT    (UF10_EXPONENT_BITS << UF10_EXPONENT_SHIFT)

 #define F32_INFINITY         0x7f800000

 static inline uint32_t f32_to_uf11(float val)
 {
    union {
       float f;
       uint32_t ui;
    } f32 = {val};

    uint16_t uf11 = 0;

    /* Decode little-endian 32-bit floating-point value */
    int sign = (f32.ui >> 16) & 0x8000;
    /* Map exponent to the range [-127,128] */
    int exponent = ((f32.ui >> 23) & 0xff) - 127;
    int mantissa = f32.ui & 0x007fffff;

    if (exponent == 128) { /* Infinity or NaN */
       /* From the GL_EXT_packed_float spec:
        *
        *     "Additionally: negative infinity is converted to zero; positive
        *      infinity is converted to positive infinity; and both positive and
        *      negative NaN are converted to positive NaN."
        */
       uf11 = UF11_MAX_EXPONENT;
       if (mantissa) {
          uf11 |= 1; /* NaN */
       } else {
          if (sign)
             uf11 = 0; /* 0.0 */
       }
    } else if (sign) {
       return 0;
    } else if (val > 65024.0f) {
       /* From the GL_EXT_packed_float spec:
        *
        *     "Likewise, finite positive values greater than 65024 (the maximum
        *      finite representable unsigned 11-bit floating-point value) are
        *      converted to 65024."
        */
       uf11 = UF11(30, 63);
    } else if (exponent > -15) { /* Normal value */
       /* Dividing by 2^exponent gives us a number in the range [1, 2).
        * Multiplying by 2^6=64 gives us our mantissa, plus an extra 1 which
        * we'll mask off.
        */
       mantissa = _mesa_lroundevenf(ldexp(val, 6 - exponent));
       if (mantissa >= 2 << UF11_EXPONENT_SHIFT) {
          /* The float32 was rounded upwards into the range of the next
           * exponent, so bump the exponent.
           */
          assert(mantissa == 2 << UF11_EXPONENT_SHIFT);
          mantissa >>= 1;
          exponent++;
       }
       assert((mantissa >> UF11_EXPONENT_SHIFT) == 1);
       mantissa &= UF11_MANTISSA_BITS;
       exponent += UF11_EXPONENT_BIAS;
       uf11 = UF11(exponent, mantissa);
    } else { /* Zero or denormal */
       /* Since exponent <= -15, Multiplying by 2^14 gives us a number in the
        * range [0, 1). Multiplying by 2^6=64 gives us our mantissa.
        */
       mantissa = _mesa_lroundevenf(ldexp(val, 6 + 14));

       /* It's possible that we get a normal after rounding */
       if ((mantissa >> UF11_EXPONENT_SHIFT) != 0) {
          assert(mantissa == (1 << UF11_EXPONENT_SHIFT));
          uf11 = UF11(1, 0);
       } else {
          uf11 = UF11(0, mantissa);
       }
    }

    return uf11;
 }

 static inline float uf11_to_f32(uint16_t val)
 {
    union {
       float f;
       uint32_t ui;
    } f32;

    int exponent = (val & 0x07c0) >> UF11_EXPONENT_SHIFT;
    int mantissa = (val & 0x003f);

    f32.f = 0.0;

    if (exponent == 0) {
       if (mantissa != 0) {
          const float scale = 1.0 / (1 << 20);
          f32.f = scale * mantissa;
       }
    } else if (exponent == 31) {
       f32.ui = F32_INFINITY | mantissa;
    } else {
       float scale, decimal;
       exponent -= 15;
       if (exponent < 0) {
          scale = 1.0f / (1 << -exponent);
       } else {
          scale = (float) (1 << exponent);
       }
       decimal = 1.0f + (float) mantissa / 64;
       f32.f = scale * decimal;
    }

    return f32.f;
 }

 static inline uint32_t f32_to_uf10(float val)
 {
    union {
       float f;
       uint32_t ui;
    } f32 = {val};

    uint16_t uf10 = 0;

    /* Decode little-endian 32-bit floating-point value */
    int sign = (f32.ui >> 16) & 0x8000;
    /* Map exponent to the range [-127,128] */
    int exponent = ((f32.ui >> 23) & 0xff) - 127;
    int mantissa = f32.ui & 0x007fffff;

    if (exponent == 128) {
       /* From the GL_EXT_packed_float spec:
        *
        *     "Additionally: negative infinity is converted to zero; positive
        *      infinity is converted to positive infinity; and both positive and
        *      negative NaN are converted to positive NaN."
        */
       uf10 = UF10_MAX_EXPONENT;
       if (mantissa) {
          uf10 |= 1; /* NaN */
       } else {
          if (sign)
             uf10 = 0; /* 0.0 */
       }
    } else if (sign) {
       return 0;
    } else if (val > 64512.0f) {
       /* From the GL_EXT_packed_float spec:
        *
        *     "Likewise, finite positive values greater than 64512 (the maximum
        *      finite representable unsigned 10-bit floating-point value) are
        *      converted to 64512."
        */
       uf10 = UF10(30, 31);
    } else if (exponent > -15) { /* Normal value */
       /* Dividing by 2^exponent gives us a number in the range [1, 2).
        * Multiplying by 2^5=32 gives us our mantissa, plus an extra 1 which
        * we'll mask off.
        */
       mantissa = _mesa_lroundevenf(ldexp(val, 5 - exponent));
       if (mantissa >= 2 << UF10_EXPONENT_SHIFT) {
          /* The float32 was rounded upwards into the range of the next
           * exponent, so bump the exponent.
           */
          assert(mantissa == 2 << UF10_EXPONENT_SHIFT);
          mantissa >>= 1;
          exponent++;
       }
       assert((mantissa >> UF10_EXPONENT_SHIFT) == 1);
       mantissa &= UF10_MANTISSA_BITS;
       exponent += UF10_EXPONENT_BIAS;
       uf10 = UF10(exponent, mantissa);
    } else { /* Zero or denormal */
       /* Since exponent <= -15, Multiplying by 2^14 gives us a number in the
        * range [0, 1). Multiplying by 2^5=32 gives us our mantissa.
        */
       mantissa = _mesa_lroundevenf(ldexp(val, 5 + 14));

       /* It's possible that we get a normal after rounding */
       if ((mantissa >> UF10_EXPONENT_SHIFT) != 0) {
          assert(mantissa == (1 << UF10_EXPONENT_SHIFT));
          uf10 = UF10(1, 0);
       } else {
          uf10 = UF10(0, mantissa);
       }
    }

    return uf10;
 }

 static inline float uf10_to_f32(uint16_t val)
 {
    union {
       float f;
       uint32_t ui;
    } f32;

    int exponent = (val & 0x03e0) >> UF10_EXPONENT_SHIFT;
    int mantissa = (val & 0x001f);

    f32.f = 0.0;

    if (exponent == 0) {
       if (mantissa != 0) {
          const float scale = 1.0 / (1 << 19);
          f32.f = scale * mantissa;
       }
    } else if (exponent == 31) {
       f32.ui = F32_INFINITY | mantissa;
    } else {
       float scale, decimal;
       exponent -= 15;
       if (exponent < 0) {
          scale = 1.0f / (1 << -exponent);
       }
       else {
          scale = (float) (1 << exponent);
       }
       decimal = 1.0f + (float) mantissa / 32;
       f32.f = scale * decimal;
    }

    return f32.f;
 }

 static inline uint32_t float3_to_r11g11b10f(const float rgb[3])
 {
    return ( f32_to_uf11(rgb[0]) & 0x7ff) |
           ((f32_to_uf11(rgb[1]) & 0x7ff) << 11) |
           ((f32_to_uf10(rgb[2]) & 0x3ff) << 22);
 }

 static inline void r11g11b10f_to_float3(uint32_t rgb, float retval[3])
 {
    retval[0] = uf11_to_f32( rgb        & 0x7ff);
    retval[1] = uf11_to_f32((rgb >> 11) & 0x7ff);
    retval[2] = uf10_to_f32((rgb >> 22) & 0x3ff);
 }

 #endif /* FORMAT_R11G11B10F_H */
	/*
	* 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.
	*/

	/* Based on code from The OpenGL Programming Guide / 7th Edition, Appendix J.
	* Available here: http://www.opengl-redbook.com/appendices/
	* The algorithm in the book contains a bug though, which is fixed in the code
	* below.
	*/

	#ifndef FORMAT_R11G11B10F_H
	#define FORMAT_R11G11B10F_H

	#include <stdint.h>

	#include "rounding.h"

	#define UF11(e, m) ((e << 6) \| (m))
	#define UF11_EXPONENT_BIAS 15
	#define UF11_EXPONENT_BITS 0x1F
	#define UF11_EXPONENT_SHIFT 6
	#define UF11_MANTISSA_BITS 0x3F
	#define UF11_MANTISSA_SHIFT (23 - UF11_EXPONENT_SHIFT)
	#define UF11_MAX_EXPONENT (UF11_EXPONENT_BITS << UF11_EXPONENT_SHIFT)

	#define UF10(e, m) ((e << 5) \| (m))
	#define UF10_EXPONENT_BIAS 15
	#define UF10_EXPONENT_BITS 0x1F
	#define UF10_EXPONENT_SHIFT 5
	#define UF10_MANTISSA_BITS 0x1F
	#define UF10_MANTISSA_SHIFT (23 - UF10_EXPONENT_SHIFT)
	#define UF10_MAX_EXPONENT (UF10_EXPONENT_BITS << UF10_EXPONENT_SHIFT)

	#define F32_INFINITY 0x7f800000

	static inline uint32_t f32_to_uf11(float val)
	{
	union {
	float f;
	uint32_t ui;
	} f32 = {val};

	uint16_t uf11 = 0;

	/* Decode little-endian 32-bit floating-point value */
	int sign = (f32.ui >> 16) & 0x8000;
	/* Map exponent to the range [-127,128] */
	int exponent = ((f32.ui >> 23) & 0xff) - 127;
	int mantissa = f32.ui & 0x007fffff;

	if (exponent == 128) { /* Infinity or NaN */
	/* From the GL_EXT_packed_float spec:
	*
	* "Additionally: negative infinity is converted to zero; positive
	* infinity is converted to positive infinity; and both positive and
	* negative NaN are converted to positive NaN."
	*/
	uf11 = UF11_MAX_EXPONENT;
	if (mantissa) {
	uf11 \|= 1; /* NaN */
	} else {
	if (sign)
	uf11 = 0; /* 0.0 */
	}
	} else if (sign) {
	return 0;
	} else if (val > 65024.0f) {
	/* From the GL_EXT_packed_float spec:
	*
	* "Likewise, finite positive values greater than 65024 (the maximum
	* finite representable unsigned 11-bit floating-point value) are
	* converted to 65024."
	*/
	uf11 = UF11(30, 63);
	} else if (exponent > -15) { /* Normal value */
	/* Dividing by 2^exponent gives us a number in the range [1, 2).
	* Multiplying by 2^6=64 gives us our mantissa, plus an extra 1 which
	* we'll mask off.
	*/
	mantissa = _mesa_lroundevenf(ldexp(val, 6 - exponent));
	if (mantissa >= 2 << UF11_EXPONENT_SHIFT) {
	/* The float32 was rounded upwards into the range of the next
	* exponent, so bump the exponent.
	*/
	assert(mantissa == 2 << UF11_EXPONENT_SHIFT);
	mantissa >>= 1;
	exponent++;
	}
	assert((mantissa >> UF11_EXPONENT_SHIFT) == 1);
	mantissa &= UF11_MANTISSA_BITS;
	exponent += UF11_EXPONENT_BIAS;
	uf11 = UF11(exponent, mantissa);
	} else { /* Zero or denormal */
	/* Since exponent <= -15, Multiplying by 2^14 gives us a number in the
	* range [0, 1). Multiplying by 2^6=64 gives us our mantissa.
	*/
	mantissa = _mesa_lroundevenf(ldexp(val, 6 + 14));

	/* It's possible that we get a normal after rounding */
	if ((mantissa >> UF11_EXPONENT_SHIFT) != 0) {
	assert(mantissa == (1 << UF11_EXPONENT_SHIFT));
	uf11 = UF11(1, 0);
	} else {
	uf11 = UF11(0, mantissa);
	}
	}

	return uf11;
	}

	static inline float uf11_to_f32(uint16_t val)
	{
	union {
	float f;
	uint32_t ui;
	} f32;

	int exponent = (val & 0x07c0) >> UF11_EXPONENT_SHIFT;
	int mantissa = (val & 0x003f);

	f32.f = 0.0;

	if (exponent == 0) {
	if (mantissa != 0) {
	const float scale = 1.0 / (1 << 20);
	f32.f = scale * mantissa;
	}
	} else if (exponent == 31) {
	f32.ui = F32_INFINITY \| mantissa;
	} else {
	float scale, decimal;
	exponent -= 15;
	if (exponent < 0) {
	scale = 1.0f / (1 << -exponent);
	} else {
	scale = (float) (1 << exponent);
	}
	decimal = 1.0f + (float) mantissa / 64;
	f32.f = scale * decimal;
	}

	return f32.f;
	}

	static inline uint32_t f32_to_uf10(float val)
	{
	union {
	float f;
	uint32_t ui;
	} f32 = {val};

	uint16_t uf10 = 0;

	/* Decode little-endian 32-bit floating-point value */
	int sign = (f32.ui >> 16) & 0x8000;
	/* Map exponent to the range [-127,128] */
	int exponent = ((f32.ui >> 23) & 0xff) - 127;
	int mantissa = f32.ui & 0x007fffff;

	if (exponent == 128) {
	/* From the GL_EXT_packed_float spec:
	*
	* "Additionally: negative infinity is converted to zero; positive
	* infinity is converted to positive infinity; and both positive and
	* negative NaN are converted to positive NaN."
	*/
	uf10 = UF10_MAX_EXPONENT;
	if (mantissa) {
	uf10 \|= 1; /* NaN */
	} else {
	if (sign)
	uf10 = 0; /* 0.0 */
	}
	} else if (sign) {
	return 0;
	} else if (val > 64512.0f) {
	/* From the GL_EXT_packed_float spec:
	*
	* "Likewise, finite positive values greater than 64512 (the maximum
	* finite representable unsigned 10-bit floating-point value) are
	* converted to 64512."
	*/
	uf10 = UF10(30, 31);
	} else if (exponent > -15) { /* Normal value */
	/* Dividing by 2^exponent gives us a number in the range [1, 2).
	* Multiplying by 2^5=32 gives us our mantissa, plus an extra 1 which
	* we'll mask off.
	*/
	mantissa = _mesa_lroundevenf(ldexp(val, 5 - exponent));
	if (mantissa >= 2 << UF10_EXPONENT_SHIFT) {
	/* The float32 was rounded upwards into the range of the next
	* exponent, so bump the exponent.
	*/
	assert(mantissa == 2 << UF10_EXPONENT_SHIFT);
	mantissa >>= 1;
	exponent++;
	}
	assert((mantissa >> UF10_EXPONENT_SHIFT) == 1);
	mantissa &= UF10_MANTISSA_BITS;
	exponent += UF10_EXPONENT_BIAS;
	uf10 = UF10(exponent, mantissa);
	} else { /* Zero or denormal */
	/* Since exponent <= -15, Multiplying by 2^14 gives us a number in the
	* range [0, 1). Multiplying by 2^5=32 gives us our mantissa.
	*/
	mantissa = _mesa_lroundevenf(ldexp(val, 5 + 14));

	/* It's possible that we get a normal after rounding */
	if ((mantissa >> UF10_EXPONENT_SHIFT) != 0) {
	assert(mantissa == (1 << UF10_EXPONENT_SHIFT));
	uf10 = UF10(1, 0);
	} else {
	uf10 = UF10(0, mantissa);
	}
	}

	return uf10;
	}

	static inline float uf10_to_f32(uint16_t val)
	{
	union {
	float f;
	uint32_t ui;
	} f32;

	int exponent = (val & 0x03e0) >> UF10_EXPONENT_SHIFT;
	int mantissa = (val & 0x001f);

	f32.f = 0.0;

	if (exponent == 0) {
	if (mantissa != 0) {
	const float scale = 1.0 / (1 << 19);
	f32.f = scale * mantissa;
	}
	} else if (exponent == 31) {
	f32.ui = F32_INFINITY \| mantissa;
	} else {
	float scale, decimal;
	exponent -= 15;
	if (exponent < 0) {
	scale = 1.0f / (1 << -exponent);
	}
	else {
	scale = (float) (1 << exponent);
	}
	decimal = 1.0f + (float) mantissa / 32;
	f32.f = scale * decimal;
	}

	return f32.f;
	}

	static inline uint32_t float3_to_r11g11b10f(const float rgb[3])
	{
	return ( f32_to_uf11(rgb[0]) & 0x7ff) \|
	((f32_to_uf11(rgb[1]) & 0x7ff) << 11) \|
	((f32_to_uf10(rgb[2]) & 0x3ff) << 22);
	}

	static inline void r11g11b10f_to_float3(uint32_t rgb, float retval[3])
	{
	retval[0] = uf11_to_f32( rgb & 0x7ff);
	retval[1] = uf11_to_f32((rgb >> 11) & 0x7ff);
	retval[2] = uf10_to_f32((rgb >> 22) & 0x3ff);
	}

	#endif /* FORMAT_R11G11B10F_H */