transform_util.c - third_party/qcms - Git at Google

 #define _ISOC99_SOURCE  /* for INFINITY */

 #include <math.h>
 #include <assert.h>
 #include <string.h> //memcpy
 #include "qcmsint.h"
 #include "transform_util.h"
 #include "matrix.h"

 #if !defined(INFINITY)
 #define INFINITY HUGE_VAL
 #endif

 #define PARAMETRIC_CURVE_TYPE 0x70617261 //'para'

 /* value must be a value between 0 and 1 */
 //XXX: is the above a good restriction to have?
 float lut_interp_linear(double value, uint16_t *table, int length)
 {
 	int upper, lower;
 	value = value * (length - 1); // scale to length of the array
 	upper = ceil(value);
 	lower = floor(value);
 	//XXX: can we be more performant here?
 	value = table[upper]*(1. - (upper - value)) + table[lower]*(upper - value);
 	/* scale the value */
 	return value * (1./65535.);
 }

 /* same as above but takes and returns a uint16_t value representing a range from 0..1 */
 uint16_t lut_interp_linear16(uint16_t input_value, uint16_t *table, int length)
 {
 	/* Start scaling input_value to the length of the array: 65535*(length-1).
 	 * We'll divide out the 65535 next */
 	uint32_t value = (input_value * (length - 1));
 	uint32_t upper = (value + 65534) / 65535; /* equivalent to ceil(value/65535) */
 	uint32_t lower = value / 65535;           /* equivalent to floor(value/65535) */
 	/* interp is the distance from upper to value scaled to 0..65535 */
 	uint32_t interp = value % 65535;

 	value = (table[upper]*(interp) + table[lower]*(65535 - interp))/65535; // 0..65535*65535

 	return value;
 }

 /* same as above but takes an input_value from 0..PRECACHE_OUTPUT_MAX
  * and returns a uint8_t value representing a range from 0..1 */
 static
 uint8_t lut_interp_linear_precache_output(uint32_t input_value, uint16_t *table, int length)
 {
 	/* Start scaling input_value to the length of the array: PRECACHE_OUTPUT_MAX*(length-1).
 	 * We'll divide out the PRECACHE_OUTPUT_MAX next */
 	uint32_t value = (input_value * (length - 1));

 	/* equivalent to ceil(value/PRECACHE_OUTPUT_MAX) */
 	uint32_t upper = (value + PRECACHE_OUTPUT_MAX-1) / PRECACHE_OUTPUT_MAX;
 	/* equivalent to floor(value/PRECACHE_OUTPUT_MAX) */
 	uint32_t lower = value / PRECACHE_OUTPUT_MAX;
 	/* interp is the distance from upper to value scaled to 0..PRECACHE_OUTPUT_MAX */
 	uint32_t interp = value % PRECACHE_OUTPUT_MAX;

 	/* the table values range from 0..65535 */
 	value = (table[upper]*(interp) + table[lower]*(PRECACHE_OUTPUT_MAX - interp)); // 0..(65535*PRECACHE_OUTPUT_MAX)

 	/* round and scale */
 	value += (PRECACHE_OUTPUT_MAX*65535/255)/2;
         value /= (PRECACHE_OUTPUT_MAX*65535/255); // scale to 0..255
 	return value;
 }

 /* value must be a value between 0 and 1 */
 //XXX: is the above a good restriction to have?
 float lut_interp_linear_float(float value, float *table, int length)
 {
         int upper, lower;
         value = value * (length - 1);
         upper = ceil(value);
         lower = floor(value);
         //XXX: can we be more performant here?
         value = table[upper]*(1. - (upper - value)) + table[lower]*(upper - value);
         /* scale the value */
         return value;
 }

 #if 0
 /* if we use a different representation i.e. one that goes from 0 to 0x1000 we can be more efficient
  * because we can avoid the divisions and use a shifting instead */
 /* same as above but takes and returns a uint16_t value representing a range from 0..1 */
 uint16_t lut_interp_linear16(uint16_t input_value, uint16_t *table, int length)
 {
 	uint32_t value = (input_value * (length - 1));
 	uint32_t upper = (value + 4095) / 4096; /* equivalent to ceil(value/4096) */
 	uint32_t lower = value / 4096;           /* equivalent to floor(value/4096) */
 	uint32_t interp = value % 4096;

 	value = (table[upper]*(interp) + table[lower]*(4096 - interp))/4096; // 0..4096*4096

 	return value;
 }
 #endif

 void compute_curve_gamma_table_type1(float gamma_table[256], double gamma)
 {
 	unsigned int i;
 	for (i = 0; i < 256; i++) {
 		gamma_table[i] = pow(i/255., gamma);
 	}
 }

 void compute_curve_gamma_table_type2(float gamma_table[256], uint16_t *table, int length)
 {
 	unsigned int i;
 	for (i = 0; i < 256; i++) {
 		gamma_table[i] = lut_interp_linear(i/255., table, length);
 	}
 }

 void compute_curve_gamma_table_type_parametric(float gamma_table[256], float parameter[7], int count)
 {
         size_t X;
         float interval;
         float a, b, c, e, f;
         float y = parameter[0];
         if (count == 0) {
                 a = 1;
                 b = 0;
                 c = 0;
                 e = 0;
                 f = 0;
                 interval = -INFINITY;
         } else if(count == 1) {
                 a = parameter[1];
                 b = parameter[2];
                 c = 0;
                 e = 0;
                 f = 0;
                 interval = -1 * parameter[2] / parameter[1];
         } else if(count == 2) {
                 a = parameter[1];
                 b = parameter[2];
                 c = 0;
                 e = parameter[3];
                 f = parameter[3];
                 interval = -1 * parameter[2] / parameter[1];
         } else if(count == 3) {
                 a = parameter[1];
                 b = parameter[2];
                 c = parameter[3];
                 e = -c;
                 f = 0;
                 interval = parameter[4];
         } else if(count == 4) {
                 a = parameter[1];
                 b = parameter[2];
                 c = parameter[3];
                 e = parameter[5] - c;
                 f = parameter[6];
                 interval = parameter[4];
         } else {
                 assert(0 && "invalid parametric function type.");
                 a = 1;
                 b = 0;
                 c = 0;
                 e = 0;
                 f = 0;
                 interval = -INFINITY;
         }
         for (X = 0; X < 256; X++) {
                 if (X >= interval) {
                         // XXX The equations are not exactly as definied in the spec but are
                         //     algebraic equivilent.
                         // TODO Should division by 255 be for the whole expression.
                         gamma_table[X] = pow(a * X / 255. + b, y) + c + e;
                 } else {
                         gamma_table[X] = c * X / 255. + f;
                 }
         }
 }

 void compute_curve_gamma_table_type0(float gamma_table[256])
 {
 	unsigned int i;
 	for (i = 0; i < 256; i++) {
 		gamma_table[i] = i/255.;
 	}
 }


 float clamp_float(float a)
 {
         if (a > 1.)
                 return 1.;
         else if (a < 0)
                 return 0;
         else
                 return a;
 }

 unsigned char clamp_u8(float v)
 {
 	if (v > 255.)
 		return 255;
 	else if (v < 0)
 		return 0;
 	else
 		return floor(v+.5);
 }

 float u8Fixed8Number_to_float(uint16_t x)
 {
 	// 0x0000 = 0.
 	// 0x0100 = 1.
 	// 0xffff = 255  + 255/256
 	return x/256.;
 }

 float *build_input_gamma_table(struct curveType *TRC)
 {
 	float *gamma_table;

 	if (!TRC) return NULL;
 	gamma_table = malloc(sizeof(float)*256);
 	if (gamma_table) {
 		if (TRC->type == PARAMETRIC_CURVE_TYPE) {
 			compute_curve_gamma_table_type_parametric(gamma_table, TRC->parameter, TRC->count);
 		} else {
 			if (TRC->count == 0) {
 				compute_curve_gamma_table_type0(gamma_table);
 			} else if (TRC->count == 1) {
 				compute_curve_gamma_table_type1(gamma_table, u8Fixed8Number_to_float(TRC->data[0]));
 			} else {
 				compute_curve_gamma_table_type2(gamma_table, TRC->data, TRC->count);
 			}
 		}
 	}
         return gamma_table;
 }

 struct matrix build_colorant_matrix(qcms_profile *p)
 {
 	struct matrix result;
 	result.m[0][0] = s15Fixed16Number_to_float(p->redColorant.X);
 	result.m[0][1] = s15Fixed16Number_to_float(p->greenColorant.X);
 	result.m[0][2] = s15Fixed16Number_to_float(p->blueColorant.X);
 	result.m[1][0] = s15Fixed16Number_to_float(p->redColorant.Y);
 	result.m[1][1] = s15Fixed16Number_to_float(p->greenColorant.Y);
 	result.m[1][2] = s15Fixed16Number_to_float(p->blueColorant.Y);
 	result.m[2][0] = s15Fixed16Number_to_float(p->redColorant.Z);
 	result.m[2][1] = s15Fixed16Number_to_float(p->greenColorant.Z);
 	result.m[2][2] = s15Fixed16Number_to_float(p->blueColorant.Z);
 	result.invalid = false;
 	return result;
 }

 /* The following code is copied nearly directly from lcms.
  * I think it could be much better. For example, Argyll seems to have better code in
  * icmTable_lookup_bwd and icmTable_setup_bwd. However, for now this is a quick way
  * to a working solution and allows for easy comparing with lcms. */
 uint16_fract_t lut_inverse_interp16(uint16_t Value, uint16_t LutTable[], int length)
 {
         int l = 1;
         int r = 0x10000;
         int x = 0, res;       // 'int' Give spacing for negative values
         int NumZeroes, NumPoles;
         int cell0, cell1;
         double val2;
         double y0, y1, x0, x1;
         double a, b, f;

         // July/27 2001 - Expanded to handle degenerated curves with an arbitrary
         // number of elements containing 0 at the begining of the table (Zeroes)
         // and another arbitrary number of poles (FFFFh) at the end.
         // First the zero and pole extents are computed, then value is compared.

         NumZeroes = 0;
         while (LutTable[NumZeroes] == 0 && NumZeroes < length-1)
                         NumZeroes++;

         // There are no zeros at the beginning and we are trying to find a zero, so
         // return anything. It seems zero would be the less destructive choice
 	/* I'm not sure that this makes sense, but oh well... */
         if (NumZeroes == 0 && Value == 0)
             return 0;

         NumPoles = 0;
         while (LutTable[length-1- NumPoles] == 0xFFFF && NumPoles < length-1)
                         NumPoles++;

         // Does the curve belong to this case?
         if (NumZeroes > 1 || NumPoles > 1)
         {
                 int a, b;

                 // Identify if value fall downto 0 or FFFF zone
                 if (Value == 0) return 0;
                // if (Value == 0xFFFF) return 0xFFFF;

                 // else restrict to valid zone

                 a = ((NumZeroes-1) * 0xFFFF) / (length-1);
                 b = ((length-1 - NumPoles) * 0xFFFF) / (length-1);

                 l = a - 1;
                 r = b + 1;
         }


         // Seems not a degenerated case... apply binary search

         while (r > l) {

                 x = (l + r) / 2;

 		res = (int) lut_interp_linear16((uint16_fract_t) (x-1), LutTable, length);

                 if (res == Value) {

                     // Found exact match.

                     return (uint16_fract_t) (x - 1);
                 }

                 if (res > Value) r = x - 1;
                 else l = x + 1;
         }

         // Not found, should we interpolate?


         // Get surrounding nodes

         val2 = (length-1) * ((double) (x - 1) / 65535.0);

         cell0 = (int) floor(val2);
         cell1 = (int) ceil(val2);

         if (cell0 == cell1) return (uint16_fract_t) x;

         y0 = LutTable[cell0] ;
         x0 = (65535.0 * cell0) / (length-1);

         y1 = LutTable[cell1] ;
         x1 = (65535.0 * cell1) / (length-1);

         a = (y1 - y0) / (x1 - x0);
         b = y0 - a * x0;

         if (fabs(a) < 0.01) return (uint16_fract_t) x;

         f = ((Value - b) / a);

         if (f < 0.0) return (uint16_fract_t) 0;
         if (f >= 65535.0) return (uint16_fract_t) 0xFFFF;

         return (uint16_fract_t) floor(f + 0.5);

 }

 /*
  The number of entries needed to invert a lookup table should not
  necessarily be the same as the original number of entries.  This is
  especially true of lookup tables that have a small number of entries.

  For example:
  Using a table like:
     {0, 3104, 14263, 34802, 65535}
  invert_lut will produce an inverse of:
     {3, 34459, 47529, 56801, 65535}
  which has an maximum error of about 9855 (pixel difference of ~38.346)

  For now, we punt the decision of output size to the caller. */
 static uint16_t *invert_lut(uint16_t *table, int length, int out_length)
 {
         int i;
         /* for now we invert the lut by creating a lut of size out_length
          * and attempting to lookup a value for each entry using lut_inverse_interp16 */
         uint16_t *output = malloc(sizeof(uint16_t)*out_length);
         if (!output)
                 return NULL;

         for (i = 0; i < out_length; i++) {
                 double x = ((double) i * 65535.) / (double) (out_length - 1);
                 uint16_fract_t input = floor(x + .5);
                 output[i] = lut_inverse_interp16(input, table, length);
         }
         return output;
 }

 static void compute_precache_pow(uint8_t *output, float gamma)
 {
 	uint32_t v = 0;
 	for (v = 0; v < PRECACHE_OUTPUT_SIZE; v++) {
 		//XXX: don't do integer/float conversion... and round?
 		output[v] = 255. * pow(v/(double)PRECACHE_OUTPUT_MAX, gamma);
 	}
 }

 void compute_precache_lut(uint8_t *output, uint16_t *table, int length)
 {
 	uint32_t v = 0;
 	for (v = 0; v < PRECACHE_OUTPUT_SIZE; v++) {
 		output[v] = lut_interp_linear_precache_output(v, table, length);
 	}
 }

 void compute_precache_linear(uint8_t *output)
 {
 	uint32_t v = 0;
 	for (v = 0; v < PRECACHE_OUTPUT_SIZE; v++) {
 		//XXX: round?
 		output[v] = v / (PRECACHE_OUTPUT_SIZE/256);
 	}
 }

 qcms_bool compute_precache(struct curveType *trc, uint8_t *output)
 {

         if (trc->type == PARAMETRIC_CURVE_TYPE) {
                         float gamma_table[256];
                         uint16_t gamma_table_uint[256];
                         uint16_t i;
                         uint16_t *inverted;
                         int inverted_size = 256;

                         compute_curve_gamma_table_type_parametric(gamma_table, trc->parameter, trc->count);
                         for(i = 0; i < 256; i++) {
                                 gamma_table_uint[i] = (uint16_t)(gamma_table[i] * 65535);
                         }

                         //XXX: the choice of a minimum of 256 here is not backed by any theory,
                         //     measurement or data, howeve r it is what lcms uses.
                         //     the maximum number we would need is 65535 because that's the
                         //     accuracy used for computing the pre cache table
                         if (inverted_size < 256)
                                 inverted_size = 256;

                         inverted = invert_lut(gamma_table_uint, 256, inverted_size);
                         if (!inverted)
                                 return false;
                         compute_precache_lut(output, inverted, inverted_size);
                         free(inverted);
         } else {
                 if (trc->count == 0) {
                         compute_precache_linear(output);
                 } else if (trc->count == 1) {
                         compute_precache_pow(output, 1./u8Fixed8Number_to_float(trc->data[0]));
                 } else {
                         uint16_t *inverted;
                         int inverted_size = trc->count;
                         //XXX: the choice of a minimum of 256 here is not backed by any theory,
                         //     measurement or data, howeve r it is what lcms uses.
                         //     the maximum number we would need is 65535 because that's the
                         //     accuracy used for computing the pre cache table
                         if (inverted_size < 256)
                                 inverted_size = 256;

                         inverted = invert_lut(trc->data, trc->count, inverted_size);
                         if (!inverted)
                                 return false;
                         compute_precache_lut(output, inverted, inverted_size);
                         free(inverted);
                 }
         }
         return true;
 }


 static uint16_t *build_linear_table(int length)
 {
         int i;
         uint16_t *output = malloc(sizeof(uint16_t)*length);
         if (!output)
                 return NULL;

         for (i = 0; i < length; i++) {
                 double x = ((double) i * 65535.) / (double) (length - 1);
                 uint16_fract_t input = floor(x + .5);
                 output[i] = input;
         }
         return output;
 }

 static uint16_t *build_pow_table(float gamma, int length)
 {
         int i;
         uint16_t *output = malloc(sizeof(uint16_t)*length);
         if (!output)
                 return NULL;

         for (i = 0; i < length; i++) {
                 uint16_fract_t result;
                 double x = ((double) i) / (double) (length - 1);
                 x = pow(x, gamma);                //XXX turn this conversion into a function
                 result = floor(x*65535. + .5);
                 output[i] = result;
         }
         return output;
 }

 void build_output_lut(struct curveType *trc,
                 uint16_t **output_gamma_lut, size_t *output_gamma_lut_length)
 {
         if (trc->type == PARAMETRIC_CURVE_TYPE) {
                 float gamma_table[256];
                 uint16_t i;
                 uint16_t *output = malloc(sizeof(uint16_t)*256);

                 if (!output) {
                         *output_gamma_lut = NULL;
                         return;
                 }

                 compute_curve_gamma_table_type_parametric(gamma_table, trc->parameter, trc->count);
                 *output_gamma_lut_length = 256;
                 for(i = 0; i < 256; i++) {
                         output[i] = (uint16_t)(gamma_table[i] * 65535);
                 }
                 *output_gamma_lut = output;
         } else {
                 if (trc->count == 0) {
                         *output_gamma_lut = build_linear_table(4096);
                         *output_gamma_lut_length = 4096;
                 } else if (trc->count == 1) {
                         float gamma = 1./u8Fixed8Number_to_float(trc->data[0]);
                         *output_gamma_lut = build_pow_table(gamma, 4096);
                         *output_gamma_lut_length = 4096;
                 } else {
                         //XXX: the choice of a minimum of 256 here is not backed by any theory,
                         //     measurement or data, however it is what lcms uses.
                         *output_gamma_lut_length = trc->count;
                         if (*output_gamma_lut_length < 256)
                                 *output_gamma_lut_length = 256;

                         *output_gamma_lut = invert_lut(trc->data, trc->count, *output_gamma_lut_length);
                 }
         }

 }
	#define _ISOC99_SOURCE /* for INFINITY */

	#include <math.h>
	#include <assert.h>
	#include <string.h> //memcpy
	#include "qcmsint.h"
	#include "transform_util.h"
	#include "matrix.h"

	#if !defined(INFINITY)
	#define INFINITY HUGE_VAL
	#endif

	#define PARAMETRIC_CURVE_TYPE 0x70617261 //'para'

	/* value must be a value between 0 and 1 */
	//XXX: is the above a good restriction to have?
	float lut_interp_linear(double value, uint16_t *table, int length)
	{
	int upper, lower;
	value = value * (length - 1); // scale to length of the array
	upper = ceil(value);
	lower = floor(value);
	//XXX: can we be more performant here?
	value = table[upper](1. - (upper - value)) + table[lower](upper - value);
	/* scale the value */
	return value * (1./65535.);
	}

	/* same as above but takes and returns a uint16_t value representing a range from 0..1 */
	uint16_t lut_interp_linear16(uint16_t input_value, uint16_t *table, int length)
	{
	/* Start scaling input_value to the length of the array: 65535*(length-1).
	* We'll divide out the 65535 next */
	uint32_t value = (input_value * (length - 1));
	uint32_t upper = (value + 65534) / 65535; /* equivalent to ceil(value/65535) */
	uint32_t lower = value / 65535; /* equivalent to floor(value/65535) */
	/* interp is the distance from upper to value scaled to 0..65535 */
	uint32_t interp = value % 65535;

	value = (table[upper](interp) + table[lower](65535 - interp))/65535; // 0..65535*65535

	return value;
	}

	/* same as above but takes an input_value from 0..PRECACHE_OUTPUT_MAX
	* and returns a uint8_t value representing a range from 0..1 */
	static
	uint8_t lut_interp_linear_precache_output(uint32_t input_value, uint16_t *table, int length)
	{
	/* Start scaling input_value to the length of the array: PRECACHE_OUTPUT_MAX*(length-1).
	* We'll divide out the PRECACHE_OUTPUT_MAX next */
	uint32_t value = (input_value * (length - 1));

	/* equivalent to ceil(value/PRECACHE_OUTPUT_MAX) */
	uint32_t upper = (value + PRECACHE_OUTPUT_MAX-1) / PRECACHE_OUTPUT_MAX;
	/* equivalent to floor(value/PRECACHE_OUTPUT_MAX) */
	uint32_t lower = value / PRECACHE_OUTPUT_MAX;
	/* interp is the distance from upper to value scaled to 0..PRECACHE_OUTPUT_MAX */
	uint32_t interp = value % PRECACHE_OUTPUT_MAX;

	/* the table values range from 0..65535 */
	value = (table[upper](interp) + table[lower](PRECACHE_OUTPUT_MAX - interp)); // 0..(65535*PRECACHE_OUTPUT_MAX)

	/* round and scale */
	value += (PRECACHE_OUTPUT_MAX*65535/255)/2;
	value /= (PRECACHE_OUTPUT_MAX*65535/255); // scale to 0..255
	return value;
	}

	/* value must be a value between 0 and 1 */
	//XXX: is the above a good restriction to have?
	float lut_interp_linear_float(float value, float *table, int length)
	{
	int upper, lower;
	value = value * (length - 1);
	upper = ceil(value);
	lower = floor(value);
	//XXX: can we be more performant here?
	value = table[upper](1. - (upper - value)) + table[lower](upper - value);
	/* scale the value */
	return value;
	}

	#if 0
	/* if we use a different representation i.e. one that goes from 0 to 0x1000 we can be more efficient
	* because we can avoid the divisions and use a shifting instead */
	/* same as above but takes and returns a uint16_t value representing a range from 0..1 */
	uint16_t lut_interp_linear16(uint16_t input_value, uint16_t *table, int length)
	{
	uint32_t value = (input_value * (length - 1));
	uint32_t upper = (value + 4095) / 4096; /* equivalent to ceil(value/4096) */
	uint32_t lower = value / 4096; /* equivalent to floor(value/4096) */
	uint32_t interp = value % 4096;

	value = (table[upper](interp) + table[lower](4096 - interp))/4096; // 0..4096*4096

	return value;
	}
	#endif

	void compute_curve_gamma_table_type1(float gamma_table[256], double gamma)
	{
	unsigned int i;
	for (i = 0; i < 256; i++) {
	gamma_table[i] = pow(i/255., gamma);
	}
	}

	void compute_curve_gamma_table_type2(float gamma_table[256], uint16_t *table, int length)
	{
	unsigned int i;
	for (i = 0; i < 256; i++) {
	gamma_table[i] = lut_interp_linear(i/255., table, length);
	}
	}

	void compute_curve_gamma_table_type_parametric(float gamma_table[256], float parameter[7], int count)
	{
	size_t X;
	float interval;
	float a, b, c, e, f;
	float y = parameter[0];
	if (count == 0) {
	a = 1;
	b = 0;
	c = 0;
	e = 0;
	f = 0;
	interval = -INFINITY;
	} else if(count == 1) {
	a = parameter[1];
	b = parameter[2];
	c = 0;
	e = 0;
	f = 0;
	interval = -1 * parameter[2] / parameter[1];
	} else if(count == 2) {
	a = parameter[1];
	b = parameter[2];
	c = 0;
	e = parameter[3];
	f = parameter[3];
	interval = -1 * parameter[2] / parameter[1];
	} else if(count == 3) {
	a = parameter[1];
	b = parameter[2];
	c = parameter[3];
	e = -c;
	f = 0;
	interval = parameter[4];
	} else if(count == 4) {
	a = parameter[1];
	b = parameter[2];
	c = parameter[3];
	e = parameter[5] - c;
	f = parameter[6];
	interval = parameter[4];
	} else {
	assert(0 && "invalid parametric function type.");
	a = 1;
	b = 0;
	c = 0;
	e = 0;
	f = 0;
	interval = -INFINITY;
	}
	for (X = 0; X < 256; X++) {
	if (X >= interval) {
	// XXX The equations are not exactly as definied in the spec but are
	// algebraic equivilent.
	// TODO Should division by 255 be for the whole expression.
	gamma_table[X] = pow(a * X / 255. + b, y) + c + e;
	} else {
	gamma_table[X] = c * X / 255. + f;
	}
	}
	}

	void compute_curve_gamma_table_type0(float gamma_table[256])
	{
	unsigned int i;
	for (i = 0; i < 256; i++) {
	gamma_table[i] = i/255.;
	}
	}


	float clamp_float(float a)
	{
	if (a > 1.)
	return 1.;
	else if (a < 0)
	return 0;
	else
	return a;
	}

	unsigned char clamp_u8(float v)
	{
	if (v > 255.)
	return 255;
	else if (v < 0)
	return 0;
	else
	return floor(v+.5);
	}

	float u8Fixed8Number_to_float(uint16_t x)
	{
	// 0x0000 = 0.
	// 0x0100 = 1.
	// 0xffff = 255 + 255/256
	return x/256.;
	}

	float build_input_gamma_table(struct curveType TRC)
	{
	float *gamma_table;

	if (!TRC) return NULL;
	gamma_table = malloc(sizeof(float)*256);
	if (gamma_table) {
	if (TRC->type == PARAMETRIC_CURVE_TYPE) {
	compute_curve_gamma_table_type_parametric(gamma_table, TRC->parameter, TRC->count);
	} else {
	if (TRC->count == 0) {
	compute_curve_gamma_table_type0(gamma_table);
	} else if (TRC->count == 1) {
	compute_curve_gamma_table_type1(gamma_table, u8Fixed8Number_to_float(TRC->data[0]));
	} else {
	compute_curve_gamma_table_type2(gamma_table, TRC->data, TRC->count);
	}
	}
	}
	return gamma_table;
	}

	struct matrix build_colorant_matrix(qcms_profile *p)
	{
	struct matrix result;
	result.m[0][0] = s15Fixed16Number_to_float(p->redColorant.X);
	result.m[0][1] = s15Fixed16Number_to_float(p->greenColorant.X);
	result.m[0][2] = s15Fixed16Number_to_float(p->blueColorant.X);
	result.m[1][0] = s15Fixed16Number_to_float(p->redColorant.Y);
	result.m[1][1] = s15Fixed16Number_to_float(p->greenColorant.Y);
	result.m[1][2] = s15Fixed16Number_to_float(p->blueColorant.Y);
	result.m[2][0] = s15Fixed16Number_to_float(p->redColorant.Z);
	result.m[2][1] = s15Fixed16Number_to_float(p->greenColorant.Z);
	result.m[2][2] = s15Fixed16Number_to_float(p->blueColorant.Z);
	result.invalid = false;
	return result;
	}

	/* The following code is copied nearly directly from lcms.
	* I think it could be much better. For example, Argyll seems to have better code in
	* icmTable_lookup_bwd and icmTable_setup_bwd. However, for now this is a quick way
	* to a working solution and allows for easy comparing with lcms. */
	uint16_fract_t lut_inverse_interp16(uint16_t Value, uint16_t LutTable[], int length)
	{
	int l = 1;
	int r = 0x10000;
	int x = 0, res; // 'int' Give spacing for negative values
	int NumZeroes, NumPoles;
	int cell0, cell1;
	double val2;
	double y0, y1, x0, x1;
	double a, b, f;

	// July/27 2001 - Expanded to handle degenerated curves with an arbitrary
	// number of elements containing 0 at the begining of the table (Zeroes)
	// and another arbitrary number of poles (FFFFh) at the end.
	// First the zero and pole extents are computed, then value is compared.

	NumZeroes = 0;
	while (LutTable[NumZeroes] == 0 && NumZeroes < length-1)
	NumZeroes++;

	// There are no zeros at the beginning and we are trying to find a zero, so
	// return anything. It seems zero would be the less destructive choice
	/* I'm not sure that this makes sense, but oh well... */
	if (NumZeroes == 0 && Value == 0)
	return 0;

	NumPoles = 0;
	while (LutTable[length-1- NumPoles] == 0xFFFF && NumPoles < length-1)
	NumPoles++;

	// Does the curve belong to this case?
	if (NumZeroes > 1 \|\| NumPoles > 1)
	{
	int a, b;

	// Identify if value fall downto 0 or FFFF zone
	if (Value == 0) return 0;
	// if (Value == 0xFFFF) return 0xFFFF;

	// else restrict to valid zone

	a = ((NumZeroes-1) * 0xFFFF) / (length-1);
	b = ((length-1 - NumPoles) * 0xFFFF) / (length-1);

	l = a - 1;
	r = b + 1;
	}


	// Seems not a degenerated case... apply binary search

	while (r > l) {

	x = (l + r) / 2;

	res = (int) lut_interp_linear16((uint16_fract_t) (x-1), LutTable, length);

	if (res == Value) {

	// Found exact match.

	return (uint16_fract_t) (x - 1);
	}

	if (res > Value) r = x - 1;
	else l = x + 1;
	}

	// Not found, should we interpolate?


	// Get surrounding nodes

	val2 = (length-1) * ((double) (x - 1) / 65535.0);

	cell0 = (int) floor(val2);
	cell1 = (int) ceil(val2);

	if (cell0 == cell1) return (uint16_fract_t) x;

	y0 = LutTable[cell0] ;
	x0 = (65535.0 * cell0) / (length-1);

	y1 = LutTable[cell1] ;
	x1 = (65535.0 * cell1) / (length-1);

	a = (y1 - y0) / (x1 - x0);
	b = y0 - a * x0;

	if (fabs(a) < 0.01) return (uint16_fract_t) x;

	f = ((Value - b) / a);

	if (f < 0.0) return (uint16_fract_t) 0;
	if (f >= 65535.0) return (uint16_fract_t) 0xFFFF;

	return (uint16_fract_t) floor(f + 0.5);

	}

	/*
	The number of entries needed to invert a lookup table should not
	necessarily be the same as the original number of entries. This is
	especially true of lookup tables that have a small number of entries.

	For example:
	Using a table like:
	{0, 3104, 14263, 34802, 65535}
	invert_lut will produce an inverse of:
	{3, 34459, 47529, 56801, 65535}
	which has an maximum error of about 9855 (pixel difference of ~38.346)

	For now, we punt the decision of output size to the caller. */
	static uint16_t invert_lut(uint16_t table, int length, int out_length)
	{
	int i;
	/* for now we invert the lut by creating a lut of size out_length
	* and attempting to lookup a value for each entry using lut_inverse_interp16 */
	uint16_t output = malloc(sizeof(uint16_t)out_length);
	if (!output)
	return NULL;

	for (i = 0; i < out_length; i++) {
	double x = ((double) i * 65535.) / (double) (out_length - 1);
	uint16_fract_t input = floor(x + .5);
	output[i] = lut_inverse_interp16(input, table, length);
	}
	return output;
	}

	static void compute_precache_pow(uint8_t *output, float gamma)
	{
	uint32_t v = 0;
	for (v = 0; v < PRECACHE_OUTPUT_SIZE; v++) {
	//XXX: don't do integer/float conversion... and round?
	output[v] = 255. * pow(v/(double)PRECACHE_OUTPUT_MAX, gamma);
	}
	}

	void compute_precache_lut(uint8_t output, uint16_t table, int length)
	{
	uint32_t v = 0;
	for (v = 0; v < PRECACHE_OUTPUT_SIZE; v++) {
	output[v] = lut_interp_linear_precache_output(v, table, length);
	}
	}

	void compute_precache_linear(uint8_t *output)
	{
	uint32_t v = 0;
	for (v = 0; v < PRECACHE_OUTPUT_SIZE; v++) {
	//XXX: round?
	output[v] = v / (PRECACHE_OUTPUT_SIZE/256);
	}
	}

	qcms_bool compute_precache(struct curveType trc, uint8_t output)
	{

	if (trc->type == PARAMETRIC_CURVE_TYPE) {
	float gamma_table[256];
	uint16_t gamma_table_uint[256];
	uint16_t i;
	uint16_t *inverted;
	int inverted_size = 256;

	compute_curve_gamma_table_type_parametric(gamma_table, trc->parameter, trc->count);
	for(i = 0; i < 256; i++) {
	gamma_table_uint[i] = (uint16_t)(gamma_table[i] * 65535);
	}

	//XXX: the choice of a minimum of 256 here is not backed by any theory,
	// measurement or data, howeve r it is what lcms uses.
	// the maximum number we would need is 65535 because that's the
	// accuracy used for computing the pre cache table
	if (inverted_size < 256)
	inverted_size = 256;

	inverted = invert_lut(gamma_table_uint, 256, inverted_size);
	if (!inverted)
	return false;
	compute_precache_lut(output, inverted, inverted_size);
	free(inverted);
	} else {
	if (trc->count == 0) {
	compute_precache_linear(output);
	} else if (trc->count == 1) {
	compute_precache_pow(output, 1./u8Fixed8Number_to_float(trc->data[0]));
	} else {
	uint16_t *inverted;
	int inverted_size = trc->count;
	//XXX: the choice of a minimum of 256 here is not backed by any theory,
	// measurement or data, howeve r it is what lcms uses.
	// the maximum number we would need is 65535 because that's the
	// accuracy used for computing the pre cache table
	if (inverted_size < 256)
	inverted_size = 256;

	inverted = invert_lut(trc->data, trc->count, inverted_size);
	if (!inverted)
	return false;
	compute_precache_lut(output, inverted, inverted_size);
	free(inverted);
	}
	}
	return true;
	}


	static uint16_t *build_linear_table(int length)
	{
	int i;
	uint16_t output = malloc(sizeof(uint16_t)length);
	if (!output)
	return NULL;

	for (i = 0; i < length; i++) {
	double x = ((double) i * 65535.) / (double) (length - 1);
	uint16_fract_t input = floor(x + .5);
	output[i] = input;
	}
	return output;
	}

	static uint16_t *build_pow_table(float gamma, int length)
	{
	int i;
	uint16_t output = malloc(sizeof(uint16_t)length);
	if (!output)
	return NULL;

	for (i = 0; i < length; i++) {
	uint16_fract_t result;
	double x = ((double) i) / (double) (length - 1);
	x = pow(x, gamma); //XXX turn this conversion into a function
	result = floor(x*65535. + .5);
	output[i] = result;
	}
	return output;
	}

	void build_output_lut(struct curveType *trc,
	uint16_t *output_gamma_lut, size_t output_gamma_lut_length)
	{
	if (trc->type == PARAMETRIC_CURVE_TYPE) {
	float gamma_table[256];
	uint16_t i;
	uint16_t output = malloc(sizeof(uint16_t)256);

	if (!output) {
	*output_gamma_lut = NULL;
	return;
	}

	compute_curve_gamma_table_type_parametric(gamma_table, trc->parameter, trc->count);
	*output_gamma_lut_length = 256;
	for(i = 0; i < 256; i++) {
	output[i] = (uint16_t)(gamma_table[i] * 65535);
	}
	*output_gamma_lut = output;
	} else {
	if (trc->count == 0) {
	*output_gamma_lut = build_linear_table(4096);
	*output_gamma_lut_length = 4096;
	} else if (trc->count == 1) {
	float gamma = 1./u8Fixed8Number_to_float(trc->data[0]);
	*output_gamma_lut = build_pow_table(gamma, 4096);
	*output_gamma_lut_length = 4096;
	} else {
	//XXX: the choice of a minimum of 256 here is not backed by any theory,
	// measurement or data, however it is what lcms uses.
	*output_gamma_lut_length = trc->count;
	if (*output_gamma_lut_length < 256)
	*output_gamma_lut_length = 256;

	output_gamma_lut = invert_lut(trc->data, trc->count, output_gamma_lut_length);
	}
	}

	}