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/*
* Lookup table routines for CUPS.
*
* Copyright 2007 by Apple Inc.
* Copyright 1993-2005 by Easy Software Products.
*
* These coded instructions, statements, and computer programs are the
* property of Apple Inc. and are protected by Federal copyright
* law. Distribution and use rights are outlined in the file "COPYING"
* which should have been included with this file.
*
* Contents:
*
* cupsLutDelete() - Free the memory used by a lookup table.
* cupsLutLoad() - Load a LUT from a PPD file.
* cupsLutNew() - Make a lookup table from a list of pixel values.
*/
/*
* Include necessary headers.
*/
#include "driver.h"
#include <math.h>
/*
* 'cupsLutDelete()' - Free the memory used by a lookup table.
*/
void
cupsLutDelete(cups_lut_t *lut) /* I - Lookup table to free */
{
if (lut != NULL)
free(lut);
}
/*
* 'cupsLutLoad()' - Load a LUT from a PPD file.
*/
cups_lut_t * /* O - New lookup table */
cupsLutLoad(ppd_file_t *ppd, /* I - PPD file */
const char *colormodel, /* I - Color model */
const char *media, /* I - Media type */
const char *resolution, /* I - Resolution */
const char *ink) /* I - Ink name */
{
char name[PPD_MAX_NAME], /* Attribute name */
spec[PPD_MAX_NAME]; /* Attribute spec */
ppd_attr_t *attr; /* Attribute */
int nvals; /* Number of values */
float vals[4]; /* Values */
/*
* Range check input...
*/
if (!ppd || !colormodel || !media || !resolution || !ink)
return (NULL);
/*
* Try to find the LUT values...
*/
snprintf(name, sizeof(name), "cups%sDither", ink);
if ((attr = cupsFindAttr(ppd, name, colormodel, media, resolution, spec,
sizeof(spec))) == NULL)
attr = cupsFindAttr(ppd, "cupsAllDither", colormodel, media,
resolution, spec, sizeof(spec));
if (!attr)
return (NULL);
vals[0] = 0.0;
vals[1] = 0.0;
vals[2] = 0.0;
vals[3] = 0.0;
nvals = sscanf(attr->value, "%f%f%f", vals + 1, vals + 2, vals + 3) + 1;
fprintf(stderr, "DEBUG: Loaded LUT %s from PPD with values [%.3f %.3f %.3f %.3f]\n",
name, vals[0], vals[1], vals[2], vals[3]);
return (cupsLutNew(nvals, vals));
}
/*
* 'cupsLutNew()' - Make a lookup table from a list of pixel values.
*
* Returns a pointer to the lookup table on success, NULL on failure.
*/
cups_lut_t * /* O - New lookup table */
cupsLutNew(int num_values, /* I - Number of values */
const float *values) /* I - Lookup table values */
{
int pixel; /* Pixel value */
cups_lut_t *lut; /* Lookup table */
int start, /* Start value */
end, /* End value */
maxval; /* Maximum value */
/*
* Range check...
*/
if (!num_values || !values)
return (NULL);
/*
* Allocate memory for the lookup table...
*/
if ((lut = (cups_lut_t *)calloc((CUPS_MAX_LUT + 1),
sizeof(cups_lut_t))) == NULL)
return (NULL);
/*
* Generate the dither lookup table. The pixel values are roughly
* defined by a piecewise linear curve that has an intensity value
* at each output pixel. This isn't perfectly accurate, but it's
* close enough for jazz.
*/
maxval = CUPS_MAX_LUT / values[num_values - 1];
for (start = 0; start <= CUPS_MAX_LUT; start ++)
lut[start].intensity = start * maxval / CUPS_MAX_LUT;
for (pixel = 0; pixel < num_values; pixel ++)
{
/*
* Select start and end values for this pixel...
*/
if (pixel == 0)
start = 0;
else
start = (int)(0.5 * maxval * (values[pixel - 1] +
values[pixel])) + 1;
if (start < 0)
start = 0;
else if (start > CUPS_MAX_LUT)
start = CUPS_MAX_LUT;
if (pixel == (num_values - 1))
end = CUPS_MAX_LUT;
else
end = (int)(0.5 * maxval * (values[pixel] + values[pixel + 1]));
if (end < 0)
end = 0;
else if (end > CUPS_MAX_LUT)
end = CUPS_MAX_LUT;
if (start == end)
break;
/*
* Generate lookup values and errors for each pixel.
*/
while (start <= end)
{
lut[start].pixel = pixel;
if (start == 0)
lut[0].error = 0;
else
lut[start].error = start - maxval * values[pixel];
start ++;
}
}
/*
* Show the lookup table...
*/
for (start = 0; start <= CUPS_MAX_LUT; start += CUPS_MAX_LUT / 15)
fprintf(stderr, "DEBUG: %d = %d/%d/%d\n", start, lut[start].intensity,
lut[start].pixel, lut[start].error);
/*
* Return the lookup table...
*/
return (lut);
}
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