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hackthelobby/libcaca/caca/dither.c

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/*
* libcaca Colour ASCII-Art library
* Copyright © 2002—2018 Sam Hocevar <sam@hocevar.net>
* All Rights Reserved
*
* This library is free software. It comes without any warranty, to
* the extent permitted by applicable law. You can redistribute it
* and/or modify it under the terms of the Do What the Fuck You Want
* to Public License, Version 2, as published by the WTFPL Task Force.
* See http://www.wtfpl.net/ for more details.
*/
/*
* This file contains bitmap dithering functions.
*/
#include "config.h"
#if !defined(__KERNEL__)
# if defined(HAVE_ENDIAN_H)
# include <endian.h>
# endif
# include <stdio.h>
# include <stdlib.h>
# include <limits.h>
# include <string.h>
#endif
#include "caca.h"
#include "caca_internals.h"
#define CP437 0
/*
* Local variables
*/
#if !defined(_DOXYGEN_SKIP_ME)
# define LOOKUP_VAL 32
# define LOOKUP_SAT 32
# define LOOKUP_HUE 16
#endif
static uint8_t hsv_distances[LOOKUP_VAL][LOOKUP_SAT][LOOKUP_HUE];
static uint16_t lookup_colors[8];
static int lookup_initialised = 0;
static int const hsv_palette[] =
{
/* weight, hue, saturation, value */
4, 0x0, 0x0, 0x0, /* black */
5, 0x0, 0x0, 0x5ff, /* 30% */
5, 0x0, 0x0, 0x9ff, /* 70% */
4, 0x0, 0x0, 0xfff, /* white */
3, 0x1000, 0xfff, 0x5ff, /* dark yellow */
2, 0x1000, 0xfff, 0xfff, /* light yellow */
3, 0x0, 0xfff, 0x5ff, /* dark red */
2, 0x0, 0xfff, 0xfff /* light red */
};
/* RGB palette for the new colour picker */
static int const rgb_palette[] =
{
0x0, 0x0, 0x0,
0x0, 0x0, 0x7ff,
0x0, 0x7ff, 0x0,
0x0, 0x7ff, 0x7ff,
0x7ff, 0x0, 0x0,
0x7ff, 0x0, 0x7ff,
0x7ff, 0x7ff, 0x0,
0xaaa, 0xaaa, 0xaaa,
0x555, 0x555, 0x555,
0x000, 0x000, 0xfff,
0x000, 0xfff, 0x000,
0x000, 0xfff, 0xfff,
0xfff, 0x000, 0x000,
0xfff, 0x000, 0xfff,
0xfff, 0xfff, 0x000,
0xfff, 0xfff, 0xfff,
};
static int const rgb_weight[] =
{
/* 2, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 2 */
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
};
/* List of glyphs */
static uint32_t ascii_glyphs[] =
{
// ' ', '.', ':', ';', 't', '%', 'S', 'X', '@', '8', '?'
'#', '#', '#', '#', '#', '#', '#', '#', '#', '#', '#'
};
static uint32_t shades_glyphs[] =
{
/* ' '. '·', '░', '▒', '?' */
' ', 0xb7, 0x2591, 0x2592, '?'
};
static uint32_t blocks_glyphs[] =
{
/* ' ', '▘', '▚', '?' */
' ', 0x2598, 0x259a, '?'
};
#if !defined(_DOXYGEN_SKIP_ME)
enum color_mode
{
COLOR_MODE_MONO,
COLOR_MODE_GRAY,
COLOR_MODE_8,
COLOR_MODE_16,
COLOR_MODE_FULLGRAY,
COLOR_MODE_FULL8,
COLOR_MODE_FULL16
};
struct caca_dither
{
int bpp, has_palette, has_alpha;
size_t w, h, pitch;
int rmask, gmask, bmask, amask;
int rright, gright, bright, aright;
int rleft, gleft, bleft, aleft;
void (*get_hsv)(caca_dither_t *, char *, int, int);
int red[256], green[256], blue[256], alpha[256];
/* Colour features */
float gamma, brightness, contrast;
int gammatab[4097];
/* Dithering features */
char const *antialias_name;
int antialias;
char const *color_name;
enum color_mode color;
char const *algo_name;
void (*init_dither) (int);
int (*get_dither) (void);
void (*increment_dither) (void);
char const *glyph_name;
uint32_t const * glyphs;
int glyph_count;
int invert;
};
#define HSV_XRATIO 6
#define HSV_YRATIO 3
#define HSV_HRATIO 3
#define HSV_DISTANCE(h, s, v, index) \
(hsv_palette[index * 4] \
* ((HSV_XRATIO * ((v) - hsv_palette[index * 4 + 3]) \
* ((v) - hsv_palette[index * 4 + 3])) \
+ (hsv_palette[index * 4 + 3] \
? (HSV_YRATIO * ((s) - hsv_palette[index * 4 + 2]) \
* ((s) - hsv_palette[index * 4 + 2])) \
: 0) \
+ (hsv_palette[index * 4 + 2] \
? (HSV_HRATIO * ((h) - hsv_palette[index * 4 + 1]) \
* ((h) - hsv_palette[index * 4 + 1])) \
: 0)))
#endif
/*
* Local prototypes
*/
static void mask2shift(uint32_t, int *, int *);
static float gammapow(float x, float y);
static void get_rgba_default(caca_dither_t const *, uint8_t const *, int, int,
unsigned int *);
static int init_lookup(void);
/* Dithering algorithms */
static void init_no_dither(int);
static int get_no_dither(void);
static void increment_no_dither(void);
static void init_fstein_dither(int);
static int get_fstein_dither(void);
static void increment_fstein_dither(void);
static void init_ordered2_dither(int);
static int get_ordered2_dither(void);
static void increment_ordered2_dither(void);
static void init_ordered4_dither(int);
static int get_ordered4_dither(void);
static void increment_ordered4_dither(void);
static void init_ordered8_dither(int);
static int get_ordered8_dither(void);
static void increment_ordered8_dither(void);
static void init_random_dither(int);
static int get_random_dither(void);
static void increment_random_dither(void);
static inline int sq(int x)
{
return x * x;
}
static inline void rgb2hsv_default(int r, int g, int b,
int *hue, int *sat, int *val)
{
int min, max, delta;
min = r; max = r;
if(min > g) min = g; if(max < g) max = g;
if(min > b) min = b; if(max < b) max = b;
delta = max - min; /* 0 - 0xfff */
*val = max; /* 0 - 0xfff */
if(delta)
{
*sat = 0xfff * delta / max; /* 0 - 0xfff */
/* Generate *hue between 0 and 0x5fff */
if( r == max )
*hue = 0x1000 + 0x1000 * (g - b) / delta;
else if( g == max )
*hue = 0x3000 + 0x1000 * (b - r) / delta;
else
*hue = 0x5000 + 0x1000 * (r - g) / delta;
}
else
{
*sat = 0;
*hue = 0;
}
}
/** \brief Create an internal dither object.
*
* Create a dither structure from its coordinates (depth, width, height and
* pitch) and pixel mask values. If the depth is 8 bits per pixel, the mask
* values are ignored and the colour palette should be set using the
* caca_set_dither_palette() function. For depths greater than 8 bits per
* pixel, a zero alpha mask causes the alpha values to be ignored.
*
* If an error occurs, NULL is returned and \b errno is set accordingly:
* - \c EINVAL Requested width, height, pitch or bits per pixel value was
* invalid.
* - \c ENOMEM Not enough memory to allocate dither structure.
*
* \param bpp Bitmap depth in bits per pixel.
* \param w Bitmap width in pixels.
* \param h Bitmap height in pixels.
* \param pitch Bitmap pitch in bytes.
* \param rmask Bitmask for red values.
* \param gmask Bitmask for green values.
* \param bmask Bitmask for blue values.
* \param amask Bitmask for alpha values.
* \return Dither object upon success, NULL if an error occurred.
*/
caca_dither_t *caca_create_dither(int bpp, int w, int h, int pitch,
uint32_t rmask, uint32_t gmask,
uint32_t bmask, uint32_t amask)
{
caca_dither_t *d;
int i;
/* Minor sanity test */
if(w < 0 || h < 0 || pitch < 0 || bpp > 32 || bpp < 8)
{
seterrno(EINVAL);
return NULL;
}
d = malloc(sizeof(caca_dither_t));
if(!d)
{
seterrno(ENOMEM);
return NULL;
}
if(!lookup_initialised)
{
/* XXX: because we do not wish to be thread-safe, there is a slight
* chance that the following code will be executed twice. It is
* totally harmless. */
init_lookup();
lookup_initialised = 1;
}
d->bpp = bpp;
d->has_palette = 0;
d->has_alpha = amask ? 1 : 0;
d->w = w;
d->h = h;
d->pitch = pitch;
d->rmask = rmask;
d->gmask = gmask;
d->bmask = bmask;
d->amask = amask;
/* Load bitmasks */
if(rmask || gmask || bmask || amask)
{
mask2shift(rmask, &d->rright, &d->rleft);
mask2shift(gmask, &d->gright, &d->gleft);
mask2shift(bmask, &d->bright, &d->bleft);
mask2shift(amask, &d->aright, &d->aleft);
}
/* In 8 bpp mode, default to a grayscale palette */
if(bpp == 8)
{
d->has_palette = 1;
d->has_alpha = 0;
for(i = 0; i < 256; i++)
{
d->red[i] = i * 0xfff / 256;
d->green[i] = i * 0xfff / 256;
d->blue[i] = i * 0xfff / 256;
}
}
/* Default gamma value */
d->gamma = 1.0;
for(i = 0; i < 4096; i++)
d->gammatab[i] = i;
/* Default colour properties */
d->brightness = 1.0;
d->contrast = 1.0;
/* Default features */
d->antialias_name = "prefilter";
d->antialias = 1;
d->color_name = "full16";
d->color = COLOR_MODE_FULL16;
d->glyph_name = "ascii";
d->glyphs = ascii_glyphs;
d->glyph_count = sizeof(ascii_glyphs) / sizeof(*ascii_glyphs);
d->algo_name = "fstein";
d->init_dither = init_fstein_dither;
d->get_dither = get_fstein_dither;
d->increment_dither = increment_fstein_dither;
d->invert = 0;
return d;
}
/** \brief Set the palette of an 8bpp dither object.
*
* Set the palette of an 8 bits per pixel bitmap. Values should be between
* 0 and 4095 (0xfff).
*
* If an error occurs, -1 is returned and \b errno is set accordingly:
* - \c EINVAL Dither bits per pixel value is not 8, or one of the pixel
* values was outside the range 0 - 4095.
*
* \param d Dither object.
* \param red Array of 256 red values.
* \param green Array of 256 green values.
* \param blue Array of 256 blue values.
* \param alpha Array of 256 alpha values.
* \return 0 in case of success, -1 if an error occurred.
*/
int caca_set_dither_palette(caca_dither_t *d,
uint32_t red[], uint32_t green[],
uint32_t blue[], uint32_t alpha[])
{
int i, has_alpha = 0;
if(d->bpp != 8)
{
seterrno(EINVAL);
return -1;
}
for(i = 0; i < 256; i++)
{
if((red[i] | green[i] | blue[i] | alpha[i]) >= 0x1000)
{
seterrno(EINVAL);
return -1;
}
}
for(i = 0; i < 256; i++)
{
d->red[i] = red[i];
d->green[i] = green[i];
d->blue[i] = blue[i];
if(alpha[i])
{
d->alpha[i] = alpha[i];
has_alpha = 1;
}
}
d->has_alpha = has_alpha;
return 0;
}
/** \brief Set the brightness of a dither object.
*
* Set the brightness of dither.
*
* If an error occurs, -1 is returned and \b errno is set accordingly:
* - \c EINVAL Brightness value was out of range.
*
* \param d Dither object.
* \param brightness brightness value.
* \return 0 in case of success, -1 if an error occurred.
*/
int caca_set_dither_brightness(caca_dither_t *d, float brightness)
{
/* FIXME */
d->brightness = brightness;
return 0;
}
/** \brief Get the brightness of a dither object.
*
* Get the brightness of the given dither object.
*
* This function never fails.
*
* \param d Dither object.
* \return Brightness value.
*/
float caca_get_dither_brightness(caca_dither_t const *d)
{
return d->brightness;
}
/** \brief Set the gamma of a dither object.
*
* Set the gamma of the given dither object. A negative value causes
* colour inversion.
*
* If an error occurs, -1 is returned and \b errno is set accordingly:
* - \c EINVAL Gamma value was out of range.
*
* \param d Dither object.
* \param gamma Gamma value.
* \return 0 in case of success, -1 if an error occurred.
*/
int caca_set_dither_gamma(caca_dither_t *d, float gamma)
{
/* FIXME: we don't need 4096 calls to gammapow(), we could just compute
* a few of them and do linear interpolation for the rest. This will
* probably speed up things a lot. */
int i;
if(gamma < 0.0)
{
d->invert = 1;
gamma = -gamma;
}
else if(gamma == 0.0)
{
seterrno(EINVAL);
return -1;
}
d->gamma = gamma;
for(i = 0; i < 4096; i++)
d->gammatab[i] = 4096.0 * gammapow((float)i / 4096.0, 1.0 / gamma);
return 0;
}
/** \brief Get the gamma of a dither object.
*
* Get the gamma of the given dither object.
*
* This function never fails.
*
* \param d Dither object.
* \return Gamma value.
*/
float caca_get_dither_gamma(caca_dither_t const *d)
{
return d->gamma;
}
/** \brief Set the contrast of a dither object.
*
* Set the contrast of dither.
*
* If an error occurs, -1 is returned and \b errno is set accordingly:
* - \c EINVAL Contrast value was out of range.
*
* \param d Dither object.
* \param contrast contrast value.
* \return 0 in case of success, -1 if an error occurred.
*/
int caca_set_dither_contrast(caca_dither_t *d, float contrast)
{
/* FIXME */
d->contrast = contrast;
return 0;
}
/** \brief Get the contrast of a dither object.
*
* Get the contrast of the given dither object.
*
* This function never fails.
*
* \param d Dither object.
* \return Contrast value.
*/
float caca_get_dither_contrast(caca_dither_t const *d)
{
return d->contrast;
}
/** \brief Set dither antialiasing
*
* Tell the renderer whether to antialias the dither. Antialiasing smoothens
* the rendered image and avoids the commonly seen staircase effect.
* - \c "none": no antialiasing.
* - \c "prefilter" or \c "default": simple prefilter antialiasing. This
* is the default value.
*
* If an error occurs, -1 is returned and \b errno is set accordingly:
* - \c EINVAL Invalid antialiasing mode.
*
* \param d Dither object.
* \param str A string describing the antialiasing method that will be used
* for the dithering.
* \return 0 in case of success, -1 if an error occurred.
*/
int caca_set_dither_antialias(caca_dither_t *d, char const *str)
{
if(!strcasecmp(str, "none"))
{
d->antialias_name = "none";
d->antialias = 0;
}
else if(!strcasecmp(str, "prefilter") || !strcasecmp(str, "default"))
{
d->antialias_name = "prefilter";
d->antialias = 1;
}
else
{
seterrno(EINVAL);
return -1;
}
return 0;
}
/** \brief Get available antialiasing methods
*
* Return a list of available antialiasing methods for a given dither. The
* list is a NULL-terminated array of strings, interleaving a string
* containing the internal value for the antialiasing method to be used with
* caca_set_dither_antialias(), and a string containing the natural
* language description for that antialiasing method.
*
* This function never fails.
*
* \param d Dither object.
* \return An array of strings.
*/
char const * const *
caca_get_dither_antialias_list(caca_dither_t const *d)
{
static char const * const list[] =
{
"none", "No antialiasing",
"prefilter", "Prefilter antialiasing",
NULL, NULL
};
return list;
}
/** \brief Get current antialiasing method
*
* Return the given dither's current antialiasing method.
*
* This function never fails.
*
* \param d Dither object.
* \return A static string.
*/
char const * caca_get_dither_antialias(caca_dither_t const *d)
{
return d->antialias_name;
}
/** \brief Choose colours used for dithering
*
* Tell the renderer which colours should be used to render the
* bitmap. Valid values for \c str are:
* - \c "mono": use light gray on a black background.
* - \c "gray": use white and two shades of gray on a black background.
* - \c "8": use the 8 ANSI colours on a black background.
* - \c "16": use the 16 ANSI colours on a black background.
* - \c "fullgray": use black, white and two shades of gray for both the
* characters and the background.
* - \c "full8": use the 8 ANSI colours for both the characters and the
* background.
* - \c "full16" or \c "default": use the 16 ANSI colours for both the
* characters and the background. This is the default value.
*
* If an error occurs, -1 is returned and \b errno is set accordingly:
* - \c EINVAL Invalid colour set.
*
* \param d Dither object.
* \param str A string describing the colour set that will be used
* for the dithering.
* \return 0 in case of success, -1 if an error occurred.
*/
int caca_set_dither_color(caca_dither_t *d, char const *str)
{
if(!strcasecmp(str, "mono"))
{
d->color_name = "mono";
d->color = COLOR_MODE_MONO;
}
else if(!strcasecmp(str, "gray"))
{
d->color_name = "gray";
d->color = COLOR_MODE_GRAY;
}
else if(!strcasecmp(str, "8"))
{
d->color_name = "8";
d->color = COLOR_MODE_8;
}
else if(!strcasecmp(str, "16"))
{
d->color_name = "16";
d->color = COLOR_MODE_16;
}
else if(!strcasecmp(str, "fullgray"))
{
d->color_name = "fullgray";
d->color = COLOR_MODE_FULLGRAY;
}
else if(!strcasecmp(str, "full8"))
{
d->color_name = "full8";
d->color = COLOR_MODE_FULL8;
}
else if(!strcasecmp(str, "full16") || !strcasecmp(str, "default"))
{
d->color_name = "full16";
d->color = COLOR_MODE_FULL16;
}
else
{
seterrno(EINVAL);
return -1;
}
return 0;
}
/** \brief Get available colour modes
*
* Return a list of available colour modes for a given dither. The list
* is a NULL-terminated array of strings, interleaving a string containing
* the internal value for the colour mode, to be used with
* caca_set_dither_color(), and a string containing the natural
* language description for that colour mode.
*
* This function never fails.
*
* \param d Dither object.
* \return An array of strings.
*/
char const * const *
caca_get_dither_color_list(caca_dither_t const *d)
{
static char const * const list[] =
{
"mono", "white on black",
"gray", "grayscale on black",
"8", "8 colours on black",
"16", "16 colours on black",
"fullgray", "full grayscale",
"full8", "full 8 colours",
"full16", "full 16 colours",
NULL, NULL
};
return list;
}
/** \brief Get current colour mode
*
* Return the given dither's current colour mode.
*
* This function never fails.
*
* \param d Dither object.
* \return A static string.
*/
char const * caca_get_dither_color(caca_dither_t const *d)
{
return d->color_name;
}
/** \brief Choose characters used for dithering
*
* Tell the renderer which characters should be used to render the
* dither. Valid values for \c str are:
* - \c "ascii" or \c "default": use only ASCII characters. This is the
* default value.
* - \c "shades": use Unicode characters "U+2591 LIGHT SHADE", "U+2592
* MEDIUM SHADE" and "U+2593 DARK SHADE". These characters are also
* present in the CP437 codepage available on DOS and VGA.
* - \c "blocks": use Unicode quarter-cell block combinations. These
* characters are only found in the Unicode set.
*
* If an error occurs, -1 is returned and \b errno is set accordingly:
* - \c EINVAL Invalid character set.
*
* \param d Dither object.
* \param str A string describing the characters that need to be used
* for the dithering.
* \return 0 in case of success, -1 if an error occurred.
*/
int caca_set_dither_charset(caca_dither_t *d, char const *str)
{
if(!strcasecmp(str, "shades"))
{
d->glyph_name = "shades";
d->glyphs = shades_glyphs;
d->glyph_count = sizeof(shades_glyphs) / sizeof(*shades_glyphs);
}
else if(!strcasecmp(str, "blocks"))
{
d->glyph_name = "blocks";
d->glyphs = blocks_glyphs;
d->glyph_count = sizeof(blocks_glyphs) / sizeof(*blocks_glyphs);
}
else if(!strcasecmp(str, "ascii") || !strcasecmp(str, "default"))
{
d->glyph_name = "ascii";
d->glyphs = ascii_glyphs;
d->glyph_count = sizeof(ascii_glyphs) / sizeof(*ascii_glyphs);
}
else
{
seterrno(EINVAL);
return -1;
}
return 0;
}
/** \brief Get available dither character sets
*
* Return a list of available character sets for a given dither. The list
* is a NULL-terminated array of strings, interleaving a string containing
* the internal value for the character set, to be used with
* caca_set_dither_charset(), and a string containing the natural
* language description for that character set.
*
* This function never fails.
*
* \param d Dither object.
* \return An array of strings.
*/
char const * const * caca_get_dither_charset_list(caca_dither_t const *d)
{
static char const * const list[] =
{
"ascii", "plain ASCII",
"shades", "CP437 shades",
"blocks", "Unicode blocks",
NULL, NULL
};
return list;
}
/** \brief Get current character set
*
* Return the given dither's current character set.
*
* This function never fails.
*
* \param d Dither object.
* \return A static string.
*/
char const * caca_get_dither_charset(caca_dither_t const *d)
{
return d->glyph_name;
}
/** \brief Set dithering algorithm
*
* Tell the renderer which dithering algorithm should be used. Dithering is
* necessary because the picture being rendered has usually far more colours
* than the available palette. Valid values for \c str are:
* - \c "none": no dithering is used, the nearest matching colour is used.
* - \c "ordered2": use a 2x2 Bayer matrix for dithering.
* - \c "ordered4": use a 4x4 Bayer matrix for dithering.
* - \c "ordered8": use a 8x8 Bayer matrix for dithering.
* - \c "random": use random dithering.
* - \c "fstein": use Floyd-Steinberg dithering. This is the default value.
*
* If an error occurs, -1 is returned and \b errno is set accordingly:
* - \c EINVAL Unknown dithering mode.
*
* \param d Dither object.
* \param str A string describing the algorithm that needs to be used
* for the dithering.
* \return 0 in case of success, -1 if an error occurred.
*/
int caca_set_dither_algorithm(caca_dither_t *d, char const *str)
{
if(!strcasecmp(str, "none"))
{
d->algo_name = "none";
d->init_dither = init_no_dither;
d->get_dither = get_no_dither;
d->increment_dither = increment_no_dither;
}
else if(!strcasecmp(str, "ordered2"))
{
d->algo_name = "ordered2";
d->init_dither = init_ordered2_dither;
d->get_dither = get_ordered2_dither;
d->increment_dither = increment_ordered2_dither;
}
else if(!strcasecmp(str, "ordered4"))
{
d->algo_name = "ordered4";
d->init_dither = init_ordered4_dither;
d->get_dither = get_ordered4_dither;
d->increment_dither = increment_ordered4_dither;
}
else if(!strcasecmp(str, "ordered8"))
{
d->algo_name = "ordered8";
d->init_dither = init_ordered8_dither;
d->get_dither = get_ordered8_dither;
d->increment_dither = increment_ordered8_dither;
}
else if(!strcasecmp(str, "random"))
{
d->algo_name = "random";
d->init_dither = init_random_dither;
d->get_dither = get_random_dither;
d->increment_dither = increment_random_dither;
}
else if(!strcasecmp(str, "fstein") || !strcasecmp(str, "default"))
{
d->algo_name = "fstein";
d->init_dither = init_fstein_dither;
d->get_dither = get_fstein_dither;
d->increment_dither = increment_fstein_dither;
}
else
{
seterrno(EINVAL);
return -1;
}
return 0;
}
/** \brief Get dithering algorithms
*
* Return a list of available dithering algorithms for a given dither. The
* list is a NULL-terminated array of strings, interleaving a string
* containing the internal value for the dithering algorithm, to be used
* with caca_set_dither_dithering(), and a string containing the natural
* language description for that algorithm.
*
* This function never fails.
*
* \param d Dither object.
* \return An array of strings.
*/
char const * const * caca_get_dither_algorithm_list(caca_dither_t const *d)
{
static char const * const list[] =
{
"none", "no dithering",
"ordered2", "2x2 ordered dithering",
"ordered4", "4x4 ordered dithering",
"ordered8", "8x8 ordered dithering",
"random", "random dithering",
"fstein", "Floyd-Steinberg dithering",
NULL, NULL
};
return list;
}
/** \brief Get current dithering algorithm
*
* Return the given dither's current dithering algorithm.
*
* This function never fails.
*
* \param d Dither object.
* \return A static string.
*/
char const * caca_get_dither_algorithm(caca_dither_t const *d)
{
return d->algo_name;
}
/** \brief Dither a bitmap on the canvas.
*
* Dither a bitmap at the given coordinates. The dither can be of any size
* and will be stretched to the text area.
*
* This function never fails.
*
* \param cv A handle to the libcaca canvas.
* \param x X coordinate of the upper-left corner of the drawing area.
* \param y Y coordinate of the upper-left corner of the drawing area.
* \param w Width of the drawing area.
* \param h Height of the drawing area.
* \param d Dither object to be drawn.
* \param pixels Bitmap's pixels.
* \return This function always returns 0.
*/
int caca_dither_bitmap(caca_canvas_t *cv, int x, int y, int w, int h,
caca_dither_t const *d, void const *pixels)
{
int *floyd_steinberg, *fs_r, *fs_g, *fs_b;
uint32_t savedattr;
int fs_length;
int x1, y1, x2, y2, pitch, deltax, deltay, dchmax;
if(!d || !pixels)
return 0;
savedattr = caca_get_attr(cv, -1, -1);
x1 = x; x2 = x + w - 1;
y1 = y; y2 = y + h - 1;
/* FIXME: do not overwrite arguments */
w = d->w;
h = d->h;
pitch = d->pitch;
deltax = x2 - x1 + 1;
deltay = y2 - y1 + 1;
dchmax = d->glyph_count;
fs_length = ((int)cv->width <= x2 ? (int)cv->width : x2) + 1;
floyd_steinberg = malloc(3 * (fs_length + 2) * sizeof(int));
memset(floyd_steinberg, 0, 3 * (fs_length + 2) * sizeof(int));
fs_r = floyd_steinberg + 1;
fs_g = fs_r + fs_length + 2;
fs_b = fs_g + fs_length + 2;
for(y = y1 > 0 ? y1 : 0; y <= y2 && y <= (int)cv->height; y++)
{
int remain_r = 0, remain_g = 0, remain_b = 0;
for(x = x1 > 0 ? x1 : 0, d->init_dither(y);
x <= x2 && x <= (int)cv->width;
x++)
{
unsigned int rgba[4];
int error[3];
int i, ch = 0, distmin;
int fg_r = 0, fg_g = 0, fg_b = 0, bg_r, bg_g, bg_b;
int fromx, fromy, tox, toy, myx, myy, dots, dist;
int outfg = 0, outbg = 0;
uint32_t outch;
rgba[0] = rgba[1] = rgba[2] = rgba[3] = 0;
/* First get RGB */
if(d->antialias)
{
fromx = (uint64_t)(x - x1) * w / deltax;
fromy = (uint64_t)(y - y1) * h / deltay;
tox = (uint64_t)(x - x1 + 1) * w / deltax;
toy = (uint64_t)(y - y1 + 1) * h / deltay;
/* We want at least one pixel */
if(tox == fromx) tox++;
if(toy == fromy) toy++;
dots = 0;
for(myx = fromx; myx < tox; myx++)
for(myy = fromy; myy < toy; myy++)
{
dots++;
get_rgba_default(d, pixels, myx, myy, rgba);
}
/* Normalize */
rgba[0] /= dots;
rgba[1] /= dots;
rgba[2] /= dots;
rgba[3] /= dots;
}
else
{
fromx = (uint64_t)(x - x1) * w / deltax;
fromy = (uint64_t)(y - y1) * h / deltay;
tox = (uint64_t)(x - x1 + 1) * w / deltax;
toy = (uint64_t)(y - y1 + 1) * h / deltay;
/* tox and toy can overflow the canvas, but they cannot overflow
* when averaged with fromx and fromy because these are guaranteed
* to be within the pixel boundaries. */
myx = (fromx + tox) / 2;
myy = (fromy + toy) / 2;
get_rgba_default(d, pixels, myx, myy, rgba);
}
/* FIXME: hack to force greyscale */
if(d->color == COLOR_MODE_FULLGRAY)
{
unsigned int gray = (3 * rgba[0] + 4 * rgba[1] + rgba[2] + 4) / 8;
rgba[0] = rgba[1] = rgba[2] = gray;
}
if(d->has_alpha && rgba[3] < 0x800)
{
remain_r = remain_g = remain_b = 0;
fs_r[x] = 0;
fs_g[x] = 0;
fs_b[x] = 0;
continue;
}
/* XXX: OMG HAX */
if(d->init_dither == init_fstein_dither)
{
rgba[0] += remain_r;
rgba[1] += remain_g;
rgba[2] += remain_b;
}
else
{
rgba[0] += (d->get_dither() - 0x80) * 4;
rgba[1] += (d->get_dither() - 0x80) * 4;
rgba[2] += (d->get_dither() - 0x80) * 4;
}
distmin = INT_MAX;
for(i = 0; i < 16; i++)
{
if(d->color == COLOR_MODE_FULLGRAY
&& (rgb_palette[i * 3] != rgb_palette[i * 3 + 1]
|| rgb_palette[i * 3] != rgb_palette[i * 3 + 2]))
continue;
dist = sq(rgba[0] - rgb_palette[i * 3])
+ sq(rgba[1] - rgb_palette[i * 3 + 1])
+ sq(rgba[2] - rgb_palette[i * 3 + 2]);
dist *= rgb_weight[i];
if(dist < distmin)
{
outbg = i;
distmin = dist;
}
}
bg_r = rgb_palette[outbg * 3];
bg_g = rgb_palette[outbg * 3 + 1];
bg_b = rgb_palette[outbg * 3 + 2];
/* FIXME: we currently only honour "full16" */
if(d->color == COLOR_MODE_FULL16 || d->color == COLOR_MODE_FULLGRAY)
{
distmin = INT_MAX;
for(i = 0; i < 16; i++)
{
if(i == outbg)
continue;
if(d->color == COLOR_MODE_FULLGRAY
&& (rgb_palette[i * 3] != rgb_palette[i * 3 + 1]
|| rgb_palette[i * 3] != rgb_palette[i * 3 + 2]))
continue;
dist = sq(rgba[0] - rgb_palette[i * 3])
+ sq(rgba[1] - rgb_palette[i * 3 + 1])
+ sq(rgba[2] - rgb_palette[i * 3 + 2]);
dist *= rgb_weight[i];
if(dist < distmin)
{
outfg = i;
distmin = dist;
}
}
fg_r = rgb_palette[outfg * 3];
fg_g = rgb_palette[outfg * 3 + 1];
fg_b = rgb_palette[outfg * 3 + 2];
distmin = INT_MAX;
for(i = 0; i < dchmax - 1; i++)
{
int newr = i * fg_r + ((2*dchmax-1) - i) * bg_r;
int newg = i * fg_g + ((2*dchmax-1) - i) * bg_g;
int newb = i * fg_b + ((2*dchmax-1) - i) * bg_b;
dist = abs(rgba[0] * (2*dchmax-1) - newr)
+ abs(rgba[1] * (2*dchmax-1) - newg)
+ abs(rgba[2] * (2*dchmax-1) - newb);
if(dist < distmin)
{
ch = i;
distmin = dist;
}
}
outch = d->glyphs[ch];
/* XXX: OMG HAX */
if(d->init_dither == init_fstein_dither)
{
error[0] = rgba[0] - (fg_r * ch + bg_r * ((2*dchmax-1) - ch)) / (2*dchmax-1);
error[1] = rgba[1] - (fg_g * ch + bg_g * ((2*dchmax-1) - ch)) / (2*dchmax-1);
error[2] = rgba[2] - (fg_b * ch + bg_b * ((2*dchmax-1) - ch)) / (2*dchmax-1);
}
}
else
{
unsigned int lum = rgba[0];
if(rgba[1] > lum) lum = rgba[1];
if(rgba[2] > lum) lum = rgba[2];
outfg = outbg;
outbg = CACA_BLACK;
ch = lum * dchmax / 0x1000;
if(ch < 0)
ch = 0;
else if(ch > (int)(dchmax - 1))
ch = dchmax - 1;
outch = d->glyphs[ch];
/* XXX: OMG HAX */
if(d->init_dither == init_fstein_dither)
{
error[0] = rgba[0] - bg_r * ch / (dchmax-1);
error[1] = rgba[1] - bg_g * ch / (dchmax-1);
error[2] = rgba[2] - bg_b * ch / (dchmax-1);
}
}
/* XXX: OMG HAX */
if(d->init_dither == init_fstein_dither)
{
remain_r = fs_r[x+1] + 7 * error[0] / 16;
remain_g = fs_g[x+1] + 7 * error[1] / 16;
remain_b = fs_b[x+1] + 7 * error[2] / 16;
fs_r[x-1] += 3 * error[0] / 16;
fs_g[x-1] += 3 * error[1] / 16;
fs_b[x-1] += 3 * error[2] / 16;
fs_r[x] = 5 * error[0] / 16;
fs_g[x] = 5 * error[1] / 16;
fs_b[x] = 5 * error[2] / 16;
fs_r[x+1] = 1 * error[0] / 16;
fs_g[x+1] = 1 * error[1] / 16;
fs_b[x+1] = 1 * error[2] / 16;
}
if(d->invert)
{
outfg = 15 - outfg;
outbg = 15 - outbg;
}
/* Now output the character */
caca_set_color_ansi(cv, outfg, outbg);
if (x == 5)
outch = '?';
caca_put_char(cv, x, y, outch);
d->increment_dither();
}
/* end loop */
}
free(floyd_steinberg);
caca_set_attr(cv, savedattr);
return 0;
}
/** \brief Free the memory associated with a dither.
*
* Free the memory allocated by caca_create_dither().
*
* This function never fails.
*
* \param d Dither object.
* \return This function always returns 0.
*/
int caca_free_dither(caca_dither_t *d)
{
if(!d)
return 0;
free(d);
return 0;
}
/*
* XXX: The following functions are local.
*/
/* Convert a mask, eg. 0x0000ff00, to shift values, eg. 8 and -4. */
static void mask2shift(uint32_t mask, int *right, int *left)
{
int rshift = 0, lshift = 0;
if(!mask)
{
*right = *left = 0;
return;
}
while(!(mask & 1))
{
mask >>= 1;
rshift++;
}
*right = rshift;
while(mask & 1)
{
mask >>= 1;
lshift++;
}
*left = 12 - lshift;
}
/* Compute x^y without relying on the math library */
static float gammapow(float x, float y)
{
#ifdef HAVE_FLDLN2
register double logx;
register long double v, e;
#else
register float tmp, t, t2, r;
int i;
#endif
if(x == 0.0)
return y == 0.0 ? 1.0 : 0.0;
#ifdef HAVE_FLDLN2
/* FIXME: this can be optimised by directly calling fyl2x for x and y */
asm volatile("fldln2; fxch; fyl2x"
: "=t" (logx) : "0" (x) : "st(1)");
asm volatile("fldl2e\n\t"
"fmul %%st(1)\n\t"
"fst %%st(1)\n\t"
"frndint\n\t"
"fxch\n\t"
"fsub %%st(1)\n\t"
"f2xm1\n\t"
: "=t" (v), "=u" (e) : "0" (y * logx));
v += 1.0;
asm volatile("fscale"
: "=t" (v) : "0" (v), "u" (e));
return v;
#else
/* Compute ln(x) for x ∈ ]0,1]
* ln(x) = 2 * (t + t^3/3 + t^5/5 + ...) with t = (x-1)/(x+1)
* The convergence is a bit slow, especially when x is near 0. */
t = (x - 1.0) / (x + 1.0);
t2 = t * t;
tmp = r = t;
for(i = 3; i < 20; i += 2)
{
r *= t2;
tmp += r / i;
}
/* Compute -y*ln(x) */
tmp = - y * 2.0 * tmp;
/* Compute x^-y as e^t where t = -y*ln(x):
* e^t = 1 + t/1! + t^2/2! + t^3/3! + t^4/4! + t^5/5! ...
* The convergence is quite faster here, thanks to the factorial. */
r = t = tmp;
tmp = 1.0 + t;
for(i = 2; i < 16; i++)
{
r = r * t / i;
tmp += r;
}
/* Return x^y as 1/(x^-y) */
return 1.0 / tmp;
#endif
}
static void get_rgba_default(caca_dither_t const *d, uint8_t const *pixels,
int x, int y, unsigned int *rgba)
{
uint32_t bits;
pixels += (d->bpp / 8) * x + d->pitch * y;
switch(d->bpp / 8)
{
case 4:
bits = *(uint32_t const *)pixels;
break;
case 3:
{
#if defined(HAVE_ENDIAN_H)
if(__BYTE_ORDER == __BIG_ENDIAN)
#else
/* This is compile-time optimised with at least -O1 or -Os */
uint32_t const tmp = 0x12345678;
if(*(uint8_t const *)&tmp == 0x12)
#endif
bits = ((uint32_t)pixels[0] << 16) |
((uint32_t)pixels[1] << 8) |
((uint32_t)pixels[2]);
else
bits = ((uint32_t)pixels[2] << 16) |
((uint32_t)pixels[1] << 8) |
((uint32_t)pixels[0]);
break;
}
case 2:
bits = *(uint16_t const *)pixels;
break;
case 1:
default:
bits = pixels[0];
break;
}
if(d->has_palette)
{
rgba[0] += d->gammatab[d->red[bits]];
rgba[1] += d->gammatab[d->green[bits]];
rgba[2] += d->gammatab[d->blue[bits]];
rgba[3] += d->alpha[bits];
}
else
{
rgba[0] += d->gammatab[((bits & d->rmask) >> d->rright) << d->rleft];
rgba[1] += d->gammatab[((bits & d->gmask) >> d->gright) << d->gleft];
rgba[2] += d->gammatab[((bits & d->bmask) >> d->bright) << d->bleft];
rgba[3] += ((bits & d->amask) >> d->aright) << d->aleft;
}
}
/*
* No dithering
*/
static void init_no_dither(int line)
{
;
}
static int get_no_dither(void)
{
return 0x80;
}
static void increment_no_dither(void)
{
return;
}
/*
* Floyd-Steinberg dithering
*/
static void init_fstein_dither(int line)
{
;
}
static int get_fstein_dither(void)
{
return 0x80;
}
static void increment_fstein_dither(void)
{
return;
}
/*
* Ordered 2 dithering
*/
static int const *ordered2_table;
static int ordered2_index;
static void init_ordered2_dither(int line)
{
static int const dither2x2[] =
{
0x00, 0x80,
0xc0, 0x40,
};
ordered2_table = dither2x2 + (line % 2) * 2;
ordered2_index = 0;
}
static int get_ordered2_dither(void)
{
return ordered2_table[ordered2_index];
}
static void increment_ordered2_dither(void)
{
ordered2_index = (ordered2_index + 1) % 2;
}
/*
* Ordered 4 dithering
*/
/*static int dither4x4[] = { 5, 0, 1, 6,
-1, -6, -5, 2,
-2, -7, -8, 3,
4, -3, -4, -7};*/
static int const *ordered4_table;
static int ordered4_index;
static void init_ordered4_dither(int line)
{
static int const dither4x4[] =
{
0x00, 0x80, 0x20, 0xa0,
0xc0, 0x40, 0xe0, 0x60,
0x30, 0xb0, 0x10, 0x90,
0xf0, 0x70, 0xd0, 0x50
};
ordered4_table = dither4x4 + (line % 4) * 4;
ordered4_index = 0;
}
static int get_ordered4_dither(void)
{
return ordered4_table[ordered4_index];
}
static void increment_ordered4_dither(void)
{
ordered4_index = (ordered4_index + 1) % 4;
}
/*
* Ordered 8 dithering
*/
static int const *ordered8_table;
static int ordered8_index;
static void init_ordered8_dither(int line)
{
static int const dither8x8[] =
{
0x00, 0x80, 0x20, 0xa0, 0x08, 0x88, 0x28, 0xa8,
0xc0, 0x40, 0xe0, 0x60, 0xc8, 0x48, 0xe8, 0x68,
0x30, 0xb0, 0x10, 0x90, 0x38, 0xb8, 0x18, 0x98,
0xf0, 0x70, 0xd0, 0x50, 0xf8, 0x78, 0xd8, 0x58,
0x0c, 0x8c, 0x2c, 0xac, 0x04, 0x84, 0x24, 0xa4,
0xcc, 0x4c, 0xec, 0x6c, 0xc4, 0x44, 0xe4, 0x64,
0x3c, 0xbc, 0x1c, 0x9c, 0x34, 0xb4, 0x14, 0x94,
0xfc, 0x7c, 0xdc, 0x5c, 0xf4, 0x74, 0xd4, 0x54,
};
ordered8_table = dither8x8 + (line % 8) * 8;
ordered8_index = 0;
}
static int get_ordered8_dither(void)
{
return ordered8_table[ordered8_index];
}
static void increment_ordered8_dither(void)
{
ordered8_index = (ordered8_index + 1) % 8;
}
/*
* Random dithering
*/
static void init_random_dither(int line)
{
;
}
static int get_random_dither(void)
{
return caca_rand(0x00, 0x100);
}
static void increment_random_dither(void)
{
return;
}
/*
* Lookup tables
*/
static int init_lookup(void)
{
int v, s, h;
/* These ones are constant */
lookup_colors[0] = CACA_BLACK;
lookup_colors[1] = CACA_DARKGRAY;
lookup_colors[2] = CACA_LIGHTGRAY;
lookup_colors[3] = CACA_WHITE;
/* These ones will be overwritten */
lookup_colors[4] = CACA_MAGENTA;
lookup_colors[5] = CACA_LIGHTMAGENTA;
lookup_colors[6] = CACA_RED;
lookup_colors[7] = CACA_LIGHTRED;
for(v = 0; v < LOOKUP_VAL; v++)
for(s = 0; s < LOOKUP_SAT; s++)
for(h = 0; h < LOOKUP_HUE; h++)
{
int i, distbg, distfg, dist;
int val, sat, hue;
uint8_t outbg, outfg;
val = 0xfff * v / (LOOKUP_VAL - 1);
sat = 0xfff * s / (LOOKUP_SAT - 1);
hue = 0xfff * h / (LOOKUP_HUE - 1);
/* Initialise distances to the distance between pure black HSV
* coordinates and our white colour (3) */
outbg = outfg = 3;
distbg = distfg = HSV_DISTANCE(0, 0, 0, 3);
/* Calculate distances to eight major colour values and store the
* two nearest points in our lookup table. */
for(i = 0; i < 8; i++)
{
dist = HSV_DISTANCE(hue, sat, val, i);
if(dist <= distbg)
{
outfg = outbg;
distfg = distbg;
outbg = i;
distbg = dist;
}
else if(dist <= distfg)
{
outfg = i;
distfg = dist;
}
}
hsv_distances[v][s][h] = (outfg << 4) | outbg;
}
return 0;
}
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