caca_dither - Online Linux Manual PageSection : 3caca
Updated : Tue Jan 26 2021
Source : Version 0.99.beta19
Note : libcaca

NAMEcaca_dither − libcaca bitmap dithering

SYNOPSIS

Moduleslibcaca character font handling

Functions__extern caca_dither_t * caca_create_dither (int, int, int, int, uint32_t, uint32_t, uint32_t, uint32_t)
Create an internal dither object​.
__extern int caca_set_dither_palette (caca_dither_t *, uint32_t r[], uint32_t g[], uint32_t b[], uint32_t a[])
Set the palette of an 8bpp dither object​.
__extern int caca_set_dither_brightness (caca_dither_t *, float)
Set the brightness of a dither object​.
__extern float caca_get_dither_brightness (caca_dither_t const *)
Get the brightness of a dither object​.
__extern int caca_set_dither_gamma (caca_dither_t *, float)
Set the gamma of a dither object​.
__extern float caca_get_dither_gamma (caca_dither_t const *)
Get the gamma of a dither object​.
__extern int caca_set_dither_contrast (caca_dither_t *, float)
Set the contrast of a dither object​.
__extern float caca_get_dither_contrast (caca_dither_t const *)
Get the contrast of a dither object​.
__extern int caca_set_dither_antialias (caca_dither_t *, char const *)
Set dither antialiasing​.
__extern char const *const * caca_get_dither_antialias_list (caca_dither_t const *)
Get available antialiasing methods​.
__extern char const * caca_get_dither_antialias (caca_dither_t const *)
Get current antialiasing method​.
__extern int caca_set_dither_color (caca_dither_t *, char const *)
Choose colours used for dithering​.
__extern char const *const * caca_get_dither_color_list (caca_dither_t const *)
Get available colour modes​.
__extern char const * caca_get_dither_color (caca_dither_t const *)
Get current colour mode​.
__extern int caca_set_dither_charset (caca_dither_t *, char const *)
Choose characters used for dithering​.
__extern char const *const * caca_get_dither_charset_list (caca_dither_t const *)
Get available dither character sets​.
__extern char const * caca_get_dither_charset (caca_dither_t const *)
Get current character set​.
__extern int caca_set_dither_algorithm (caca_dither_t *, char const *)
Set dithering algorithm​.
__extern char const *const * caca_get_dither_algorithm_list (caca_dither_t const *)
Get dithering algorithms​.
__extern char const * caca_get_dither_algorithm (caca_dither_t const *)
Get current dithering algorithm​.
__extern int caca_dither_bitmap (caca_canvas_t *, int, int, int, int, caca_dither_t const *, void const *)
Dither a bitmap on the canvas​.
__extern int caca_free_dither (caca_dither_t *)
Free the memory associated with a dither​.

Detailed DescriptionThese functions provide high level routines for dither allocation and rendering​.

Function Documentation

__extern 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)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 errno is set accordingly: • EINVAL Requested width, height, pitch or bits per pixel value was invalid​. • ENOMEM Not enough memory to allocate dither structure​. Parameters bpp Bitmap depth in bits per pixel​.
w Bitmap width in pixels​.
h Bitmap height in pixels​.
pitch Bitmap pitch in bytes​.
rmask Bitmask for red values​.
gmask Bitmask for green values​.
bmask Bitmask for blue values​.
amask Bitmask for alpha values​.
Returns Dither object upon success, NULL if an error occurred​.

__extern int caca_set_dither_palette (caca_dither_t * d, uint32_t red[], uint32_t green[], uint32_t blue[], uint32_t alpha[])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 errno is set accordingly: • EINVAL Dither bits per pixel value is not 8, or one of the pixel values was outside the range 0 - 4095​. Parameters d Dither object​.
red Array of 256 red values​.
green Array of 256 green values​.
blue Array of 256 blue values​.
alpha Array of 256 alpha values​.
Returns 0 in case of success, -1 if an error occurred​.

__extern int caca_set_dither_brightness (caca_dither_t * d, float brightness)Set the brightness of dither​. If an error occurs, -1 is returned and errno is set accordingly: • EINVAL Brightness value was out of range​. Parameters d Dither object​.
brightness brightness value​.
Returns 0 in case of success, -1 if an error occurred​.

__extern float caca_get_dither_brightness (caca_dither_t const * d)Get the brightness of the given dither object​. This function never fails​. Parameters d Dither object​. Returns Brightness value​.

__extern int caca_set_dither_gamma (caca_dither_t * d, float gamma)Set the gamma of the given dither object​. A negative value causes colour inversion​. If an error occurs, -1 is returned and errno is set accordingly: • EINVAL Gamma value was out of range​. Parameters d Dither object​.
gamma Gamma value​.
Returns 0 in case of success, -1 if an error occurred​.

__extern float caca_get_dither_gamma (caca_dither_t const * d)Get the gamma of the given dither object​. This function never fails​. Parameters d Dither object​. Returns Gamma value​.

__extern int caca_set_dither_contrast (caca_dither_t * d, float contrast)Set the contrast of dither​. If an error occurs, -1 is returned and errno is set accordingly: • EINVAL Contrast value was out of range​. Parameters d Dither object​.
contrast contrast value​.
Returns 0 in case of success, -1 if an error occurred​.

__extern float caca_get_dither_contrast (caca_dither_t const * d)Get the contrast of the given dither object​. This function never fails​. Parameters d Dither object​. Returns Contrast value​.

__extern int caca_set_dither_antialias (caca_dither_t * d, char const * str)Tell the renderer whether to antialias the dither​. Antialiasing smoothens the rendered image and avoids the commonly seen staircase effect​. • "none": no antialiasing​. • "prefilter" or "default": simple prefilter antialiasing​. This is the default value​. If an error occurs, -1 is returned and errno is set accordingly: • EINVAL Invalid antialiasing mode​. Parameters d Dither object​.
str A string describing the antialiasing method that will be used for the dithering​.
Returns 0 in case of success, -1 if an error occurred​.

__extern char const* const* caca_get_dither_antialias_list (caca_dither_t const * d)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​. Parameters d Dither object​. Returns An array of strings​.

__extern char const* caca_get_dither_antialias (caca_dither_t const * d)Return the given dither's current antialiasing method​. This function never fails​. Parameters d Dither object​. Returns A static string​.

__extern int caca_set_dither_color (caca_dither_t * d, char const * str)Tell the renderer which colours should be used to render the bitmap​. Valid values for str are: • "mono": use light gray on a black background​. • "gray": use white and two shades of gray on a black background​. • "8": use the 8 ANSI colours on a black background​. • "16": use the 16 ANSI colours on a black background​. • "fullgray": use black, white and two shades of gray for both the characters and the background​. • "full8": use the 8 ANSI colours for both the characters and the background​. • "full16" or "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 errno is set accordingly: • EINVAL Invalid colour set​. Parameters d Dither object​.
str A string describing the colour set that will be used for the dithering​.
Returns 0 in case of success, -1 if an error occurred​.

__extern char const* const* caca_get_dither_color_list (caca_dither_t const * d)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​. Parameters d Dither object​. Returns An array of strings​.

__extern char const* caca_get_dither_color (caca_dither_t const * d)Return the given dither's current colour mode​. This function never fails​. Parameters d Dither object​. Returns A static string​.

__extern int caca_set_dither_charset (caca_dither_t * d, char const * str)Tell the renderer which characters should be used to render the dither​. Valid values for str are: • "ascii" or "default": use only ASCII characters​. This is the default value​. • "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​.
• "blocks": use Unicode quarter-cell block combinations​. These characters are only found in the Unicode set​. If an error occurs, -1 is returned and errno is set accordingly: • EINVAL Invalid character set​. Parameters d Dither object​.
str A string describing the characters that need to be used for the dithering​.
Returns 0 in case of success, -1 if an error occurred​.

__extern char const* const* caca_get_dither_charset_list (caca_dither_t const * d)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​. Parameters d Dither object​. Returns An array of strings​.

__extern char const* caca_get_dither_charset (caca_dither_t const * d)Return the given dither's current character set​. This function never fails​. Parameters d Dither object​. Returns A static string​.

__extern int caca_set_dither_algorithm (caca_dither_t * d, char const * str)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 str are: • "none": no dithering is used, the nearest matching colour is used​. • "ordered2": use a 2x2 Bayer matrix for dithering​. • "ordered4": use a 4x4 Bayer matrix for dithering​. • "ordered8": use a 8x8 Bayer matrix for dithering​. • "random": use random dithering​. • "fstein": use Floyd-Steinberg dithering​. This is the default value​. If an error occurs, -1 is returned and errno is set accordingly: • EINVAL Unknown dithering mode​. Parameters d Dither object​.
str A string describing the algorithm that needs to be used for the dithering​.
Returns 0 in case of success, -1 if an error occurred​.

__extern char const* const* caca_get_dither_algorithm_list (caca_dither_t const * d)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​. Parameters d Dither object​. Returns An array of strings​.

__extern char const* caca_get_dither_algorithm (caca_dither_t const * d)Return the given dither's current dithering algorithm​. This function never fails​. Parameters d Dither object​. Returns A static string​.

__extern int caca_dither_bitmap (caca_canvas_t * cv, int x, int y, int w, int h, caca_dither_t const * d, void const * pixels)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​. Parameters cv A handle to the libcaca canvas​.
x X coordinate of the upper-left corner of the drawing area​.
y Y coordinate of the upper-left corner of the drawing area​.
w Width of the drawing area​.
h Height of the drawing area​.
d Dither object to be drawn​.
pixels Bitmap's pixels​.
Returns This function always returns 0​. References CACA_BLACK, caca_get_attr(), caca_put_char(), caca_set_attr(), and caca_set_color_ansi()​.

__extern int caca_free_dither (caca_dither_t * d)Free the memory allocated by caca_create_dither()​. This function never fails​. Parameters d Dither object​. Returns This function always returns 0​.

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