caca_set_dither_contrast (3)

NAME

caca_dither - libcaca bitmap dithering

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 Description

These 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.

Author

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