9.2 KiB
% notcurses_visual(3) % nick black nickblack@linux.com % v2.1.1
NAME
notcurses_visual - notcurses multimedia
SYNOPSIS
#include <notcurses/notcurses.h>
typedef enum {
NCSCALE_NONE,
NCSCALE_SCALE,
NCSCALE_STRETCH,
} ncscale_e;
typedef enum {
NCBLIT_DEFAULT, // let the ncvisual pick
NCBLIT_1x1, // spaces only
NCBLIT_2x1, // halves + 1x1
NCBLIT_2x2, // quadrants + 2x1
NCBLIT_3x2, // sextants + 1x1
NCBLIT_4x1, // four vertical levels
NCBLIT_BRAILLE, // 4 rows, 2 cols (braille)
NCBLIT_8x1, // eight vertical levels
NCBLIT_SIXEL, // not yet implemented
} ncblitter_e;
#define NCVISUAL_OPTION_NODEGRADE 0x0001
#define NCVISUAL_OPTION_BLEND 0x0002
struct ncvisual_options {
struct ncplane* n;
ncscale_e scaling;
int ***y***, x;
int begy, begx; // origin of rendered section
int leny, lenx; // size of rendered section
ncblitter_e blitter; // glyph set to use
uint64_t flags; // bitmask over NCVISUAL_OPTION_*
};
typedef int (*streamcb)(struct notcurses*, struct ncvisual*, void*);
bool notcurses_canopen_images(const struct notcurses nc);*
bool notcurses_canopen_videos(const struct notcurses nc);*
bool notcurses_cansixel(const struct notcurses nc);*
struct ncvisual ncvisual_from_file(const char file);**
struct ncvisual ncvisual_from_rgba(const void rgba, int rows, int rowstride, int cols);**
struct ncvisual ncvisual_from_bgra(const void bgra, int rows, int rowstride, int cols);**
struct ncvisual ncvisual_from_plane(struct ncplane n, ncblitter_e blit, int begy, int begx, int leny, int lenx);**
int ncvisual_geom(const struct notcurses nc, const struct ncvisual n, const struct ncvisual_options* vopts, int* y, int* x, int* toy, int* tox);**
void ncvisual_destroy(struct ncvisual ncv);*
int ncvisual_decode(struct ncvisual ncv);*
int ncvisual_decode_loop(struct ncvisual ncv);*
struct ncplane ncvisual_render(struct notcurses nc, struct ncvisual* ncv, const struct ncvisual_options* vopts);**
int ncvisual_simple_streamer(struct ncplane n, struct ncvisual ncv, const struct timespec* disptime, void* curry);**
int ncvisual_stream(struct notcurses nc, struct ncvisual ncv, float timescale, streamcb streamer, const struct ncvisual_options* vopts, void* curry);**
int ncvisual_rotate(struct ncvisual n, double rads);*
int ncvisual_resize(struct ncvisual n, int rows, int cols);*
int ncvisual_polyfill_yx(struct ncvisual n, int y, int x, uint32_t rgba);*
int ncvisual_at_yx(const struct ncvisual n, int y, int x, uint32_t pixel);**
int ncvisual_set_yx(const struct ncvisual n, int y, int x, uint32_t pixel);*
char ncvisual_subtitle(const struct ncvisual ncv);**
int notcurses_lex_scalemode(const char op, ncscale_e scaling);**
const char notcurses_str_scalemode(ncscale_e scaling);*
int notcurses_lex_blitter(const char op, ncblitter_e blitter);**
const char notcurses_str_blitter(ncblitter_e blitter);*
ncblitter_e ncvisual_default_blitter(bool utf8, ncscale_e scaling);
DESCRIPTION
An ncvisual is a virtual pixel framebuffer. They can be created from RGBA/BGRA data in memory (ncvisual_from_rgba/ncvisual_from_bgra), or from the content of a suitable ncplane (ncvisual_from_ncplane). If Notcurses was built against a multimedia engine (FFMpeg or OpenImageIO), image and video files can be loaded into visuals using ncvisual_from_file. ncvisual_from_file discovers the container and codecs, but does not verify that the entire file is well-formed. ncvisual_decode ought be invoked to recover subsequent frames, once per frame. ncvisual_decode_loop will return to the first frame, as if ncvisual_decode had never been called.
Once the visual is loaded, it can be transformed using ncvisual_rotate and ncvisual_resize. These are persistent operations, unlike any scaling that takes place at render time. If a subtitle is associated with the frame, it can be acquired with ncvisual_subtitle.
ncvisual_from_rgba and ncvisual_from_bgra both require a number of rows, a number of image columns cols, and a virtual row length of rowstride / 4 columns. The input data must provide 32 bits per pixel, and thus must be at least rowstride * rows bytes, of which a cols * rows * 4-byte subset is used. It is not possible to mmap(2) an image file and use it directly--decompressed, decoded data is necessary. The resulting plane will be ceil(rows/2) rows, and cols columns. ncvisual_from_plane requires specification of a rectangle via begy, begx, leny, and lenx. The only valid characters within this region are those used by the NCBLIT_2x2 blitter, though this may change in the future.
ncvisual_rotate executes a rotation of rads radians, in the clockwise (positive) or counterclockwise (negative) direction.
ncvisual_subtitle will return a UTF-8-encoded subtitle corresponding to the current frame if such a subtitle was decoded. Note that a subtitle might be returned for multiple frames, or might not.
ncvisual_render blits the visual to an ncplane, based on the contents of its struct ncvisual_options. If n is not NULL, it specifies the plane on which to render, and y/x specify a location within that plane. Otherwise, a new plane will be created, and placed at y/x relative to the rendering area. begy/begx specify the upper left corner of a subsection of the ncvisual to render, while leny/lenx specify the geometry of same. flags is a bitfield over:
- NCVISUAL_OPTION_NODEGRADE If the specified blitter is not available, fail rather than degrading.
- NCVISUAL_OPTION_BLEND: Render with CELL_ALPHA_BLEND.
BLITTERS
The different ncblitter_e values select from among available glyph sets:
- NCBLIT_DEFAULT: Let the ncvisual choose its own blitter.
- NCBLIT_1x1: Spaces only. Works in ASCII, unlike other blitters.
- NCBLIT_2x1: Adds the half blocks (▄▀) to NCBLIT_1x1.
- NCBLIT_2x2: Adds left and right half blocks (▌▐) and quadrants (▖▗▟▙) to NCBLIT_2x1.
- NCBLIT_3x2: Adds sextants to NCBLIT_1x1.
- NCBLIT_4x1: Adds ¼ and ¾ blocks (▂▆) to NCBLIT_2x1.
- NCBLIT_BRAILLE: 4 rows and 2 columns of braille (⡀⡄⡆⡇⢀⣀⣄⣆⣇⢠⣠⣤⣦⣧⢰⣰⣴⣶⣷⢸⣸⣼⣾⣿).
- NCBLIT_8x1: Adds ⅛, ⅜, ⅝, and ⅞ blocks (▇▅▃▁) to NCBLIT_4x1.
- NCBLIT_SIXEL: Not yet implemented.
NCBLIT_4x1 and NCBLIT_8x1 are intended for use with plots, and are not really applicable for general visuals.
RETURN VALUES
notcurses_canopen_images and notcurses_canopen_videos returns true if images and videos, respecitvely, can be decoded, or false if Notcurses was built with insufficient multimedia support.
ncvisual_from_file returns an ncvisual object on success, or NULL on failure. Success indicates that the specified file was opened, and enough data was read to make a firm codec identification. It does not imply that the entire file is properly-formed.
ncvisual_decode returns 0 on success, or 1 on end of file, or -1 on failure. It is only necessary for multimedia-based visuals. It advances one frame for each call. ncvisual_decode_loop has the same return values: when called following decoding of the last frame, it will return 1, but a subsequent ncvisual_render will return the first frame.
ncvisual_from_plane returns NULL if the ncvisual cannot be created and bound. This is usually due to illegal content in the source ncplane.
ncvisual_render returns NULL on error, and otherwise the plane to which the visual was rendered. If opts->n is provided, this will be opts->n. Otherwise, a plane will be created, perfectly sized for the visual and the specified blitter.
ncvisual_geom returns non-zero if the blitter is invalid.
ncvisual_default_blitter returns the blitter selected by NCBLIT_DEFAULT in the specified configuration. If UTF8 is not enabled, this will always be NCBLIT_1x1. Otherwise, if NCSCALE_STRETCH is in use, this will be NCBLIT_3x2; if the scaling is any other value, NCBLIT_2x1 will be used.
NOTES
Multimedia decoding requires that Notcurses be built with either FFmpeg or OpenImageIO support. What formats can be decoded is totally dependent on the linked library. OpenImageIO does not support subtitles.
BUGS
ncvisual_rotate currently supports only M_PI/2 and -M_PI/2 radians for rads, but this will change soon.
NCBLIT_SIXEL is not yet implemented, and is only infrequently supported among terminals.
Bad font support can ruin NCBLIT_2x2, NCBLIT_3x2, NCBLIT_4x1, NCBLIT_BRAILLE, and NCBLIT_8x1.
SEE ALSO
notcurses(3), notcurses_plane(3), utf-8(7)