gfx_subpixel.h File Reference

gfx's anti-aliased disc, capsule and ring placed in fractions of a pixel. More...

#include "gfx.h"

Go to the source code of this file.

Functions
void	gfx_fill_circle_aaf (gfx_canvas_t *c, float cx, float cy, float r, gfx_color_t col)
	A disc of radius r centred on (cx, cy), anti-aliased from each pixel's distance to the centre.
void	gfx_capsule_aaf (gfx_canvas_t *c, float ax, float ay, float bx, float by, float thickness, gfx_color_t col)
	A capsule, a thick line with round ends, from (ax, ay) to (bx, by), anti-aliased from each pixel's distance to its spine.
void	gfx_ring_aaf (gfx_canvas_t *c, float cx, float cy, float r, float thickness, float a0_deg, float a1_deg, gfx_color_t col, gfx_color_t into, float fade_deg)
	A ring, or an arc of one, solved per pixel from its distance and direction to the centre.

Detailed Description

gfx's anti-aliased disc, capsule and ring placed in fractions of a pixel.

The whole-pixel shapes of gfx.h jump a pixel at a time when the thing they draw moves: a servo horn turning by a tenth of a degree moves its tip by a sixth of a pixel and is drawn where it was, then a pixel further. These take their centres, ends, radii and widths as floats and blend their edge pixels from the exact distance, so a shape that moves by a tenth of a pixel changes its edge pixels' coverage by about a tenth. At whole numbers the disc and the capsule give the same pixels as gfx_fill_circle_aa() and gfx_capsule_aa(), which are drawn through them.

They follow gfx.h's contracts: everything clips to canvas->clip, and coverage is blended per call.

SPDX-License-Identifier: MIT

Function Documentation

gfx_capsule_aaf()

void gfx_capsule_aaf	(	gfx_canvas_t *	c,
		float	ax,
		float	ay,
		float	bx,
		float	by,
		float	thickness,
		gfx_color_t	col )

A capsule, a thick line with round ends, from (ax, ay) to (bx, by), anti-aliased from each pixel's distance to its spine.

Parameters

c	the canvas
ax	one end's column, px
ay	its row, px
bx	the other end's column, px
by	its row, px
thickness	the width, px; 0 or less draws nothing
col	the colour

gfx_fill_circle_aaf()

void gfx_fill_circle_aaf	(	gfx_canvas_t *	c,
		float	cx,
		float	cy,
		float	r,
		gfx_color_t	col )

A disc of radius r centred on (cx, cy), anti-aliased from each pixel's distance to the centre.

Parameters

c	the canvas
cx	the centre's column, px
cy	the centre's row, px
r	the radius, px; 0 or less draws nothing
col	the colour

gfx_ring_aaf()

void gfx_ring_aaf	(	gfx_canvas_t *	c,
		float	cx,
		float	cy,
		float	r,
		float	thickness,
		float	a0_deg,
		float	a1_deg,
		gfx_color_t	col,
		gfx_color_t	into,
		float	fade_deg )

A ring, or an arc of one, solved per pixel from its distance and direction to the centre.

gfx_arc_fade() walks its arc and rounds each step to a pixel. This one blends the band's two edges and the arc's two ends over half a pixel either side, the ends measured along the arc at each pixel's radius. A span of 360deg or more is the whole ring. A pixel whose centre lies half a pixel or more beyond the band or past an end is not touched.

Parameters

c	the canvas
cx	the centre's column, px
cy	the centre's row, px
r	the band's middle radius, px
thickness	the band's width, px
a0_deg	one end, degrees counter-clockwise from +x (90 is up)
a1_deg	the other end, degrees
col	the colour
into	the colour each end fades from over fade_deg
fade_deg	the fade's length, degrees; 0 for none