Span sprites

The compact run-length sprite format (sprite4): plain, scaled, recoloured and rotated. More...

Functions
void	gfx_sprite4 (const uint8_t *spr, int x, int y, const uint8_t *remap=nullptr, int scale=256)
	Draws a span sprite, optionally recoloured and scaled.
static int	gfx_sprite4W (const uint8_t *spr)
	A span sprite's width.
static int	gfx_sprite4H (const uint8_t *spr)
	A span sprite's height.
void	gfx_sprite4Rot (const uint8_t *spr, int ax, int ay, int px, int py, uint8_t angle, int scale=256, const uint8_t *remap=nullptr)
	Draws a span sprite rotated and scaled about a pivot.

Detailed Description

The compact run-length sprite format (sprite4): plain, scaled, recoloured and rotated.

The compact sprite format two CHGame titles arrived at independently. Each row is a list of runs of one colour, so the art is small and a run is a fill, not a pixel loop:

w, h, then per row:  n, then n bytes of  (len - 1) << 4 | colour

Runs are 1..16 px. Colour 15 is transparent (a skip), and trailing transparency is left out. extras/sprite4.py packs a PNG.

Every pixel is drawn through remap[colour] (nullptr = as is), so ONE image serves many looks: a team colour, a red damage flash, a white hit flash, a solid silhouette for an outline. With 16 colours, palette swapping is the natural way to get variety.

#include "slime.h"   // python extras/sprite4.py slime.png SLIME > slime.h
gfx_sprite4(SLIME, 40, 60);                // as drawn
gfx_sprite4(SLIME, 40, 60, redFlash);      // through a 16-entry remap
gfx_sprite4(SLIME, 40, 60, nullptr, 512);  // double size

Function Documentation

gfx_sprite4()

void gfx_sprite4	(	const uint8_t *	spr,
		int	x,
		int	y,
		const uint8_t *	remap = nullptr,
		int	scale = 256
	)

Draws a span sprite, optionally recoloured and scaled.

Scaling is nearest neighbour, about the top-left corner. 1:1 has its own fast path, so leave it at 256 unless you mean it.

Parameters

spr	The sprite data (w, h, then the rows of runs).
x	Left edge on screen.
y	Top edge on screen.
remap	16 palette indices to draw each colour as, or nullptr (the default) for the colours as they are.
scale	Q8 scale: 256 = 1:1 (the default), 512 = double, 128 = half. 0 or less draws nothing.

gfx_sprite4W()

static int gfx_sprite4W ( const uint8_t *  spr )

inlinestatic

A span sprite's width.

Parameters

spr	The sprite data.

Returns

Its width in pixels, at 1:1.

gfx_sprite4H()

static int gfx_sprite4H ( const uint8_t *  spr )

inlinestatic

A span sprite's height.

Parameters

spr	The sprite data.

Returns

Its height in pixels, at 1:1.

gfx_sprite4Rot()

void gfx_sprite4Rot	(	const uint8_t *	spr,
		int	ax,
		int	ay,
		int	px,
		int	py,
		uint8_t	angle,
		int	scale = 256,
		const uint8_t *	remap = nullptr
	)

Draws a span sprite rotated and scaled about a pivot.

The sprite's pixel (ax, ay) lands on screen at (px, py), turned by angle and scaled by scale. The art is decoded into gfx_chunkScratch(), so it must fit in 1 KB at 4 bpp (32x64, 45x45; a larger sprite draws nothing) and this call waits for any flush in flight first. Per pixel, so costlier than gfx_sprite4().

Parameters

spr	The sprite data.
ax	Pivot column in the sprite.
ay	Pivot row in the sprite.
px	Screen column the pivot lands on.
py	Screen row the pivot lands on.
angle	Rotation, 256 = a full turn, clockwise on screen.
scale	Q8 scale, 256 = 1:1 (the default); below 8 counts as 8, 0 or less draws nothing.
remap	16 palette indices to draw each colour as, or nullptr.