Pixels and framebuffer modes

PixelRAM supports four software framebuffer formats.

Mode	Bytes per pixel	Use
pixel_indexed8	1	Palette graphics and classic effects
pixel_rgb565	2	Compact 16-bit direct color
pixel_rgb24	3	24-bit RGB
pixel_rgba32	4	32-bit RGBA

Indexed pixels

In pixel_indexed8, the framebuffer stores one palette index per pixel.

set_pixel(20, 10, 15);
uint8_t color = get_pixel(20, 10);

set_pixel() ignores coordinates outside the screen. get_pixel() returns 0 for coordinates outside the screen. This behavior is intentional: neighborhood filters can read around the edges without special boundary code.

set_pixel() and get_pixel() operate only in pixel_indexed8 mode.

Use clear() to fill the entire indexed framebuffer with one palette index:

clear(0);

Direct-color pixels

Use set_pixel_rgb() in one of the RGB modes:

set_pixel_rgb(20, 10, 255, 80, 20);

Use clear_rgb() to fill the whole framebuffer in pixel_rgb565, pixel_rgb24, or pixel_rgba32 mode:

clear_rgb(20, 40, 80);

clear_rgb() does nothing in indexed mode; use clear() with a palette index there. In RGBA32 mode it writes alpha as 255.

get_pixel_rgb() works in every mode. In indexed mode it resolves the stored palette index to its current RGB color.

uint8_t r, g, b;
if (get_pixel_rgb(20, 10, &r, &g, &b)) {
    /* use r, g and b */
}

Changing mode

screen_set_mode(320, 200, pixel_rgb565);

Changing mode replaces the framebuffer, so retrieve its address again if you previously stored it:

uint16_t *pixels = framebuffer();