embedded-3dgfx 0.5.2

3D graphics rendering for embedded systems (fork of embedded-gfx by Kezii)
Documentation 
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#[cfg(feature = "aa")]
use core::fmt::Debug;
#[cfg(feature = "aa")]
use embedded_graphics_core::draw_target::DrawTarget;
#[cfg(feature = "aa")]
use embedded_graphics_core::pixelcolor::{Rgb565, RgbColor};
#[cfg(feature = "aa")]
use embedded_graphics_core::prelude::Point;

#[cfg(feature = "aa")]
use crate::raster::aa::ReadPixel;

/// Component-wise blend in 8-bit fixed-point coverage.
/// `coverage_q8` ∈ [0, 256]; 256 = full line color, 0 = full background.
#[cfg(feature = "aa")]
#[inline(always)]
fn blend_q8(bg: Rgb565, fg: Rgb565, coverage_q8: u32) -> Rgb565 {
    let inv = 256 - coverage_q8;
    let r = (bg.r() as u32 * inv + fg.r() as u32 * coverage_q8) >> 8;
    let g = (bg.g() as u32 * inv + fg.g() as u32 * coverage_q8) >> 8;
    let b = (bg.b() as u32 * inv + fg.b() as u32 * coverage_q8) >> 8;
    Rgb565::new(r as u8, g as u8, b as u8)
}

#[cfg(feature = "aa")]
#[inline(always)]
fn plot_aa<D>(fb: &mut D, x: i32, y: i32, color: Rgb565, coverage_q8: u32)
where
    D: DrawTarget<Color = Rgb565> + ReadPixel,
    <D as DrawTarget>::Error: Debug,
{
    if coverage_q8 == 0 {
        return;
    }
    let final_color = if coverage_q8 >= 256 {
        color
    } else {
        let bg = fb.read_pixel(Point::new(x, y));
        blend_q8(bg, color, coverage_q8)
    };
    fb.draw_iter([embedded_graphics_core::Pixel(Point::new(x, y), final_color)])
        .unwrap();
}

/// Wu's anti-aliased line algorithm.
///
/// Walks the major axis one integer step at a time; at each step writes two
/// pixels straddling the line with complementary fractional coverage.
#[cfg(feature = "aa")]
pub fn draw_line_aa<D>(x0: i32, y0: i32, x1: i32, y1: i32, color: Rgb565, fb: &mut D)
where
    D: DrawTarget<Color = Rgb565> + ReadPixel,
    <D as DrawTarget>::Error: Debug,
{
    let dx = (x1 - x0).abs();
    let dy = (y1 - y0).abs();
    let steep = dy > dx;
    let (x0, y0, x1, y1) = if steep {
        (y0, x0, y1, x1)
    } else {
        (x0, y0, x1, y1)
    };
    let (x0, y0, x1, y1) = if x0 > x1 {
        (x1, y1, x0, y0)
    } else {
        (x0, y0, x1, y1)
    };
    let dx = x1 - x0;
    let dy = y1 - y0;
    if dx == 0 {
        // Single pixel
        let (px, py) = if steep { (y0, x0) } else { (x0, y0) };
        plot_aa(fb, px, py, color, 256);
        return;
    }
    // 16.16 fixed-point gradient
    let gradient: i32 = ((dy as i64) << 16) as i32 / dx;
    // Start at exact (x0, y0); intery accumulates the y position in 16.16.
    let mut intery: i32 = y0 << 16;
    for x in x0..=x1 {
        let y_int = intery >> 16;
        let frac_q16 = (intery & 0xFFFF) as u32;
        let cov_top = 256 - (frac_q16 >> 8); // pixel at y_int
        let cov_bot = frac_q16 >> 8; //         pixel at y_int + 1
        if steep {
            plot_aa(fb, y_int, x, color, cov_top);
            plot_aa(fb, y_int + 1, x, color, cov_bot);
        } else {
            plot_aa(fb, x, y_int, color, cov_top);
            plot_aa(fb, x, y_int + 1, color, cov_bot);
        }
        intery += gradient;
    }
}