open-standards/wai/wai-vector/tests/raster.rs

//! The raster stage family RS1–RS9 and the frame procedure (§3.5–§3.11): the values
//! and properties each test names, on the vectors of `vector-conformance/` and on
//! shapes built here. Reference values for the negative-coordinate and fold cases come
//! from review A's independent implementation of §3.3–§3.8.

use wai_vector::arith::div255;
use wai_vector::cover::{self, Cov};
use wai_vector::frame::{render, render_request};
use wai_vector::geom::Pt;
use wai_vector::refuse::Code;
use wai_vector::vectors::raster::{comb, height_for_alpha, j3_triples};
use wai_vector::vectors::{corpus_store, find};
use wai_vector::wvg1::{self, Loaded};

fn load(group: &str, name: &str) -> Loaded {
    let v = find(group, name).unwrap_or_else(|| panic!("no vector {group}/{name}"));
    wvg1::load(&v.bytes, &mut corpus_store()).unwrap_or_else(|e| panic!("{group}/{name}: {e:?}"))
}

fn closed(pts: &[(i64, i64)]) -> Vec<Pt> {
    let mut v: Vec<Pt> = pts.iter().map(|&(x, y)| [x, y]).collect();
    v.push(v[0]);
    v
}

fn dense(c: &Cov, w: i64, h: i64) -> Vec<Vec<i32>> {
    (0..h).map(|r| (0..w).map(|x| c.at(x, r)).collect()).collect()
}

/// Rows and cells at negative coordinates: the crossings are floors of negative
/// rationals. The values are review A's `core.py` on the same polygons.
#[test]
fn rows_and_cells_at_negative_coordinates() {
    let a = closed(&[(-700, -300), (900, 200), (300, 1100), (-1000, 800)]);
    let want_a = vec![
        vec![-131072, -111416, -70656, -18200, 0],
        vec![-131072, -131072, -122332, -13254, 0],
        vec![-131072, -131072, -48384, 0, 0],
        vec![-131072, -91706, -117, 0, 0],
        vec![-18176, -10004, 0, 0, 0],
    ];
    assert_eq!(dense(&cover::accumulate(&[a], 5, 5, 4), 5, 5), want_a);
    let c = closed(&[(-1500, -1300), (700, -200), (-301, 1333)]);
    let want_c = vec![vec![-131072, -112482, -4959, 0], vec![-130379, -32558, 0, 0], vec![-77312, 0, 0, 0], vec![-6834, 0, 0, 0], vec![0; 4], vec![0; 4]];
    assert_eq!(dense(&cover::accumulate(&[c], 4, 6, 3), 4, 6), want_c);
}

/// The left fold: a fill crossing the left edge has, on every canvas pixel, the
/// values of the same fill moved 8 pixels right onto a wider canvas, unclipped.
#[test]
fn the_left_fold() {
    let d = [(-1800, 100), (600, 350), (200, 900), (-2600, 700)];
    let folded = cover::accumulate(&[closed(&d)], 4, 4, 4);
    let moved: Vec<(i64, i64)> = d.iter().map(|&(x, y)| (x + 8 * 256, y)).collect();
    let wide = cover::accumulate(&[closed(&moved)], 12, 4, 4);
    for r in 0..4 {
        for c in 0..4 {
            assert_eq!(folded.at(c, r), wide.at(c + 8, r), "pixel ({c}, {r})");
        }
    }
    // review A's core.py on the same polygon.
    assert_eq!(dense(&folded, 4, 4), vec![vec![0, 0, 0, 0], vec![-108288, -93460, -11440, 0], vec![-131072, -68096, 0, 0], vec![-60272, -2200, 0, 0]]);
    // A contour wholly left of the canvas folds to zero sums: it draws nothing (P5).
    let left = cover::accumulate(&[closed(&[(-30_000, 1_000), (-25_000, 1_000), (-26_000, 3_000)])], 4, 4, 3);
    assert!(left.v.iter().all(|&x| x == 0));
}

/// A-F5's triangle pins `v_k`: the snapped polygon's area, `|v|` = 1280 and 512 in its
/// two pixels, not the outline's (1152 and 384).
#[test]
fn triangle_pins_v_to_the_snapped_polygon() {
    let t = cover::accumulate(&[closed(&[(0, 0), (512, 3), (0, 3)])], 4, 1, 3);
    let v = [t.at(0, 0).abs(), t.at(1, 0).abs()];
    assert_eq!(v, [1280, 512]);
    assert_ne!(v, [1152, 384], "an exact-area value");
    // The vector renders the same: alpha 2 and 1 in a white fill.
    let l = load("fills", "triangle-af5");
    let px = render(&l, 0, 0, 0).unwrap();
    assert_eq!(&px[0..8], &[2, 2, 2, 2, 1, 1, 1, 1]);
}

/// The glyph-wise union: three glyphs of one run abutting mid-pixel leave no seam; two
/// runs abutting composite by source-over and do.
#[test]
fn abutting_run_seam_pixel_is_255() {
    let l = load("runs", "abutting");
    let px = render(&l, 0, 0, 0).unwrap();
    let w = 16;
    // Glyph 1 spans x [0, 384) and y [512, 1536): rows 2..=5. The glyphs at 0, 384 and
    // 768 meet mid-pixel at x = 384 (column 1); the last ends at 1152, half of column 4.
    for r in 2..6 {
        let at = 4 * (r * w + 1);
        assert_eq!(&px[at..at + 4], &[255, 255, 255, 255], "the seam at (1, {r})");
        let at = 4 * (r * w + 4);
        assert_eq!(&px[at..at + 4], &[128, 128, 128, 128], "half of (4, {r})");
    }
    // The same two glyphs in two runs: source-over at the seam, 128 + div255(128·127).
    let l = load("runs", "two-runs");
    let px = render(&l, 0, 0, 0).unwrap();
    let at = 4 * (2 * w + 1);
    let over = 128 + div255(128 * 127) as u8;
    assert_eq!(&px[at..at + 4], &[over; 4], "across runs the seam returns");
    assert!(over < 255);
}

/// J3's discriminating triples: each pixel has the frozen fill order's bytes,
/// `div255(div255(p·o)·α)`, which the other order does not give.
#[test]
fn j3_triples_and_group_isolation() {
    let l = load("composite", "j3-triples");
    let px = render(&l, 0, 0, 0).unwrap();
    for (i, (p, o, a)) in j3_triples().into_iter().enumerate() {
        assert!(height_for_alpha(a) > 0);
        let frozen = div255(div255(u32::from(p) * u32::from(o)) * u32::from(a)) as u8;
        let other = div255(u32::from(p) * div255(u32::from(a) * u32::from(o))) as u8;
        assert_ne!(frozen, other);
        let at = 4 * (2 * i);
        assert_eq!(&px[at..at + 4], &[frozen; 4], "triple {i}: ({p}, {o}, {a})");
    }
    // Isolation: the overlap of two opaque fills in a group at 128 is the top fill at
    // half, div255(c·128), the group composited as one layer.
    let l = load("composite", "isolation");
    let px = render(&l, 0, 0, 0).unwrap();
    let at = 4 * (16 * 3 + 7);
    let green = [40u32, 180, 80, 255].map(|c| div255(c * 128) as u8);
    assert_eq!(&px[at..at + 4], &green);
}

/// P1: reversing every contour of a fill changes no byte of any frame.
#[test]
fn whole_fill_reversal_changes_nothing() {
    let mut n = 0;
    for name in ["rect", "hole", "star-nonzero", "star-evenodd", "random-0", "random-1", "random-2", "random-3", "curves"] {
        let (a, b) = (load("fills", name), load("fills", &format!("{name}-reversed")));
        assert_ne!(a.doc.write(), b.doc.write());
        for z in 0..a.doc.sizes.len() {
            assert_eq!(render(&a, z, 0, 0).unwrap(), render(&b, z, 0, 0).unwrap(), "{name}");
            n += 1;
        }
    }
    assert_eq!(n, 9);
}

/// P2: a roll at an integer speed with keys on frame ticks: frame k is frame 0 moved
/// up 2k pixels at the design size and 4k at twice it.
#[test]
fn integer_speed_roll_shifts_whole_pixels() {
    let l = load("motion", "roll-integer");
    for (z, step) in [(0usize, 2usize), (1, 4)] {
        let (w, h) = (l.doc.sizes[z].w as usize, l.doc.sizes[z].h as usize);
        let f0 = render(&l, z, 0, 0).unwrap();
        for k in 1..10u64 {
            let fk = render(&l, z, 0, k).unwrap();
            let s = step * k as usize;
            for r in 0..h {
                let want: &[u8] = if r + s < h { &f0[4 * w * (r + s)..4 * w * (r + s + 1)] } else { &[0u8; 0] };
                let got = &fk[4 * w * r..4 * w * (r + 1)];
                if want.is_empty() {
                    assert!(got.iter().all(|&x| x == 0), "size {z}, frame {k}, row {r}: below the moved content");
                } else {
                    assert_eq!(got, want, "size {z}, frame {k}, row {r}");
                }
            }
        }
    }
}

/// P7: each piece's frames equal the whole's at the same frame number.
#[test]
fn slicing_piece_frames_equal_the_whole() {
    let whole = load("slicing", "whole");
    let mut n = 0;
    for i in 0..3 {
        let p = load("slicing", &format!("piece-{i}"));
        for (r, rate) in p.doc.rates.iter().enumerate() {
            let ticks = rate.ticks_per_frame(p.doc.header.tb);
            for g in wai_vector::clock::frames(p.doc.header.t0, p.doc.header.dur, ticks) {
                assert_eq!(render(&p, 0, r, g).unwrap(), render(&whole, 0, r, g).unwrap(), "piece {i}, rate {r}, frame {g}");
                n += 1;
            }
        }
    }
    assert_eq!(n, 90);
}

/// §3.7: the comb of 16,382 points attains `D_r = 256·p`, and renders with every
/// value in `i32` (a debug build checks each addition).
#[test]
fn the_comb_attains_the_density_bound() {
    let pts: Vec<Pt> = comb(16_382, 0, 1, 512, 768).iter().map(|p| [i64::from(p.x), i64::from(p.y)]).chain(std::iter::once([0, 512])).collect();
    let d = cover::row_density(std::slice::from_ref(&pts), 0, 15);
    assert_eq!(d[2], 256 * 16_382);
    assert_eq!(d.iter().copied().max(), Some(256 * 16_382));
    let c = cover::accumulate(&[pts], 64, 16, 16_382);
    assert!(c.v.iter().all(|&x| x.unsigned_abs() <= 512 * 256 * 16_382));
    let l = load("fills", "comb-16382");
    render(&l, 0, 0, 0).unwrap();
    let l = load("fills", "points-16383");
    render(&l, 0, 0, 0).unwrap();
}

/// The density assertion is live: a comb of 16,384 points, built here past the cap a
/// payload enforces, attains `D_r = 2^22 > 2^22 − 256`, and a debug build stops it.
#[cfg(debug_assertions)]
#[test]
#[should_panic(expected = "D_r = 4194304")]
fn the_density_assertion_fires_past_the_cap() {
    let pts: Vec<Pt> = comb(16_384, 0, 1, 512, 768).iter().map(|p| [i64::from(p.x), i64::from(p.y)]).chain(std::iter::once([0, 512])).collect();
    cover::accumulate(&[pts], 64, 16, 16_384);
}

/// The render request errors, and the frame range by division.
#[test]
fn render_requests() {
    let l = load("motion", "roll-integer");
    assert!(render_request(&l, 160, 90, 25, 1, 0).is_ok());
    assert_eq!(render_request(&l, 161, 90, 25, 1, 0).unwrap_err().code, Code::SizeUnlisted);
    assert_eq!(render_request(&l, 160, 90, 30, 1, 0).unwrap_err().code, Code::RateUnlisted);
    assert_eq!(render_request(&l, 160, 90, 25, 1, 10).unwrap_err().code, Code::FrameRange);
    assert_eq!(render_request(&l, 160, 90, 25, 1, u64::MAX).unwrap_err().code, Code::FrameRange);
}

/// RS9 and P4: every rendered pixel has `R, G, B ≤ A`, and the straight-alpha view is
/// `R_rat(255·c, A)`.
#[test]
fn premultiplied_closure_and_the_straight_view() {
    for (g, n) in [("composite", "groups-depth-4"), ("composite", "overlap-opacity"), ("composite", "group-pop"), ("motion", "lower-third")] {
        let l = load(g, n);
        let px = render(&l, 0, 0, 0).unwrap();
        assert!(px.as_chunks::<4>().0.iter().all(|p| p[0] <= p[3] && p[1] <= p[3] && p[2] <= p[3]), "{n}");
        let s = wai_vector::paint::unpremul_buffer(&px);
        for (p, q) in px.as_chunks::<4>().0.iter().zip(s.as_chunks::<4>().0) {
            if p[3] == 0 {
                assert_eq!(q, &[0, 0, 0, 0]);
            } else {
                for ch in 0..3 {
                    assert_eq!(i64::from(q[ch]), wai_vector::arith::r_rat(255 * i64::from(p[ch]), i64::from(p[3])));
                }
            }
        }
    }
}