ezu-paint 0.3.0

Paint GIS features onto a hokusai surface for ezu
Documentation 
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//! Gradient nodes: linear, radial, conic, diamond.

mod common;
use common::render;

#[test]
fn gradient_linear_top_to_bottom() {
    // Vertical black-to-white gradient. Top row is black, bottom row is white.
    let json = r##"{
      "name": "demo",
      "tile-size": 16,
      "nodes": {
        "out": {
          "op": "gradient-linear",
          "start": [0, 0], "end": [0, 1],
          "stops": [[0, "#000000"], [1, "#ffffff"]]
        }
      },
      "output": "@out"
    }"##;
    let r = render(json, 16, 0);
    assert!(
        r.pixel(8, 0)[0] < 16,
        "top row should be black: {:?}",
        r.pixel(8, 0)
    );
    assert!(
        r.pixel(8, 15)[0] > 240,
        "bottom row should be white: {:?}",
        r.pixel(8, 15)
    );
    // Middle row should be roughly grey.
    let mid = r.pixel(8, 8)[0];
    assert!(
        (mid as i32 - 128).abs() < 16,
        "mid should be grey, got {mid}"
    );
}

#[test]
fn gradient_radial_center_to_edge() {
    let json = r##"{
      "name": "demo",
      "tile-size": 16,
      "nodes": {
        "out": {
          "op": "gradient-radial",
          "center": [0.5, 0.5], "radius": 0.5,
          "stops": [[0, "#ffffff"], [1, "#000000"]]
        }
      },
      "output": "@out"
    }"##;
    let r = render(json, 16, 0);
    let center = r.pixel(8, 8)[0];
    let corner = r.pixel(0, 0)[0];
    // Pixel sample center is offset by 0.5 from `[0.5, 0.5]`, so the
    // closest pixel is slightly off-center but still mostly white.
    assert!(center > 220, "center should be near white: {center}");
    assert!(
        corner < 32,
        "corner past radius should be near black: {corner}"
    );
}

#[test]
fn gradient_conic_sweeps_around_center() {
    // A full red→green→blue→red sweep. At 0° (right of center), red;
    // at 180° (left of center), should reach mid-stop colors.
    let json = r##"{
      "name": "demo",
      "tile-size": 32,
      "nodes": {
        "out": {
          "op": "gradient-conic",
          "center": [0.5, 0.5],
          "stops": [[0, "#ff0000"], [0.333, "#00ff00"], [0.667, "#0000ff"], [1, "#ff0000"]]
        }
      },
      "output": "@out"
    }"##;
    let r = render(json, 32, 0);
    // Pixel to the right of center (ang ~ 0): red dominant.
    let right = r.pixel(24, 16);
    assert!(
        right[0] > 200 && right[1] < 64 && right[2] < 64,
        "right should be red: {right:?}"
    );
}

#[test]
fn gradient_diamond_has_axis_aligned_corners() {
    let json = r##"{
      "name": "demo",
      "tile-size": 16,
      "nodes": {
        "out": {
          "op": "gradient-diamond",
          "center": [0.5, 0.5], "radius": 0.5,
          "stops": [[0, "#ffffff"], [1, "#000000"]]
        }
      },
      "output": "@out"
    }"##;
    let r = render(json, 16, 0);
    // Diamond: the four cardinal-direction tips (at distance 0.5 along
    // an axis) reach t=1 (black). The corner (0.5+0.5=1.0 Manhattan
    // distance from center / 0.5 radius = 2.0 → clamped to 1 → black).
    assert!(r.pixel(8, 8)[0] > 200, "center should be near white");
    assert!(r.pixel(0, 0)[0] < 32, "corner should be near black");
    // A pixel halfway to the tip along an axis: Manhattan ~0.25, t ~0.5 → grey.
    let half = r.pixel(8, 4)[0];
    assert!(
        (half as i32 - 128).abs() < 40,
        "axial half should be grey, got {half}"
    );
}