Inside colourbar¶

use ironlab::prelude::*;

pub const TITLE: &str = "Inside colourbar";
pub const DESCRIPTION: &str = "The elevation of the sea floor around a synthetic volcanic island, which rises from a \
     continental slope falling from 200 m to 4000 m below sea level. The depths are drawn through the cividis colour \
     scale from −4000 to 0 m, shown by a colourbar inside the plot area along its east edge, where the open ocean \
     leaves room for it; the bar stands on a white box so that its ticks read over the field. Land lies above the \
     range of the scale, so it is drawn in one brown, and the bar's key names it. The black line is the coastline.";

/// The number of samples east to west.
const COLUMNS: usize = 201;

/// The number of samples south to north.
const ROWS: usize = 161;

/// Returns the elevation, in metres, at a point `x` kilometres east and `y` kilometres north of the origin.
///
/// The continental slope is a hyperbolic tangent centred 60 km east of the origin, and the island is a Gaussian
/// cone 4600 m high and about 12 km in radius standing on it at (35, 50) km, with a smaller seamount to the south.
fn elevation(x: f64, y: f64) -> f64 {
    let slope = -2100.0 - 1900.0 * ((x - 60.0) / 25.0).tanh();
    let island = 4600.0 * (-((x - 35.0).powi(2) + (y - 50.0).powi(2)) / (2.0 * 12.0_f64.powi(2))).exp();
    let seamount = 1800.0 * (-((x - 70.0).powi(2) + (y - 15.0).powi(2)) / (2.0 * 8.0_f64.powi(2))).exp();
    slope + island + seamount
}

pub fn figure() -> Figure {
    let x = linspace(0.0, 125.0, COLUMNS);
    let y = linspace(0.0, 100.0, ROWS);
    let z = Matrix::from_fn(ROWS, COLUMNS, |row, col| elevation(x[col], y[row]));

    let mut fig = Figure::new()
        .size_mm(150.0, 115.0)
        .title("Bathymetry around a volcanic island")
        .tag("image")
        .tag("contour")
        .tag("color-scale")
        .tag("colorbar")
        .tag("out-of-range")
        .tag("aspect")
        .tag("map")
        .parameter("dimensionality", "2D")
        .parameter("artists", 2)
        .parameter("data_points", 32_723)
        .parameter("has_legend", false);
    let z = fig.data("elevation (m)", z).id();
    let depth = fig
        .color_scale()
        .colormap(Colormap::Cividis)
        .limits(-4000.0, 0.0)
        .above(Color::rgb(0.55, 0.42, 0.28))
        .key_label(ColorScaleKey::Above, "Land")
        .tick_step(1000.0)
        .title("Elevation (m)")
        .id();

    let mut ax = fig.axes(0, 0);
    ax.scalar_image(z)
        .pixel_columns(x[0], x[COLUMNS - 1])
        .pixel_rows(y[0], y[ROWS - 1])
        .color_scale(depth);
    ax.contour(&x, &y, z)
        .level_values([0.0])
        .color(Color::BLACK)
        .line_width(0.75);
    ax.colorbar(depth, InsideColorbarSide::East).length(0.7);
    ax.xlabel("Distance east (km)")
        .ylabel("Distance north (km)")
        .aspect(Aspect::Equal);
    fig
}