Barometer Sheet Generation

barometer.rs

// Exercice on Rust programming:
// Draw an SVG file to replicate this kind of barometric measurement sheet:
// https://www.naudet.com/diagrammes-6mm-c2x15057112

use svg::Document;
use svg::node::element::{Path, Text, Circle, Rectangle, Line};
use svg::node::element::path::Data;

fn main() {
    println!("Génération de feuille barométrique.");

    // All values in millimeters
    let paper_size = (306, 90);
    let arm_length = 185.; // that is the circle radius
    let day_width = 279.5 / 7.;

    let color = "#ff9500"; // #ff9500 is orange-ish

    // Create SVG document
    let header_offset = 50.; // Graph is 80mm, header 10mm, so offset is half a graph plus a full header
    let mut document = Document::new()
        .set("viewBox", (0, -header_offset, paper_size.0, paper_size.1)) // Viewbox centered on the "y=0" line
        .set("width", format!("{}mm", paper_size.0))
        .set("height", format!("{}mm", paper_size.1));

    // Draw days
    let days = vec!["Lundi", "Mardi", "Mercredi", "Jeudi", "Vendredi", "Samedi", "Dimanche", ""]; // One additional day for paper overflow
    for (i, day) in days.into_iter().enumerate() {
        let midday_x = i as f64 * day_width + day_width / 2.;

        // Circles of hours
        for hour in (0..24).step_by(1) {
            let width = if hour == 0 { 1. } else if hour == 12 { 0.5 } else if hour % 2 == 0 { 0.25 } else { 0.1 };
            let hour_circle = Circle::new()
                .set("cx", midday_x + ((hour - 12) as f64) / 24. * day_width + arm_length)
                .set("cy", 0)
                .set("r", arm_length)
                .set("style", format!("fill: none; stroke: {}; stroke-width: {}", color, width));
            document = document.add(hour_circle);
        }

        // Lines of pressure
        let central_pressure = 755;
        let start_pressure = 715;
        let end_pressure = 795;
        let range_mm = 80.;
        for pressure in start_pressure..=end_pressure {
            let width = if pressure % 10 == 0 { 0.3 } else if pressure % 5 == 0 { 0.2 } else { 0.1 };
            let y_pos = -(pressure - central_pressure) as f64 / (end_pressure - start_pressure) as f64 * range_mm;
            let line = Line::new()
                .set("x1", midday_x - day_width / 2. + offset(y_pos, arm_length))
                .set("x2", midday_x + day_width / 2. + offset(y_pos, arm_length))
                .set("y1", y_pos)
                .set("y2", y_pos)
                .set("style", format!("fill: none; stroke: {}; stroke-width: {}", color, width));
            document = document.add(line);
        }

        // Texts of pressure (separated from the lines, to avoid improper objects overlaps)
        for pressure in start_pressure..=end_pressure {
            let y_pos = -(pressure - central_pressure) as f64 / (end_pressure - start_pressure) as f64 * range_mm;
            if pressure % 10 == 0 {
                let background = Rectangle::new()
                    .set("x", midday_x + offset(y_pos, arm_length) - 3.)
                    .set("y", y_pos - 1.5)
                    .set("width", 6)
                    .set("height", 3)
                    .set("fill", "white");
                let text = Text::new()
                    .set("x", midday_x + offset(y_pos, arm_length))
                    .set("y", y_pos + 1.)
                    .set("style", format!("font-size:4px;text-align:center;text-anchor:middle;fill:{};font-family:Trattatello", color))
                    .add(svg::node::Text::new(format!("{}", pressure)));
                document = document.add(background);
                document = document.add(text);
            }
        }

        // Day name
        // It needs a white background to be readable, but a rectangle doesn't look good so I draw
        // a slanted rectangle (parallelogram) to follow the "midnight" arcs in the header
        let x_start = midday_x - day_width / 2. + 1.;
        let data_path_background = Data::new()
            .move_to((x_start + offset(-header_offset, arm_length), -header_offset))
            .line_to((x_start + day_width - 2. + offset(-header_offset, arm_length), -header_offset))
            .line_to((x_start + day_width - 2. + offset(-header_offset + 8., arm_length), -header_offset + 8.))
            .line_to((x_start + offset(-header_offset + 8., arm_length), -header_offset + 8.))
            .close();
        let header_background = Path::new()
            .set("fill", "white")
            .set("stroke", "none")
            .set("d", data_path_background);

        let text = Text::new()
            .set("x", midday_x + offset(-header_offset + 4.5, arm_length))
            .set("y", -header_offset + 4.5)
            .set("style", format!("font-size:7px;text-align:center;text-anchor:middle;fill:{};font-family:Trattatello", color))
            .add(svg::node::Text::new(day.to_uppercase()));
        document = document.add(header_background);
        document = document.add(text);

        // Texts of hours
        for hour in (0..24).skip(2).step_by(2) {
            let text = Text::new()
                .set("x", midday_x + ((hour - 12) as f64) / 24. * day_width + offset(-header_offset + 7.5, arm_length)) // Adding an offset compared to the horizontal line
                .set("y", -header_offset + 7.5)
                .set("style", format!("font-size:3px;text-align:center;text-anchor:middle;fill:{};font-family:Trattatello", color))
                .add(svg::node::Text::new(format!("{}", hour)));
            document = document.add(text);
        }
    }
    svg::save("image.svg", &document).unwrap();
}

// Computes the x-offset depending on the arm's length and the y position
fn offset(y_position: f64, arm_length: f64) -> f64 {
    let angle = f64::asin(y_position / -arm_length);
    let offset = arm_length - (arm_length * f64::cos(angle));
    offset // No trailing semi-colon to return the value
}