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Schuwi
227
src/render.rs
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227
src/render.rs
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use crate::projection::OrthoProjection;
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use anyhow::{Context, Result};
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use font8x8::{UnicodeFonts, BASIC_FONTS};
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use plotters::prelude::*;
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use std::path::Path;
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const IMG_WIDTH: u32 = 900;
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const IMG_HEIGHT: u32 = 600;
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/// Map image centre and view window (must match what the Python script used).
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const CENTER_LAT: f64 = 52.56;
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const CENTER_LON: f64 = 13.08;
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const HALF_W_DEG: f64 = 0.8; // horizontal half-extent in degrees of arc
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const HALF_H_DEG: f64 = 0.4; // vertical half-extent
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/// Cloud-cover thresholds and their associated RGB colours.
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/// Values below the first threshold are drawn as the background colour.
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const LEVELS: [(f32, (u8, u8, u8)); 7] = [
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(1.0, (208, 232, 248)), // very thin
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(2.0, (160, 200, 232)),
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(5.0, (112, 168, 216)),
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(10.0, ( 64, 128, 192)),
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(20.0, ( 32, 80, 160)),
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(50.0, ( 16, 32, 96)),
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(100.0, ( 5, 10, 48)),
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];
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const BACKGROUND: RGBColor = RGBColor(240, 248, 255); // pale sky-blue
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const LAND_BG: RGBColor = RGBColor(232, 236, 220); // muted green for land
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const BLACK: RGBColor = RGBColor( 0, 0, 0);
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const RED: RGBColor = RGBColor(220, 30, 30);
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/// Locations to mark on the map: (label, longitude, latitude)
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const LOCATIONS: &[(&str, f64, f64)] = &[
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("Falkensee", 13.08, 52.56),
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("Pausin", 13.04, 52.64),
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("Nauen", 12.88, 52.605),
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("Hennigsdorf", 13.205, 52.64),
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("Ketzin/Brueckenkopf", 12.82, 52.49),
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("Potsdam", 13.06, 52.40),
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("Berlin (Mitte)", 13.39, 52.52),
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];
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fn cloud_color(cover: f32) -> Option<RGBColor> {
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if cover < 1.0 {
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return None; // clear sky — use background
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}
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for &(threshold, (r, g, b)) in LEVELS.iter().rev() {
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if cover >= threshold {
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return Some(RGBColor(r, g, b));
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}
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}
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Some(RGBColor(LEVELS[0].1 .0, LEVELS[0].1 .1, LEVELS[0].1 .2))
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}
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/// Draw ASCII text using the built-in 8×8 pixel font.
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///
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/// Coordinates are in the drawing area's local coordinate system.
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/// `scale` is the pixel-multiplier: 1 → 8×8 px/glyph, 2 → 16×16, etc.
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/// Characters outside Basic Latin are rendered as '?'.
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fn draw_pixel_text(
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area: &DrawingArea<BitMapBackend, plotters::coord::Shift>,
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text: &str,
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x: i32,
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y: i32,
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scale: i32,
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color: &RGBColor,
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) {
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let mut cx = x;
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for ch in text.chars() {
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let glyph_ch = if BASIC_FONTS.get(ch).is_some() { ch } else { '?' };
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if let Some(glyph) = BASIC_FONTS.get(glyph_ch) {
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for (row, &bits) in glyph.iter().enumerate() {
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for col in 0i32..8 {
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if bits & (1 << col) != 0 {
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for dy in 0..scale {
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for dx in 0..scale {
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area.draw_pixel(
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(cx + col * scale + dx, y + row as i32 * scale + dy),
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color,
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)
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.ok();
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}
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}
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}
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}
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}
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}
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cx += 8 * scale;
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}
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}
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/// Render one forecast frame as a PNG.
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///
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/// - `lats`, `lons`, `cloud_cover` must all have the same length.
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/// - `title` is displayed at the top of the image.
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/// - Output is written to `output_path`.
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pub fn render_frame(
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output_path: &Path,
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lats: &[f32],
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lons: &[f32],
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cloud_cover: &[f32],
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title: &str,
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) -> Result<()> {
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let proj = OrthoProjection::new(CENTER_LAT, CENTER_LON, HALF_W_DEG, HALF_H_DEG);
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let root = BitMapBackend::new(output_path, (IMG_WIDTH, IMG_HEIGHT)).into_drawing_area();
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root.fill(&BACKGROUND).context("fill background")?;
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const LEGEND_W: u32 = 130;
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const TITLE_H: u32 = 40;
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const MARGIN: u32 = 8;
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let map_area = root.margin(TITLE_H, MARGIN, MARGIN, LEGEND_W + MARGIN);
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let map_w = IMG_WIDTH - LEGEND_W - MARGIN * 2;
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let map_h = IMG_HEIGHT - TITLE_H - MARGIN * 2;
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map_area.fill(&LAND_BG).context("fill map area")?;
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// Plot grid points
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for i in 0..lats.len() {
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let lat = lats[i] as f64;
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let lon = lons[i] as f64;
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let Some((px, py)) = proj.project(lat, lon) else { continue };
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let Some((col, row)) = proj.to_pixel(px, py, map_w, map_h) else { continue };
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let cover = cloud_cover[i];
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if cover.is_nan() {
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continue; // missing value (bitmap) — keep background
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}
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let color = match cloud_color(cover) {
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Some(c) => c,
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None => continue, // clear sky — keep land background
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};
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// Paint a 2×2 block to avoid gaps between grid points
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for dy in 0..2i32 {
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for dx in 0..2i32 {
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let c = col + dx;
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let r = row + dy;
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if c >= 0 && c < map_w as i32 && r >= 0 && r < map_h as i32 {
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map_area.draw_pixel((c, r), &color).ok();
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}
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}
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}
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}
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// Draw city markers and labels
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for &(label, lon, lat) in LOCATIONS {
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let Some((px, py)) = proj.project(lat, lon) else { continue };
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let Some((col, row)) = proj.to_pixel(px, py, map_w, map_h) else { continue };
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// Small cross marker
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for d in -3i32..=3i32 {
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map_area.draw_pixel((col + d, row), &RED).ok();
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map_area.draw_pixel((col, row + d), &RED).ok();
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}
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// Label offset slightly above and to the right of the marker
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draw_pixel_text(&map_area, label, col + 5, row - 9, 1, &BLACK);
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}
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// Draw title (scale=2 → 16px tall)
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draw_pixel_text(&root, title, MARGIN as i32, (TITLE_H / 2 - 8) as i32, 2, &BLACK);
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// Draw legend
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draw_legend(&root, IMG_WIDTH - LEGEND_W, TITLE_H)?;
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root.present().context("write PNG")?;
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Ok(())
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}
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fn draw_legend(
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root: &DrawingArea<BitMapBackend, plotters::coord::Shift>,
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x: u32,
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y: u32,
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) -> Result<()> {
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draw_pixel_text(root, "Cloud cover", x as i32 + 4, y as i32 + 4, 1, &BLACK);
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let box_h = 18i32;
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let box_w = 24i32;
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// Helper: draw one legend entry
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let draw_entry = |label: &str, color: RGBColor, row_y: i32| {
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root.draw(&Rectangle::new(
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[(x as i32 + 4, row_y), (x as i32 + 4 + box_w, row_y + box_h)],
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ShapeStyle { color: color.to_rgba(), filled: true, stroke_width: 0 },
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))
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.ok();
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root.draw(&Rectangle::new(
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[(x as i32 + 4, row_y), (x as i32 + 4 + box_w, row_y + box_h)],
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ShapeStyle { color: BLACK.to_rgba(), filled: false, stroke_width: 1 },
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))
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.ok();
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draw_pixel_text(
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root,
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label,
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x as i32 + 4 + box_w + 4,
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row_y + (box_h - 8) / 2,
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1,
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&BLACK,
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);
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};
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// "< 1%" row (clear sky)
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draw_entry("< 1%", LAND_BG, y as i32 + 22);
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// Remaining threshold rows — use ASCII hyphen instead of en-dash
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let entries = [
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(1.0f32, "1-2%"),
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(2.0, "2-5%"),
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(5.0, "5-10%"),
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(10.0, "10-20%"),
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(20.0, "20-50%"),
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(50.0, "50-100%"),
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];
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for (i, &(lo, label)) in entries.iter().enumerate() {
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let row_y = y as i32 + 22 + (i as i32 + 1) * (box_h + 2);
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let color = cloud_color(lo).unwrap_or(BACKGROUND);
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draw_entry(label, color, row_y);
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}
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Ok(())
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}
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