From 4e8ce5bbaf5aa71f7e00e7a131fc6b25e623c992 Mon Sep 17 00:00:00 2001 From: Daniel Schadt Date: Sat, 11 Mar 2023 19:38:16 +0100 Subject: abstract away tile rendering logic This is in prepration for the tilehunt mode, where we want to render tiles differently. --- src/renderer/heatmap.rs | 209 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 209 insertions(+) create mode 100644 src/renderer/heatmap.rs (limited to 'src/renderer/heatmap.rs') diff --git a/src/renderer/heatmap.rs b/src/renderer/heatmap.rs new file mode 100644 index 0000000..c4af7a6 --- /dev/null +++ b/src/renderer/heatmap.rs @@ -0,0 +1,209 @@ +//! Actual rendering functions for heatmaps. +//! +//! We begin the rendering by using [`render_heatcounter`] to turn a list of GPX tracks into a +//! [`HeatCounter`], which is basically a grayscale heatmap, where each pixel represents the number +//! of tracks that goes through this pixel. +//! +//! We then render the colored heatmap tiles using [`lazy_colorization`], which provides us with +//! colorful PNG data. +use color_eyre::{eyre::Result, Report}; +use crossbeam_channel::Sender; +use image::{ImageBuffer, Luma, Pixel, RgbaImage}; +use nalgebra::{vector, Vector2}; +use rayon::iter::ParallelIterator; + +use super::{ + super::{ + gpx::Coordinates, + layer::{self, TileLayer}, + }, + RenderedTile, +}; + +/// Type for the intermediate heat counters. +pub type HeatCounter = TileLayer>; + +fn render_circle(layer: &mut TileLayer

, center: (u64, u64), radius: u64, pixel: P) { + let topleft = (center.0 - radius, center.1 - radius); + let rad_32: u32 = radius.try_into().unwrap(); + let mut circle = ImageBuffer::>::new(rad_32 * 2 + 1, rad_32 * 2 + 1); + imageproc::drawing::draw_filled_circle_mut( + &mut circle, + ( + i32::try_from(radius).unwrap(), + i32::try_from(radius).unwrap(), + ), + radius.try_into().unwrap(), + pixel, + ); + layer.blit_nonzero(topleft.0, topleft.1, &circle); +} + +fn direction_vector(a: (u64, u64), b: (u64, u64)) -> Vector2 { + let dx = if b.0 > a.0 { + (b.0 - a.0) as f64 + } else { + -((a.0 - b.0) as f64) + }; + let dy = if b.1 > a.1 { + (b.1 - a.1) as f64 + } else { + -((a.1 - b.1) as f64) + }; + vector![dx, dy] +} + +fn render_line( + layer: &mut TileLayer

, + start: (u64, u64), + end: (u64, u64), + thickness: u64, + pixel: P, +) { + use imageproc::point::Point; + + if start == end { + return; + } + + fn unsigned_add(a: Vector2, b: Vector2) -> Vector2 { + let x = if b[0] < 0 { + a[0] - u64::from(b[0].unsigned_abs()) + } else { + a[0] + u64::try_from(b[0]).unwrap() + }; + let y = if b[1] < 0 { + a[1] - u64::from(b[1].unsigned_abs()) + } else { + a[1] + u64::try_from(b[1]).unwrap() + }; + vector![x, y] + } + + let r = direction_vector(start, end); + let normal = vector![r[1], -r[0]].normalize(); + + let start = vector![start.0, start.1]; + let end = vector![end.0, end.1]; + + let displacement = normal * thickness as f64; + let displacement = displacement.map(|x| x as i32); + if displacement == vector![0, 0] { + return; + } + let polygon = [ + unsigned_add(start, displacement), + unsigned_add(end, displacement), + unsigned_add(end, -displacement), + unsigned_add(start, -displacement), + ]; + let min_x = polygon.iter().map(|p| p[0]).min().unwrap(); + let min_y = polygon.iter().map(|p| p[1]).min().unwrap(); + let max_x = polygon.iter().map(|p| p[0]).max().unwrap(); + let max_y = polygon.iter().map(|p| p[1]).max().unwrap(); + + let mut overlay = ImageBuffer::>::new( + (max_x - min_x).try_into().unwrap(), + (max_y - min_y).try_into().unwrap(), + ); + let adjusted_poly = polygon + .into_iter() + .map(|p| Point::new((p[0] - min_x) as i32, (p[1] - min_y) as i32)) + .collect::>(); + imageproc::drawing::draw_polygon_mut(&mut overlay, &adjusted_poly, pixel); + + layer.blit_nonzero(min_x, min_y, &overlay); +} + +fn merge_heat_counter(base: &mut HeatCounter, overlay: &HeatCounter) { + for (tx, ty, source) in overlay.enumerate_tiles() { + let target = base.tile_mut(tx, ty); + for (x, y, source) in source.enumerate_pixels() { + let target = target.get_pixel_mut(x, y); + target[0] += source[0]; + } + } +} + +fn colorize_tile(tile: &ImageBuffer, Vec>, max: u32) -> RgbaImage { + let gradient = colorgrad::yl_or_rd(); + let mut result = ImageBuffer::from_pixel(tile.width(), tile.height(), [0, 0, 0, 0].into()); + for (x, y, pixel) in tile.enumerate_pixels() { + if pixel[0] > 0 { + let alpha = pixel[0] as f64 / max as f64; + let color = gradient.at(1.0 - alpha); + let target = result.get_pixel_mut(x, y); + *target = color.to_rgba8().into(); + } + } + result +} + +#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)] +pub struct Renderer; + +impl super::Renderer for Renderer { + type Prepared = HeatCounter; + + /// Renders the heat counter for the given zoom level and track points. + /// + /// The given callback will be called when a track has been rendered and merged into the + /// accumulator, to allow for UI feedback. The passed parameter is the number of tracks that have + /// been rendered since the last call. + fn prepare(zoom: u32, tracks: &[Vec], tick: Sender<()>) -> Result { + let mut heatcounter = TileLayer::from_pixel([0].into()); + + for track in tracks { + let mut layer = TileLayer::from_pixel([0].into()); + + let points = track + .iter() + .map(|coords| coords.web_mercator(zoom)) + .collect::>(); + + for point in points.iter() { + render_circle(&mut layer, *point, (zoom as u64 / 4).max(2) - 1, [1].into()); + } + + for (a, b) in points.iter().zip(points.iter().skip(1)) { + render_line(&mut layer, *a, *b, (zoom as u64 / 4).max(1), [1].into()); + } + + merge_heat_counter(&mut heatcounter, &layer); + tick.send(()).unwrap(); + } + Ok(heatcounter) + } + + /// Lazily colorizes a [`HeatCounter`] by colorizing it tile-by-tile and saving a tile before + /// rendering the next one. + /// + /// This function calls the given callback with each rendered tile, and the function is responsible + /// for saving it. If the callback returns an `Err(...)`, the error is passed through. + /// + /// Note that this function internally uses `rayon` for parallization. If you want to limit the + /// number of threads used, set up the global [`rayon::ThreadPool`] first. + fn colorize(layer: HeatCounter, tx: Sender) -> Result<()> { + let max = layer.pixels().map(|l| l.0[0]).max().unwrap_or_default(); + if max == 0 { + return Ok(()); + } + + layer + .into_parallel_tiles() + .try_for_each_with(tx, |tx, (tile_x, tile_y, tile)| { + let colorized = colorize_tile(&tile, max.into()); + let data = layer::compress_png_as_bytes(&colorized)?; + tx.send(RenderedTile { + x: tile_x, + y: tile_y, + data, + })?; + Ok::<(), Report>(()) + }) + } + + fn tile_count(layer: &HeatCounter) -> Result { + Ok(layer.tile_count().try_into().unwrap()) + } +} -- cgit v1.2.3