egui/examples/save_plot/src/main.rs

#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release

use eframe::egui;
use eframe::egui::ColorImage;
use egui_plot::{Legend, Line, Plot, PlotPoints};

fn main() -> Result<(), eframe::Error> {
    env_logger::init(); // Log to stderr (if you run with `RUST_LOG=debug`).

    let options = eframe::NativeOptions {
        initial_window_size: Some(egui::vec2(350.0, 200.0)),
        ..Default::default()
    };
    eframe::run_native(
        "My egui App with a plot",
        options,
        Box::new(|_cc| Box::<MyApp>::default()),
    )
}

#[derive(Default)]
struct MyApp {
    screenshot: Option<ColorImage>,
}

impl eframe::App for MyApp {
    fn update(&mut self, ctx: &egui::Context, frame: &mut eframe::Frame) {
        let mut plot_rect = None;
        egui::CentralPanel::default().show(ctx, |ui| {
            if ui.button("Save Plot").clicked() {
                frame.request_screenshot();
            }

            let my_plot = Plot::new("My Plot").legend(Legend::default());

            // let's create a dummy line in the plot
            let graph: Vec<[f64; 2]> = vec![[0.0, 1.0], [2.0, 3.0], [3.0, 2.0]];
            let inner = my_plot.show(ui, |plot_ui| {
                plot_ui.line(Line::new(PlotPoints::from(graph)).name("curve"));
            });
            // Remember the position of the plot
            plot_rect = Some(inner.response.rect);
        });

        if let (Some(screenshot), Some(plot_location)) = (self.screenshot.take(), plot_rect) {
            if let Some(mut path) = rfd::FileDialog::new().save_file() {
                path.set_extension("png");

                // for a full size application, we should put this in a different thread,
                // so that the GUI doesn't lag during saving

                let pixels_per_point = frame.info().native_pixels_per_point;
                let plot = screenshot.region(&plot_location, pixels_per_point);
                // save the plot to png
                image::save_buffer(
                    &path,
                    plot.as_raw(),
                    plot.width() as u32,
                    plot.height() as u32,
                    image::ColorType::Rgba8,
                )
                .unwrap();
            }
        }
    }

    fn post_rendering(&mut self, _screen_size_px: [u32; 2], frame: &eframe::Frame) {
        // this is inspired by the Egui screenshot example
        if let Some(screenshot) = frame.screenshot() {
            self.screenshot = Some(screenshot);
        }
    }
}