wcloud 0.1.0

Generate beautiful word clouds with support for masks, custom fonts, custom coloring functions, and more.
Documentation 
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// Naive implementation of a summed-area table
// https://en.wikipedia.org/wiki/Summed-area_table
use nanorand::{Rng, WyRand};

#[cfg(feature = "visualize")]
use std::io::{BufWriter, stdout, Write};
#[cfg(feature = "visualize")]
use crate::visualize::{Message, CheckRect};

#[derive(Debug, Copy, Clone)]
pub struct Region {
    pub x: u32,
    pub y: u32,
    pub width: u32,
    pub height: u32,
}

#[derive(Debug)]
pub struct Rect {
    pub width: u32,
    pub height: u32,
}

#[derive(Clone, Debug)]
pub struct Point {
    pub x: u32,
    pub y: u32,
}

pub fn region_is_empty(table: &[u32], table_width: usize, x: usize, y: usize, width: usize, height: usize) -> bool {
    let tl = table[y * table_width + x];
    let tr = table[y * table_width + x + width];

    let bl = table[(y + height) * table_width + x];
    let br = table[(y + height) * table_width + x + width];

    tl as i32 + br as i32 - tr as i32 - bl as i32 == 0
}

pub fn find_space_for_rect(
    table: &[u32],
    table_width: u32,
    table_height: u32,
    rect: &Rect,
    rng: &mut WyRand,
) -> Option<Point> {
    let max_x = table_width - rect.width;
    let max_y = table_height - rect.height;

    let mut available_points = 0;
    let mut random_point = None;

    #[cfg(feature = "visualize")]
    let mut visualize_buf = BufWriter::new(stdout());

    for y in 0..max_y {
        for x in 0..max_x {
            let empty = region_is_empty(table, table_width as usize, x as usize, y as usize, rect.width as usize, rect.height as usize);

            #[cfg(feature = "visualize")]
            {
                let serialized = serde_json::to_string(&Message::CheckRectMessage(CheckRect {
                    x,
                    y,
                    empty,
                })).unwrap();
                writeln!(visualize_buf, "{}", serialized).unwrap();
            };

            if empty {
                // https://en.wikipedia.org/wiki/Reservoir_sampling
                let random_num = rng.generate_range(0..=available_points);
                if random_num == available_points {
                    random_point = Some(Point { x, y });
                }
                available_points += 1;
            }
        }
    }

    random_point
}

pub fn find_space_for_rect_masked(
    table: &[u32],
    table_width: u32,
    table_height: u32,
    skip_list: &[(usize, usize)],
    rect: &Rect,
    rng: &mut WyRand,
) -> Option<Point> {
    let max_x = table_width - rect.width;
    let max_y = table_height - rect.height;

    let mut available_points = 0;
    let mut random_point = None;

    #[cfg(feature = "visualize")]
    let mut visualize_buf = BufWriter::new(stdout());

    for y in 0..max_y {
        let (furthest_right, furthest_left) = skip_list[y as usize];
        for x in furthest_right..furthest_left.min(max_x as usize) {
            let empty = region_is_empty(table, table_width as usize, x, y as usize, rect.width as usize, rect.height as usize);

            #[cfg(feature = "visualize")]
            {
                let serialized = serde_json::to_string(&Message::CheckRectMessage(CheckRect {
                    x: x as u32,
                    y,
                    empty,
                })).unwrap();
                writeln!(visualize_buf, "{}", serialized).unwrap();
            };

            if empty {
                // https://en.wikipedia.org/wiki/Reservoir_sampling
                let random_num: u32 = rng.generate_range(0..=available_points);
                if random_num == available_points {
                    random_point = Some(Point { x: x as u32, y });
                }
                available_points += 1;
            }
        }
    }

    // println!("stopped_at: {} / {}", stopped_at, available_points);
    // println!("{}", available_points);

    random_point
}

pub fn to_summed_area_table(table: &mut [u32], width: usize, start_row: usize) {
    let mut prev_row = vec![0; width];

    table
        .chunks_exact_mut(width)
        .skip(start_row)
        .for_each(|row| {
            let mut sum = 0;
            row.iter_mut()
                .zip(prev_row.iter())
                .for_each(|(el, prev_row_el)| {
                    let original_value = *el;
                    *el += sum + prev_row_el;
                    sum += original_value;
                });

            prev_row.clone_from_slice(row);
        });
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn simplest_sat() {
        let mut table = [1, 1, 1, 1, 1, 1, 1, 1, 1];
        to_summed_area_table(&mut table, 3, 0);

        let expected = [1, 2, 3, 2, 4, 6, 3, 6, 9];
        assert_eq!(table, expected);
    }

    #[test]
    fn simple_sat() {
        let mut table = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 100, 200, 300, 400, 500, 600];
        to_summed_area_table(&mut table, 4, 0);

        let expected = [
            1, 3, 6, 10, 6, 14, 24, 36, 15, 33, 143, 355, 315, 733, 1343, 2155,
        ];
        assert_eq!(table, expected);
    }
    #[test]
    fn uneven_sat() {
        let mut table = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 100, 200, 300, 400, 500, 600];
        to_summed_area_table(&mut table, 8, 0);

        let expected = [
            1, 3, 6, 10, 15, 21, 28, 36, 10, 22, 125, 329, 634, 1040, 1547, 2155,
        ];
        assert_eq!(table, expected);
    }
}