pixtra 0.2.5

Pixtra aims to be a very simple and easy-to-use image manipulation tool by being opionated and contain a lot of examples
Documentation 
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use crate::canvas::Canvas;
use crate::pixels::Pixel;
use std::cmp;
use std::collections::HashMap;

pub fn to_grey_lightness(p: &Pixel) -> Pixel {
    let lightness = max(p.r, p.g, p.b) + min(p.r, p.g, p.b) / 2;
    from_grey(lightness)
}

pub fn to_grey_average(p: &Pixel) -> Pixel {
    let average = (p.r + p.g + p.b) / 3;
    from_grey(average)
}

pub fn to_grey_lumiosity(p: &Pixel) -> Pixel {
    to_grey_custom(p, 0.21, 0.72, 0.07)
}

// Used for finding error
pub fn to_grey_mean(p: &Pixel) -> Pixel {
    to_grey_custom(p, 0.299, 0.587, 0.114)
}

pub fn to_grey_custom(p: &Pixel, v1: f32, v2: f32, v3: f32) -> Pixel {
    let value = (p.r as f32 * v1 + p.g as f32 * v2 + p.b as f32 * v3) as u8;
    from_grey(value)
}

pub fn from_grey(grey: u8) -> Pixel {
    Pixel {
        r: grey,
        g: grey,
        b: grey,
        a: 255,
    }
}

/// Three way maximum function
pub fn max<T>(v1: T, v2: T, v3: T) -> T
where
    T: Ord,
{
    cmp::max(v1, cmp::max(v2, v3))
}

/// Three way minimum function
pub fn min<T>(v1: T, v2: T, v3: T) -> T
where
    T: Ord,
{
    cmp::min(v1, cmp::min(v2, v3))
}

/// Clamp value `value` to be between `min` and `max`.
/// `min` needs to be less than `max`
pub fn clamp<T: PartialOrd>(min: T, max: T, val: T) -> T {
    assert!(min < max);
    if val > max {
        return max;
    }
    if val < min {
        return min;
    }
    val
}

pub fn find_center_and_size(canvas: &Canvas) -> (Pixel, f32) {
    let (center_r, max_r) = center(&canvas, |p| p.r);
    let (center_g, max_g) = center(&canvas, |p| p.g);
    let (center_b, max_b) = center(&canvas, |p| p.b);
    let (center_a, max_a) = center(&canvas, |p| p.a);
    let center = Pixel::new(center_r, center_g, center_b, center_a);
    let corner = Pixel::new(max_r, max_g, max_b, max_a);
    let distance = center.distance(&corner);

    (center, distance)
}

fn center<F>(canvas: &Canvas, map_color: F) -> (u8, u8) 
where F: Fn(Pixel) -> u8{
    let min = canvas.iter().map(|p| map_color(p)).min().unwrap();
    let max = canvas.iter().map(|p| map_color(p)).max().unwrap();
    ((max - min) / 2 + min, max)
}

pub fn diff_squared(p1: &Pixel, p2: &Pixel) -> (u32, u32, u32, u32) {
    (
        (p1.r - p2.r).pow(2).into(),
        (p1.g - p2.g).pow(2).into(),
        (p1.b - p2.b).pow(2).into(),
        (p1.a - p2.a).pow(2).into(),
    )
}

// TODO: We can do this with a fold and hashmap, right?
pub fn count_colors(c: &Canvas) -> HashMap<Pixel, usize> {
    let mut map = HashMap::new();
    for pixel in c.pixels() {
        *map.entry(pixel.clone()).or_insert(0) += 1;
    }
    map
}

pub fn counted_colors_to_html(map: &HashMap<Pixel, usize>) -> String {
    let mut pairs: Vec<(Pixel, usize)> = map.iter().map(|(x, y)| (x.clone(), y.clone())).collect();
    pairs.sort_by_key(|x| x.1);
    pairs.reverse();
    let output: String = pairs.iter().map(|x| format!("<tr> <td> {} </td> <td bgcolor=\"RGB({}, {}, {})\"> ({}, {}, {}) </td> </tr>", x.1, x.0.r, x.0.g, x.0.b, x.0.r, x.0.g, x.0.b).to_string()).collect();
    output
}

pub fn diff(c1: &Canvas, c2: &Canvas) -> Canvas {
    let c = Canvas::new(1, 1);
    c
}

pub fn diff_debug(c1: &Canvas, c2: &Canvas) -> Canvas {
    let c1_dim = c1.dimensions();
    let c2_dim = c2.dimensions();
    let res = if c1_dim.width == c2_dim.width && c1_dim.height == c2_dim.height {
        let pixels = c1
            .pixels()
            .zip(c2.pixels())
            .map(|(p1, p2)| p1.diff(p2))
            .collect();
        Canvas::new_with_data(c1_dim.width, c1_dim.height, pixels)
    } else {
        c1.clone()
    };
    res
}

// https://stackoverflow.com/questions/20271479/what-does-it-mean-to-get-the-mse-mean-error-squared-for-2-images
pub fn error(c1: &Canvas, c2: &Canvas) -> u128 {
    let c1_dim = c1.dimensions();
    let c2_dim = c2.dimensions();
    let width = c1_dim.width.min(c2_dim.width);
    let height = c1_dim.height.min(c2_dim.height);
    let (mut r, mut g, mut b, mut a) = (0u128, 0u128, 0u128, 0u128);
    // TODO: Get iterator from both, zip them and fold and then map
    for x in 0..width {
        for y in 0..height {
            let p1 = c1.get_pixel(x, y);
            let p2 = c2.get_pixel(x, y);
            let diff = p1.diff(&p2);
            r += (diff.r as u128).pow(2) as u128;
            g += (diff.g as u128).pow(2) as u128;
            b += (diff.b as u128).pow(2) as u128;
            a += (diff.a as u128).pow(2) as u128;
        }
    }
    (r + g + b + a) / ((4 * width * height) as u128)
}

// TODO: Should these exist here or only in the Canvas as private members?
pub fn apply_alpha_color(
    source_color: f32,
    source_alpha: f32,
    destination_color: f32,
    _destination_alpha: f32,
) -> f32 {
    source_color * source_alpha + destination_color * (1.0f32 - source_alpha)
}

//TODO: RENAME
// We draw source onto destination
pub fn overlap_colors(destination: &Pixel, source: &Pixel) -> Pixel {
    /*if source.a == 255 {
        return source.clone();
    }*/
    let source_normalized = source.normalize();
    let destination_normalized = destination.normalize();
    let new_r = apply_alpha_color(
        source_normalized.0,
        source_normalized.3,
        destination_normalized.0,
        destination_normalized.3,
    );
    let new_g = apply_alpha_color(
        source_normalized.1,
        source_normalized.3,
        destination_normalized.1,
        destination_normalized.3,
    );
    let new_b = apply_alpha_color(
        source_normalized.2,
        source_normalized.3,
        destination_normalized.2,
        destination_normalized.3,
    );
    let new_a = apply_alpha_color(
        source_normalized.3,
        source_normalized.3,
        destination_normalized.3,
        destination_normalized.3,
    );

    Pixel::denormalize(new_r, new_g, new_b, new_a)
}

pub fn merge_chunks_vertically(chunks: &Vec<Canvas>) -> Canvas {
    let width = chunks.iter().map(|x| x.dimensions().width).max().unwrap_or_default(); 
    let height = chunks.iter().map(|x| x.dimensions().height).sum();
    let mut vec = vec![0];
    chunks.iter().map(|x| x.dimensions().height).fold(0, |acc, x| { vec.push(acc + x); acc + x });

    let mut canvas = Canvas::new(width, height);
    for (i, e) in chunks.iter().enumerate() {
        canvas.set_subimage_mut(0, vec[i], e);
    }
    canvas
}

pub fn merge_chunks_horizontally(chunks: &Vec<Canvas>) -> Canvas {
    let height = chunks.iter().map(|x| x.dimensions().height).max().unwrap_or_default(); 
    let width = chunks.iter().map(|x| x.dimensions().width).sum();
    let mut vec = vec![0];
    chunks.iter().map(|x| x.dimensions().width).fold(0, |acc, x| { vec.push(acc + x); acc + x });

    let mut canvas = Canvas::new(width, height);
    for (i, e) in chunks.iter().enumerate() {
        canvas.set_subimage_mut(vec[i], 0,  e);
    }
    canvas
}