png file support

src/palette.rs

@@ -2,6 +2,8 @@ use std::fs::read_to_string;
 use std::path::PathBuf;
 use serde_derive::{Serialize, Deserialize};
 use crate::colour::Colour;
+use image::{GenericImageView, Rgba, DynamicImage, Rgb, GenericImage};
+use image::io::Reader as ImageReader;
 
 /// todo enumerate original format
 #[derive(Debug, Eq, PartialEq, Serialize, Deserialize)]
@@ -153,6 +155,39 @@ impl Palette {
 
         format!("{}\r\n", colours.join("\r\n"))
     }
+
+    pub fn from_png(path: PathBuf) -> Self {
+        let name = path.file_stem().unwrap().to_str().unwrap().into();
+        let image = ImageReader::open(path).unwrap().decode().unwrap();
+
+        let mut colours: Vec<Rgba<u8>> = Vec::new();
+
+        for (_x, _y, pixel) in image.pixels() {
+            if !colours.contains(&pixel) {
+                colours.push(pixel);
+            }
+        }
+
+        let colours = colours.iter().map(|colour|
+            Colour { red: colour.0[0], green: colour.0[1], blue: colour.0[2] }
+        ).collect();
+
+        // todo preserve original image?
+        Self { name, colours }
+    }
+
+    pub fn to_png(&self) -> DynamicImage {
+        let mut image = DynamicImage::new_rgb8(
+            self.colours.len() as u32, 1 as u32
+        );
+
+        for (x, colour) in self.colours.iter().enumerate() {
+            let pixel = Rgba::from([colour.red, colour.green, colour.blue, 255]);
+            image.put_pixel(x as u32, 0, pixel);
+        }
+
+        image
+    }
 }
 
 /// for toml purposes
@@ -261,6 +296,24 @@ mod test {
         assert_eq!(output, expected);
     }
 
+    #[test]
+    fn palette_from_png() {
+        let path = PathBuf::from("src/test-resources/basic/palettes/soup11.png");
+        let output = Palette::from_png(path);
+        let expected = crate::mock::palette::soup11();
+        assert_eq!(output, expected);
+    }
+
+    #[test]
+    fn palette_to_png() {
+        use image::io::Reader as ImageReader;
+
+        let output = crate::mock::palette::soup11().to_png();
+        let path = PathBuf::from("src/test-resources/basic/palettes/soup11.png");
+        let expected = ImageReader::open(path).unwrap().decode().unwrap();
+        assert_eq!(output, expected);
+    }
+
     #[test]
     fn palette_from_toml() {
         let output = Palette::from(