add image rendering support

Cargo.toml

@@ -11,6 +11,7 @@ path = "src/cli.rs"
 required-features = ["cli"]
 
 [dependencies]
+image = { version = "0.25.8", optional = true }
 rug = "1.27"
 
 [dependencies.clap]
@@ -21,3 +22,4 @@ optional = true
 [features]
 default = []
 cli = ["dep:clap"]
+image = ["dep:image"]

src/lib.rs

@@ -1,3 +1,6 @@
+#[cfg(feature = "image")]
+use image::{ImageBuffer, Pixel};
+
 use rug::Integer as Int;
 
 #[derive(Debug)]
@@ -45,6 +48,7 @@ impl Dollcode {
         }
 
         out.reverse();
+
         Dollcode(out.into_iter().collect())
     }
 
@@ -94,8 +98,52 @@ impl Dollcode {
         }
 
         out.reverse();
+
         out.into_iter().collect()
     }
+
+    #[cfg(feature = "image")]
+    pub fn render_image<Pix>(&self) -> ImageBuffer<Pix, Vec<u8>>
+    where
+        Pix: Pixel<Subpixel = u8> + 'static,
+    {
+        let char_width = 16u32;
+        let char_height = char_width * 4u32;
+
+        let img_width = ((char_width * 2) * self.0.chars().count() as u32) - char_width;
+        let img_height = char_height;
+
+        let mut dark_pixel =
+            *Pix::from_slice(&vec![Pix::Subpixel::MIN; Pix::CHANNEL_COUNT as usize]);
+        let mut light_pixel =
+            *Pix::from_slice(&vec![Pix::Subpixel::MAX; Pix::CHANNEL_COUNT as usize]);
+
+        if matches!(Pix::CHANNEL_COUNT, 2 | 4) {
+            dark_pixel.channels_mut()[Pix::CHANNEL_COUNT as usize - 1] = Pix::Subpixel::MAX;
+            light_pixel.channels_mut()[Pix::CHANNEL_COUNT as usize - 1] = Pix::Subpixel::MIN;
+        }
+
+        let mut img = ImageBuffer::from_pixel(img_width, img_height, light_pixel);
+
+        for (i, ch) in self.0.chars().enumerate() {
+            let x_offset = (i as u32) * char_width * 2;
+
+            let (x, y, width, height) = match ch {
+                '▖' => (x_offset, char_height / 2, char_width, char_height / 2),
+                '▘' => (x_offset, 0, char_width, char_height / 2),
+                '▌' => (x_offset, 0, char_width, char_height),
+                _ => unreachable!(),
+            };
+
+            for y_ in y..(y + height) {
+                for x_ in x..(x + width) {
+                    img.put_pixel(x_, y_, dark_pixel)
+                }
+            }
+        }
+
+        img
+    }
 }
 
 impl std::str::FromStr for Dollcode {