From 6d2f9a023792af127e53d90d3f34aeecd33fbb3b Mon Sep 17 00:00:00 2001
From: julianknodt <julianknodt@gmail.com>
Date: Wed, 21 Jul 2021 18:14:47 -0700
Subject: [PATCH] Add example for quantization

This adds an example for the result of quantizing, which can be used to manually verify
correctness.
---
 examples/quantize.rs | 66 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 examples/quantize.rs

diff --git a/examples/quantize.rs b/examples/quantize.rs
new file mode 100644
index 0000000..b7109eb
--- /dev/null
+++ b/examples/quantize.rs
@@ -0,0 +1,66 @@
+#![feature(array_chunks)]
+
+extern crate color_quant;
+
+use color_quant::NeuQuant;
+use std::fs::write;
+
+fn main() {
+    let header = b"P6\n256\n256\n255\n";
+    let mut pixels = vec![0; 4 * 256 * 256];
+    let mut r: u8 = 0;
+    let mut g: u8 = 0;
+    let mut b: u8 = 0;
+
+    for (i, p) in pixels.iter_mut().enumerate() {
+        match i % 4 {
+            0 => *p = r,
+            1 => *p = g,
+            2 => {
+                *p = b;
+                if let Some(next_r) = r.checked_add(1) {
+                    r = next_r;
+                    continue;
+                }
+                r = 0;
+                if let Some(next_g) = g.checked_add(1) {
+                    g = next_g;
+                    continue;
+                }
+                g = 0;
+                b += 1
+            }
+            3 => *p = 255,
+            _ => unreachable!(),
+        }
+    }
+    let raw = &header
+        .into_iter()
+        .chain(
+            pixels
+                .array_chunks::<4>()
+                .map(|[r, g, b, _a]| [r, g, b])
+                .flatten(),
+        )
+        .copied()
+        .collect::<Vec<u8>>();
+    write("img.ppm", raw).expect("Failed to write");
+    let nq = NeuQuant::new(10, 256, &pixels);
+
+    let quantized = &header
+        .into_iter()
+        .copied()
+        .chain(
+            pixels
+                .array_chunks::<4>()
+                .map(|&[r, g, b, a]| {
+                    let mut color = [r, g, b, a];
+                    nq.map_pixel(&mut color[..]);
+                    let [r, g, b, _a] = color;
+                    [r, g, b]
+                })
+                .flatten(),
+        )
+        .collect::<Vec<u8>>();
+    write("quantized.ppm", quantized).expect("Failed to write");
+}