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 <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/image-0.23.14/./src/imageops/colorops.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>colorops.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="../../../source-script.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../image/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../image/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span>
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 </pre><pre class="rust"><code><span class="doccomment">//! Functions for altering and converting the color of pixelbufs

 </span><span class="kw">use </span>num_traits::{Bounded, Num, NumCast};
 <span class="kw">use </span>std::f64::consts::PI;

 <span class="kw">use </span><span class="kw">crate</span>::color::{Luma, Rgba};
 <span class="kw">use </span><span class="kw">crate</span>::image::{GenericImage, GenericImageView};
 <span class="attribute">#[allow(deprecated)]
 </span><span class="kw">use </span><span class="kw">crate</span>::math::nq;
 <span class="kw">use </span><span class="kw">crate</span>::traits::{Pixel, Primitive};
 <span class="kw">use </span><span class="kw">crate</span>::utils::clamp;
 <span class="kw">use </span><span class="kw">crate</span>::ImageBuffer;

 <span class="kw">type </span>Subpixel&lt;I&gt; = &lt;&lt;I <span class="kw">as </span>GenericImageView&gt;::Pixel <span class="kw">as </span>Pixel&gt;::Subpixel;

 <span class="doccomment">/// Convert the supplied image to grayscale
 </span><span class="kw">pub fn </span>grayscale&lt;I: GenericImageView&gt;(image: <span class="kw-2">&amp;</span>I) -&gt; ImageBuffer&lt;Luma&lt;Subpixel&lt;I&gt;&gt;, Vec&lt;Subpixel&lt;I&gt;&gt;&gt;
 <span class="kw">where
     </span>Subpixel&lt;I&gt;: <span class="lifetime">&#39;static</span>,
     &lt;Subpixel&lt;I&gt; <span class="kw">as </span>Num&gt;::FromStrRadixErr: <span class="lifetime">&#39;static</span>,
 {
     <span class="kw">let </span>(width, height) = image.dimensions();
     <span class="kw">let </span><span class="kw-2">mut </span>out = ImageBuffer::new(width, height);

     <span class="kw">for </span>y <span class="kw">in </span><span class="number">0</span>..height {
         <span class="kw">for </span>x <span class="kw">in </span><span class="number">0</span>..width {
             <span class="kw">let </span>p = image.get_pixel(x, y).to_luma();
             out.put_pixel(x, y, p);
         }
     }

     out
 }

 <span class="doccomment">/// Invert each pixel within the supplied image.
 /// This function operates in place.
 </span><span class="kw">pub fn </span>invert&lt;I: GenericImage&gt;(image: <span class="kw-2">&amp;mut </span>I) {
     <span class="kw">let </span>(width, height) = image.dimensions();

     <span class="kw">for </span>y <span class="kw">in </span><span class="number">0</span>..height {
         <span class="kw">for </span>x <span class="kw">in </span><span class="number">0</span>..width {
             <span class="kw">let </span><span class="kw-2">mut </span>p = image.get_pixel(x, y);
             p.invert();

             image.put_pixel(x, y, p);
         }
     }
 }

 <span class="doccomment">/// Adjust the contrast of the supplied image.
 /// ```contrast``` is the amount to adjust the contrast by.
 /// Negative values decrease the contrast and positive values increase the contrast.
 ///
 /// *[See also `contrast_in_place`.][contrast_in_place]*
 </span><span class="kw">pub fn </span>contrast&lt;I, P, S&gt;(image: <span class="kw-2">&amp;</span>I, contrast: f32) -&gt; ImageBuffer&lt;P, Vec&lt;S&gt;&gt;
 <span class="kw">where
     </span>I: GenericImageView&lt;Pixel = P&gt;,
     P: Pixel&lt;Subpixel = S&gt; + <span class="lifetime">&#39;static</span>,
     S: Primitive + <span class="lifetime">&#39;static</span>,
 {
     <span class="kw">let </span>(width, height) = image.dimensions();
     <span class="kw">let </span><span class="kw-2">mut </span>out = ImageBuffer::new(width, height);

     <span class="kw">let </span>max = S::max_value();
     <span class="kw">let </span>max: f32 = NumCast::from(max).unwrap();

     <span class="kw">let </span>percent = ((<span class="number">100.0 </span>+ contrast) / <span class="number">100.0</span>).powi(<span class="number">2</span>);

     <span class="kw">for </span>y <span class="kw">in </span><span class="number">0</span>..height {
         <span class="kw">for </span>x <span class="kw">in </span><span class="number">0</span>..width {
             <span class="kw">let </span>f = image.get_pixel(x, y).map(|b| {
                 <span class="kw">let </span>c: f32 = NumCast::from(b).unwrap();

                 <span class="kw">let </span>d = ((c / max - <span class="number">0.5</span>) * percent + <span class="number">0.5</span>) * max;
                 <span class="kw">let </span>e = clamp(d, <span class="number">0.0</span>, max);

                 NumCast::from(e).unwrap()
             });

             out.put_pixel(x, y, f);
         }
     }

     out
 }

 <span class="doccomment">/// Adjust the contrast of the supplied image in place.
 /// ```contrast``` is the amount to adjust the contrast by.
 /// Negative values decrease the contrast and positive values increase the contrast.
 ///
 /// *[See also `contrast`.][contrast]*
 </span><span class="kw">pub fn </span>contrast_in_place&lt;I&gt;(image: <span class="kw-2">&amp;mut </span>I, contrast: f32)
 <span class="kw">where
     </span>I: GenericImage,
 {
     <span class="kw">let </span>(width, height) = image.dimensions();

     <span class="kw">let </span>max = &lt;&lt;I::Pixel <span class="kw">as </span>Pixel&gt;::Subpixel <span class="kw">as </span>Bounded&gt;::max_value();
     <span class="kw">let </span>max: f32 = NumCast::from(max).unwrap();

     <span class="kw">let </span>percent = ((<span class="number">100.0 </span>+ contrast) / <span class="number">100.0</span>).powi(<span class="number">2</span>);

     <span class="kw">for </span>y <span class="kw">in </span><span class="number">0</span>..height {
         <span class="kw">for </span>x <span class="kw">in </span><span class="number">0</span>..width {
             <span class="kw">let </span>f = image.get_pixel(x, y).map(|b| {
                 <span class="kw">let </span>c: f32 = NumCast::from(b).unwrap();

                 <span class="kw">let </span>d = ((c / max - <span class="number">0.5</span>) * percent + <span class="number">0.5</span>) * max;
                 <span class="kw">let </span>e = clamp(d, <span class="number">0.0</span>, max);

                 NumCast::from(e).unwrap()
             });

             image.put_pixel(x, y, f);
         }
     }
 }

 <span class="doccomment">/// Brighten the supplied image.
 /// ```value``` is the amount to brighten each pixel by.
 /// Negative values decrease the brightness and positive values increase it.
 ///
 /// *[See also `brighten_in_place`.][brighten_in_place]*
 </span><span class="kw">pub fn </span>brighten&lt;I, P, S&gt;(image: <span class="kw-2">&amp;</span>I, value: i32) -&gt; ImageBuffer&lt;P, Vec&lt;S&gt;&gt;
 <span class="kw">where
     </span>I: GenericImageView&lt;Pixel = P&gt;,
     P: Pixel&lt;Subpixel = S&gt; + <span class="lifetime">&#39;static</span>,
     S: Primitive + <span class="lifetime">&#39;static</span>,
 {
     <span class="kw">let </span>(width, height) = image.dimensions();
     <span class="kw">let </span><span class="kw-2">mut </span>out = ImageBuffer::new(width, height);

     <span class="kw">let </span>max = S::max_value();
     <span class="kw">let </span>max: i32 = NumCast::from(max).unwrap();

     <span class="kw">for </span>y <span class="kw">in </span><span class="number">0</span>..height {
         <span class="kw">for </span>x <span class="kw">in </span><span class="number">0</span>..width {
             <span class="kw">let </span>e = image.get_pixel(x, y).map_with_alpha(
                 |b| {
                     <span class="kw">let </span>c: i32 = NumCast::from(b).unwrap();
                     <span class="kw">let </span>d = clamp(c + value, <span class="number">0</span>, max);

                     NumCast::from(d).unwrap()
                 },
                 |alpha| alpha,
             );

             out.put_pixel(x, y, e);
         }
     }

     out
 }

 <span class="doccomment">/// Brighten the supplied image in place.
 /// ```value``` is the amount to brighten each pixel by.
 /// Negative values decrease the brightness and positive values increase it.
 ///
 /// *[See also `brighten`.][brighten]*
 </span><span class="kw">pub fn </span>brighten_in_place&lt;I&gt;(image: <span class="kw-2">&amp;mut </span>I, value: i32)
 <span class="kw">where
     </span>I: GenericImage,
 {
     <span class="kw">let </span>(width, height) = image.dimensions();

     <span class="kw">let </span>max = &lt;&lt;I::Pixel <span class="kw">as </span>Pixel&gt;::Subpixel <span class="kw">as </span>Bounded&gt;::max_value();
     <span class="kw">let </span>max: i32 = NumCast::from(max).unwrap();

     <span class="kw">for </span>y <span class="kw">in </span><span class="number">0</span>..height {
         <span class="kw">for </span>x <span class="kw">in </span><span class="number">0</span>..width {
             <span class="kw">let </span>e = image.get_pixel(x, y).map_with_alpha(
                 |b| {
                     <span class="kw">let </span>c: i32 = NumCast::from(b).unwrap();
                     <span class="kw">let </span>d = clamp(c + value, <span class="number">0</span>, max);

                     NumCast::from(d).unwrap()
                 },
                 |alpha| alpha,
             );

             image.put_pixel(x, y, e);
         }
     }
 }

 <span class="doccomment">/// Hue rotate the supplied image.
 /// `value` is the degrees to rotate each pixel by.
 /// 0 and 360 do nothing, the rest rotates by the given degree value.
 /// just like the css webkit filter hue-rotate(180)
 ///
 /// *[See also `huerotate_in_place`.][huerotate_in_place]*
 </span><span class="kw">pub fn </span>huerotate&lt;I, P, S&gt;(image: <span class="kw-2">&amp;</span>I, value: i32) -&gt; ImageBuffer&lt;P, Vec&lt;S&gt;&gt;
 <span class="kw">where
     </span>I: GenericImageView&lt;Pixel = P&gt;,
     P: Pixel&lt;Subpixel = S&gt; + <span class="lifetime">&#39;static</span>,
     S: Primitive + <span class="lifetime">&#39;static</span>,
 {
     <span class="kw">let </span>(width, height) = image.dimensions();
     <span class="kw">let </span><span class="kw-2">mut </span>out = ImageBuffer::new(width, height);

     <span class="kw">let </span>angle: f64 = NumCast::from(value).unwrap();

     <span class="kw">let </span>cosv = (angle * PI / <span class="number">180.0</span>).cos();
     <span class="kw">let </span>sinv = (angle * PI / <span class="number">180.0</span>).sin();
     <span class="kw">let </span>matrix: [f64; <span class="number">9</span>] = [
         <span class="comment">// Reds
         </span><span class="number">0.213 </span>+ cosv * <span class="number">0.787 </span>- sinv * <span class="number">0.213</span>,
         <span class="number">0.715 </span>- cosv * <span class="number">0.715 </span>- sinv * <span class="number">0.715</span>,
         <span class="number">0.072 </span>- cosv * <span class="number">0.072 </span>+ sinv * <span class="number">0.928</span>,
         <span class="comment">// Greens
         </span><span class="number">0.213 </span>- cosv * <span class="number">0.213 </span>+ sinv * <span class="number">0.143</span>,
         <span class="number">0.715 </span>+ cosv * <span class="number">0.285 </span>+ sinv * <span class="number">0.140</span>,
         <span class="number">0.072 </span>- cosv * <span class="number">0.072 </span>- sinv * <span class="number">0.283</span>,
         <span class="comment">// Blues
         </span><span class="number">0.213 </span>- cosv * <span class="number">0.213 </span>- sinv * <span class="number">0.787</span>,
         <span class="number">0.715 </span>- cosv * <span class="number">0.715 </span>+ sinv * <span class="number">0.715</span>,
         <span class="number">0.072 </span>+ cosv * <span class="number">0.928 </span>+ sinv * <span class="number">0.072</span>,
     ];
     <span class="kw">for </span>(x, y, pixel) <span class="kw">in </span>out.enumerate_pixels_mut() {
         <span class="kw">let </span>p = image.get_pixel(x, y);
         <span class="kw">let </span>(k1, k2, k3, k4) = p.channels4();
         <span class="kw">let </span>vec: (f64, f64, f64, f64) = (
             NumCast::from(k1).unwrap(),
             NumCast::from(k2).unwrap(),
             NumCast::from(k3).unwrap(),
             NumCast::from(k4).unwrap(),
         );

         <span class="kw">let </span>r = vec.<span class="number">0</span>;
         <span class="kw">let </span>g = vec.<span class="number">1</span>;
         <span class="kw">let </span>b = vec.<span class="number">2</span>;

         <span class="kw">let </span>new_r = matrix[<span class="number">0</span>] * r + matrix[<span class="number">1</span>] * g + matrix[<span class="number">2</span>] * b;
         <span class="kw">let </span>new_g = matrix[<span class="number">3</span>] * r + matrix[<span class="number">4</span>] * g + matrix[<span class="number">5</span>] * b;
         <span class="kw">let </span>new_b = matrix[<span class="number">6</span>] * r + matrix[<span class="number">7</span>] * g + matrix[<span class="number">8</span>] * b;
         <span class="kw">let </span>max = <span class="number">255f64</span>;
         <span class="kw">let </span>outpixel = Pixel::from_channels(
             NumCast::from(clamp(new_r, <span class="number">0.0</span>, max)).unwrap(),
             NumCast::from(clamp(new_g, <span class="number">0.0</span>, max)).unwrap(),
             NumCast::from(clamp(new_b, <span class="number">0.0</span>, max)).unwrap(),
             NumCast::from(clamp(vec.<span class="number">3</span>, <span class="number">0.0</span>, max)).unwrap(),
         );
         <span class="kw-2">*</span>pixel = outpixel;
     }
     out
 }

 <span class="doccomment">/// Hue rotate the supplied image in place.
 /// `value` is the degrees to rotate each pixel by.
 /// 0 and 360 do nothing, the rest rotates by the given degree value.
 /// just like the css webkit filter hue-rotate(180)
 ///
 /// *[See also `huerotate`.][huerotate]*
 </span><span class="kw">pub fn </span>huerotate_in_place&lt;I&gt;(image: <span class="kw-2">&amp;mut </span>I, value: i32)
 <span class="kw">where
     </span>I: GenericImage,
 {
     <span class="kw">let </span>(width, height) = image.dimensions();

     <span class="kw">let </span>angle: f64 = NumCast::from(value).unwrap();

     <span class="kw">let </span>cosv = (angle * PI / <span class="number">180.0</span>).cos();
     <span class="kw">let </span>sinv = (angle * PI / <span class="number">180.0</span>).sin();
     <span class="kw">let </span>matrix: [f64; <span class="number">9</span>] = [
         <span class="comment">// Reds
         </span><span class="number">0.213 </span>+ cosv * <span class="number">0.787 </span>- sinv * <span class="number">0.213</span>,
         <span class="number">0.715 </span>- cosv * <span class="number">0.715 </span>- sinv * <span class="number">0.715</span>,
         <span class="number">0.072 </span>- cosv * <span class="number">0.072 </span>+ sinv * <span class="number">0.928</span>,
         <span class="comment">// Greens
         </span><span class="number">0.213 </span>- cosv * <span class="number">0.213 </span>+ sinv * <span class="number">0.143</span>,
         <span class="number">0.715 </span>+ cosv * <span class="number">0.285 </span>+ sinv * <span class="number">0.140</span>,
         <span class="number">0.072 </span>- cosv * <span class="number">0.072 </span>- sinv * <span class="number">0.283</span>,
         <span class="comment">// Blues
         </span><span class="number">0.213 </span>- cosv * <span class="number">0.213 </span>- sinv * <span class="number">0.787</span>,
         <span class="number">0.715 </span>- cosv * <span class="number">0.715 </span>+ sinv * <span class="number">0.715</span>,
         <span class="number">0.072 </span>+ cosv * <span class="number">0.928 </span>+ sinv * <span class="number">0.072</span>,
     ];
     <span class="kw">for </span>y <span class="kw">in </span><span class="number">0</span>..height {
         <span class="kw">for </span>x <span class="kw">in </span><span class="number">0</span>..width {
             <span class="kw">let </span>pixel = image.get_pixel(x, y);
             <span class="kw">let </span>(k1, k2, k3, k4) = pixel.channels4();
             <span class="kw">let </span>vec: (f64, f64, f64, f64) = (
                 NumCast::from(k1).unwrap(),
                 NumCast::from(k2).unwrap(),
                 NumCast::from(k3).unwrap(),
                 NumCast::from(k4).unwrap(),
             );

             <span class="kw">let </span>r = vec.<span class="number">0</span>;
             <span class="kw">let </span>g = vec.<span class="number">1</span>;
             <span class="kw">let </span>b = vec.<span class="number">2</span>;

             <span class="kw">let </span>new_r = matrix[<span class="number">0</span>] * r + matrix[<span class="number">1</span>] * g + matrix[<span class="number">2</span>] * b;
             <span class="kw">let </span>new_g = matrix[<span class="number">3</span>] * r + matrix[<span class="number">4</span>] * g + matrix[<span class="number">5</span>] * b;
             <span class="kw">let </span>new_b = matrix[<span class="number">6</span>] * r + matrix[<span class="number">7</span>] * g + matrix[<span class="number">8</span>] * b;
             <span class="kw">let </span>max = <span class="number">255f64</span>;
             <span class="kw">let </span>outpixel = Pixel::from_channels(
                 NumCast::from(clamp(new_r, <span class="number">0.0</span>, max)).unwrap(),
                 NumCast::from(clamp(new_g, <span class="number">0.0</span>, max)).unwrap(),
                 NumCast::from(clamp(new_b, <span class="number">0.0</span>, max)).unwrap(),
                 NumCast::from(clamp(vec.<span class="number">3</span>, <span class="number">0.0</span>, max)).unwrap(),
             );

             image.put_pixel(x, y, outpixel);
         }
     }
 }

 <span class="doccomment">/// A color map
 </span><span class="kw">pub trait </span>ColorMap {
     <span class="doccomment">/// The color type on which the map operates on
     </span><span class="kw">type </span>Color;
     <span class="doccomment">/// Returns the index of the closest match of `color`
     /// in the color map.
     </span><span class="kw">fn </span>index_of(<span class="kw-2">&amp;</span><span class="self">self</span>, color: <span class="kw-2">&amp;</span><span class="self">Self</span>::Color) -&gt; usize;
     <span class="doccomment">/// Looks up color by index in the color map.  If `idx` is out of range for the color map, or
     /// ColorMap doesn&#39;t implement `lookup` `None` is returned.
     </span><span class="kw">fn </span>lookup(<span class="kw-2">&amp;</span><span class="self">self</span>, index: usize) -&gt; <span class="prelude-ty">Option</span>&lt;<span class="self">Self</span>::Color&gt; {
         <span class="kw">let _ </span>= index;
         <span class="prelude-val">None
     </span>}
     <span class="doccomment">/// Determine if this implementation of ColorMap overrides the default `lookup`.
     </span><span class="kw">fn </span>has_lookup(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; bool {
         <span class="bool-val">false
     </span>}
     <span class="doccomment">/// Maps `color` to the closest color in the color map.
     </span><span class="kw">fn </span>map_color(<span class="kw-2">&amp;</span><span class="self">self</span>, color: <span class="kw-2">&amp;mut </span><span class="self">Self</span>::Color);
 }

 <span class="doccomment">/// A bi-level color map
 ///
 /// # Examples
 /// ```
 /// use image::imageops::colorops::{index_colors, BiLevel, ColorMap};
 /// use image::{ImageBuffer, Luma};
 ///
 /// let (w, h) = (16, 16);
 /// // Create an image with a smooth horizontal gradient from black (0) to white (255).
 /// let gray = ImageBuffer::from_fn(w, h, |x, y| -&gt; Luma&lt;u8&gt; { [(255 * x / w) as u8].into() });
 /// // Mapping the gray image through the `BiLevel` filter should map gray pixels less than half
 /// // intensity (127) to black (0), and anything greater to white (255).
 /// let cmap = BiLevel;
 /// let palletized = index_colors(&amp;gray, &amp;cmap);
 /// let mapped = ImageBuffer::from_fn(w, h, |x, y| {
 ///     let p = palletized.get_pixel(x, y);
 ///     cmap.lookup(p.0[0] as usize)
 ///         .expect(&quot;indexed color out-of-range&quot;)
 /// });
 /// // Create an black and white image of expected output.
 /// let bw = ImageBuffer::from_fn(w, h, |x, y| -&gt; Luma&lt;u8&gt; {
 ///     if x &lt;= (w / 2) {
 ///         [0].into()
 ///     } else {
 ///         [255].into()
 ///     }
 /// });
 /// assert_eq!(mapped, bw);
 /// ```
 </span><span class="attribute">#[derive(Clone, Copy)]
 </span><span class="kw">pub struct </span>BiLevel;

 <span class="kw">impl </span>ColorMap <span class="kw">for </span>BiLevel {
     <span class="kw">type </span>Color = Luma&lt;u8&gt;;

     <span class="attribute">#[inline(always)]
     </span><span class="kw">fn </span>index_of(<span class="kw-2">&amp;</span><span class="self">self</span>, color: <span class="kw-2">&amp;</span>Luma&lt;u8&gt;) -&gt; usize {
         <span class="kw">let </span>luma = color.<span class="number">0</span>;
         <span class="kw">if </span>luma[<span class="number">0</span>] &gt; <span class="number">127 </span>{
             <span class="number">1
         </span>} <span class="kw">else </span>{
             <span class="number">0
         </span>}
     }

     <span class="attribute">#[inline(always)]
     </span><span class="kw">fn </span>lookup(<span class="kw-2">&amp;</span><span class="self">self</span>, idx: usize) -&gt; <span class="prelude-ty">Option</span>&lt;<span class="self">Self</span>::Color&gt; {
         <span class="kw">match </span>idx {
             <span class="number">0 </span>=&gt; <span class="prelude-val">Some</span>([<span class="number">0</span>].into()),
             <span class="number">1 </span>=&gt; <span class="prelude-val">Some</span>([<span class="number">255</span>].into()),
             <span class="kw">_ </span>=&gt; <span class="prelude-val">None</span>,
         }
     }

     <span class="doccomment">/// Indicate NeuQuant implements `lookup`.
     </span><span class="kw">fn </span>has_lookup(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; bool {
         <span class="bool-val">true
     </span>}

     <span class="attribute">#[inline(always)]
     </span><span class="kw">fn </span>map_color(<span class="kw-2">&amp;</span><span class="self">self</span>, color: <span class="kw-2">&amp;mut </span>Luma&lt;u8&gt;) {
         <span class="kw">let </span>new_color = <span class="number">0xFF </span>* <span class="self">self</span>.index_of(color) <span class="kw">as </span>u8;
         <span class="kw">let </span>luma = <span class="kw-2">&amp;mut </span>color.<span class="number">0</span>;
         luma[<span class="number">0</span>] = new_color;
     }
 }

 <span class="attribute">#[allow(deprecated)]
 </span><span class="kw">impl </span>ColorMap <span class="kw">for </span>nq::NeuQuant {
     <span class="kw">type </span>Color = Rgba&lt;u8&gt;;

     <span class="attribute">#[inline(always)]
     </span><span class="kw">fn </span>index_of(<span class="kw-2">&amp;</span><span class="self">self</span>, color: <span class="kw-2">&amp;</span>Rgba&lt;u8&gt;) -&gt; usize {
         <span class="self">self</span>.index_of(color.channels())
     }

     <span class="attribute">#[inline(always)]
     </span><span class="kw">fn </span>lookup(<span class="kw-2">&amp;</span><span class="self">self</span>, idx: usize) -&gt; <span class="prelude-ty">Option</span>&lt;<span class="self">Self</span>::Color&gt; {
         <span class="self">self</span>.lookup(idx).map(|p| p.into())
     }

     <span class="doccomment">/// Indicate NeuQuant implements `lookup`.
     </span><span class="kw">fn </span>has_lookup(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; bool {
         <span class="bool-val">true
     </span>}

     <span class="attribute">#[inline(always)]
     </span><span class="kw">fn </span>map_color(<span class="kw-2">&amp;</span><span class="self">self</span>, color: <span class="kw-2">&amp;mut </span>Rgba&lt;u8&gt;) {
         <span class="self">self</span>.map_pixel(color.channels_mut())
     }
 }

 <span class="kw">impl </span>ColorMap <span class="kw">for </span>color_quant::NeuQuant {
     <span class="kw">type </span>Color = Rgba&lt;u8&gt;;

     <span class="attribute">#[inline(always)]
     </span><span class="kw">fn </span>index_of(<span class="kw-2">&amp;</span><span class="self">self</span>, color: <span class="kw-2">&amp;</span>Rgba&lt;u8&gt;) -&gt; usize {
         <span class="self">self</span>.index_of(color.channels())
     }

     <span class="attribute">#[inline(always)]
     </span><span class="kw">fn </span>lookup(<span class="kw-2">&amp;</span><span class="self">self</span>, idx: usize) -&gt; <span class="prelude-ty">Option</span>&lt;<span class="self">Self</span>::Color&gt; {
         <span class="self">self</span>.lookup(idx).map(|p| p.into())
     }

     <span class="doccomment">/// Indicate NeuQuant implements `lookup`.
     </span><span class="kw">fn </span>has_lookup(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; bool {
         <span class="bool-val">true
     </span>}

     <span class="attribute">#[inline(always)]
     </span><span class="kw">fn </span>map_color(<span class="kw-2">&amp;</span><span class="self">self</span>, color: <span class="kw-2">&amp;mut </span>Rgba&lt;u8&gt;) {
         <span class="self">self</span>.map_pixel(color.channels_mut())
     }
 }

 <span class="doccomment">/// Floyd-Steinberg error diffusion
 </span><span class="kw">fn </span>diffuse_err&lt;P: Pixel&lt;Subpixel = u8&gt;&gt;(pixel: <span class="kw-2">&amp;mut </span>P, error: [i16; <span class="number">3</span>], factor: i16) {
     <span class="kw">for </span>(e, c) <span class="kw">in </span>error.iter().zip(pixel.channels_mut().iter_mut()) {
         <span class="kw-2">*</span>c = <span class="kw">match </span>&lt;i16 <span class="kw">as </span>From&lt;<span class="kw">_</span>&gt;&gt;::from(<span class="kw-2">*</span>c) + e * factor / <span class="number">16 </span>{
             val <span class="kw">if </span>val &lt; <span class="number">0 </span>=&gt; <span class="number">0</span>,
             val <span class="kw">if </span>val &gt; <span class="number">0xFF </span>=&gt; <span class="number">0xFF</span>,
             val =&gt; val <span class="kw">as </span>u8,
         }
     }
 }

 <span class="macro">macro_rules! </span>do_dithering(
     (<span class="macro-nonterminal">$map</span>:expr, <span class="macro-nonterminal">$image</span>:expr, <span class="macro-nonterminal">$err</span>:expr, <span class="macro-nonterminal">$x</span>:expr, <span class="macro-nonterminal">$y</span>:expr) =&gt; (
         {
             <span class="kw">let </span>old_pixel = <span class="macro-nonterminal">$image</span>[(<span class="macro-nonterminal">$x</span>, <span class="macro-nonterminal">$y</span>)];
             <span class="kw">let </span>new_pixel = <span class="macro-nonterminal">$image</span>.get_pixel_mut(<span class="macro-nonterminal">$x</span>, <span class="macro-nonterminal">$y</span>);
             <span class="macro-nonterminal">$map</span>.map_color(new_pixel);
             <span class="kw">for </span>((e, <span class="kw-2">&amp;</span>old), <span class="kw-2">&amp;</span>new) <span class="kw">in </span><span class="macro-nonterminal">$err</span>.iter_mut()
                                         .zip(old_pixel.channels().iter())
                                         .zip(new_pixel.channels().iter())
             {
                 <span class="kw-2">*</span>e = &lt;i16 <span class="kw">as </span>From&lt;<span class="kw">_</span>&gt;&gt;::from(old) - &lt;i16 <span class="kw">as </span>From&lt;<span class="kw">_</span>&gt;&gt;::from(new)
             }
         }
     )
 );

 <span class="doccomment">/// Reduces the colors of the image using the supplied `color_map` while applying
 /// Floyd-Steinberg dithering to improve the visual conception
 </span><span class="kw">pub fn </span>dither&lt;Pix, Map&gt;(image: <span class="kw-2">&amp;mut </span>ImageBuffer&lt;Pix, Vec&lt;u8&gt;&gt;, color_map: <span class="kw-2">&amp;</span>Map)
 <span class="kw">where
     </span>Map: ColorMap&lt;Color = Pix&gt; + <span class="question-mark">?</span>Sized,
     Pix: Pixel&lt;Subpixel = u8&gt; + <span class="lifetime">&#39;static</span>,
 {
     <span class="kw">let </span>(width, height) = image.dimensions();
     <span class="kw">let </span><span class="kw-2">mut </span>err: [i16; <span class="number">3</span>] = [<span class="number">0</span>; <span class="number">3</span>];
     <span class="kw">for </span>y <span class="kw">in </span><span class="number">0</span>..height - <span class="number">1 </span>{
         <span class="kw">let </span>x = <span class="number">0</span>;
         <span class="macro">do_dithering!</span>(color_map, image, err, x, y);
         diffuse_err(image.get_pixel_mut(x + <span class="number">1</span>, y), err, <span class="number">7</span>);
         diffuse_err(image.get_pixel_mut(x, y + <span class="number">1</span>), err, <span class="number">5</span>);
         diffuse_err(image.get_pixel_mut(x + <span class="number">1</span>, y + <span class="number">1</span>), err, <span class="number">1</span>);
         <span class="kw">for </span>x <span class="kw">in </span><span class="number">1</span>..width - <span class="number">1 </span>{
             <span class="macro">do_dithering!</span>(color_map, image, err, x, y);
             diffuse_err(image.get_pixel_mut(x + <span class="number">1</span>, y), err, <span class="number">7</span>);
             diffuse_err(image.get_pixel_mut(x - <span class="number">1</span>, y + <span class="number">1</span>), err, <span class="number">3</span>);
             diffuse_err(image.get_pixel_mut(x, y + <span class="number">1</span>), err, <span class="number">5</span>);
             diffuse_err(image.get_pixel_mut(x + <span class="number">1</span>, y + <span class="number">1</span>), err, <span class="number">1</span>);
         }
         <span class="kw">let </span>x = width - <span class="number">1</span>;
         <span class="macro">do_dithering!</span>(color_map, image, err, x, y);
         diffuse_err(image.get_pixel_mut(x - <span class="number">1</span>, y + <span class="number">1</span>), err, <span class="number">3</span>);
         diffuse_err(image.get_pixel_mut(x, y + <span class="number">1</span>), err, <span class="number">5</span>);
     }
     <span class="kw">let </span>y = height - <span class="number">1</span>;
     <span class="kw">let </span>x = <span class="number">0</span>;
     <span class="macro">do_dithering!</span>(color_map, image, err, x, y);
     diffuse_err(image.get_pixel_mut(x + <span class="number">1</span>, y), err, <span class="number">7</span>);
     <span class="kw">for </span>x <span class="kw">in </span><span class="number">1</span>..width - <span class="number">1 </span>{
         <span class="macro">do_dithering!</span>(color_map, image, err, x, y);
         diffuse_err(image.get_pixel_mut(x + <span class="number">1</span>, y), err, <span class="number">7</span>);
     }
     <span class="kw">let </span>x = width - <span class="number">1</span>;
     <span class="macro">do_dithering!</span>(color_map, image, err, x, y);
 }

 <span class="doccomment">/// Reduces the colors using the supplied `color_map` and returns an image of the indices
 </span><span class="kw">pub fn </span>index_colors&lt;Pix, Map&gt;(
     image: <span class="kw-2">&amp;</span>ImageBuffer&lt;Pix, Vec&lt;u8&gt;&gt;,
     color_map: <span class="kw-2">&amp;</span>Map,
 ) -&gt; ImageBuffer&lt;Luma&lt;u8&gt;, Vec&lt;u8&gt;&gt;
 <span class="kw">where
     </span>Map: ColorMap&lt;Color = Pix&gt; + <span class="question-mark">?</span>Sized,
     Pix: Pixel&lt;Subpixel = u8&gt; + <span class="lifetime">&#39;static</span>,
 {
     <span class="kw">let </span><span class="kw-2">mut </span>indices = ImageBuffer::new(image.width(), image.height());
     <span class="kw">for </span>(pixel, idx) <span class="kw">in </span>image.pixels().zip(indices.pixels_mut()) {
         <span class="kw-2">*</span>idx = Luma([color_map.index_of(pixel) <span class="kw">as </span>u8])
     }
     indices
 }

 <span class="attribute">#[cfg(test)]
 </span><span class="kw">mod </span>test {

     <span class="kw">use super</span>::<span class="kw-2">*</span>;
     <span class="kw">use </span><span class="kw">crate</span>::ImageBuffer;

     <span class="attribute">#[test]
     </span><span class="kw">fn </span>test_dither() {
         <span class="kw">let </span><span class="kw-2">mut </span>image = ImageBuffer::from_raw(<span class="number">2</span>, <span class="number">2</span>, <span class="macro">vec!</span>[<span class="number">127</span>, <span class="number">127</span>, <span class="number">127</span>, <span class="number">127</span>]).unwrap();
         <span class="kw">let </span>cmap = BiLevel;
         dither(<span class="kw-2">&amp;mut </span>image, <span class="kw-2">&amp;</span>cmap);
         <span class="macro">assert_eq!</span>(<span class="kw-2">&amp;*</span>image, <span class="kw-2">&amp;</span>[<span class="number">0</span>, <span class="number">0xFF</span>, <span class="number">0xFF</span>, <span class="number">0</span>]);
         <span class="macro">assert_eq!</span>(index_colors(<span class="kw-2">&amp;</span>image, <span class="kw-2">&amp;</span>cmap).into_raw(), <span class="macro">vec!</span>[<span class="number">0</span>, <span class="number">1</span>, <span class="number">1</span>, <span class="number">0</span>])
     }
 }
 </code></pre></div>
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