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</pre><div class="example-wrap"><pre class="rust ">
<span class="kw">use</span> <span class="ident">geom</span>::{<span class="ident">Bounds</span>, <span class="ident">Histogram</span>, <span class="ident">Polygon</span>, <span class="ident">Pt2D</span>, <span class="ident">Statistic</span>};
<span class="kw">use</span> <span class="ident">widgetry</span>::{<span class="ident">Choice</span>, <span class="ident">Color</span>, <span class="ident">EventCtx</span>, <span class="ident">GeomBatch</span>, <span class="ident">Panel</span>, <span class="ident">Spinner</span>, <span class="ident">TextExt</span>, <span class="ident">Toggle</span>, <span class="ident">Widget</span>};

<span class="kw">use</span> <span class="kw">crate</span>::<span class="ident">tools</span>::{<span class="ident">ColorLegend</span>, <span class="ident">ColorScale</span>};

<span class="kw">const</span> <span class="ident">NEIGHBORS</span>: [[<span class="ident">isize</span>; <span class="number">2</span>]; <span class="number">9</span>] <span class="op">=</span> [
    [<span class="number">0</span>, <span class="number">0</span>],
    [<span class="op">-</span><span class="number">1</span>, <span class="number">1</span>],
    [<span class="op">-</span><span class="number">1</span>, <span class="number">0</span>],
    [<span class="op">-</span><span class="number">1</span>, <span class="op">-</span><span class="number">1</span>],
    [<span class="number">0</span>, <span class="op">-</span><span class="number">1</span>],
    [<span class="number">1</span>, <span class="op">-</span><span class="number">1</span>],
    [<span class="number">1</span>, <span class="number">0</span>],
    [<span class="number">1</span>, <span class="number">1</span>],
    [<span class="number">0</span>, <span class="number">1</span>],
];

<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">PartialEq</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">HeatmapOptions</span> {
    <span class="comment">// In meters</span>
    <span class="ident">resolution</span>: <span class="ident">usize</span>,
    <span class="ident">radius</span>: <span class="ident">usize</span>,
    <span class="ident">smoothing</span>: <span class="ident">bool</span>,
    <span class="ident">contours</span>: <span class="ident">bool</span>,
    <span class="ident">color_scheme</span>: <span class="ident">String</span>,
}

<span class="kw">impl</span> <span class="ident">HeatmapOptions</span> {
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-</span><span class="op">&gt;</span> <span class="ident">HeatmapOptions</span> {
        <span class="ident">HeatmapOptions</span> {
            <span class="ident">resolution</span>: <span class="number">10</span>,
            <span class="ident">radius</span>: <span class="number">3</span>,
            <span class="ident">smoothing</span>: <span class="bool-val">true</span>,
            <span class="ident">contours</span>: <span class="bool-val">true</span>,
            <span class="ident">color_scheme</span>: <span class="string">&quot;Turbo&quot;</span>.<span class="ident">to_string</span>(),
        }
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">to_controls</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">ctx</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">EventCtx</span>, <span class="ident">legend</span>: <span class="ident">Widget</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Widget</span><span class="op">&gt;</span> {
        <span class="macro">vec</span><span class="macro">!</span>[
            <span class="comment">// TODO Display the value...</span>
            <span class="ident">Widget</span>::<span class="ident">row</span>(<span class="macro">vec</span><span class="macro">!</span>[
                <span class="string">&quot;Resolution (meters)&quot;</span>.<span class="ident">text_widget</span>(<span class="ident">ctx</span>).<span class="ident">centered_vert</span>(),
                <span class="ident">Spinner</span>::<span class="ident">widget</span>(<span class="ident">ctx</span>, (<span class="number">1</span>, <span class="number">100</span>), <span class="self">self</span>.<span class="ident">resolution</span> <span class="kw">as</span> <span class="ident">isize</span>)
                    .<span class="ident">named</span>(<span class="string">&quot;resolution&quot;</span>)
                    .<span class="ident">align_right</span>(),
            ]),
            <span class="ident">Widget</span>::<span class="ident">row</span>(<span class="macro">vec</span><span class="macro">!</span>[
                <span class="string">&quot;Radius (resolution multiplier)&quot;</span>
                    .<span class="ident">text_widget</span>(<span class="ident">ctx</span>)
                    .<span class="ident">centered_vert</span>(),
                <span class="ident">Spinner</span>::<span class="ident">widget</span>(<span class="ident">ctx</span>, (<span class="number">0</span>, <span class="number">10</span>), <span class="self">self</span>.<span class="ident">radius</span> <span class="kw">as</span> <span class="ident">isize</span>)
                    .<span class="ident">named</span>(<span class="string">&quot;radius&quot;</span>)
                    .<span class="ident">align_right</span>(),
            ]),
            <span class="ident">Toggle</span>::<span class="ident">switch</span>(<span class="ident">ctx</span>, <span class="string">&quot;smoothing&quot;</span>, <span class="prelude-val">None</span>, <span class="self">self</span>.<span class="ident">smoothing</span>),
            <span class="ident">Toggle</span>::<span class="ident">switch</span>(<span class="ident">ctx</span>, <span class="string">&quot;contours&quot;</span>, <span class="prelude-val">None</span>, <span class="self">self</span>.<span class="ident">contours</span>),
            <span class="ident">Widget</span>::<span class="ident">row</span>(<span class="macro">vec</span><span class="macro">!</span>[
                <span class="string">&quot;Color scheme&quot;</span>.<span class="ident">text_widget</span>(<span class="ident">ctx</span>).<span class="ident">centered_vert</span>(),
                <span class="ident">Widget</span>::<span class="ident">dropdown</span>(
                    <span class="ident">ctx</span>,
                    <span class="string">&quot;Color scheme&quot;</span>,
                    <span class="self">self</span>.<span class="ident">color_scheme</span>.<span class="ident">clone</span>(),
                    <span class="macro">vec</span><span class="macro">!</span>[<span class="string">&quot;Turbo&quot;</span>, <span class="string">&quot;Inferno&quot;</span>, <span class="string">&quot;Warm&quot;</span>, <span class="string">&quot;Cool&quot;</span>, <span class="string">&quot;Oranges&quot;</span>, <span class="string">&quot;Spectral&quot;</span>]
                        .<span class="ident">into_iter</span>()
                        .<span class="ident">map</span>(<span class="op">|</span><span class="ident">x</span><span class="op">|</span> <span class="ident">Choice</span>::<span class="ident">string</span>(<span class="ident">x</span>))
                        .<span class="ident">collect</span>(),
                ),
            ]),
            <span class="ident">legend</span>,
        ]
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">from_controls</span>(<span class="ident">c</span>: <span class="kw-2">&amp;</span><span class="ident">Panel</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">HeatmapOptions</span> {
        <span class="comment">// Did we just change?</span>
        <span class="kw">if</span> <span class="ident">c</span>.<span class="ident">has_widget</span>(<span class="string">&quot;resolution&quot;</span>) {
            <span class="ident">HeatmapOptions</span> {
                <span class="ident">resolution</span>: <span class="ident">c</span>.<span class="ident">spinner</span>(<span class="string">&quot;resolution&quot;</span>) <span class="kw">as</span> <span class="ident">usize</span>,
                <span class="ident">radius</span>: <span class="ident">c</span>.<span class="ident">spinner</span>(<span class="string">&quot;radius&quot;</span>) <span class="kw">as</span> <span class="ident">usize</span>,
                <span class="ident">smoothing</span>: <span class="ident">c</span>.<span class="ident">is_checked</span>(<span class="string">&quot;smoothing&quot;</span>),
                <span class="ident">contours</span>: <span class="ident">c</span>.<span class="ident">is_checked</span>(<span class="string">&quot;contours&quot;</span>),
                <span class="ident">color_scheme</span>: <span class="ident">c</span>.<span class="ident">dropdown_value</span>(<span class="string">&quot;Color scheme&quot;</span>),
            }
        } <span class="kw">else</span> {
            <span class="ident">HeatmapOptions</span>::<span class="ident">new</span>()
        }
    }
}

<span class="comment">// Returns a legend</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">make_heatmap</span>(
    <span class="ident">ctx</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">EventCtx</span>,
    <span class="ident">batch</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">GeomBatch</span>,
    <span class="ident">bounds</span>: <span class="kw-2">&amp;</span><span class="ident">Bounds</span>,
    <span class="ident">pts</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span>,
    <span class="ident">opts</span>: <span class="kw-2">&amp;</span><span class="ident">HeatmapOptions</span>,
) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Widget</span> {
    <span class="comment">// 7 colors, 8 labels</span>
    <span class="kw">let</span> <span class="ident">num_colors</span> <span class="op">=</span> <span class="number">7</span>;
    <span class="kw">let</span> <span class="ident">gradient</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">opts</span>.<span class="ident">color_scheme</span>.<span class="ident">as_ref</span>() {
        <span class="string">&quot;Turbo&quot;</span> <span class="op">=</span><span class="op">&gt;</span> <span class="ident">colorous</span>::<span class="ident">TURBO</span>,
        <span class="string">&quot;Inferno&quot;</span> <span class="op">=</span><span class="op">&gt;</span> <span class="ident">colorous</span>::<span class="ident">INFERNO</span>,
        <span class="string">&quot;Warm&quot;</span> <span class="op">=</span><span class="op">&gt;</span> <span class="ident">colorous</span>::<span class="ident">WARM</span>,
        <span class="string">&quot;Cool&quot;</span> <span class="op">=</span><span class="op">&gt;</span> <span class="ident">colorous</span>::<span class="ident">COOL</span>,
        <span class="string">&quot;Oranges&quot;</span> <span class="op">=</span><span class="op">&gt;</span> <span class="ident">colorous</span>::<span class="ident">ORANGES</span>,
        <span class="string">&quot;Spectral&quot;</span> <span class="op">=</span><span class="op">&gt;</span> <span class="ident">colorous</span>::<span class="ident">SPECTRAL</span>,
        <span class="kw">_</span> <span class="op">=</span><span class="op">&gt;</span> <span class="macro">unreachable</span><span class="macro">!</span>(),
    };
    <span class="kw">let</span> <span class="ident">colors</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Color</span><span class="op">&gt;</span> <span class="op">=</span> (<span class="number">0</span>..<span class="ident">num_colors</span>)
        .<span class="ident">map</span>(<span class="op">|</span><span class="ident">i</span><span class="op">|</span> {
            <span class="kw">let</span> <span class="ident">c</span> <span class="op">=</span> <span class="ident">gradient</span>.<span class="ident">eval_rational</span>(<span class="ident">i</span>, <span class="ident">num_colors</span>);
            <span class="ident">Color</span>::<span class="ident">rgb</span>(<span class="ident">c</span>.<span class="ident">r</span> <span class="kw">as</span> <span class="ident">usize</span>, <span class="ident">c</span>.<span class="ident">g</span> <span class="kw">as</span> <span class="ident">usize</span>, <span class="ident">c</span>.<span class="ident">b</span> <span class="kw">as</span> <span class="ident">usize</span>)
        })
        .<span class="ident">collect</span>();

    <span class="kw">if</span> <span class="ident">pts</span>.<span class="ident">is_empty</span>() {
        <span class="kw">let</span> <span class="ident">labels</span> <span class="op">=</span> <span class="ident">std</span>::<span class="ident">iter</span>::<span class="ident">repeat</span>(<span class="string">&quot;0&quot;</span>.<span class="ident">to_string</span>())
            .<span class="ident">take</span>(<span class="ident">num_colors</span> <span class="op">+</span> <span class="number">1</span>)
            .<span class="ident">collect</span>();
        <span class="kw">return</span> <span class="ident">ColorLegend</span>::<span class="ident">gradient</span>(<span class="ident">ctx</span>, <span class="kw-2">&amp;</span><span class="ident">ColorScale</span>(<span class="ident">colors</span>), <span class="ident">labels</span>);
    }

    <span class="comment">// At each point, add a 2D Gaussian kernel centered at the point.</span>
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">raw_grid</span>: <span class="ident">Grid</span><span class="op">&lt;</span><span class="ident">f64</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">Grid</span>::<span class="ident">new</span>(
        (<span class="ident">bounds</span>.<span class="ident">width</span>() <span class="op">/</span> <span class="ident">opts</span>.<span class="ident">resolution</span> <span class="kw">as</span> <span class="ident">f64</span>).<span class="ident">ceil</span>() <span class="kw">as</span> <span class="ident">usize</span>,
        (<span class="ident">bounds</span>.<span class="ident">height</span>() <span class="op">/</span> <span class="ident">opts</span>.<span class="ident">resolution</span> <span class="kw">as</span> <span class="ident">f64</span>).<span class="ident">ceil</span>() <span class="kw">as</span> <span class="ident">usize</span>,
        <span class="number">0.0</span>,
    );
    <span class="kw">for</span> <span class="ident">pt</span> <span class="kw">in</span> <span class="ident">pts</span> {
        <span class="kw">let</span> <span class="ident">base_x</span> <span class="op">=</span> ((<span class="ident">pt</span>.<span class="ident">x</span>() <span class="op">-</span> <span class="ident">bounds</span>.<span class="ident">min_x</span>) <span class="op">/</span> <span class="ident">opts</span>.<span class="ident">resolution</span> <span class="kw">as</span> <span class="ident">f64</span>) <span class="kw">as</span> <span class="ident">isize</span>;
        <span class="kw">let</span> <span class="ident">base_y</span> <span class="op">=</span> ((<span class="ident">pt</span>.<span class="ident">y</span>() <span class="op">-</span> <span class="ident">bounds</span>.<span class="ident">min_y</span>) <span class="op">/</span> <span class="ident">opts</span>.<span class="ident">resolution</span> <span class="kw">as</span> <span class="ident">f64</span>) <span class="kw">as</span> <span class="ident">isize</span>;
        <span class="kw">let</span> <span class="ident">denom</span> <span class="op">=</span> <span class="number">2.0</span> <span class="op">*</span> (<span class="ident">opts</span>.<span class="ident">radius</span> <span class="kw">as</span> <span class="ident">f64</span> <span class="op">/</span> <span class="number">2.0</span>).<span class="ident">powi</span>(<span class="number">2</span>);

        <span class="kw">let</span> <span class="ident">r</span> <span class="op">=</span> <span class="ident">opts</span>.<span class="ident">radius</span> <span class="kw">as</span> <span class="ident">isize</span>;
        <span class="kw">for</span> <span class="ident">x</span> <span class="kw">in</span> <span class="ident">base_x</span> <span class="op">-</span> <span class="ident">r</span>..<span class="op">=</span><span class="ident">base_x</span> <span class="op">+</span> <span class="ident">r</span> {
            <span class="kw">for</span> <span class="ident">y</span> <span class="kw">in</span> <span class="ident">base_y</span> <span class="op">-</span> <span class="ident">r</span>..<span class="op">=</span><span class="ident">base_y</span> <span class="op">+</span> <span class="ident">r</span> {
                <span class="kw">let</span> <span class="ident">loc_r2</span> <span class="op">=</span> (<span class="ident">x</span> <span class="op">-</span> <span class="ident">base_x</span>).<span class="ident">pow</span>(<span class="number">2</span>) <span class="op">+</span> (<span class="ident">y</span> <span class="op">-</span> <span class="ident">base_y</span>).<span class="ident">pow</span>(<span class="number">2</span>);
                <span class="kw">if</span> <span class="ident">x</span> <span class="op">&gt;</span> <span class="number">0</span>
                    <span class="op">&amp;&amp;</span> <span class="ident">y</span> <span class="op">&gt;</span> <span class="number">0</span>
                    <span class="op">&amp;&amp;</span> <span class="ident">x</span> <span class="op">&lt;</span> (<span class="ident">raw_grid</span>.<span class="ident">width</span> <span class="kw">as</span> <span class="ident">isize</span>)
                    <span class="op">&amp;&amp;</span> <span class="ident">y</span> <span class="op">&lt;</span> (<span class="ident">raw_grid</span>.<span class="ident">height</span> <span class="kw">as</span> <span class="ident">isize</span>)
                    <span class="op">&amp;&amp;</span> <span class="ident">loc_r2</span> <span class="op">&lt;</span><span class="op">=</span> <span class="ident">r</span> <span class="op">*</span> <span class="ident">r</span>
                {
                    <span class="comment">// https://en.wikipedia.org/wiki/Gaussian_function#Two-dimensional_Gaussian_function</span>
                    <span class="kw">let</span> <span class="ident">value</span> <span class="op">=</span> (<span class="op">-</span>(((<span class="ident">x</span> <span class="op">-</span> <span class="ident">base_x</span>) <span class="kw">as</span> <span class="ident">f64</span>).<span class="ident">powi</span>(<span class="number">2</span>) <span class="op">/</span> <span class="ident">denom</span>
                        <span class="op">+</span> ((<span class="ident">y</span> <span class="op">-</span> <span class="ident">base_y</span>) <span class="kw">as</span> <span class="ident">f64</span>).<span class="ident">powi</span>(<span class="number">2</span>) <span class="op">/</span> <span class="ident">denom</span>))
                        .<span class="ident">exp</span>();
                    <span class="kw">let</span> <span class="ident">idx</span> <span class="op">=</span> <span class="ident">raw_grid</span>.<span class="ident">idx</span>(<span class="ident">x</span> <span class="kw">as</span> <span class="ident">usize</span>, <span class="ident">y</span> <span class="kw">as</span> <span class="ident">usize</span>);
                    <span class="ident">raw_grid</span>.<span class="ident">data</span>[<span class="ident">idx</span>] <span class="op">+</span><span class="op">=</span> <span class="ident">value</span>;
                }
            }
        }
    }

    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">grid</span>: <span class="ident">Grid</span><span class="op">&lt;</span><span class="ident">f64</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">Grid</span>::<span class="ident">new</span>(
        (<span class="ident">bounds</span>.<span class="ident">width</span>() <span class="op">/</span> <span class="ident">opts</span>.<span class="ident">resolution</span> <span class="kw">as</span> <span class="ident">f64</span>).<span class="ident">ceil</span>() <span class="kw">as</span> <span class="ident">usize</span>,
        (<span class="ident">bounds</span>.<span class="ident">height</span>() <span class="op">/</span> <span class="ident">opts</span>.<span class="ident">resolution</span> <span class="kw">as</span> <span class="ident">f64</span>).<span class="ident">ceil</span>() <span class="kw">as</span> <span class="ident">usize</span>,
        <span class="number">0.0</span>,
    );
    <span class="kw">if</span> <span class="ident">opts</span>.<span class="ident">smoothing</span> {
        <span class="kw">for</span> <span class="ident">y</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">raw_grid</span>.<span class="ident">height</span> {
            <span class="kw">for</span> <span class="ident">x</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">raw_grid</span>.<span class="ident">width</span> {
                <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">div</span> <span class="op">=</span> <span class="number">1</span>;
                <span class="kw">let</span> <span class="ident">idx</span> <span class="op">=</span> <span class="ident">grid</span>.<span class="ident">idx</span>(<span class="ident">x</span>, <span class="ident">y</span>);
                <span class="ident">grid</span>.<span class="ident">data</span>[<span class="ident">idx</span>] <span class="op">=</span> <span class="ident">raw_grid</span>.<span class="ident">data</span>[<span class="ident">idx</span>];
                <span class="kw">for</span> <span class="ident">offset</span> <span class="kw">in</span> <span class="kw-2">&amp;</span><span class="ident">NEIGHBORS</span> {
                    <span class="kw">let</span> <span class="ident">next_x</span> <span class="op">=</span> <span class="ident">x</span> <span class="kw">as</span> <span class="ident">isize</span> <span class="op">+</span> <span class="ident">offset</span>[<span class="number">0</span>];
                    <span class="kw">let</span> <span class="ident">next_y</span> <span class="op">=</span> <span class="ident">y</span> <span class="kw">as</span> <span class="ident">isize</span> <span class="op">+</span> <span class="ident">offset</span>[<span class="number">1</span>];
                    <span class="kw">if</span> <span class="ident">next_x</span> <span class="op">&gt;</span> <span class="number">0</span>
                        <span class="op">&amp;&amp;</span> <span class="ident">next_y</span> <span class="op">&gt;</span> <span class="number">0</span>
                        <span class="op">&amp;&amp;</span> <span class="ident">next_x</span> <span class="op">&lt;</span> (<span class="ident">raw_grid</span>.<span class="ident">width</span> <span class="kw">as</span> <span class="ident">isize</span>)
                        <span class="op">&amp;&amp;</span> <span class="ident">next_y</span> <span class="op">&lt;</span> (<span class="ident">raw_grid</span>.<span class="ident">height</span> <span class="kw">as</span> <span class="ident">isize</span>)
                    {
                        <span class="ident">div</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
                        <span class="kw">let</span> <span class="ident">next_idx</span> <span class="op">=</span> <span class="ident">grid</span>.<span class="ident">idx</span>(<span class="ident">next_x</span> <span class="kw">as</span> <span class="ident">usize</span>, <span class="ident">next_y</span> <span class="kw">as</span> <span class="ident">usize</span>);
                        <span class="ident">grid</span>.<span class="ident">data</span>[<span class="ident">idx</span>] <span class="op">+</span><span class="op">=</span> <span class="ident">raw_grid</span>.<span class="ident">data</span>[<span class="ident">next_idx</span>];
                    }
                }
                <span class="ident">grid</span>.<span class="ident">data</span>[<span class="ident">idx</span>] <span class="op">/</span><span class="op">=</span> <span class="ident">div</span> <span class="kw">as</span> <span class="ident">f64</span>;
            }
        }
    } <span class="kw">else</span> {
        <span class="ident">grid</span> <span class="op">=</span> <span class="ident">raw_grid</span>;
    }

    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">distrib</span> <span class="op">=</span> <span class="ident">Histogram</span>::<span class="ident">new</span>();
    <span class="kw">for</span> <span class="ident">count</span> <span class="kw">in</span> <span class="kw-2">&amp;</span><span class="ident">grid</span>.<span class="ident">data</span> {
        <span class="comment">// TODO Just truncate the decimal?</span>
        <span class="ident">distrib</span>.<span class="ident">add</span>(<span class="kw-2">*</span><span class="ident">count</span> <span class="kw">as</span> <span class="ident">usize</span>);
    }

    <span class="kw">if</span> <span class="ident">opts</span>.<span class="ident">contours</span> {
        <span class="kw">let</span> <span class="ident">max</span> <span class="op">=</span> <span class="ident">distrib</span>.<span class="ident">select</span>(<span class="ident">Statistic</span>::<span class="ident">Max</span>).<span class="ident">unwrap</span>() <span class="kw">as</span> <span class="ident">f64</span>;
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">thresholds</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">f64</span><span class="op">&gt;</span> <span class="op">=</span> (<span class="number">0</span>..<span class="op">=</span><span class="number">5</span>).<span class="ident">map</span>(<span class="op">|</span><span class="ident">i</span><span class="op">|</span> (<span class="ident">i</span> <span class="kw">as</span> <span class="ident">f64</span>) <span class="op">/</span> <span class="number">5.0</span> <span class="op">*</span> <span class="ident">max</span>).<span class="ident">collect</span>();
        <span class="comment">// Skip 0; it&#39;ll cover the entire map. But have a low value to distinguish</span>
        <span class="comment">// nothing/something.</span>
        <span class="ident">thresholds</span>[<span class="number">0</span>] <span class="op">=</span> <span class="number">0.1</span>;
        <span class="kw">let</span> <span class="ident">c</span> <span class="op">=</span> <span class="ident">contour</span>::<span class="ident">ContourBuilder</span>::<span class="ident">new</span>(<span class="ident">grid</span>.<span class="ident">width</span> <span class="kw">as</span> <span class="ident">u32</span>, <span class="ident">grid</span>.<span class="ident">height</span> <span class="kw">as</span> <span class="ident">u32</span>, <span class="bool-val">false</span>);
        <span class="kw">for</span> (<span class="ident">feature</span>, <span class="ident">value</span>) <span class="kw">in</span> <span class="ident">c</span>
            .<span class="ident">contours</span>(<span class="kw-2">&amp;</span><span class="ident">grid</span>.<span class="ident">data</span>, <span class="kw-2">&amp;</span><span class="ident">thresholds</span>)
            .<span class="ident">unwrap</span>()
            .<span class="ident">into_iter</span>()
            .<span class="ident">zip</span>(<span class="ident">thresholds</span>)
        {
            <span class="comment">// TODO We should technically not depend on the order of features matching the input</span>
            <span class="comment">// thresholds, but extracting geojson values doesn&#39;t sound fun</span>
            <span class="kw">match</span> <span class="ident">feature</span>.<span class="ident">geometry</span>.<span class="ident">unwrap</span>().<span class="ident">value</span> {
                <span class="ident">geojson</span>::<span class="ident">Value</span>::<span class="ident">MultiPolygon</span>(<span class="ident">polygons</span>) <span class="op">=</span><span class="op">&gt;</span> {
                    <span class="kw">let</span> <span class="ident">c</span> <span class="op">=</span> <span class="ident">gradient</span>.<span class="ident">eval_continuous</span>(<span class="ident">value</span> <span class="op">/</span> <span class="ident">max</span>);
                    <span class="comment">// Don&#39;t block the map underneath</span>
                    <span class="kw">let</span> <span class="ident">color</span> <span class="op">=</span> <span class="ident">Color</span>::<span class="ident">rgb</span>(<span class="ident">c</span>.<span class="ident">r</span> <span class="kw">as</span> <span class="ident">usize</span>, <span class="ident">c</span>.<span class="ident">g</span> <span class="kw">as</span> <span class="ident">usize</span>, <span class="ident">c</span>.<span class="ident">b</span> <span class="kw">as</span> <span class="ident">usize</span>).<span class="ident">alpha</span>(<span class="number">0.6</span>);
                    <span class="kw">for</span> <span class="ident">p</span> <span class="kw">in</span> <span class="ident">polygons</span> {
                        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Ok</span>(<span class="ident">poly</span>) <span class="op">=</span> <span class="ident">Polygon</span>::<span class="ident">from_geojson</span>(<span class="kw-2">&amp;</span><span class="ident">p</span>) {
                            <span class="ident">batch</span>.<span class="ident">push</span>(<span class="ident">color</span>, <span class="ident">poly</span>.<span class="ident">scale</span>(<span class="ident">opts</span>.<span class="ident">resolution</span> <span class="kw">as</span> <span class="ident">f64</span>));
                        }
                    }
                }
                <span class="kw">_</span> <span class="op">=</span><span class="op">&gt;</span> <span class="macro">unreachable</span><span class="macro">!</span>(),
            }
        }
    } <span class="kw">else</span> {
        <span class="comment">// Now draw rectangles</span>
        <span class="kw">let</span> <span class="ident">square</span> <span class="op">=</span> <span class="ident">Polygon</span>::<span class="ident">rectangle</span>(<span class="ident">opts</span>.<span class="ident">resolution</span> <span class="kw">as</span> <span class="ident">f64</span>, <span class="ident">opts</span>.<span class="ident">resolution</span> <span class="kw">as</span> <span class="ident">f64</span>);
        <span class="kw">for</span> <span class="ident">y</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">grid</span>.<span class="ident">height</span> {
            <span class="kw">for</span> <span class="ident">x</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">grid</span>.<span class="ident">width</span> {
                <span class="kw">let</span> <span class="ident">count</span> <span class="op">=</span> <span class="ident">grid</span>.<span class="ident">data</span>[<span class="ident">grid</span>.<span class="ident">idx</span>(<span class="ident">x</span>, <span class="ident">y</span>)];
                <span class="kw">if</span> <span class="ident">count</span> <span class="op">&gt;</span> <span class="number">0.0</span> {
                    <span class="kw">let</span> <span class="ident">pct</span> <span class="op">=</span> (<span class="ident">count</span> <span class="kw">as</span> <span class="ident">f64</span>) <span class="op">/</span> (<span class="ident">distrib</span>.<span class="ident">select</span>(<span class="ident">Statistic</span>::<span class="ident">Max</span>).<span class="ident">unwrap</span>() <span class="kw">as</span> <span class="ident">f64</span>);
                    <span class="kw">let</span> <span class="ident">c</span> <span class="op">=</span> <span class="ident">gradient</span>.<span class="ident">eval_continuous</span>(<span class="ident">pct</span>);
                    <span class="comment">// Don&#39;t block the map underneath</span>
                    <span class="kw">let</span> <span class="ident">color</span> <span class="op">=</span> <span class="ident">Color</span>::<span class="ident">rgb</span>(<span class="ident">c</span>.<span class="ident">r</span> <span class="kw">as</span> <span class="ident">usize</span>, <span class="ident">c</span>.<span class="ident">g</span> <span class="kw">as</span> <span class="ident">usize</span>, <span class="ident">c</span>.<span class="ident">b</span> <span class="kw">as</span> <span class="ident">usize</span>).<span class="ident">alpha</span>(<span class="number">0.6</span>);
                    <span class="ident">batch</span>.<span class="ident">push</span>(
                        <span class="ident">color</span>,
                        <span class="ident">square</span>
                            .<span class="ident">translate</span>((<span class="ident">x</span> <span class="op">*</span> <span class="ident">opts</span>.<span class="ident">resolution</span>) <span class="kw">as</span> <span class="ident">f64</span>, (<span class="ident">y</span> <span class="op">*</span> <span class="ident">opts</span>.<span class="ident">resolution</span>) <span class="kw">as</span> <span class="ident">f64</span>),
                    );
                }
            }
        }
    }

    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">labels</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="string">&quot;0&quot;</span>.<span class="ident">to_string</span>()];
    <span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">1</span>..<span class="op">=</span><span class="ident">num_colors</span> {
        <span class="kw">let</span> <span class="ident">pct</span> <span class="op">=</span> (<span class="ident">i</span> <span class="kw">as</span> <span class="ident">f64</span>) <span class="op">/</span> (<span class="ident">num_colors</span> <span class="kw">as</span> <span class="ident">f64</span>);
        <span class="ident">labels</span>.<span class="ident">push</span>(
            (<span class="ident">pct</span> <span class="op">*</span> (<span class="ident">distrib</span>.<span class="ident">select</span>(<span class="ident">Statistic</span>::<span class="ident">Max</span>).<span class="ident">unwrap</span>() <span class="kw">as</span> <span class="ident">f64</span>))
                .<span class="ident">round</span>()
                .<span class="ident">to_string</span>(),
        );
    }
    <span class="ident">ColorLegend</span>::<span class="ident">gradient</span>(<span class="ident">ctx</span>, <span class="kw-2">&amp;</span><span class="ident">ColorScale</span>(<span class="ident">colors</span>), <span class="ident">labels</span>)
}

<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Grid</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> {
    <span class="kw">pub</span> <span class="ident">data</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span>,
    <span class="kw">pub</span> <span class="ident">width</span>: <span class="ident">usize</span>,
    <span class="kw">pub</span> <span class="ident">height</span>: <span class="ident">usize</span>,
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">T</span>: <span class="ident">Copy</span><span class="op">&gt;</span> <span class="ident">Grid</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> {
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">width</span>: <span class="ident">usize</span>, <span class="ident">height</span>: <span class="ident">usize</span>, <span class="ident">default</span>: <span class="ident">T</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Grid</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> {
        <span class="ident">Grid</span> {
            <span class="ident">data</span>: <span class="ident">std</span>::<span class="ident">iter</span>::<span class="ident">repeat</span>(<span class="ident">default</span>).<span class="ident">take</span>(<span class="ident">width</span> <span class="op">*</span> <span class="ident">height</span>).<span class="ident">collect</span>(),
            <span class="ident">width</span>,
            <span class="ident">height</span>,
        }
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">idx</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">x</span>: <span class="ident">usize</span>, <span class="ident">y</span>: <span class="ident">usize</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">usize</span> {
        <span class="comment">// Row-major</span>
        <span class="ident">y</span> <span class="op">*</span> <span class="self">self</span>.<span class="ident">width</span> <span class="op">+</span> <span class="ident">x</span>
    }
}
</pre></div>
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