scrawl-canvas
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<h1 id="assetadvancedfunctionality-mixin">AssetAdvancedFunctionality mixin</h1>
<p>The following functionality is shared between NoiseAsset and RdAsset objects</p>
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<h4 id="imports">Imports</h4>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">import</span> { mergeOver, pushUnique, λ<span class="hljs-literal">null</span>, Ωempty } <span class="hljs-keyword">from</span> <span class="hljs-string">'../core/utilities.js'</span>;
<span class="hljs-keyword">import</span> { makeGradient } <span class="hljs-keyword">from</span> <span class="hljs-string">'../factory/gradient.js'</span>;</pre></div></div>
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<h4 id="export-function">Export function</h4>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">export</span> <span class="hljs-keyword">default</span> <span class="hljs-keyword">function</span> (<span class="hljs-params">P = Ωempty</span>) {</pre></div></div>
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<h4 id="shared-attributes">Shared attributes</h4>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> defaultAttributes = {
<span class="hljs-attr">choke</span>: <span class="hljs-number">15</span>,</pre></div></div>
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<p><strong>paletteStart</strong>, <strong>paletteEnd</strong> <em>pseudo-attributes</em> - We don’t need to use the entire palette when building a gradient; we can restrict the palette using these start and end attributes.</p>
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<p>The <strong>cyclePalette</strong> <em>pseudo-attribute</em> tells the Palette object how to handle situations where the paletteStart value is greater than the paletteEnd value:</p>
<ul>
<li>when false, we reverse the color stops</li>
<li>when true, we keep the normal order of color stops and pass through the 1/0 border</li>
</ul>
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<p>The Gradient’s <strong>delta</strong> object is not stored in the defs object; it acts in a similar way to the artefact delta object - though it is restricted to adding delta values to Number and ‘String%’ attributes.</p>
<p>The <strong>colors</strong> <em>pseudo-attribute</em> can be used to pass through an array of palette color objects to the Gradient Palette object. The data is not retained by the gradient object.</p>
<ul>
<li>A better approach to managing gradient colors after it has been created is to use the <code>gradient.updateColor</code> and <code>gradient.removeColor</code> functions</li>
</ul>
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<p>The <strong>easing</strong> <em>pseudo-attribute</em> represents a transformation that will be applied to a copy of the color stops Array - this allows us to create non-linear gradients. Value is passed through to the Palette object</p>
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<p>The <strong>precision</strong> <em>pseudo-attribute</em> - value is passed through to the Gradient Palette object</p>
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<p>The <strong>colorSpace</strong> - String <em>pseudo-attribute</em> defines the color space to be used by the Gradient Palette’s Color object for its internal calculations - value is passed through to the Palette object</p>
<ul>
<li>Accepted values from: <code>'RGB', 'HSL', 'HWB', 'XYZ', 'LAB', 'LCH', 'OKLAB', 'OKLCH'</code> with <code>RGB</code> as the default</li>
</ul>
<p>The <strong>returnColorAs</strong> - String <em>pseudo-attribute</em> defines the type of color String the Gradient Palette’s Color object will return - value is passed through to the Gradient Palette object</p>
<ul>
<li>Accepted values from: <code>'RGB', 'HSL', 'HWB', 'LAB', 'LCH', 'OKLAB', 'OKLCH'</code> with <code>RGB</code> as the default</li>
</ul>
</div>
<div class="content"><div class='highlight'><pre> };
P.<span class="hljs-property">defs</span> = <span class="hljs-title function_">mergeOver</span>(P.<span class="hljs-property">defs</span>, defaultAttributes);</pre></div></div>
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<h4 id="packet-management">Packet management</h4>
<p>No additional packet management functionality defined here</p>
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<h4 id="clone-management">Clone management</h4>
<p>No additional clone functionality defined here</p>
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<h4 id="kill-management">Kill management</h4>
<p>No additional kill functionality defined here</p>
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<h4 id="get-set-deltaset">Get, Set, deltaSet</h4>
<p>These all route get/set/setDelta attribute changes through to the Gradient object</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> S = P.<span class="hljs-property">setters</span>,
D = P.<span class="hljs-property">deltaSetters</span>;
S.<span class="hljs-property">paletteStart</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>.<span class="hljs-title function_">set</span>({ <span class="hljs-attr">paletteStart</span>: item });
};
D.<span class="hljs-property">paletteStart</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>.<span class="hljs-title function_">setDelta</span>({ <span class="hljs-attr">paletteStart</span>: item });
};
S.<span class="hljs-property">paletteEnd</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>.<span class="hljs-title function_">set</span>({ <span class="hljs-attr">paletteEnd</span>: item });
};
D.<span class="hljs-property">paletteEnd</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>.<span class="hljs-title function_">setDelta</span>({ <span class="hljs-attr">paletteEnd</span>: item });
};
S.<span class="hljs-property">colors</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>.<span class="hljs-title function_">set</span>({ <span class="hljs-attr">colors</span>: item });
};
S.<span class="hljs-property">precision</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>.<span class="hljs-title function_">set</span>({ <span class="hljs-attr">precision</span>: item });
};
S.<span class="hljs-property">easing</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>.<span class="hljs-title function_">set</span>({ <span class="hljs-attr">easing</span>: item });
};
S.<span class="hljs-property">easingFunction</span> = S.<span class="hljs-property">easing</span>;
S.<span class="hljs-property">colorSpace</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>.<span class="hljs-title function_">set</span>({ <span class="hljs-attr">colorSpace</span>: item });
};
S.<span class="hljs-property">returnColorAs</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>.<span class="hljs-title function_">set</span>({ <span class="hljs-attr">returnColorAs</span>: item });
};
S.<span class="hljs-property">cyclePalette</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>.<span class="hljs-title function_">set</span>({ <span class="hljs-attr">cyclePalette</span>: item });
};
S.<span class="hljs-property">delta</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">items = Ωempty</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span>.<span class="hljs-title function_">set</span>({ <span class="hljs-attr">delta</span>: items });
};</pre></div></div>
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<h4 id="prototype-functions">Prototype functions</h4>
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<p><code>installElement</code> - internal function, used by the constructor</p>
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<div class="content"><div class='highlight'><pre> P.<span class="hljs-property">installElement</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">name</span>) {
<span class="hljs-keyword">let</span> element = <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">createElement</span>(<span class="hljs-string">'canvas'</span>);
element.<span class="hljs-property">id</span> = name;
<span class="hljs-variable language_">this</span>.<span class="hljs-property">element</span> = element;
<span class="hljs-variable language_">this</span>.<span class="hljs-property">engine</span> = <span class="hljs-variable language_">this</span>.<span class="hljs-property">element</span>.<span class="hljs-title function_">getContext</span>(<span class="hljs-string">'2d'</span>);</pre></div></div>
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<p>The color canvas allows us to map contour-like lines across a noise or rd asset’s output.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> color = <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">createElement</span>(<span class="hljs-string">'canvas'</span>);
color.<span class="hljs-property">id</span> = <span class="hljs-string">`<span class="hljs-subst">${name}</span>-color`</span>;
color.<span class="hljs-property">width</span> = <span class="hljs-number">256</span>;
color.<span class="hljs-property">height</span> = <span class="hljs-number">1</span>;
<span class="hljs-variable language_">this</span>.<span class="hljs-property">colorElement</span> = color;
<span class="hljs-variable language_">this</span>.<span class="hljs-property">colorEngine</span> = <span class="hljs-variable language_">this</span>.<span class="hljs-property">colorElement</span>.<span class="hljs-title function_">getContext</span>(<span class="hljs-string">'2d'</span>);
<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradient</span> = <span class="hljs-title function_">makeGradient</span>({
<span class="hljs-attr">name</span>: <span class="hljs-string">`<span class="hljs-subst">${name}</span>-gradient`</span>,
<span class="hljs-attr">endX</span>: <span class="hljs-string">'100%'</span>,
<span class="hljs-attr">delta</span>: {
<span class="hljs-attr">paletteStart</span>: <span class="hljs-number">0</span>,
<span class="hljs-attr">paletteEnd</span>: <span class="hljs-number">0</span>,
},
<span class="hljs-attr">cyclePalette</span>: <span class="hljs-literal">false</span>,
});
<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradientLastUpdated</span> = <span class="hljs-number">0</span>;
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p><code>checkSource</code></p>
<ul>
<li>Gets invoked by subscribers (who have a handle to the asset instance object) as part of the display cycle.</li>
<li>Assets will automatically pass this call onto <code>notifySubscribers</code>, where dirty flags get checked and rectified</li>
</ul>
</div>
<div class="content"><div class='highlight'><pre> P.<span class="hljs-property">checkSource</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">width, height</span>) {
<span class="hljs-variable language_">this</span>.<span class="hljs-title function_">notifySubscribers</span>();
};</pre></div></div>
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<p><code>getData</code> function called by Cell objects when calculating required updates to its CanvasRenderingContext2D engine, specifically for an entity’s <strong>fillStyle</strong>, <strong>strokeStyle</strong> and <strong>shadowColor</strong> attributes.</p>
<ul>
<li>This is the point when we clean Scrawl-canvas assets which have told their subscribers that asset data/attributes have updated</li>
</ul>
</div>
<div class="content"><div class='highlight'><pre> P.<span class="hljs-property">getData</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">entity, cell</span>) {
<span class="hljs-variable language_">this</span>.<span class="hljs-title function_">notifySubscribers</span>();
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">buildStyle</span>(cell);
};</pre></div></div>
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<p><code>notifySubscribers</code> - If the gradient is to be animated, then we need to update the asset at some point (generally the start) of each Display cycle by invoking this function</p>
</div>
<div class="content"><div class='highlight'><pre> P.<span class="hljs-property">update</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) {
<span class="hljs-variable language_">this</span>.<span class="hljs-property">dirtyOutput</span> = <span class="hljs-literal">true</span>;
};</pre></div></div>
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<p><code>notifySubscribers</code>, <code>notifySubscriber</code> - overwrites the functions defined in mixin/asset.js</p>
</div>
<div class="content"><div class='highlight'><pre> P.<span class="hljs-property">notifySubscribers</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">dirtyOutput</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">cleanOutput</span>();
<span class="hljs-variable language_">this</span>.<span class="hljs-property">subscribers</span>.<span class="hljs-title function_">forEach</span>(<span class="hljs-function"><span class="hljs-params">sub</span> =></span> <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">notifySubscriber</span>(sub), <span class="hljs-variable language_">this</span>);
};
P.<span class="hljs-property">notifySubscriber</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">sub</span>) {
sub.<span class="hljs-property">sourceNaturalWidth</span> = <span class="hljs-variable language_">this</span>.<span class="hljs-property">width</span>;
sub.<span class="hljs-property">sourceNaturalHeight</span> = <span class="hljs-variable language_">this</span>.<span class="hljs-property">height</span>;
sub.<span class="hljs-property">sourceLoaded</span> = <span class="hljs-literal">true</span>;
sub.<span class="hljs-property">source</span> = <span class="hljs-variable language_">this</span>.<span class="hljs-property">element</span>;
sub.<span class="hljs-property">dirtyImage</span> = <span class="hljs-literal">true</span>;
sub.<span class="hljs-property">dirtyCopyStart</span> = <span class="hljs-literal">true</span>;
sub.<span class="hljs-property">dirtyCopyDimensions</span> = <span class="hljs-literal">true</span>;
sub.<span class="hljs-property">dirtyImageSubscribers</span> = <span class="hljs-literal">true</span>;
};</pre></div></div>
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<p><code>paintCanvas</code> - internal function called by the <code>cleanOutput</code> function</p>
</div>
<div class="content"><div class='highlight'><pre> P.<span class="hljs-property">paintCanvas</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-title function_">checkOutputValuesExist</span>()) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">dirtyOutput</span>) {
<span class="hljs-variable language_">this</span>.<span class="hljs-property">dirtyOutput</span> = <span class="hljs-literal">false</span>;
<span class="hljs-keyword">const</span> {element, engine, width, height, colorElement, colorEngine, gradient, choke, gradientLastUpdated } = <span class="hljs-variable language_">this</span>;
<span class="hljs-keyword">const</span> palette = gradient.<span class="hljs-property">palette</span>;</pre></div></div>
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<p>Update the Canvas element’s dimensions - this will also clear the canvas display</p>
</div>
<div class="content"><div class='highlight'><pre> element.<span class="hljs-property">width</span> = width;
element.<span class="hljs-property">height</span> = height;
<span class="hljs-keyword">let</span> img = engine.<span class="hljs-title function_">getImageData</span>(<span class="hljs-number">0</span>, <span class="hljs-number">0</span>, width, height),
iData = img.<span class="hljs-property">data</span>,
len = width * height,
i, v, c;
<span class="hljs-keyword">const</span> now = <span class="hljs-title class_">Date</span>.<span class="hljs-title function_">now</span>();
<span class="hljs-keyword">if</span> (gradientLastUpdated + choke < now) {
gradient.<span class="hljs-title function_">updateByDelta</span>();
<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradientLastUpdated</span> = now;
}
<span class="hljs-keyword">if</span> (palette.<span class="hljs-property">dirtyPalette</span>) palette.<span class="hljs-title function_">recalculate</span>();
<span class="hljs-keyword">let</span> G = colorEngine.<span class="hljs-title function_">createLinearGradient</span>(<span class="hljs-number">0</span>, <span class="hljs-number">0</span>, <span class="hljs-number">255</span>, <span class="hljs-number">0</span>);
gradient.<span class="hljs-title function_">addStopsToGradient</span>(G, gradient.<span class="hljs-property">paletteStart</span>, gradient.<span class="hljs-property">paletteEnd</span>, gradient.<span class="hljs-property">cyclePalette</span>);
colorEngine.<span class="hljs-property">fillStyle</span> = G;
colorEngine.<span class="hljs-title function_">fillRect</span>(<span class="hljs-number">0</span>, <span class="hljs-number">0</span>, <span class="hljs-number">256</span>, <span class="hljs-number">1</span>);
<span class="hljs-keyword">let</span> gData = colorEngine.<span class="hljs-title function_">getImageData</span>(<span class="hljs-number">0</span>, <span class="hljs-number">0</span>, <span class="hljs-number">256</span>, <span class="hljs-number">1</span>).<span class="hljs-property">data</span>;
<span class="hljs-keyword">for</span> (i = <span class="hljs-number">0</span>; i < len; i++) {
v = <span class="hljs-title class_">Math</span>.<span class="hljs-title function_">floor</span>(<span class="hljs-variable language_">this</span>.<span class="hljs-title function_">getOutputValue</span>(i, width) * <span class="hljs-number">255</span>) * <span class="hljs-number">4</span>;
c = i * <span class="hljs-number">4</span>;
iData[c] = gData[v];
iData[++c] = gData[++v];
iData[++c] = gData[++v];
iData[++c] = gData[++v];
}
engine.<span class="hljs-title function_">putImageData</span>(img, <span class="hljs-number">0</span>, <span class="hljs-number">0</span>);
}
}
};</pre></div></div>
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<p>Return the prototype</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">return</span> P;
};</pre></div></div>
</li>
</ul>
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