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canvas-background.html
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<!DOCTYPE html>
<html lang="en-US">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>Canvas background | Chart.js</title>
<meta name="generator" content="VuePress 1.8.2">
<link rel="icon" href="/docs/3.0.2/favicon.ico">
<meta name="description" content="Open source HTML5 Charts for your website">
<link rel="preload" href="/docs/3.0.2/assets/css/0.styles.167a146f.css" as="style"><link rel="preload" href="/docs/3.0.2/assets/js/app.6bf3e574.js" as="script"><link rel="preload" href="/docs/3.0.2/assets/js/2.12eeefd0.js" as="script"><link rel="preload" href="/docs/3.0.2/assets/js/141.61ca28e4.js" as="script"><link rel="preload" href="/docs/3.0.2/assets/js/3.1e2ae757.js" as="script"><link rel="prefetch" href="/docs/3.0.2/assets/js/10.f55d851f.js"><link rel="prefetch" href="/docs/3.0.2/assets/js/100.5a2b4083.js"><link rel="prefetch" href="/docs/3.0.2/assets/js/101.a8bd2fd6.js"><link rel="prefetch" href="/docs/3.0.2/assets/js/102.33de6359.js"><link rel="prefetch" href="/docs/3.0.2/assets/js/103.dcd6e6a8.js"><link rel="prefetch" href="/docs/3.0.2/assets/js/104.ab312fc7.js"><link rel="prefetch" href="/docs/3.0.2/assets/js/105.fe2ab4d8.js"><link rel="prefetch" href="/docs/3.0.2/assets/js/106.844a25c8.js"><link rel="prefetch" href="/docs/3.0.2/assets/js/107.c9dc1e9f.js"><link rel="prefetch" 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<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav> <ul class="sidebar-links"><li><a href="/docs/3.0.2/" aria-current="page" class="sidebar-link">Chart.js</a></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Getting Started</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>General</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading open"><span>Configuration</span> <span class="arrow down"></span></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/docs/3.0.2/configuration/" aria-current="page" class="sidebar-link">Configuration</a></li><li><a href="/docs/3.0.2/configuration/responsive.html" class="sidebar-link">Responsive Charts</a></li><li><a href="/docs/3.0.2/configuration/device-pixel-ratio.html" class="sidebar-link">Device Pixel Ratio</a></li><li><a href="/docs/3.0.2/configuration/locale.html" class="sidebar-link">Locale</a></li><li><a href="/docs/3.0.2/configuration/interactions.html" class="sidebar-link">Interactions</a></li><li><a href="/docs/3.0.2/configuration/canvas-background.html" aria-current="page" class="active sidebar-link">Canvas background</a></li><li><a href="/docs/3.0.2/configuration/animations.html" class="sidebar-link">Animations</a></li><li><a href="/docs/3.0.2/configuration/layout.html" class="sidebar-link">Layout</a></li><li><a href="/docs/3.0.2/configuration/legend.html" class="sidebar-link">Legend</a></li><li><a href="/docs/3.0.2/configuration/title.html" class="sidebar-link">Title</a></li><li><a href="/docs/3.0.2/configuration/tooltip.html" class="sidebar-link">Tooltip</a></li><li><a href="/docs/3.0.2/configuration/elements.html" class="sidebar-link">Elements</a></li><li><a href="/docs/3.0.2/configuration/decimation.html" class="sidebar-link">Data Decimation</a></li></ul></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Chart Types</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Axes</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Developers</span> <span class="arrow right"></span></p> <!----></section></li></ul> </aside> <main class="page"> <div class="theme-default-content content__default"><h1 id="canvas-background"><a href="#canvas-background" class="header-anchor">#</a> Canvas background</h1> <p>In some use cases you would want a background image or color over the whole canvas. There is no build in support for this, the way you can achieve this is by writing a custom plugin.</p> <p>In the two example plugins underneath here you can see how you can draw an color or image to the canvas as background. This way of giving the chart a background is only necessary if you want to export the chart with that specific background.
For normal use you can set the background more easily with <a href="https://www.w3schools.com/cssref/css3_pr_background.asp" target="_blank" rel="noopener noreferrer">CSS<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a>.</p> <div class="tabs-component"><ul role="tablist" class="tabs-component-tabs"></ul> <div class="tabs-component-panels"><section aria-hidden="true" id="color" role="tabpanel" class="tabs-component-panel" style="display:none;"><div class="chart-editor" data-v-365c20ab><div class="chart-view" data-v-365c20ab><canvas></canvas></div> <div class="chart-actions" data-v-2afd21f1 data-v-365c20ab></div> <div class="code-editor" data-v-66ca8197 data-v-365c20ab><div class="code-editor-header" data-v-66ca8197><div class="code-editor-tabs" data-v-66ca8197><button class="code-editor-tab active" data-v-66ca8197>
config
</button><button class="code-editor-tab" data-v-66ca8197>
setup
</button><button class="code-editor-tab" data-v-66ca8197>
plugin
</button></div> <div class="code-editor-tools" data-v-66ca8197><!----> <a href="https://github.com/chartjs/Chart.js/blob/master/docs/configuration/canvas-background.md" title="View on GitHub" target="_blank" class="code-editor-tool fab fa-github fa-lg" data-v-66ca8197></a></div></div> <div class="code-editor-views" data-v-66ca8197><div class="editor-textarea ps" data-v-05f11386 data-v-66ca8197><div class="editor-textarea-content" data-v-05f11386><div class="prism-editor-wrapper" data-v-05f11386><div class="prism-editor__container"><textarea spellCheck="false" autocapitalize="off" autocomplete="off" autocorrect="off" data-gramm="false" placeholder="" data-testid="textarea" class="prism-editor__textarea">const config = {
type: 'doughnut',
data: data,
plugins: [plugin],
};</textarea><pre data-testid="preview" class="prism-editor__editor"><span class="token keyword">const</span> config <span class="token operator">=</span> <span class="token punctuation">{</span>
type<span class="token operator">:</span> <span class="token string">'doughnut'</span><span class="token punctuation">,</span>
data<span class="token operator">:</span> data<span class="token punctuation">,</span>
plugins<span class="token operator">:</span> <span class="token punctuation">[</span>plugin<span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span><br /></pre></div></div></div></div><div class="editor-textarea ps" style="display:none;" data-v-05f11386 data-v-66ca8197><div class="editor-textarea-content" data-v-05f11386><div class="prism-editor-wrapper" data-v-05f11386><div class="prism-editor__container"><textarea spellCheck="false" autocapitalize="off" autocomplete="off" autocorrect="off" data-gramm="false" placeholder="" data-testid="textarea" class="prism-editor__textarea">const data = {
labels: [
'Red',
'Blue',
'Yellow'
],
datasets: [{
label: 'My First Dataset',
data: [300, 50, 100],
backgroundColor: [
'rgb(255, 99, 132)',
'rgb(54, 162, 235)',
'rgb(255, 205, 86)'
],
hoverOffset: 4
}]
};</textarea><pre data-testid="preview" class="prism-editor__editor"><span class="token keyword">const</span> data <span class="token operator">=</span> <span class="token punctuation">{</span>
labels<span class="token operator">:</span> <span class="token punctuation">[</span>
<span class="token string">'Red'</span><span class="token punctuation">,</span>
<span class="token string">'Blue'</span><span class="token punctuation">,</span>
<span class="token string">'Yellow'</span>
<span class="token punctuation">]</span><span class="token punctuation">,</span>
datasets<span class="token operator">:</span> <span class="token punctuation">[</span><span class="token punctuation">{</span>
label<span class="token operator">:</span> <span class="token string">'My First Dataset'</span><span class="token punctuation">,</span>
data<span class="token operator">:</span> <span class="token punctuation">[</span><span class="token number">300</span><span class="token punctuation">,</span> <span class="token number">50</span><span class="token punctuation">,</span> <span class="token number">100</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
backgroundColor<span class="token operator">:</span> <span class="token punctuation">[</span>
<span class="token string">'rgb(255, 99, 132)'</span><span class="token punctuation">,</span>
<span class="token string">'rgb(54, 162, 235)'</span><span class="token punctuation">,</span>
<span class="token string">'rgb(255, 205, 86)'</span>
<span class="token punctuation">]</span><span class="token punctuation">,</span>
hoverOffset<span class="token operator">:</span> <span class="token number">4</span>
<span class="token punctuation">}</span><span class="token punctuation">]</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span><br /></pre></div></div></div></div><div class="editor-textarea ps" style="display:none;" data-v-05f11386 data-v-66ca8197><div class="editor-textarea-content" data-v-05f11386><div class="prism-editor-wrapper" data-v-05f11386><div class="prism-editor__container"><textarea spellCheck="false" autocapitalize="off" autocomplete="off" autocorrect="off" data-gramm="false" placeholder="" data-testid="textarea" class="prism-editor__textarea">// Note: changes to the plugin code is not reflected to the chart, because the plugin is loaded at chart construction time and editor changes only trigger an chart.update().
const plugin = {
id: 'custom_canvas_background_color',
beforeDraw: (chart) => {
const ctx = chart.canvas.getContext('2d');
ctx.save();
ctx.globalCompositeOperation = 'destination-over';
ctx.fillStyle = 'lightGreen';
ctx.fillRect(0, 0, chart.width, chart.height);
ctx.restore();
}
};</textarea><pre data-testid="preview" class="prism-editor__editor"><span class="token comment">// Note: changes to the plugin code is not reflected to the chart, because the plugin is loaded at chart construction time and editor changes only trigger an chart.update().</span>
<span class="token keyword">const</span> plugin <span class="token operator">=</span> <span class="token punctuation">{</span>
id<span class="token operator">:</span> <span class="token string">'custom_canvas_background_color'</span><span class="token punctuation">,</span>
<span class="token function-variable function">beforeDraw</span><span class="token operator">:</span> <span class="token punctuation">(</span><span class="token parameter">chart</span><span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token punctuation">{</span>
<span class="token keyword">const</span> ctx <span class="token operator">=</span> chart<span class="token punctuation">.</span>canvas<span class="token punctuation">.</span><span class="token function">getContext</span><span class="token punctuation">(</span><span class="token string">'2d'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
ctx<span class="token punctuation">.</span><span class="token function">save</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
ctx<span class="token punctuation">.</span>globalCompositeOperation <span class="token operator">=</span> <span class="token string">'destination-over'</span><span class="token punctuation">;</span>
ctx<span class="token punctuation">.</span>fillStyle <span class="token operator">=</span> <span class="token string">'lightGreen'</span><span class="token punctuation">;</span>
ctx<span class="token punctuation">.</span><span class="token function">fillRect</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> chart<span class="token punctuation">.</span>width<span class="token punctuation">,</span> chart<span class="token punctuation">.</span>height<span class="token punctuation">)</span><span class="token punctuation">;</span>
ctx<span class="token punctuation">.</span><span class="token function">restore</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span><br /></pre></div></div></div></div></div></div></div></section> <section aria-hidden="true" id="image" role="tabpanel" class="tabs-component-panel" style="display:none;"><div class="chart-editor" data-v-365c20ab><div class="chart-view" data-v-365c20ab><canvas></canvas></div> <div class="chart-actions" data-v-2afd21f1 data-v-365c20ab></div> <div class="code-editor" data-v-66ca8197 data-v-365c20ab><div class="code-editor-header" data-v-66ca8197><div class="code-editor-tabs" data-v-66ca8197><button class="code-editor-tab active" data-v-66ca8197>
config
</button><button class="code-editor-tab" data-v-66ca8197>
setup
</button><button class="code-editor-tab" data-v-66ca8197>
plugin
</button></div> <div class="code-editor-tools" data-v-66ca8197><!----> <a href="https://github.com/chartjs/Chart.js/blob/master/docs/configuration/canvas-background.md" title="View on GitHub" target="_blank" class="code-editor-tool fab fa-github fa-lg" data-v-66ca8197></a></div></div> <div class="code-editor-views" data-v-66ca8197><div class="editor-textarea ps" data-v-05f11386 data-v-66ca8197><div class="editor-textarea-content" data-v-05f11386><div class="prism-editor-wrapper" data-v-05f11386><div class="prism-editor__container"><textarea spellCheck="false" autocapitalize="off" autocomplete="off" autocorrect="off" data-gramm="false" placeholder="" data-testid="textarea" class="prism-editor__textarea">const config = {
type: 'doughnut',
data: data,
plugins: [plugin],
};</textarea><pre data-testid="preview" class="prism-editor__editor"><span class="token keyword">const</span> config <span class="token operator">=</span> <span class="token punctuation">{</span>
type<span class="token operator">:</span> <span class="token string">'doughnut'</span><span class="token punctuation">,</span>
data<span class="token operator">:</span> data<span class="token punctuation">,</span>
plugins<span class="token operator">:</span> <span class="token punctuation">[</span>plugin<span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span><br /></pre></div></div></div></div><div class="editor-textarea ps" style="display:none;" data-v-05f11386 data-v-66ca8197><div class="editor-textarea-content" data-v-05f11386><div class="prism-editor-wrapper" data-v-05f11386><div class="prism-editor__container"><textarea spellCheck="false" autocapitalize="off" autocomplete="off" autocorrect="off" data-gramm="false" placeholder="" data-testid="textarea" class="prism-editor__textarea">const data = {
labels: [
'Red',
'Blue',
'Yellow'
],
datasets: [{
label: 'My First Dataset',
data: [300, 50, 100],
backgroundColor: [
'rgb(255, 99, 132)',
'rgb(54, 162, 235)',
'rgb(255, 205, 86)'
],
hoverOffset: 4
}]
};</textarea><pre data-testid="preview" class="prism-editor__editor"><span class="token keyword">const</span> data <span class="token operator">=</span> <span class="token punctuation">{</span>
labels<span class="token operator">:</span> <span class="token punctuation">[</span>
<span class="token string">'Red'</span><span class="token punctuation">,</span>
<span class="token string">'Blue'</span><span class="token punctuation">,</span>
<span class="token string">'Yellow'</span>
<span class="token punctuation">]</span><span class="token punctuation">,</span>
datasets<span class="token operator">:</span> <span class="token punctuation">[</span><span class="token punctuation">{</span>
label<span class="token operator">:</span> <span class="token string">'My First Dataset'</span><span class="token punctuation">,</span>
data<span class="token operator">:</span> <span class="token punctuation">[</span><span class="token number">300</span><span class="token punctuation">,</span> <span class="token number">50</span><span class="token punctuation">,</span> <span class="token number">100</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
backgroundColor<span class="token operator">:</span> <span class="token punctuation">[</span>
<span class="token string">'rgb(255, 99, 132)'</span><span class="token punctuation">,</span>
<span class="token string">'rgb(54, 162, 235)'</span><span class="token punctuation">,</span>
<span class="token string">'rgb(255, 205, 86)'</span>
<span class="token punctuation">]</span><span class="token punctuation">,</span>
hoverOffset<span class="token operator">:</span> <span class="token number">4</span>
<span class="token punctuation">}</span><span class="token punctuation">]</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span><br /></pre></div></div></div></div><div class="editor-textarea ps" style="display:none;" data-v-05f11386 data-v-66ca8197><div class="editor-textarea-content" data-v-05f11386><div class="prism-editor-wrapper" data-v-05f11386><div class="prism-editor__container"><textarea spellCheck="false" autocapitalize="off" autocomplete="off" autocorrect="off" data-gramm="false" placeholder="" data-testid="textarea" class="prism-editor__textarea">// Note: changes to the plugin code is not reflected to the chart, because the plugin is loaded at chart construction time and editor changes only trigger an chart.update().
const image = new Image();
image.src = 'https://www.chartjs.org/img/chartjs-logo.svg';
const plugin = {
id: 'custom_canvas_background_image',
beforeDraw: (chart) => {
if (image.complete) {
const ctx = chart.ctx;
const {top, left, width, height} = chart.chartArea;
const x = left + width / 2 - image.width / 2;
const y = top + height / 2 - image.height / 2;
ctx.drawImage(image, x, y);
} else {
image.onload = () => chart.draw();
}
}
};</textarea><pre data-testid="preview" class="prism-editor__editor"><span class="token comment">// Note: changes to the plugin code is not reflected to the chart, because the plugin is loaded at chart construction time and editor changes only trigger an chart.update().</span>
<span class="token keyword">const</span> image <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Image</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
image<span class="token punctuation">.</span>src <span class="token operator">=</span> <span class="token string">'https://www.chartjs.org/img/chartjs-logo.svg'</span><span class="token punctuation">;</span>
<span class="token keyword">const</span> plugin <span class="token operator">=</span> <span class="token punctuation">{</span>
id<span class="token operator">:</span> <span class="token string">'custom_canvas_background_image'</span><span class="token punctuation">,</span>
<span class="token function-variable function">beforeDraw</span><span class="token operator">:</span> <span class="token punctuation">(</span><span class="token parameter">chart</span><span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token punctuation">{</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span>image<span class="token punctuation">.</span>complete<span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">const</span> ctx <span class="token operator">=</span> chart<span class="token punctuation">.</span>ctx<span class="token punctuation">;</span>
<span class="token keyword">const</span> <span class="token punctuation">{</span>top<span class="token punctuation">,</span> left<span class="token punctuation">,</span> width<span class="token punctuation">,</span> height<span class="token punctuation">}</span> <span class="token operator">=</span> chart<span class="token punctuation">.</span>chartArea<span class="token punctuation">;</span>
<span class="token keyword">const</span> x <span class="token operator">=</span> left <span class="token operator">+</span> width <span class="token operator">/</span> <span class="token number">2</span> <span class="token operator">-</span> image<span class="token punctuation">.</span>width <span class="token operator">/</span> <span class="token number">2</span><span class="token punctuation">;</span>
<span class="token keyword">const</span> y <span class="token operator">=</span> top <span class="token operator">+</span> height <span class="token operator">/</span> <span class="token number">2</span> <span class="token operator">-</span> image<span class="token punctuation">.</span>height <span class="token operator">/</span> <span class="token number">2</span><span class="token punctuation">;</span>
ctx<span class="token punctuation">.</span><span class="token function">drawImage</span><span class="token punctuation">(</span>image<span class="token punctuation">,</span> x<span class="token punctuation">,</span> y<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
image<span class="token punctuation">.</span><span class="token function-variable function">onload</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=></span> chart<span class="token punctuation">.</span><span class="token function">draw</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span><br /></pre></div></div></div></div></div></div></div></section></div></div></div> <footer class="page-edit"><!----> <div class="last-updated"><span class="prefix">Last Updated:</span> <span class="time">4/4/2021, 1:26:41 PM</span></div></footer> <div class="page-nav"><p class="inner"><span class="prev">
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