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<!DOCTYPE html><html><head><meta charset="utf-8"><meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"><title>React Native | Build Native Apps Using React</title><meta name="viewport" content="width=device-width"><meta property="og:title" content="React Native | Build Native Apps Using React"><meta property="og:type" content="website"><meta property="og:url" content="http://facebook.github.io/react-native/index.html"><meta property="og:image" content="http://facebook.github.io/react-native/img/opengraph.png"><meta property="og:description" content="Build Native Apps Using React"><link rel="shortcut icon" href="/react-native/img/favicon.png"><link rel="stylesheet" href="/react-native/css/react-native.css"><script type="text/javascript" src="//use.typekit.net/vqa1hcx.js"></script><script type="text/javascript">try{Typekit.load();}catch(e){}</script></head><body><div class="container"><div class="nav-main"><div class="wrap"><a class="nav-home" href="/react-native/"><img src="/react-native/img/logo.png">React Native</a><ul class="nav-site"><li><a href="/react-native/docs/getting-started.html#content" class="active">docs</a></li><li><a href="/react-native/support.html" class="">support</a></li><li><a href="http://github.com/facebook/react-native" class="">github</a></li></ul></div></div><section class="content wrap documentationContent"><div class="nav-docs"><div class="nav-docs-section"><h3>Quick Start</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/getting-started.html#content">Getting Started</a></li></ul></div><div class="nav-docs-section"><h3>Guides</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/pixels.html#content">Physical vs Logical Pixels</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/style.html#content">Style</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/nativemodulesios.html#content">Native Modules (iOS)</a></li></ul></div><div class="nav-docs-section"><h3>components</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/activityindicatorios.html#content">ActivityIndicatorIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/datepickerios.html#content">DatePickerIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/image.html#content">Image</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/listview.html#content">ListView</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/mapview.html#content">MapView</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/navigatorios.html#content">NavigatorIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/pickerios.html#content">PickerIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/scrollview.html#content">ScrollView</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/sliderios.html#content">SliderIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/switchios.html#content">SwitchIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/tabbarios.html#content">TabBarIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/text.html#content">Text</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/textinput.html#content">TextInput</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/touchablehighlight.html#content">TouchableHighlight</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/touchableopacity.html#content">TouchableOpacity</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/touchablewithoutfeedback.html#content">TouchableWithoutFeedback</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/view.html#content">View</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/webview.html#content">WebView</a></li></ul></div><div class="nav-docs-section"><h3>apis</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/alertios.html#content">AlertIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/animation.html#content">Animation</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/appregistry.html#content">AppRegistry</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/appstate.html#content">AppState</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/appstateios.html#content">AppStateIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/asyncstorage.html#content">AsyncStorage</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/cameraroll.html#content">CameraRoll</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/interactionmanager.html#content">InteractionManager</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/layoutanimation.html#content">LayoutAnimation</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/netinfo.html#content">NetInfo</a></li><li><a style="margin-left:0;" class="active" href="/react-native/docs/pixelratio.html#content">PixelRatio</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/statusbarios.html#content">StatusBarIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/stylesheet.html#content">StyleSheet</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/vibrationios.html#content">VibrationIOS</a></li></ul></div><div class="nav-docs-section"><h3>Polyfills</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/network.html#content">Network</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/timers.html#content">Timers</a></li></ul></div></div><div class="inner-content"><a id="content"></a><h1>PixelRatio</h1><div><div><p>PixelRatio class gives access to the device pixel density.</p><p>There are a few use cases for using PixelRatio:</p><h3><a class="anchor" name="displaying-a-line-that-s-as-thin-as-the-device-permits"></a>Displaying a line that's as thin as the device permits <a class="hash-link" href="#displaying-a-line-that-s-as-thin-as-the-device-permits">#</a></h3><p>A width of 1 is actually pretty thick on an iPhone 4+, we can do one that's
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thinner using a width of <code>1 / PixelRatio.get()</code>. It's a technique that works
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on all the devices independent of their pixel density.</p><div class="prism language-javascript">style<span class="token operator">=</span><span class="token punctuation">{</span><span class="token punctuation">{</span> borderWidth<span class="token punctuation">:</span> <span class="token number">1</span> <span class="token operator">/</span> PixelRatio<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">}</span><span class="token punctuation">}</span></div><h3><a class="anchor" name="fetching-a-correctly-sized-image"></a>Fetching a correctly sized image <a class="hash-link" href="#fetching-a-correctly-sized-image">#</a></h3><p>You should get a higher resolution image if you are on a high pixel density
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device. A good rule of thumb is to multiply the size of the image you display
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by the pixel ratio.</p><div class="prism language-javascript"><span class="token keyword">var</span> image <span class="token operator">=</span> <span class="token function">getImage<span class="token punctuation">(</span></span><span class="token punctuation">{</span>
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width<span class="token punctuation">:</span> <span class="token number">200</span> <span class="token operator">*</span> PixelRatio<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
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height<span class="token punctuation">:</span> <span class="token number">100</span> <span class="token operator">*</span> PixelRatio<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
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<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<Image source<span class="token operator">=</span><span class="token punctuation">{</span>image<span class="token punctuation">}</span> style<span class="token operator">=</span><span class="token punctuation">{</span><span class="token punctuation">{</span>width<span class="token punctuation">:</span> <span class="token number">200</span><span class="token punctuation">,</span> height<span class="token punctuation">:</span> <span class="token number">100</span><span class="token punctuation">}</span><span class="token punctuation">}</span> <span class="token operator">/</span><span class="token operator">></span></div></div><h3><a class="anchor" name="methods"></a>Methods <a class="hash-link" href="#methods">#</a></h3><div class="props"><div class="prop"><h4 class="propTitle"><a class="anchor" name="get"></a><span class="propType">static </span>get<span class="propType">()</span> <a class="hash-link" href="#get">#</a></h4><div><p>Returns the device pixel density. Some examples:</p><ul><li>PixelRatio.get() === 2<ul><li>iPhone 4, 4S</li><li>iPhone 5, 5c, 5s</li><li>iPhone 6</li></ul></li><li>PixelRatio.get() === 3<ul><li>iPhone 6 plus</li></ul></li></ul></div></div></div></div><noscript></noscript><div class="docs-prevnext"><a class="docs-next" href="statusbarios.html#content">Next →</a></div></div></section><footer class="wrap"><div class="right">© 2015 Facebook Inc.</div></footer></div><div id="fb-root"></div><script>
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