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href="#!" tabindex="0">iOS APIs</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/actionsheetios">ActionSheetIOS</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/dynamiccolorios">DynamicColorIOS</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/settings">Settings</a></li></ul></li></ul></li></ul></div></div></div><main class="docMainContainer_1rYT"><div class="container padding-vert--lg docItemWrapper_1Hme"><div class="row"><div class="col docItemCol_2AGf"><div class="docItemContainer_1tAC"><article><header><h1 class="docTitle_cWlf">PixelRatio</h1></header><div class="markdown"><p><code>PixelRatio</code> gives you access to the device's pixel density and font scale.</p><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_3pqN" id="fetching-a-correctly-sized-image"></a>Fetching a correctly sized image<a aria-hidden="true" tabindex="-1" class="hash-link" href="#fetching-a-correctly-sized-image" title="Direct link to heading">#</a></h2><p>You should get a higher resolution image if you are on a high pixel density device. A good rule of thumb is to multiply the size of the image you display by the pixel ratio.</p><div class="mdxCodeBlock_xYIz"><div class="codeBlockContent_rlEb"><button tabindex="0" type="button" aria-label="Copy code to clipboard" class="copyButton_kOW4">Copy</button><div class="prism-code language-jsx codeBlock_1AP7"><div class="codeBlockLines_1boI" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token keyword" style="color:#c5a5c5">var</span><span class="token plain"> image </span><span class="token operator" style="color:#fc929e">=</span><span class="token plain"> </span><span class="token function" style="color:#79b6f2">getImage</span><span class="token punctuation" style="color:#657b83">(</span><span class="token punctuation" style="color:#657b83">{</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> width</span><span class="token punctuation" style="color:#657b83">:</span><span class="token plain"> PixelRatio</span><span class="token punctuation" style="color:#657b83">.</span><span class="token function" style="color:#79b6f2">getPixelSizeForLayoutSize</span><span class="token punctuation" style="color:#657b83">(</span><span class="token number" style="color:#5a9bcf">200</span><span class="token punctuation" style="color:#657b83">)</span><span class="token punctuation" style="color:#657b83">,</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> height</span><span class="token punctuation" style="color:#657b83">:</span><span class="token plain"> PixelRatio</span><span class="token punctuation" style="color:#657b83">.</span><span class="token function" style="color:#79b6f2">getPixelSizeForLayoutSize</span><span class="token punctuation" style="color:#657b83">(</span><span class="token number" style="color:#5a9bcf">100</span><span class="token punctuation" style="color:#657b83">)</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"></span><span class="token punctuation" style="color:#657b83">}</span><span class="token punctuation" style="color:#657b83">)</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"></span><span class="token tag punctuation" style="color:#657b83"><</span><span class="token tag class-name" style="color:#fac863">Image</span><span class="token tag" style="color:#fc929e"> </span><span class="token tag attr-name" style="color:#c5a5c5">source</span><span class="token tag script language-javascript script-punctuation punctuation" style="color:#657b83">=</span><span class="token tag script language-javascript punctuation" style="color:#657b83">{</span><span class="token tag script language-javascript" style="color:#fc929e">image</span><span class="token tag script language-javascript punctuation" style="color:#657b83">}</span><span class="token tag" style="color:#fc929e"> </span><span class="token tag attr-name" style="color:#c5a5c5">style</span><span class="token tag script language-javascript script-punctuation punctuation" style="color:#657b83">=</span><span class="token tag script language-javascript punctuation" style="color:#657b83">{</span><span class="token tag script language-javascript punctuation" style="color:#657b83">{</span><span class="token tag script language-javascript" style="color:#fc929e"> width</span><span class="token tag script language-javascript punctuation" style="color:#657b83">:</span><span class="token tag script language-javascript" style="color:#fc929e"> </span><span class="token tag script language-javascript number" style="color:#5a9bcf">200</span><span class="token tag script language-javascript punctuation" style="color:#657b83">,</span><span class="token tag script language-javascript" style="color:#fc929e"> height</span><span class="token tag script language-javascript punctuation" style="color:#657b83">:</span><span class="token tag script language-javascript" style="color:#fc929e"> </span><span class="token tag script language-javascript number" style="color:#5a9bcf">100</span><span class="token tag script language-javascript" style="color:#fc929e"> </span><span class="token tag script language-javascript punctuation" style="color:#657b83">}</span><span class="token tag script language-javascript punctuation" style="color:#657b83">}</span><span class="token tag" style="color:#fc929e"> </span><span class="token tag punctuation" style="color:#657b83">/></span><span class="token punctuation" style="color:#657b83">;</span></div></div></div></div></div><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_3pqN" id="pixel-grid-snapping"></a>Pixel grid snapping<a aria-hidden="true" tabindex="-1" class="hash-link" href="#pixel-grid-snapping" title="Direct link to heading">#</a></h2><p>In iOS, you can specify positions and dimensions for elements with arbitrary precision, for example 29.674825. But, ultimately the physical display only have a fixed number of pixels, for example 640×960 for iPhone 4 or 750×1334 for iPhone 6. iOS tries to be as faithful as possible to the user value by spreading one original pixel into multiple ones to trick the eye. The downside of this technique is that it makes the resulting element look blurry.</p><p>In practice, we found out that developers do not want this feature and they have to work around it by doing manual rounding in order to avoid having blurry elements. In React Native, we are rounding all the pixels automatically.</p><p>We have to be careful when to do this rounding. You never want to work with rounded and unrounded values at the same time as you're going to accumulate rounding errors. Having even one rounding error is deadly because a one pixel border may vanish or be twice as big.</p><p>In React Native, everything in JavaScript and within the layout engine works with arbitrary precision numbers. It's only when we set the position and dimensions of the native element on the main thread that we round. Also, rounding is done relative to the root rather than the parent, again to avoid accumulating rounding errors.</p><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_3pqN" id="example"></a>Example<a aria-hidden="true" tabindex="-1" class="hash-link" href="#example" title="Direct link to heading">#</a></h2><div class="snack-player" data-snack-name="PixelRatio Example" data-snack-description="Example usage" data-snack-code="import%20React%20from%20%22react%22%3B%0Aimport%20%7B%20Image%2C%20PixelRatio%2C%20ScrollView%2C%20StyleSheet%2C%20Text%2C%20TextInput%2C%20View%20%7D%20from%20%22react-native%22%3B%0A%0Aconst%20size%20%3D%2050%3B%0Aconst%20cat%20%3D%20%7B%0A%20%20uri%3A%20%22https%3A%2F%2Freactnative.dev%2Fdocs%2Fassets%2Fp_cat1.png%22%2C%0A%20%20width%3A%20size%2C%0A%20%20height%3A%20size%0A%7D%3B%0A%0Aconst%20App%20%3D%20()%20%3D%3E%20(%0A%20%20%3CScrollView%20style%3D%7Bstyles.scrollContainer%7D%3E%0A%20%20%20%20%3CView%20style%3D%7Bstyles.container%7D%3E%0A%20%20%20%20%20%20%3CText%3ECurrent%20Pixel%20Ratio%20is%3A%3C%2FText%3E%0A%20%20%20%20%20%20%3CText%20style%3D%7Bstyles.value%7D%3E%7BPixelRatio.get()%7D%3C%2FText%3E%0A%20%20%20%20%3C%2FView%3E%0A%20%20%20%20%3CView%20style%3D%7Bstyles.container%7D%3E%0A%20%20%20%20%20%20%3CText%3ECurrent%20Font%20Scale%20is%3A%3C%2FText%3E%0A%20%20%20%20%20%20%3CText%20style%3D%7Bstyles.value%7D%3E%7BPixelRatio.getFontScale()%7D%3C%2FText%3E%0A%20%20%20%20%3C%2FView%3E%0A%20%20%20%20%3CView%20style%3D%7Bstyles.container%7D%3E%0A%20%20%20%20%20%20%3CText%3EOn%20this%20device%20images%20with%20a%20layout%20width%20of%3C%2FText%3E%0A%20%20%20%20%20%20%3CText%20style%3D%7Bstyles.value%7D%3E%7Bsize%7D%20px%3C%2FText%3E%0A%20%20%20%20%20%20%3CImage%20source%3D%7Bcat%7D%20%2F%3E%0A%20%20%20%20%3C%2FView%3E%0A%20%20%20%20%3CView%20style%3D%7Bstyles.container%7D%3E%0A%20%20%20%20%20%20%3CText%3Erequire%20images%20with%20a%20pixel%20width%20of%3C%2FText%3E%0A%20%20%20%20%20%20%3CText%20style%3D%7Bstyles.value%7D%3E%0A%20%20%20%20%20%20%20%20%7BPixelRatio.getPixelSizeForLayoutSize(size)%7D%20px%0A%20%20%20%20%20%20%3C%2FText%3E%0A%20%20%20%20%20%20%3CImage%0A%20%20%20%20%20%20%20%20source%3D%7Bcat%7D%0A%20%20%20%20%20%20%20%20style%3D%7B%7B%0A%20%20%20%20%20%20%20%20%20%20width%3A%20PixelRatio.getPixelSizeForLayoutSize(size)%2C%0A%20%20%20%20%20%20%20%20%20%20height%3A%20PixelRatio.getPixelSizeForLayoutSize(size)%0A%20%20%20%20%20%20%20%20%7D%7D%0A%20%20%20%20%20%20%2F%3E%0A%20%20%20%20%3C%2FView%3E%0A%20%20%3C%2FScrollView%3E%0A)%3B%0A%0Aconst%20styles%20%3D%20StyleSheet.create(%7B%0A%20%20scrollContainer%3A%20%7B%0A%20%20%20%20flext%3A%201%2C%0A%20%20%20%20marginTop%3A%20%222em%22%2C%0A%20%20%20%20justifyContent%3A%20%22center%22%2C%0A%20%20%7D%2C%0A%20%20container%3A%20%7B%0A%20%20%20%20justifyContent%3A%20%22center%22%2C%0A%20%20%20%20alignItems%3A%20%22center%22%0A%20%20%7D%2C%0A%20%20value%3A%20%7B%0A%20%20%20%20fontSize%3A%2024%2C%0A%20%20%20%20marginBottom%3A%2012%2C%0A%20%20%20%20marginTop%3A%204%0A%20%20%7D%0A%7D)%3B%0A%0Aexport%20default%20App%3B" data-snack-platform="web" data-snack-supported-platforms="ios,android,web" data-snack-theme="light" data-snack-preview="true"></div><hr><h1><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_3pqN" id="reference"></a>Reference<a aria-hidden="true" tabindex="-1" class="hash-link" href="#reference" title="Direct link to heading">#</a></h1><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_3pqN" id="methods"></a>Methods<a aria-hidden="true" tabindex="-1" class="hash-link" href="#methods" title="Direct link to heading">#</a></h2><h3><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_3pqN" id="get"></a><code>get()</code><a aria-hidden="true" tabindex="-1" class="hash-link" href="#get" title="Direct link to heading">#</a></h3><div class="mdxCodeBlock_xYIz"><div class="codeBlockContent_rlEb"><button tabindex="0" type="button" aria-label="Copy code to clipboard" class="copyButton_kOW4">Copy</button><div class="prism-code language-jsx codeBlock_1AP7"><div class="codeBlockLines_1boI" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token keyword" style="color:#c5a5c5">static</span><span class="token plain"> </span><span class="token keyword" style="color:#c5a5c5">get</span><span class="token punctuation" style="color:#657b83">(</span><span class="token punctuation" style="color:#657b83">)</span></div></div></div></div></div><p>Returns the device pixel density. Some examples:</p><ul><li><code>PixelRatio.get() === 1</code><ul><li><a href="https://material.io/tools/devices/" target="_blank" rel="noopener noreferrer">mdpi Android devices</a></li></ul></li><li><code>PixelRatio.get() === 1.5</code><ul><li><a href="https://material.io/tools/devices/" target="_blank" rel="noopener noreferrer">hdpi Android devices</a></li></ul></li><li><code>PixelRatio.get() === 2</code><ul><li>iPhone SE, 6S, 7, 8</li><li>iPhone XR</li><li>iPhone 11</li><li><a href="https://material.io/tools/devices/" target="_blank" rel="noopener noreferrer">xhdpi Android devices</a></li></ul></li><li><code>PixelRatio.get() === 3</code><ul><li>iPhone 6S Plus, 7 Plus, 8 Plus</li><li>iPhone X, XS, XS Max</li><li>iPhone 11 Pro, 11 Pro Max</li><li>Pixel, Pixel 2</li><li><a href="https://material.io/tools/devices/" target="_blank" rel="noopener noreferrer">xxhdpi Android devices</a></li></ul></li><li><code>PixelRatio.get() === 3.5</code><ul><li>Nexus 6</li><li>Pixel XL, Pixel 2 XL</li><li><a href="https://material.io/tools/devices/" target="_blank" rel="noopener noreferrer">xxxhdpi Android devices</a></li></ul></li></ul><hr><h3><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_3pqN" id="getfontscale"></a><code>getFontScale()</code><a aria-hidden="true" tabindex="-1" class="hash-link" href="#getfontscale" title="Direct link to heading">#</a></h3><div class="mdxCodeBlock_xYIz"><div class="codeBlockContent_rlEb"><button tabindex="0" type="button" aria-label="Copy code to clipboard" class="copyButton_kOW4">Copy</button><div class="prism-code language-jsx codeBlock_1AP7"><div class="codeBlockLines_1boI" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token keyword" style="color:#c5a5c5">static</span><span class="token plain"> </span><span class="token function" style="color:#79b6f2">getFontScale</span><span class="token punctuation" style="color:#657b83">(</span><span class="token punctuation" style="color:#657b83">)</span><span class="token punctuation" style="color:#657b83">:</span><span class="token plain"> number</span></div></div></div></div></div><p>Returns the scaling factor for font sizes. This is the ratio that is used to calculate the absolute font size, so any elements that heavily depend on that should use this to do calculations.</p><ul><li>on Android value reflects the user preference set in <strong>Settings > Display > Font size</strong></li><li>on iOS value reflects the user preference set in <strong>Settings > Display & Brightness > Text Size</strong>, value can also be updated in <strong>Settings > Accessibilty > Display & Test Size > Larger Text</strong></li></ul><p>If a font scale is not set, this returns the device pixel ratio.</p><hr><h3><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_3pqN" id="getpixelsizeforlayoutsize"></a><code>getPixelSizeForLayoutSize()</code><a aria-hidden="true" tabindex="-1" class="hash-link" href="#getpixelsizeforlayoutsize" title="Direct link to heading">#</a></h3><div class="mdxCodeBlock_xYIz"><div class="codeBlockContent_rlEb"><button tabindex="0" type="button" aria-label="Copy code to clipboard" class="copyButton_kOW4">Copy</button><div class="prism-code language-jsx codeBlock_1AP7"><div class="codeBlockLines_1boI" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token keyword" style="color:#c5a5c5">static</span><span class="token plain"> </span><span class="token function" style="color:#79b6f2">getPixelSizeForLayoutSize</span><span class="token punctuation" style="color:#657b83">(</span><span class="token plain">layoutSize</span><span class="token punctuation" style="color:#657b83">:</span><span class="token plain"> number</span><span class="token punctuation" style="color:#657b83">)</span><span class="token punctuation" style="color:#657b83">:</span><span class="token plain"> number</span></div></div></div></div></div><p>Converts a layout size (dp) to pixel size (px).</p><p>Guaranteed to return an integer number.</p><hr><h3><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_3pqN" id="roundtonearestpixel"></a><code>roundToNearestPixel()</code><a aria-hidden="true" tabindex="-1" class="hash-link" href="#roundtonearestpixel" title="Direct link to heading">#</a></h3><div class="mdxCodeBlock_xYIz"><div class="codeBlockContent_rlEb"><button tabindex="0" type="button" aria-label="Copy code to clipboard" class="copyButton_kOW4">Copy</button><div class="prism-code language-jsx codeBlock_1AP7"><div class="codeBlockLines_1boI" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token keyword" style="color:#c5a5c5">static</span><span class="token plain"> </span><span class="token function" style="color:#79b6f2">roundToNearestPixel</span><span class="token punctuation" style="color:#657b83">(</span><span class="token plain">layoutSize</span><span class="token punctuation" style="color:#657b83">:</span><span class="token plain"> number</span><span class="token punctuation" style="color:#657b83">)</span><span class="token punctuation" style="color:#657b83">:</span><span class="token plain"> number</span></div></div></div></div></div><p>Rounds a layout size (dp) to the nearest layout size that corresponds to an integer number of pixels. For example, on a device with a PixelRatio of 3, <code>PixelRatio.roundToNearestPixel(8.4) = 8.33</code>, which corresponds to exactly (8.33 * 3) = 25 pixels.</p></div></article><div class="docMetadata margin-vert--xl"><div class="row"><div class="col"><a href="https://github.com/facebook/react-native-website/blob/master/website/versioned_docs/version-0.63/pixelratio.md" target="_blank" rel="noreferrer noopener"><svg fill="currentColor" height="1.2em" width="1.2em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 40 40" style="margin-right:0.3em;vertical-align:sub"><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"></path></g></svg>Edit this page</a></div><div class="col text--right"><em><small class="docMetadata-updated">Last updated on <time datetime="2020-10-29T04:19:29.000Z" class="docLastUpdatedAt_1gIo">10/29/2020</time></small></em></div></div></div><div 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