kylefang/AsyncDisplayKit
1
0
Fork 0
mirror of https://github.com/HackPlan/AsyncDisplayKit.git synced 2026-05-04 19:38:32 +08:00
Code Issues Packages Projects Releases Wiki Activity
Files
8e7a5c4a60dc287436630cb2d52c736e88daa8a0
AsyncDisplayKit/_site/docs/debug-tool-pixel-scaling.html

5703 lines
75 KiB
HTML
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

<!DOCTYPE html>
<html prefix="og: http://ogp.me/ns#">
<head>
<meta charset='utf-8'>
<title>AsyncDisplayKit | Image Scaling</title>
<link rel='stylesheet' href='/static/main.css' type='text/css'/>
<link rel="stylesheet" href='/static/pygments.css' type='text/css'/>
<link rel='shortcut icon' href='/static/favicon.png'>
<meta name='viewport' content='width=480'>
<meta property="og:title" content="Image Scaling" />
<meta property="og:site_name" content="AsyncDisplayKit">
<meta property='og:description' content='AsyncDisplayKit: A Library for Functional UI on iOS.'>
<meta property='og:image' content='http://asyncdisplaykit.org/static/asyncdisplaykit-og-image.png'>
<meta property='og:url' content="http://asyncdisplaykit.org/docs/debug-tool-pixel-scaling.html">
<meta property='og:type' content='website'>
<script type="text/javascript" src="//use.typekit.net/vqa1hcx.js"></script>
<script type="text/javascript">{'try{Typekit.load();}catch(e){}'}</script>
</head>
<body>
<header class='topbar site-header'><nav class='width'>
<a class="site-title" href="/">AsyncDisplayKit</a>
<ul>
<li><a href="/docs/getting-started.html" class="active" >
docs
</a></li>
<li><a href="/appledocs.html" >api</a></li>
<li><a href="/resources.html" >resources</a></li>
<li><a href="http://github.com/facebook/AsyncDisplayKit">github</a>
</ul>
</nav></header>
<section class='content'><div class='width'>
<nav class='toc'>
<section>
<h3>Quick Start</h3>
<ul>
<li>
<a href=/docs/getting-started.html>
Getting Started
</a>
</li>
<li>
<a href=/docs/philosophy.html>
Philosophy
</a>
</li>
<li>
<a href=/docs/installation.html>
Installation
</a>
</li>
<li>
<a href=/docs/references.html>
References
</a>
</li>
</ul>
</section>
<section>
<h3>Core Concepts</h3>
<ul>
<li>
<a href=/docs/intelligent-preloading.html>
Intelligent Preloading
</a>
</li>
<li>
<a href=/docs/subclassing.html>
Subclassing
</a>
</li>
<li>
<a href=/docs/layout-engine.html>
Layout Engine
</a>
</li>
</ul>
</section>
<section>
<h3>Node Containers</h3>
<ul>
<li>
<a href=/docs/asviewcontroller.html>
ASViewController
</a>
</li>
<li>
<a href=/docs/aspagernode.html>
ASPagerNode
</a>
</li>
<li>
<a href=/docs/ascollectionnode.html>
ASCollectionNode
</a>
</li>
<li>
<a href=/docs/astablenode.html>
ASTableNode
</a>
</li>
</ul>
</section>
<section>
<h3>Nodes</h3>
<ul>
<li>
<a href=/docs/display-node.html>
ASDisplayNode
</a>
</li>
<li>
<a href=/docs/cell-node.html>
ASCellNode
</a>
</li>
<li>
<a href=/docs/text-cell-node.html>
ASTextCellNode
</a>
</li>
<li>
<a href=/docs/control-node.html>
ASControlNode
</a>
</li>
<li>
<a href=/docs/button-node.html>
ASButtonNode
</a>
</li>
<li>
<a href=/docs/text-node.html>
ASTextNode
</a>
</li>
<li>
<a href=/docs/editable-text-node.html>
ASEditableTextNode
</a>
</li>
<li>
<a href=/docs/image-node.html>
ASImageNode
</a>
</li>
<li>
<a href=/docs/network-image-node.html>
ASNetworkImageNode
</a>
</li>
<li>
<a href=/docs/map-node.html>
ASMapNode
</a>
</li>
<li>
<a href=/docs/video-node.html>
ASVideoNode
</a>
</li>
<li>
<a href=/docs/scroll-node.html>
ASScrollNode
</a>
</li>
</ul>
</section>
<section>
<h3>Layout Engine</h3>
<ul>
<li>
<a href=/docs/automatic-layout-basics.html>
Layout Basics
</a>
</li>
<li>
<a href=/docs/automatic-layout-containers.html>
Layout Containers
</a>
</li>
<li>
<a href=/docs/automatic-layout-examples.html>
Layout Examples
</a>
</li>
<li>
<a href=/docs/automatic-layout-debugging.html>
Layout Debugging
</a>
</li>
<li>
<a href=/docs/layout-options.html>
Layout Options
</a>
</li>
</ul>
</section>
<section>
<h3>Optimizations</h3>
<ul>
<li>
<a href=/docs/layer-backing.html>
Layer Backing
</a>
</li>
<li>
<a href=/docs/synchronous-concurrency.html>
Synchronous Concurrency
</a>
</li>
<li>
<a href=/docs/subtree-rasterization.html>
Subtree Rasterization
</a>
</li>
<li>
<a href=/docs/drawing-priority.html>
Drawing Priority
</a>
</li>
</ul>
</section>
<section>
<h3>Conveniences</h3>
<ul>
<li>
<a href=/docs/hit-test-slop.html>
Hit Test Slop
</a>
</li>
<li>
<a href=/docs/image-modification-block.html>
Image Modification Blocks
</a>
</li>
<li>
<a href=/docs/placeholder-fade-duration.html>
Placeholder Fade Duration
</a>
</li>
</ul>
</section>
<section>
<h3>Debug Tools</h3>
<ul>
<li>
<a href=/docs/debug-tool-pixel-scaling.html class="active">
Image Scaling
</a>
</li>
<li>
<a href=/docs/debug-tool-hit-test-slop.html>
Hit Test Visualization
</a>
</li>
<li>
<a href=/docs/debug-tool-ASRangeController.html>
Range Visualization
</a>
</li>
</ul>
</section>
</nav>
<article class='withtoc'>
<h1>
Image Scaling
<a class="edit-page-link" href="https://github.com/facebook/asyncdisplaykit/tree/gh-pages/_docs/debug-tool-pixel-scaling.md" target="_blank">Edit on GitHub</a>
</h1>
<p></p>
<h2>Visualize ASImageNode.image’s pixel scaling</h2>
<h3>Description</h3>
<p>This debug feature adds a red text label overlay on the bottom right hand corner of an ASImageNode if (and only if) the image’s size in pixels does not match it’s bounds size in pixels, e.g.</p>
<p><code>imageSizeInPixels = image.size * image.scale</code>
<code>boundsSizeInPixels = bounds.size * contentsScale</code>
<code>scaleFactor = imageSizeInPixels / boundsSizeInPixels</code></p>
<p><code>if (scaleFactor != 1.0) {</code>
<code>NSString *scaleString = [NSString stringWithFormat:@&quot;%.2fx&quot;, scaleFactor];</code>
<code>_debugLabelNode.hidden = NO;</code>
<code>}</code></p>
<p>This debug feature is useful for <strong>quickly determining if you are (1) downloading and rendering excessive amounts of image data or (2) upscaling a low quality image</strong>. In the screenshot below, you can quickly see that the avatar image is unnecessarily large for it’s bounds size and that the center picture is more optimized, but not perfectly so. If you are using an external data source (such as the 500px API used in the example), it&#39;s likely that you won’t be able to get the scaleFactor to exactly 1.0. However, if you control your own endpoint, optimize your API / app to return a correctly sized image!</p>
<p><img src="https://cloud.githubusercontent.com/assets/3419380/14056994/15561daa-f2b1-11e5-9606-59d54d2b5354.png" alt="screen shot 2016-03-25 at 4 04 59 pm"></p>
<h3>Usage</h3>
<p>In your AppDelegate, (1) import <code>AsyncDisplayKit+Debug.h</code> and (2) at the top of <code>didFinishLaunchingWithOptions:</code> enable this feature by adding <code>[ASImageNode setShouldShowImageScalingOverlay:YES];</code> Make sure to call this method before initializing any ASImageNodes.</p>
<div class="docs-prevnext">
</div>
<a id="_"></a>
</article>
</div></section>
<footer class="copyright"-><div class='width'>
a Facebook &amp; Instagram collaboration &#x2665;
</div></footer>
<script src="/static/linkify.js"></script>
<script>
(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,'script','//www.google-analytics.com/analytics.js','ga');
ga('create', 'UA-44373548-4', 'auto');
ga('send', 'pageview');
!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="https://platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");
</script>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink