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| 1 // Copyright 2014 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 /* | |
| 5 * Looks on the page to find the image that could be the most representative | |
| 6 * one. | |
| 7 */ | |
| 8 (function() { | |
| 9 // Extract the referrer policy from the page. | |
| 10 var referrerPolicy = ""; | |
| 11 if (window.__gCrWeb && __gCrWeb['getPageReferrerPolicy']) { | |
| 12 referrerPolicy = __gCrWeb['getPageReferrerPolicy']; | |
| 13 } | |
| 14 | |
| 15 // See what to use for JSON. Some pages uses a library that overrides JSON. | |
| 16 var jsonEncoder = JSON.stringify; | |
| 17 if (!jsonEncoder) | |
| 18 jsonEncoder = JSON.encode; | |
| 19 | |
| 20 // First look if there is an Open Graph Image property available. | |
| 21 var ogImage = document.querySelector('meta[property=\"og:image\"]'); | |
| 22 if (ogImage) { | |
| 23 // Checks that the url in ogImage has a path that conatians more than just a | |
| 24 // simple '/'. | |
| 25 var url = ogImage.content; | |
| 26 var location = document.createElement("a"); | |
| 27 location.href = url; | |
| 28 if (location.pathname.length > 1) { | |
| 29 return jsonEncoder({ | |
| 30 'imageUrl': url, | |
| 31 'referrerPolicy': referrerPolicy | |
| 32 }); | |
| 33 } | |
| 34 } | |
| 35 | |
| 36 // Iterates through the images on the page, find the largest one that doesn't | |
| 37 // look like a banner. | |
| 38 var maxPointSize = 0; | |
| 39 var maxImage = null; | |
| 40 | |
| 41 var images = document.getElementsByTagName('img'); | |
| 42 for (var ii = 0; ii < images.length; ii++) { | |
| 43 var currentImage = images[ii]; | |
| 44 var aspectRatio = currentImage.width / currentImage.height; | |
| 45 if (aspectRatio >= 2.4 || aspectRatio <= 0.5) { | |
| 46 continue; // Skip weirdly shaped images. Those are ads or headers. | |
| 47 } | |
| 48 var pointSize = currentImage.width * currentImage.height; | |
| 49 if (pointSize > maxPointSize) { | |
| 50 maxPointSize = pointSize; | |
| 51 maxImage = currentImage; | |
| 52 } | |
| 53 } | |
| 54 | |
| 55 // Only keep images larger than 320*160. | |
| 56 if (maxPointSize <= 51200.0 || maxImage === null) | |
| 57 return ""; | |
| 58 | |
| 59 return jsonEncoder({ | |
| 60 'imageUrl': maxImage.src, | |
| 61 'referrerPolicy': referrerPolicy | |
| 62 }); | |
| 63 })(); | |
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