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December 17, 2025 19:04
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This code detects which image formats the browser supports and adds classes to the <html> based on the result.
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| "use strict"; | |
| (function (document) { | |
| let checkCount = 0, | |
| formatFound = false; | |
| const setHTMLClass = (height, className) => { | |
| checkCount++; | |
| if (height == 2) { | |
| formatFound = true; | |
| document.documentElement.className += " " + className; | |
| } else { | |
| document.documentElement.className += " not" + className; | |
| if (checkCount == 4 && !formatFound) | |
| document.implementation.hasFeature( | |
| "http://www.w3.org/TR/SVG11/feature#Image", | |
| "1.1" | |
| ) | |
| ? (document.documentElement.className += " svg") | |
| : (document.documentElement.className += " notsvg png"); | |
| } | |
| }; | |
| let JXL = new Image(); | |
| JXL.onload = JXL.onerror = () => setHTMLClass(JXL.height, "jxl"); | |
| JXL.src = | |
| "data:image/jxl;base64,/woIELASCAgQAFwASxLFgkWAHL0xqnCBCV0qDp901Te/5QM="; | |
| let AVIF = new Image(); | |
| AVIF.onload = AVIF.onerror = () => setHTMLClass(AVIF.height, "avif"); | |
| AVIF.src = | |
| "data:image/avif;base64,AAAAIGZ0eXBhdmlmAAAAAGF2aWZtaWYxbWlhZk1BMUIAAADybWV0YQAAAAAAAAAoaGRscgAAAAAAAAAAcGljdAAAAAAAAAAAAAAAAGxpYmF2aWYAAAAADnBpdG0AAAAAAAEAAAAeaWxvYwAAAABEAAABAAEAAAABAAABGgAAAB0AAAAoaWluZgAAAAAAAQAAABppbmZlAgAAAAABAABhdjAxQ29sb3IAAAAAamlwcnAAAABLaXBjbwAAABRpc3BlAAAAAAAAAAIAAAACAAAAEHBpeGkAAAAAAwgICAAAAAxhdjFDgQ0MAAAAABNjb2xybmNseAACAAIAAYAAAAAXaXBtYQAAAAAAAAABAAEEAQKDBAAAACVtZGF0EgAKCBgANogQEAwgMg8f8D///8WfhwB8+ErK42A="; | |
| let WebP = new Image(); | |
| WebP.onload = WebP.onerror = () => setHTMLClass(WebP.height, "webp"); | |
| WebP.src = | |
| "data:image/webp;base64,UklGRjoAAABXRUJQVlA4IC4AAACyAgCdASoCAAIALmk0mk0iIiIiIgBoSygABc6WWgAA/veff/0PP8bA//LwYAAA"; | |
| let JPX = new Image(); | |
| JPX.onload = JPX.onerror = () => setHTMLClass(JPX.height, "jpx"); | |
| JPX.src = | |
| "data:image/vnd.ms-photo;base64,SUm8AQgAAAAFAAG8AQAQAAAASgAAAIC8BAABAAAAAQAAAIG8BAABAAAAAgAAAMC8BAABAAAAWgAAAMG8BAABAAAARgAAAAAAAAAkw91vA07+S7GFPXd2jckQV01QSE9UTwAZAMFxAAAAATAAoAAKAACgAAAQgCAIAAAEb/8AAQAAAQDCPwCAAAAAAAAAAAAAAAAAjkI/AIAAAAAAAAABIAA="; | |
| let JP2 = new Image(); | |
| JP2.onload = JP2.onerror = () => setHTMLClass(JP2.height, "jp2"); | |
| JP2.src = | |
| "data:image/jp2;base64,/0//UQAyAAAAAAABAAAAAgAAAAAAAAAAAAAABAAAAAQAAAAAAAAAAAAEBwEBBwEBBwEBBwEB/1IADAAAAAEAAAQEAAH/XAAEQED/ZAAlAAFDcmVhdGVkIGJ5IE9wZW5KUEVHIHZlcnNpb24gMi4wLjD/kAAKAAAAAABYAAH/UwAJAQAABAQAAf9dAAUBQED/UwAJAgAABAQAAf9dAAUCQED/UwAJAwAABAQAAf9dAAUDQED/k8+kEAGvz6QQAa/PpBABr994EAk//9k="; | |
| })( | |
| (window.sandboxApi && | |
| window.sandboxApi.parentWindow && | |
| window.sandboxApi.parentWindow.document) || | |
| document | |
| ); |
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