javascript - 检测 WebP 支持

Question

如何通过 Javascript 检测对 WebP 的支持？如果可能的话，我想使用特征检测而不是浏览器检测，但我找不到这样做的方法。Modernizr ( www.modernizr.com ) 不检查它。

Answer 1

这是我的解决方案 - 大约需要 6 毫秒，我认为 WebP 只是现代浏览器的一项功能。使用 canvas.toDataUrl() 函数而不是 image 作为检测特征的方法，使用不同的方法：

function support_format_webp()
{
 var elem = document.createElement('canvas');

 if (!!(elem.getContext && elem.getContext('2d')))
 {
  // was able or not to get WebP representation
  return elem.toDataURL('image/webp').indexOf('data:image/webp') == 0;
 }
 else
 {
  // very old browser like IE 8, canvas not supported
  return false;
 }
}

Answer 2

我认为这样的事情可能会奏效：

var hasWebP = false;
(function() {
  var img = new Image();
  img.onload = function() {
    hasWebP = !!(img.height > 0 && img.width > 0);
  };
  img.onerror = function() {
    hasWebP = false;
  };
  img.src = 'http://www.gstatic.com/webp/gallery/1.webp';
})();

在 Firefox 和 IE 中，如果图像无法理解，则根本不会调用“onload”处理程序，而是调用“onerror”。

您没有提到 jQuery，但作为如何处理该检查的异步性质的示例，您可以返回一个 jQuery“Deferred”对象：

function hasWebP() {
  var rv = $.Deferred();
  var img = new Image();
  img.onload = function() { rv.resolve(); };
  img.onerror = function() { rv.reject(); };
  img.src = 'http://www.gstatic.com/webp/gallery/1.webp';
  return rv.promise();
}

然后你可以写：

hasWebP().then(function() {
  // ... code to take advantage of WebP ...
}, function() {
  // ... code to deal with the lack of WebP ...
});

这是一个jsfiddle示例。

---

更高级的检查器：http: //jsfiddle.net/JMzj2/29/。这个从数据 URL 加载图像并检查它是否加载成功。由于 WebP 现在也支持无损图像，您可以检查当前浏览器是否仅支持有损 WebP 或也支持无损 WebP。（注意：这也隐含地检查数据 URL 支持。）

var hasWebP = (function() {
    // some small (2x1 px) test images for each feature
    var images = {
        basic: "data:image/webp;base64,UklGRjIAAABXRUJQVlA4ICYAAACyAgCdASoCAAEALmk0mk0iIiIiIgBoSygABc6zbAAA/v56QAAAAA==",
        lossless: "data:image/webp;base64,UklGRh4AAABXRUJQVlA4TBEAAAAvAQAAAAfQ//73v/+BiOh/AAA="
    };

    return function(feature) {
        var deferred = $.Deferred();

        $("<img>").on("load", function() {
            // the images should have these dimensions
            if(this.width === 2 && this.height === 1) {
                deferred.resolve();
            } else {
                deferred.reject();
            }
        }).on("error", function() {
            deferred.reject();
        }).attr("src", images[feature || "basic"]);

        return deferred.promise();
    }
})();

var add = function(msg) {
    $("<p>").text(msg).appendTo("#x");
};

hasWebP().then(function() {
    add("Basic WebP available");
}, function() {
    add("Basic WebP *not* available");
});

hasWebP("lossless").then(function() {
    add("Lossless WebP available");
}, function() {
    add("Lossless WebP *not* available");
});

Answer 3

首选解决方案HTML5

<picture>
  <source srcset="/path/to/image.webp" type="image/webp">
  <img src="/path/to/image.jpg" alt="insert alt text here">
</picture>

W3C 上的维基

Answer 4

谷歌官方方式：

由于一些旧浏览器对 webp 有部分支持，因此最好更具体地说明您正在尝试使用哪个 webp 功能并检测此特定功能，以下是谷歌关于如何检测特定 webp 功能的官方建议：

// check_webp_feature:
//   'feature' can be one of 'lossy', 'lossless', 'alpha' or 'animation'.
//   'callback(feature, isSupported)' will be passed back the detection result (in an asynchronous way!)
function check_webp_feature(feature, callback) {
    var kTestImages = {
        lossy: "UklGRiIAAABXRUJQVlA4IBYAAAAwAQCdASoBAAEADsD+JaQAA3AAAAAA",
        lossless: "UklGRhoAAABXRUJQVlA4TA0AAAAvAAAAEAcQERGIiP4HAA==",
        alpha: "UklGRkoAAABXRUJQVlA4WAoAAAAQAAAAAAAAAAAAQUxQSAwAAAARBxAR/Q9ERP8DAABWUDggGAAAABQBAJ0BKgEAAQAAAP4AAA3AAP7mtQAAAA==",
        animation: "UklGRlIAAABXRUJQVlA4WAoAAAASAAAAAAAAAAAAQU5JTQYAAAD/////AABBTk1GJgAAAAAAAAAAAAAAAAAAAGQAAABWUDhMDQAAAC8AAAAQBxAREYiI/gcA"
    };
    var img = new Image();
    img.onload = function () {
        var result = (img.width > 0) && (img.height > 0);
        callback(feature, result);
    };
    img.onerror = function () {
        callback(feature, false);
    };
    img.src = "data:image/webp;base64," + kTestImages[feature];
}

示例用法：

check_webp_feature('lossy', function (feature, isSupported) {
    if (isSupported) {
        // webp is supported, 
        // you can cache the result here if you want
    }
});

请注意，图像加载是非阻塞和异步的。这意味着任何依赖于 WebP 支持的代码最好放在回调函数中。

另请注意，其他同步解决方案不适用于Firefox 65

Answer 5

这是一个老问题，但 Modernizr 现在支持 Webp 检测。

http://modernizr.com/download/

img-webp在非核心检测下查找。

Answer 6

这是 ES6 中 James Westgate 的答案的一个版本。

function testWebP() {
    return new Promise(res => {
        const webP = new Image();
        webP.src = 'data:image/webp;base64,UklGRjoAAABXRUJQVlA4IC4AAACyAgCdASoCAAIALmk0mk0iIiIiIgBoSygABc6WWgAA/veff/0PP8bA//LwYAAA';
        webP.onload = webP.onerror = () => {
            res(webP.height === 2);
        };        
    })
};

testWebP().then(hasWebP => console.log(hasWebP));

FF64：错误

FF65：真的

铬：是的

我喜欢 Rui Marques 的同步回答，但不幸的是，尽管 FF65 能够显示 WebP，但仍然返回 false。

Answer 7

这是无需请求图像的代码。更新了 qwerty 的新小提琴。

http://jsfiddle.net/z6kH9/

function testWebP(callback) {
    var webP = new Image();
    webP.onload = webP.onerror = function () {
        callback(webP.height == 2);
    };
    webP.src = 'data:image/webp;base64,UklGRjoAAABXRUJQVlA4IC4AAACyAgCdASoCAAIALmk0mk0iIiIiIgBoSygABc6WWgAA/veff/0PP8bA//LwYAAA';
};

testWebP(function(support) {
    document.body.innerHTML = support ? 'Yeah man!' : 'Nope';
});

Answer 8

WebPJS 使用更智能的 WebP 支持检测，无需外部图像： http ://webpjs.appspot.com/

Answer 9

我发现当页面的 JavaScript 很重时，webp 支持功能检测需要 300+ms。所以我写了一个带有缓存功能的脚本：

• 脚本缓存
• 本地存储缓存

它只会在用户第一次访问页面时检测一次。

/**
 * @fileOverview WebP Support Detect.
 * @author ChenCheng<sorrycc@gmail.com>
 */
(function() {

  if (this.WebP) return;
  this.WebP = {};

  WebP._cb = function(isSupport, _cb) {
    this.isSupport = function(cb) {
      cb(isSupport);
    };
    _cb(isSupport);
    if (window.chrome || window.opera && window.localStorage) {
      window.localStorage.setItem("webpsupport", isSupport);
    }
  };

  WebP.isSupport = function(cb) {
    if (!cb) return;
    if (!window.chrome && !window.opera) return WebP._cb(false, cb);
    if (window.localStorage && window.localStorage.getItem("webpsupport") !== null) {
      var val = window.localStorage.getItem("webpsupport");
      WebP._cb(val === "true", cb);
      return;
    }
    var img = new Image();
    img.src = "data:image/webp;base64,UklGRjoAAABXRUJQVlA4IC4AAACyAgCdASoCAAIALmk0mk0iIiIiIgBoSygABc6WWgAA/veff/0PP8bA//LwYAAA";
    img.onload = img.onerror = function() {
      WebP._cb(img.width === 2 && img.height === 2, cb);
    };
  };

  WebP.run = function(cb) {
    this.isSupport(function(isSupport) {
      if (isSupport) cb();
    });
  };

})();

Answer 10

/* Here's a one-liner hack that works (without the use/need of any 
   externals...save bytes)...

Your CSS... */

body.no-webp .logo {
  background-image: url('logo.png');
}

body.webp .logo {
  background-image: url('logo.webp');
}

...
<body>
  <!--
  The following img tag is the *webp* support checker. I'd advise you use any 
  (small-sized) image that would be utilized on the current page eventually 
  (probably an image common to all your pages, maybe a logo) so that when 
  it'll be (really) used on the page, it'll be loaded from cache by the 
  browser instead of making another call to the server (for some other image 
  that won't be).

  Sidebar: Using 'display: none' so it's not detected by screen readers and 
  so it's also not displayed (obviously). :)
  -->
  <img 
    style='display: none'
    src='/path/to/low-sized-image.webp'
    onload="this.parentNode.classList.add('webp')"
    onerror="this.parentNode.classList.add('no-webp')"
  />
  ...
</body>


   <!-- PS. It's my first answer on SO. Thank you. :) -->

Answer 11

带有 htaccess 的 WebP 图像

将以下内容放入您的.htaccess文件中，如果在同一文件夹中找到 jpg/png 图像，它将被替换为 WebP 图像。

<IfModule mod_rewrite.c>
  RewriteEngine On

  # Check if browser support WebP images
  RewriteCond %{HTTP_ACCEPT} image/webp

  # Check if WebP replacement image exists
  RewriteCond %{DOCUMENT_ROOT}/$1.webp -f

  # Serve WebP image instead
  RewriteRule (.+)\.(jpe?g|png)$ $1.webp [T=image/webp,E=accept:1]
</IfModule>

<IfModule mod_headers.c>
  Header append Vary Accept env=REDIRECT_accept
</IfModule>

<IfModule mod_mime.c>
  AddType image/webp .webp
</IfModule>

在这里阅读更多

Answer 12

这是一个基于 Pointy 响应的带有 Promise 的简单函数

let webpSupport = undefined // so we won't have to create the image multiple times
const webp1Px = 'data:image/webp;base64,UklGRjoAAABXRUJQVlA4IC4AAACyAgCdASoCAAIALmk0mk0iIiIiIgBoSygABc6WWgAA/veff/0PP8bA//LwYAAA'

function isWebpSupported () {
  if (webpSupport !== undefined) {
    return Promise.resolve(webpSupport)
  }

  return new Promise((resolve, _reject) => {
    const img = new Image()
    img.onload = () => {
      webpSupport = !!(img.height > 0 && img.width > 0);
      resolve(webpSupport)
    }
    img.onerror = () => {
      webpSupport = false
      resolve(webpSupport)
    }
    img.src = webp1Px
  })
}

Answer 13

我的短版。我用它来给浏览器 webP 或 jpg/png。

谷歌吃这个，旧 iphone ( f̶u̶c̶k̶i̶n̶g̶ ̶s̶h̶e̶e̶t̶ -safari) 也很好用！

function checkWebP(callback) {
    var webP = new Image();
    webP.onload = webP.onerror = function () {
        callback(webP.height == 2);
    };
    webP.src = 'data:image/webp;base64,UklGRjoAAABXRUJQVlA4IC4AAACyAgCdASoCAAIALmk0mk0iIiIiIgBoSygABc6WWgAA/veff/0PP8bA//LwYAAA';
};

checkWebP(function(support) {
      if(support) {
          //Do what you whant =)
         console.log('work webp');
      }else{
          //Do what you whant =)
         console.log('not work, use jgp/png')
      }
      
})

Answer 14

有一种方法可以立即测试 webP 支持。它是同步且准确的，因此无需等待回调即可渲染图像。

function testWebP = () => {
    const canvas = typeof document === 'object' ? 
    document.createElement('canvas') : {};
    canvas.width = canvas.height = 1;
    return canvas.toDataURL ? canvas.toDataURL('image/webp').indexOf('image/webp') === 5 : false;
}

这种方法显着改善了我的渲染时间

Answer 15

Webp 扩展检测和替换 JavaScript：

 async function supportsWebp() {
  if (!self.createImageBitmap) return false;

  const webpData = 'data:image/webp;base64,UklGRh4AAABXRUJQVlA4TBEAAAAvAAAAAAfQ//73v/+BiOh/AAA=';
  const blob = await fetch(webpData).then(r => r.blob());
  return createImageBitmap(blob).then(() => true, () => false);
}

(async () => {
  if(await supportsWebp()) {
    console.log('webp does support');
  }
  else {
    $('#banners .item').each(function(){
        var src=$(this).find('img').attr('src');
        src = src.replace(".webp", ".jpg");
        $(this).find('img').attr('src',src);
    });
    console.log('webp does not support');
  }
})();

Answer 16

基于 Rui Marques 处理 Firefox 的改进版本。我根据对该答案的评论添加了对不同字符串的扫描。

如果社区接受此改进，则应将其编辑到该答案中。

function canUseWebP()
{
    var elem = document.createElement('canvas');

    if (!!(elem.getContext && elem.getContext('2d')))
    {
        var testString = (!(window.mozInnerScreenX == null)) ? 'png' : 'webp';
        // was able or not to get WebP representation
        return elem.toDataURL('image/webp').indexOf('data:image/' + testString) == 0;
    }

    // very old browser like IE 8, canvas not supported
    return false;
}

Answer 17

这是一种混合 HTML/Javascript 方法，可让您按优先顺序（您的偏好）确定支持的图像类型。在此示例中，它将返回浏览器中第一个支持的图像类型并检查 AVIF、WebP、JpegXL 和 JPG。

<picture style="display:none;">
<source type=image/avif srcset="data:image/avif;base64,AAAAFGZ0eXBhdmlmAAAAAG1pZjEAAACgbWV0YQAAAAAAAAAOcGl0bQAAAAAAAQAAAB5pbG9jAAAAAEQAAAEAAQAAAAEAAAC8AAAAGwAAACNpaW5mAAAAAAABAAAAFWluZmUCAAAAAAEAAGF2MDEAAAAARWlwcnAAAAAoaXBjbwAAABRpc3BlAAAAAAAAAAQAAAAEAAAADGF2MUOBAAAAAAAAFWlwbWEAAAAAAAAAAQABAgECAAAAI21kYXQSAAoIP8R8hAQ0BUAyDWeeUy0JG+QAACANEkA= 1x">
<source type=image/webp srcset="data:image/webp;base64,UklGRiIAAABXRUJQVlA4IBYAAAAwAQCdASoBAAEADsD+JaQAA3AAAAAA 1x">
<source type=image/jxl srcset="data:image/jxl;base64,/woAEBAJCAQBACwASxLFgoUJEP3D/wA= 1x">
<img onload=console.log(this.currentSrc.substring(this.currentSrc.indexOf(':')+1,this.currentSrc.indexOf(';'))) src="data:image/jpg;base64,/9j/4AAQSkZJRgABAQIAHAAcAAD/2wBDAAMDAwMDAwMDAwMEBAQEBAYFBQUFBgkGBwYHBgkOCAoICAoIDgwPDAsMDwwWEQ8PERYZFRQVGR4bGx4mJCYyMkP/wgALCAABAAEBAREA/8QAFAABAAAAAAAAAAAAAAAAAAAACf/aAAgBAQAAAABU/wD/xAAUEAEAAAAAAAAAAAAAAAAAAAAA/9oACAEBAAE/AH//2Q==">
</picture>

您可以用您需要的任何内容替换日志功能。

这种方法的好处是：

1. 您不必在 Javascript 中创建和查询一堆对象，因此它很高效
2. 浏览器不必获取任何图像，它们是内联编码的，因此它是快速和同步的。您可以将其粘贴在任何地方，并在下一行中得到答案而无需回调。
3. 浏览器只会为支持的第一行创建一个图像结果，因此它是高效的。
4. 通过添加一行很容易添加未来的图像支持。
5. 您可以按照您将在应用程序中使用的任何优先级对图像进行排序。
6. 您可以通过修剪您不关心的图像类型将其转变为单独的测试。
7. 即使不支持 PICTURE 元素但需要 currentSrc，这也应该有效，因此 IE11 将失败.. 在这种情况下，只需在 img 中测试 currentSrc 或假设始终支持 JPG 支持。

编辑：删除进入示例的换行符，谢谢。

Answer 18

好消息。它适用于 Safari。

document.addEventListener('DOMContentLoaded', function() {
  testWebP(document.body)
})

function testWebP(elem) {
  const webP = new Image();
  webP.src = 'data:image/webp;base64,UklGRjoAAABXRUJQVlA4IC4AAACyAgCdASoCAAIALmk0mk0iIiIiIgBoSygABc6WWgAA/veff/0PP8bA//LwYAAA';
  webP.onload = webP.onerror = function () {
    webP.height === 2 ? elem.classList.add('webp-true') : elem.classList.add('webp-false')
  }
  console.log(webP)
}

来源：https ://gist.github.com/Protoff/d6643387f03d47b44b2d7c3cf7b3e0a0

Answer 19

使用@Pointy 的答案是为了Angular 2+：

import { Injectable } from '@angular/core';
import { Subject }    from 'rxjs/Subject';

@Injectable()
export class ImageService {
    private isWebpEnabledSource = new Subject<boolean>();

    isWebpEnabledAnnounced$ = this.isWebpEnabledSource.asObservable();

    isWebpEnabled() {
        let webpImage = new Image();

        webpImage.src = 'data:image/webp;base64,UklGRjIAAABXRUJQVlA4ICYAAACyAgCdASoCAAEALmk0mk0iIiIiIgBoSygABc6zbAAA/v56QAAAAA==';

        webpImage.onload = () => {
            if (webpImage.width === 2 && webpImage.height === 1) {
                this.isWebpEnabledSource.next(true);
            } else {
                this.isWebpEnabledSource.next(false);
            }
        }
    }
}

Answer 20

上述解决方案可能不适用于 safari 和 firefox。所以我开始寻找更强大的解决方案，并偶然发现了一个关于 webp 支持的优秀库：webp-hero我们只能detectWebpSupport从这个库中获取函数：

var __awaiter = (this && this.__awaiter) || function(thisArg, _arguments, P, generator) {
  function adopt(value) {
    return value instanceof P ? value : new P(function(resolve) {
      resolve(value);
    });
  }
  return new(P || (P = Promise))(function(resolve, reject) {
    function fulfilled(value) {
      try {
        step(generator.next(value));
      } catch (e) {
        reject(e);
      }
    }

    function rejected(value) {
      try {
        step(generator["throw"](value));
      } catch (e) {
        reject(e);
      }
    }

    function step(result) {
      result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected);
    }
    step((generator = generator.apply(thisArg, _arguments || [])).next());
  });
};
var __generator = (this && this.__generator) || function(thisArg, body) {
  var _ = {
      label: 0,
      sent: function() {
        if (t[0] & 1) throw t[1];
        return t[1];
      },
      trys: [],
      ops: []
    },
    f, y, t, g;
  return g = {
    next: verb(0),
    "throw": verb(1),
    "return": verb(2)
  }, typeof Symbol === "function" && (g[Symbol.iterator] = function() {
    return this;
  }), g;

  function verb(n) {
    return function(v) {
      return step([n, v]);
    };
  }

  function step(op) {
    if (f) throw new TypeError("Generator is already executing.");
    while (_) try {
      if (f = 1, y && (t = op[0] & 2 ? y["return"] : op[0] ? y["throw"] || ((t = y["return"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;
      if (y = 0, t) op = [op[0] & 2, t.value];
      switch (op[0]) {
        case 0:
        case 1:
          t = op;
          break;
        case 4:
          _.label++;
          return {
            value: op[1],
            done: false
          };
        case 5:
          _.label++;
          y = op[1];
          op = [0];
          continue;
        case 7:
          op = _.ops.pop();
          _.trys.pop();
          continue;
        default:
          if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) {
            _ = 0;
            continue;
          }
          if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) {
            _.label = op[1];
            break;
          }
          if (op[0] === 6 && _.label < t[1]) {
            _.label = t[1];
            t = op;
            break;
          }
          if (t && _.label < t[2]) {
            _.label = t[2];
            _.ops.push(op);
            break;
          }
          if (t[2]) _.ops.pop();
          _.trys.pop();
          continue;
      }
      op = body.call(thisArg, _);
    } catch (e) {
      op = [6, e];
      y = 0;
    } finally {
      f = t = 0;
    }
    if (op[0] & 5) throw op[1];
    return {
      value: op[0] ? op[1] : void 0,
      done: true
    };
  }
};

function detectWebpSupport() {
  return __awaiter(this, void 0, void 0, function() {
    var testImageSources, testImage, results;
    return __generator(this, function(_a) {
      switch (_a.label) {
        case 0:
          testImageSources = [
            "data:image/webp;base64,UklGRjIAAABXRUJQVlA4ICYAAACyAgCdASoCAAEALmk0mk0iIiIiIgBoSygABc6zbAAA/v56QAAAAA==",
            "data:image/webp;base64,UklGRh4AAABXRUJQVlA4TBEAAAAvAQAAAAfQ//73v/+BiOh/AAA="
          ];
          testImage = function(src) {
            return new Promise(function(resolve, reject) {
              var img = document.createElement("img");
              img.onerror = function(error) {
                return resolve(false);
              };
              img.onload = function() {
                return resolve(true);
              };
              img.src = src;
            });
          };
          return [4 /*yield*/ , Promise.all(testImageSources.map(testImage))];
        case 1:
          results = _a.sent();
          return [2 /*return*/ , results.every(function(result) {
            return !!result;
          })];
      }
    });
  });
}

detectWebpSupport().then(d => console.log('does it support?', d))

Answer 21

//* WebP 支持检查 import { useState, useEffect } from "react";

const WebpSupportCheck = (feature, callback) => {

    var kTestImages = {
        lossy: "UklGRiIAAABXRUJQVlA4IBYAAAAwAQCdASoBAAEADsD+JaQAA3AAAAAA",
        lossless: "UklGRhoAAABXRUJQVlA4TA0AAAAvAAAAEAcQERGIiP4HAA==",
        alpha: "UklGRkoAAABXRUJQVlA4WAoAAAAQAAAAAAAAAAAAQUxQSAwAAAARBxAR/Q9ERP8DAABWUDggGAAAABQBAJ0BKgEAAQAAAP4AAA3AAP7mtQAAAA==",
        animation: "UklGRlIAAABXRUJQVlA4WAoAAAASAAAAAAAAAAAAQU5JTQYAAAD/////AABBTk1GJgAAAAAAAAAAAAAAAAAAAGQAAABWUDhMDQAAAC8AAAAQBxAREYiI/gcA"
    };
    var img = new Image();
    img.onload = function () {
        var result = (img.width > 0) && (img.height > 0);
        callback(feature, result);
    };
    img.onerror = function () {
        callback(feature, false);
    };
    img.src = "data:image/webp;base64," + kTestImages[feature];
}

const IsWebpSupported = () => {
    const [state, setState] = useState()
    useEffect(() => {

        WebpSupportCheck('lossy', function (feature, isSupported) {
            if (isSupported) {
                setState(true)
            } else {
                setState(false)
            }
        })

    }, [state])
    return state
}

export default IsWebpSupported