在我的例子中，我有一个File类型(保证是一个图像)，我想要图像的尺寸，而不是将其加载到DOM上。

一般策略:将文件转换为ArrayBuffer→将ArrayBuffer转换为base64字符串→使用此作为image类的图像源→使用naturalHeight和naturalWidth来获取维度。

const fr = new FileReader();
fr.readAsArrayBuffer(image); // Image the 'File' object
fr.onload = () => {
  const arrayBuffer: ArrayBuffer = fr.result as ArrayBuffer;

  // Convert to base64. String.fromCharCode can hit a stack overflow error if you pass
  // the entire arrayBuffer in, and iteration gets around this
  let binary = '';
  const bytes = new Uint8Array(arrayBuffer);
  bytes.forEach(b => binary += String.fromCharCode(b));
  const base64Data = window.btoa(binary);

  // Create an image object. Note, a default width/height MUST be given to the constructor (per
  // the documentation) or naturalWidth/Height will always return 0.
  const imageObj = new Image(100, 100);
  imageObj.src = `data:${image.type};base64,${base64Data}`;
  imageObj.onload = () => {
    console.log(imageObj.naturalWidth, imageObj.naturalHeight);
  }
}

这允许您从文件中获得图像尺寸和纵横比，而无需渲染它。它可以使用fromEvent轻松地将onload函数转换为RxJS Observables，以获得更好的异步体验:

// fr is the file reader, and this is the same as fr.onload = () => { ... }
fromEvent(fr, 'load')

我认为这可能对2019年使用JavaScript和/或TypeScript的人有所帮助。

我发现以下内容是不正确的，就像一些人认为的那样:

let img = new Image();
img.onload = function() {
  console.log(this.width, this.height) // Error: undefined is not an object
};
img.src = "http://example.com/myimage.jpg";

这是正确的:

let img = new Image();
img.onload = function() {
  console.log(img.width, img.height)
};
img.src = "http://example.com/myimage.jpg";

结论:

在onload函数中使用img，而不是this。

让我们将在这里学到的所有内容组合成一个简单的函数(imageDimensions())。它使用承诺。

// helper to get dimensions of an image const imageDimensions = file => new Promise((resolve, reject) => { const img = new Image() // the following handler will fire after a successful loading of the image img.onload = () => { const { naturalWidth: width, naturalHeight: height } = img resolve({ width, height }) } // and this handler will fire if there was an error with the image (like if it's not really an image or a corrupted one) img.onerror = () => { reject('There was some problem with the image.') } img.src = URL.createObjectURL(file) }) // here's how to use the helper const getInfo = async ({ target: { files } }) => { const [file] = files try { const dimensions = await imageDimensions(file) console.info(dimensions) } catch(error) { console.error(error) } } <script src="https://cdnjs.cloudflare.com/ajax/libs/babel-standalone/7.0.0-beta.3/babel.min.js"></script> Select an image: <input type="file" onchange="getInfo(event)" /> <br /> <small>It works offline.</small>

jQuery的答案:

$height = $('#image_id').height();
$width  = $('#image_id').width();

尼基·德·梅耶要了一张背景照片;我只是从CSS内容中获取它，并替换“url()””:

var div = $('#my-bg-div');
var url = div.css('background-image').replace(/^url\(\'?(.*)\'?\)$/, '$1');
var img = new Image();
img.src = url;
console.log('img:', img.width + 'x' + img.height); // Zero, image not yet loaded
console.log('div:', div.width() + 'x' + div.height());
img.onload = function() {
  console.log('img:', img.width + 'x' + img.height, (img.width/div.width()));
}

简单地说，您可以像这样进行测试。

  <script>
  (function($) {
        $(document).ready(function() {
            console.log("ready....");
            var i = 0;
            var img;
            for(i=1; i<13; i++) {
                img = new Image();
                img.src = 'img/' + i + '.jpg';
                console.log("name : " + img.src);
                img.onload = function() {
                    if(this.height > this.width) {
                        console.log(this.src + " : portrait");
                    }
                    else if(this.width > this.height) {
                        console.log(this.src + " : landscape");
                    }
                    else {
                        console.log(this.src + " : square");
                    }
                }
            }
        });
    }(jQuery));
  </script>