JS - get image width and height from the base64 co

问题:

I have a base64 img encoded that you can find here. How can I get the height and the width of it?

回答1:

var i = new Image(); 

i.onload = function(){
 alert( i.width+", "+i.height );
};

i.src = imageData; 

回答2:

For synchronous use just wrap it into a promise like this:

function getImageDimensions(file) {
  return new Promise (function (resolved, rejected) {
    var i = new Image()
    i.onload = function(){
      resolved({w: i.width, h: i.height})
    };
    i.src = file
  })
}

then you can use await to get the data in synchronous coding style:

var dimensions = await getImageDimensions(file)

回答3:

I found that using .naturalWidth and .naturalHeight had the best results.

var img = new Image();

img.onload = function() {
    var imgWidth = img.naturalWidth,
        imgHeight = img.naturalHeight;
};

This is only supported in modern browsers. http://www.jacklmoore.com/notes/naturalwidth-and-naturalheight-in-ie/

回答4:

Create a hidden <img> with that image and then use jquery .width() and . height()

$("body").append("<img id='hiddenImage' src='"+imageData+"' />");
var width = $('#hiddenImage').width();
var height = $('#hiddenImage').height();
$('#hiddenImage').remove();
alert("width:"+width+" height:"+height);

Test here: FIDDLE

Image is not initially created hidden. it gets created, then you get width and height and then remove it. This may cause a very short visibility in large images in this case you have to wrap the image in another container and make that container hidden not the image itself.

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Another Fiddle that does not add to dom as per gp.'s anser : HERE