本文介绍了如果 src 是 base64 字符串，如何获取新创建的 Image() 的文件大小?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着跟版网的小编来一起学习吧！
问题描述
How can I get the size of the newly created new Image() in bytes if this image's src is base64 data image?
I have such coffeescript code:
# This string is received after some original image preprocessing
base64String = "data:image/jpeg;base64......"
newImageObj = new Image()
newImageObj.src = base64String
newImageObj.onload = ->
console.log "Resized image width is " + this.width
console.log "New file size in bytes is " + newImageObj.fileSize
The output is always like this:
Resized image width is 500
New file size in bytes is undefined
This newImageObj.fileSize is always undefined.
解决方案
here is the algorithm to find file size from base64 string:
base64String = "data:image/jpeg;base64......";
var stringLength = base64String.length - 'data:image/png;base64,'.length;
var sizeInBytes = 4 * Math.ceil((stringLength / 3))*0.5624896334383812;
var sizeInKb=sizeInBytes/1000;
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