[JavaScript]Base64 ←→ 图像

1 Base64 → 图像

[demo1]

document.getElementById('img').setAttribute( 'src', 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0 DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==' );

[demo2]

(HTML源码下)

展开HTML源码

效果：↓

2 JavaScript源码(base64图片编码 转 图片)

var dom = document.querySelector("div");
var tmpImgUrl = dom.style.background;
var base64Img = tmpImgUrl.substring(5,tmpImgUrl.length-2); // base64编码的图片数据
// base64Img = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0 DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg=='";//形如←←←

var imgDom = document.querySelector("#img");
imgDom.setAttribute("src", base64Img);

效果：↓

3 Base64 ← 图像

function getBase64Image(img) {
     var canvas = document.createElement("canvas");
     canvas.width = img.width;
     canvas.height = img.height;
     var ctx = canvas.getContext("2d");
     ctx.drawImage(img, 0, 0, img.width, img.height);
     var ext = img.src.substring(img.src.lastIndexOf(".")+1).toLowerCase();
     var dataURL = canvas.toDataURL("image/"+ext);
     return dataURL;
}

• demo1

var image = new Image();
image.src = img;
image.onload = function(){
  var base64 = getBase64Image(image);
  console.log(base64);
}

• demo2

var imageDom = document.querySelector("img");
var base64 = getBase64Image(imageDom);
console.log(base64);

4 参考文献

• 图片⇋Base64编码转换
• js将图片转换为base64 - 博客园
• js 将图片转换为base64编码 yyshang - 简书