image 转 Blob
export function imageToBlob(src, cb){ imageToCanvas(src, function (canvas){ cb(dataURLToBlob(canvasToDataURL(canvas))) })}Blob 转 image
export function blobToImage (blob, cb) { fileOrBlobToDataURL(blob, function (dataurl){ var img = new Image() img.src = dataurl cb(img) })}export function canvasToDataURL (canvas, format, quality) { return canvas.toDataURL(format||'image/jpeg', quality||1.0)}export function dataURLToBlob(dataurl){ var arr = dataurl.split(',') var mime = arr[0].match(/:(.*?);/)[1] var bstr = atob(arr[1]) var n = bstr.length var u8arr = new Uint8Array(n) while(n--){ u8arr[n] = bstr.charCodeAt(n) } return new Blob([u8arr], {type:mime})}export function imageToCanvas(src, cb){ var canvas = document.createElement('CANVAS') var ctx = canvas.getContext('2d') var img = new Image() img.src = src img.onload = function (){ canvas.width = img.width canvas.height = img.height ctx.drawImage(img, 0, 0) cb(canvas) }}export function fileOrBlobToDataURL(obj, cb){ var a = new FileReader() a.readAsDataURL(obj) a.onload = function (e){ cb(e.target.result) }}欢送补充～～