mand-mobile/components/image-reader/image-processor.js

import {dataURIToArrayBuffer, dataURItoBlob} from './image-dataurl'
import {noop, requireRemoteScript} from '../_util'

const UA = (userAgent => {
  const isOldIos = /OS (\d)_.* like Mac OS X/g.exec(userAgent)
  const isOldAndroid = /Android (\d.*?);/g.exec(userAgent) || /Android\/(\d.*?) /g.exec(userAgent)

  // IOS8.3-
  // ndroid4.5-
  // ios
  // android
  // QQ Browser
  return {
    oldIOS: isOldIos ? +isOldIos.pop() < 8.3 : false,
    oldAndroid: isOldAndroid ? +isOldAndroid.pop().substr(0, 3) < 4.5 : false,
    ios: /\(i[^;]+;( U;)? CPU.+Mac OS X/.test(userAgent),
    android: /Android/g.test(userAgent),
    mQQBrowser: /MQQBrowser/g.test(userAgent),
  }
})(navigator.userAgent)

/**
* Get Orientation of EXIF
* @param  {Object}   dataURL
* @souce http://stackoverflow.com/questions/7584794/accessing-jpeg-exif-rotation-data-in-javascript-on-the-client-side
*/
/* istanbul ignore next */
function getOrientation(dataURL) {
  const buffer = dataURIToArrayBuffer(dataURL)
  const view = new DataView(buffer)

  if (view.getUint16(0, false) !== 0xffd8) {
    return -2
  }

  const length = view.byteLength
  let offset = 2

  while (offset < length) {
    const marker = view.getUint16(offset, false)
    offset += 2

    if (marker === 0xffe1) {
      const tmp = view.getUint32((offset += 2), false)

      if (tmp !== 0x45786966) {
        return -1
      }

      const little = view.getUint16((offset += 6), false) === 0x4949
      offset += view.getUint32(offset + 4, little)

      const tags = view.getUint16(offset, little)
      offset += 2

      for (let i = 0; i < tags; i++) {
        if (view.getUint16(offset + i * 12, little) === 0x0112) {
          return view.getUint16(offset + i * 12 + 8, little)
        }
      }
    } else if ((marker & 0xff00) !== 0xff00) {
      break
    } else {
      offset += view.getUint16(offset, false)
    }
  }

  return -1
}
/* istanbul ignore next */
function getImageSize(img, orientation, maxWidth, maxHeight) {
  const ret = {
    width: img.width,
    height: img.height,
  }

  if ('5678'.indexOf(orientation) > -1) {
    ret.width = img.height
    ret.height = img.width
  }

  // 如果原图小于设定，采用原图
  if (ret.width < maxWidth || ret.height < maxHeight) {
    return ret
  }

  const scale = ret.width / ret.height

  if (maxWidth && maxHeight) {
    if (scale >= maxWidth / maxHeight) {
      if (ret.width > maxWidth) {
        ret.width = maxWidth
        ret.height = Math.ceil(maxWidth / scale)
      }
    } else {
      if (ret.height > maxHeight) {
        ret.height = maxHeight
        ret.width = Math.ceil(maxHeight * scale)
      }
    }
  } else if (maxWidth) {
    if (maxWidth < ret.width) {
      ret.width = maxWidth
      ret.height = Math.ceil(maxWidth / scale)
    }
  } else if (maxHeight < ret.height) {
    ret.width = Math.ceil(maxHeight * scale)
    ret.height = maxHeight
  }

  // 超过这个值base64无法生成，在IOS上
  if (ret.width >= 3264 || ret.height >= 2448) {
    ret.width *= 0.8
    ret.height *= 0.8
  }

  return ret
}
/* istanbul ignore next */
function makeCanvas(img, orientation, maxWidth, maxHeight, quality) {
  const {width, height} = getImageSize(img, orientation, maxWidth, maxHeight)
  const canvas = document.createElement('canvas')
  const ctx = canvas.getContext('2d')

  canvas.width = width
  canvas.height = height
  ctx.drawImage(img, 0, 0, width, height)

  let base64 = null
  if (CSS && CSS.supports && !CSS.supports('image-orientation:none')) {
    switch (orientation) {
      case 3:
        ctx.rotate(180 * Math.PI / 180)
        ctx.drawImage(img, -width, -height, width, height)
        break
      case 6:
        ctx.rotate(90 * Math.PI / 180)
        ctx.drawImage(img, 0, -width, height, width)
        break
      case 8:
        ctx.rotate(270 * Math.PI / 180)
        ctx.drawImage(img, -height, 0, height, width)
        break
      case 2:
        ctx.translate(width, 0)
        ctx.scale(-1, 1)
        ctx.drawImage(img, 0, 0, width, height)
        break
      case 4:
        ctx.translate(width, 0)
        ctx.scale(-1, 1)
        ctx.rotate(180 * Math.PI / 180)
        ctx.drawImage(img, -width, -height, width, height)
        break
      case 5:
        ctx.translate(width, 0)
        ctx.scale(-1, 1)
        ctx.rotate(90 * Math.PI / 180)
        ctx.drawImage(img, 0, -width, height, width)
        break
      case 7:
        ctx.translate(width, 0)
        ctx.scale(-1, 1)
        ctx.rotate(270 * Math.PI / 180)
        ctx.drawImage(img, -height, 0, height, width)
        break
      default:
        ctx.drawImage(img, 0, 0, width, height)
    }
  } else {
    if ('5678'.includes(orientation)) {
      ctx.drawImage(img, 0, 0, height, width)
    } else {
      ctx.drawImage(img, 0, 0, width, height)
    }
  }

  if ((UA.oldIOS || UA.oldAndroid || UA.mQQBrowser || !navigator.userAgent) && window.JPEGEncoder) {
    /* global JPEGEncoder */
    const encoder = new JPEGEncoder()
    const newImg = ctx.getImageData(0, 0, canvas.width, canvas.height)
    base64 = encoder.encode(newImg, quality * 100)
  } else {
    base64 = canvas.toDataURL('image/jpeg', quality)
  }

  return base64
}
/**
 * Image Process
 * @param options Object: { dataUrl, width, height, quality}
 * @param fn dataUrl => void
 */
export default function(options, fn = noop) {
  return new Promise((resolve, reject) => {
    const {dataUrl, width, height, quality} = options
    const orientation = getOrientation(dataUrl)
    const blob = dataURItoBlob(dataUrl)
    /* istanbul ignore next */
    if (orientation > 1 || quality < 1 || width || height) {
      const img = new Image()
      img.src = dataUrl
      img.onload = () => {
        const newDataUrl = makeCanvas(img, orientation, width, height, quality)
        const newBlob = dataURItoBlob(newDataUrl)
        fn(newDataUrl, newBlob)
        resolve({
          dataUrl: newDataUrl,
          blob: newBlob,
        })
      }
      img.onerror = () => {
        fn(null)
        reject(new Error('image load error'))
      }
    } else {
      fn(dataUrl, blob)
      resolve({
        dataUrl,
        blob,
      })
    }
  })
}

// Import jpeg_encoder_basic for compatibility if necessary
if ((UA.oldIOS || UA.oldAndroid || UA.mQQBrowser || !navigator.userAgent) && !window.JPEGEncoder) {
  /* istanbul ignore next */
  requireRemoteScript('//manhattan.didistatic.com/static/manhattan/mfd/image-reader/jpeg_encoder_basic.js')
}