截图功能基本ok，代码可能还有小修改

packages/shell-chrome/js/content.js

@@ -0,0 +1,121 @@
+
+var jcrop,selection
+
+var overlay = ((active) => (state) => {
+  active = typeof state === 'boolean' ? state : state === null ? active : !active
+  $('.jcrop-holder')[active ? 'show' : 'hide']()
+  chrome.runtime.sendMessage({message: 'active', active})
+})(false)
+
+var image = (done) => {
+  var image = new Image()
+  image.id = 'fake-image'
+  image.src = chrome.runtime.getURL('/images/pixel.png')
+  image.onload = () => {
+    $('body').append(image)
+    done()
+  }
+}
+
+var init = (done) => {
+  $('#fake-image').Jcrop({
+    bgColor: 'none',
+    onSelect: (e) => {
+      selection = e
+      capture()
+    },
+    onChange: (e) => {
+      selection = e
+    },
+    onRelease: (e) => {
+      setTimeout(() => {
+        selection = null
+      }, 100)
+    }
+  }, function ready () {
+    jcrop = this
+
+    $('.jcrop-hline, .jcrop-vline').css({
+      backgroundImage: `url(${chrome.runtime.getURL('/images/Jcrop.gif')})`
+    })
+
+    if (selection) {
+      jcrop.setSelect([
+        selection.x, selection.y,
+        selection.x2, selection.y2
+      ])
+    }
+
+    done && done()
+  })
+}
+
+var capture = (force) => {
+  chrome.storage.sync.get((config) => {
+    if (selection && (config.method === 'crop' || (config.method === 'wait' && force))) {
+      jcrop.release()
+      setTimeout(() => {
+        chrome.runtime.sendMessage({
+          message: 'capture', area: selection, dpr: devicePixelRatio
+        }, (res) => {
+          overlay(false)
+          selection = null
+          save(res.image, config.format, config.save)
+        })
+      }, 50)
+    }
+    else if (config.method === 'view') {
+      chrome.runtime.sendMessage({
+        message: 'capture',
+        area: {x: 0, y: 0, w: innerWidth, h: innerHeight}, dpr: devicePixelRatio
+      }, (res) => {
+        overlay(false)
+        save(res.image, config.format, config.save)
+      })
+    }
+  })
+}
+
+var filename = (format) => {
+  var pad = (n) => (n = n + '', n.length >= 2 ? n : `0${n}`)
+  var ext = (format) => format === 'jpeg' ? 'jpg' : format === 'png' ? 'png' : 'png'
+  var timestamp = (now) =>
+    [pad(now.getFullYear()), pad(now.getMonth() + 1), pad(now.getDate())].join('-')
+    + ' - ' +
+    [pad(now.getHours()), pad(now.getMinutes()), pad(now.getSeconds())].join('-')
+  return `Screenshot Capture - ${timestamp(new Date())}.${ext(format)}`
+}
+
+var save = (image, format, save) => {
+    var link = document.createElement('a')
+    link.download = filename(format)
+    link.href = image
+    link.click()
+  
+}
+
+window.addEventListener('resize', ((timeout) => () => {
+  clearTimeout(timeout)
+  timeout = setTimeout(() => {
+    jcrop.destroy()
+    init(() => overlay(null))
+  }, 100)
+})())
+
+chrome.runtime.onMessage.addListener((req, sender, res) => {
+  if (req.message === 'init') {
+    res({}) // prevent re-injecting
+
+    if (!jcrop) {
+      image(() => init(() => {
+        overlay()
+        capture()
+      }))
+    }
+    else {
+      overlay()
+      capture(true)
+    }
+  }
+  return true
+})