diff --git a/example/package-lock.json b/example/package-lock.json
index 015399f..b31d505 100644
--- a/example/package-lock.json
+++ b/example/package-lock.json
@@ -4,6 +4,107 @@
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
+    "@mapbox/node-pre-gyp": {
+      "version": "1.0.11",
+      "resolved": "https://registry.npmjs.org/@mapbox/node-pre-gyp/-/node-pre-gyp-1.0.11.tgz",
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+      "dev": true,
+      "optional": true,
+      "requires": {
+        "detect-libc": "^2.0.0",
+        "https-proxy-agent": "^5.0.0",
+        "make-dir": "^3.1.0",
+        "node-fetch": "^2.6.7",
+        "nopt": "^5.0.0",
+        "npmlog": "^5.0.1",
+        "rimraf": "^3.0.2",
+        "semver": "^7.3.5",
+        "tar": "^6.1.11"
+      },
+      "dependencies": {
+        "glob": {
+          "version": "7.2.3",
+          "resolved": "https://registry.npmjs.org/glob/-/glob-7.2.3.tgz",
+          "integrity": "sha512-nFR0zLpU2YCaRxwoCJvL6UvCH2JFyFVIvwTLsIf21AuHlMskA1hhTdk+LlYJtOlYt9v6dvszD2BGRqBL+iQK9Q==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "fs.realpath": "^1.0.0",
+            "inflight": "^1.0.4",
+            "inherits": "2",
+            "minimatch": "^3.1.1",
+            "once": "^1.3.0",
+            "path-is-absolute": "^1.0.0"
+          }
+        },
+        "lru-cache": {
+          "version": "6.0.0",
+          "resolved": "https://registry.npmjs.org/lru-cache/-/lru-cache-6.0.0.tgz",
+          "integrity": "sha512-Jo6dJ04CmSjuznwJSS3pUeWmd/H0ffTlkXXgwZi+eq1UCmqQwCh+eLsYOYCwY991i2Fah4h1BEMCx4qThGbsiA==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "yallist": "^4.0.0"
+          }
+        },
+        "make-dir": {
+          "version": "3.1.0",
+          "resolved": "https://registry.npmjs.org/make-dir/-/make-dir-3.1.0.tgz",
+          "integrity": "sha512-g3FeP20LNwhALb/6Cz6Dd4F2ngze0jz7tbzrD2wAV+o9FeNHe4rL+yK2md0J/fiSf1sa1ADhXqi5+oVwOM/eGw==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "semver": "^6.0.0"
+          },
+          "dependencies": {
+            "semver": {
+              "version": "6.3.1",
+              "resolved": "https://registry.npmjs.org/semver/-/semver-6.3.1.tgz",
+              "integrity": "sha512-BR7VvDCVHO+q2xBEWskxS6DJE1qRnb7DxzUrogb71CWoSficBxYsiAGd+Kl0mmq/MprG9yArRkyrQxTO6XjMzA==",
+              "dev": true,
+              "optional": true
+            }
+          }
+        },
+        "minimatch": {
+          "version": "3.1.2",
+          "resolved": "https://registry.npmjs.org/minimatch/-/minimatch-3.1.2.tgz",
+          "integrity": "sha512-J7p63hRiAjw1NDEww1W7i37+ByIrOWO5XQQAzZ3VOcL0PNybwpfmV/N05zFAzwQ9USyEcX6t3UO+K5aqBQOIHw==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "brace-expansion": "^1.1.7"
+          }
+        },
+        "rimraf": {
+          "version": "3.0.2",
+          "resolved": "https://registry.npmjs.org/rimraf/-/rimraf-3.0.2.tgz",
+          "integrity": "sha512-JZkJMZkAGFFPP2YqXZXPbMlMBgsxzE8ILs4lMIX/2o0L9UBw9O/Y3o6wFw/i9YLapcUJWwqbi3kdxIPdC62TIA==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "glob": "^7.1.3"
+          }
+        },
+        "semver": {
+          "version": "7.6.0",
+          "resolved": "https://registry.npmjs.org/semver/-/semver-7.6.0.tgz",
+          "integrity": "sha512-EnwXhrlwXMk9gKu5/flx5sv/an57AkRplG3hTK68W7FRDN+k+OWBj65M7719OkA82XLBxrcX0KSHj+X5COhOVg==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "lru-cache": "^6.0.0"
+          }
+        },
+        "yallist": {
+          "version": "4.0.0",
+          "resolved": "https://registry.npmjs.org/yallist/-/yallist-4.0.0.tgz",
+          "integrity": "sha512-3wdGidZyq5PB084XLES5TpOSRA3wjXAlIWMhum2kRcv/41Sn2emQ0dycQW4uZXLejwKvg6EsvbdlVL+FYEct7A==",
+          "dev": true,
+          "optional": true
+        }
+      }
+    },
     "@webassemblyjs/ast": {
       "version": "1.5.13",
       "resolved": "https://registry.npmjs.org/@webassemblyjs/ast/-/ast-1.5.13.tgz",
@@ -197,6 +298,13 @@
         "long": "^3.2.0"
       }
     },
+    "abbrev": {
+      "version": "1.1.1",
+      "resolved": "https://registry.npmjs.org/abbrev/-/abbrev-1.1.1.tgz",
+      "integrity": "sha512-nne9/IiQ/hzIhY6pdDnbBtz7DjPTKrY00P/zvPSm5pOFkl6xuGrGnXn/VtTNNfNtAfZ9/1RtehkszU9qcTii0Q==",
+      "dev": true,
+      "optional": true
+    },
     "acorn": {
       "version": "5.7.4",
       "resolved": "https://registry.npmjs.org/acorn/-/acorn-5.7.4.tgz",
@@ -212,6 +320,35 @@
         "acorn": "^5.0.0"
       }
     },
+    "agent-base": {
+      "version": "6.0.2",
+      "resolved": "https://registry.npmjs.org/agent-base/-/agent-base-6.0.2.tgz",
+      "integrity": "sha512-RZNwNclF7+MS/8bDg70amg32dyeZGZxiDuQmZxKLAlQjr3jGyLx+4Kkk58UO7D2QdgFIQCovuSuZESne6RG6XQ==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "debug": "4"
+      },
+      "dependencies": {
+        "debug": {
+          "version": "4.3.4",
+          "resolved": "https://registry.npmjs.org/debug/-/debug-4.3.4.tgz",
+          "integrity": "sha512-PRWFHuSU3eDtQJPvnNY7Jcket1j0t5OuOsFzPPzsekD52Zl8qUfFIPEiswXqIvHWGVHOgX+7G/vCNNhehwxfkQ==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "ms": "2.1.2"
+          }
+        },
+        "ms": {
+          "version": "2.1.2",
+          "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.2.tgz",
+          "integrity": "sha512-sGkPx+VjMtmA6MX27oA4FBFELFCZZ4S4XqeGOXCv68tT+jb3vk/RyaKWP0PTKyWtmLSM0b+adUTEvbs1PEaH2w==",
+          "dev": true,
+          "optional": true
+        }
+      }
+    },
     "ajv": {
       "version": "6.5.2",
       "resolved": "https://registry.npmjs.org/ajv/-/ajv-6.5.2.tgz",
@@ -267,6 +404,31 @@
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       "dev": true
     },
+    "are-we-there-yet": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/are-we-there-yet/-/are-we-there-yet-2.0.0.tgz",
+      "integrity": "sha512-Ci/qENmwHnsYo9xKIcUJN5LeDKdJ6R1Z1j9V/J5wyq8nh/mYPEpIKJbBZXtZjG04HiK7zV/p6Vs9952MrMeUIw==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "delegates": "^1.0.0",
+        "readable-stream": "^3.6.0"
+      },
+      "dependencies": {
+        "readable-stream": {
+          "version": "3.6.2",
+          "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-3.6.2.tgz",
+          "integrity": "sha512-9u/sniCrY3D5WdsERHzHE4G2YCXqoG5FTHUiCC4SIbr6XcLZBY05ya9EKjYek9O5xOAwjGq+1JdGBAS7Q9ScoA==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "inherits": "^2.0.3",
+            "string_decoder": "^1.1.1",
+            "util-deprecate": "^1.0.1"
+          }
+        }
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+    },
     "arr-diff": {
       "version": "4.0.0",
       "resolved": "https://registry.npmjs.org/arr-diff/-/arr-diff-4.0.0.tgz",
@@ -626,6 +788,27 @@
       "integrity": "sha1-1UVjW+HjPFQmScaRc+Xeas+uNN0=",
       "dev": true
     },
+    "canvas": {
+      "version": "2.11.2",
+      "resolved": "https://registry.npmjs.org/canvas/-/canvas-2.11.2.tgz",
+      "integrity": "sha512-ItanGBMrmRV7Py2Z+Xhs7cT+FNt5K0vPL4p9EZ/UX/Mu7hFbkxSjKF2KVtPwX7UYWp7dRKnrTvReflgrItJbdw==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "@mapbox/node-pre-gyp": "^1.0.0",
+        "nan": "^2.17.0",
+        "simple-get": "^3.0.3"
+      },
+      "dependencies": {
+        "nan": {
+          "version": "2.19.0",
+          "resolved": "https://registry.npmjs.org/nan/-/nan-2.19.0.tgz",
+          "integrity": "sha512-nO1xXxfh/RWNxfd/XPfbIfFk5vgLsAxUR9y5O0cHMJu/AW9U95JLXqthYHjEp+8gQ5p96K9jUp8nbVOxCdRbtw==",
+          "dev": true,
+          "optional": true
+        }
+      }
+    },
     "chalk": {
       "version": "2.4.1",
       "resolved": "https://registry.npmjs.org/chalk/-/chalk-2.4.1.tgz",
@@ -769,6 +952,13 @@
       "integrity": "sha1-SxQVMEz1ACjqgWQ2Q72C6gWANok=",
       "dev": true
     },
+    "color-support": {
+      "version": "1.1.3",
+      "resolved": "https://registry.npmjs.org/color-support/-/color-support-1.1.3.tgz",
+      "integrity": "sha512-qiBjkpbMLO/HL68y+lh4q0/O1MZFj2RX6X/KmMa3+gJD3z+WwI1ZzDHysvqHGS3mP6mznPckpXmw1nI9cJjyRg==",
+      "dev": true,
+      "optional": true
+    },
     "commander": {
       "version": "2.13.0",
       "resolved": "https://registry.npmjs.org/commander/-/commander-2.13.0.tgz",
@@ -814,6 +1004,13 @@
         "date-now": "^0.1.4"
       }
     },
+    "console-control-strings": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/console-control-strings/-/console-control-strings-1.1.0.tgz",
+      "integrity": "sha512-ty/fTekppD2fIwRvnZAVdeOiGd1c7YXEixbgJTNzqcxJWKQnjJ/V1bNEEE6hygpM3WjwHFUVK6HTjWSzV4a8sQ==",
+      "dev": true,
+      "optional": true
+    },
     "constants-browserify": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/constants-browserify/-/constants-browserify-1.0.0.tgz",
@@ -951,6 +1148,16 @@
       "integrity": "sha1-6zkTMzRYd1y4TNGh+uBiEGu4dUU=",
       "dev": true
     },
+    "decompress-response": {
+      "version": "4.2.1",
+      "resolved": "https://registry.npmjs.org/decompress-response/-/decompress-response-4.2.1.tgz",
+      "integrity": "sha512-jOSne2qbyE+/r8G1VU+G/82LBs2Fs4LAsTiLSHOCOMZQl2OKZ6i8i4IyHemTe+/yIXOtTcRQMzPcgyhoFlqPkw==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "mimic-response": "^2.0.0"
+      }
+    },
     "define-property": {
       "version": "2.0.2",
       "resolved": "https://registry.npmjs.org/define-property/-/define-property-2.0.2.tgz",
@@ -992,6 +1199,13 @@
         }
       }
     },
+    "delegates": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/delegates/-/delegates-1.0.0.tgz",
+      "integrity": "sha512-bd2L678uiWATM6m5Z1VzNCErI3jiGzt6HGY8OVICs40JQq/HALfbyNJmp0UDakEY4pMMaN0Ly5om/B1VI/+xfQ==",
+      "dev": true,
+      "optional": true
+    },
     "des.js": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/des.js/-/des.js-1.0.0.tgz",
@@ -1002,6 +1216,13 @@
         "minimalistic-assert": "^1.0.0"
       }
     },
+    "detect-libc": {
+      "version": "2.0.3",
+      "resolved": "https://registry.npmjs.org/detect-libc/-/detect-libc-2.0.3.tgz",
+      "integrity": "sha512-bwy0MGW55bG41VqxxypOsdSdGqLwXPI/focwgTYCFMbdUiBAxLg9CFzG08sz2aqzknwiX7Hkl0bQENjg8iLByw==",
+      "dev": true,
+      "optional": true
+    },
     "diffie-hellman": {
       "version": "5.0.3",
       "resolved": "https://registry.npmjs.org/diffie-hellman/-/diffie-hellman-5.0.3.tgz",
@@ -1046,6 +1267,13 @@
         "minimalistic-crypto-utils": "^1.0.0"
       }
     },
+    "emoji-regex": {
+      "version": "8.0.0",
+      "resolved": "https://registry.npmjs.org/emoji-regex/-/emoji-regex-8.0.0.tgz",
+      "integrity": "sha512-MSjYzcWNOA0ewAHpz0MxpYFvwg6yjy1NG3xteoqz644VCo/RPgnr1/GGt+ic3iJTzQ8Eu3TdM14SawnVUmGE6A==",
+      "dev": true,
+      "optional": true
+    },
     "emojis-list": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/emojis-list/-/emojis-list-2.1.0.tgz",
@@ -1396,6 +1624,35 @@
         "readable-stream": "^2.0.0"
       }
     },
+    "fs-minipass": {
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/fs-minipass/-/fs-minipass-2.1.0.tgz",
+      "integrity": "sha512-V/JgOLFCS+R6Vcq0slCuaeWEdNC3ouDlJMNIsacH2VtALiu9mV4LPrHc5cDl8k5aw6J8jwgWWpiTo5RYhmIzvg==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "minipass": "^3.0.0"
+      },
+      "dependencies": {
+        "minipass": {
+          "version": "3.3.6",
+          "resolved": "https://registry.npmjs.org/minipass/-/minipass-3.3.6.tgz",
+          "integrity": "sha512-DxiNidxSEK+tHG6zOIklvNOwm3hvCrbUrdtzY74U6HKTJxvIDfOUL5W5P2Ghd3DTkhhKPYGqeNUIh5qcM4YBfw==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "yallist": "^4.0.0"
+          }
+        },
+        "yallist": {
+          "version": "4.0.0",
+          "resolved": "https://registry.npmjs.org/yallist/-/yallist-4.0.0.tgz",
+          "integrity": "sha512-3wdGidZyq5PB084XLES5TpOSRA3wjXAlIWMhum2kRcv/41Sn2emQ0dycQW4uZXLejwKvg6EsvbdlVL+FYEct7A==",
+          "dev": true,
+          "optional": true
+        }
+      }
+    },
     "fs-write-stream-atomic": {
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       "resolved": "https://registry.npmjs.org/fs-write-stream-atomic/-/fs-write-stream-atomic-1.0.10.tgz",
@@ -1962,6 +2219,62 @@
         }
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+    "gauge": {
+      "version": "3.0.2",
+      "resolved": "https://registry.npmjs.org/gauge/-/gauge-3.0.2.tgz",
+      "integrity": "sha512-+5J6MS/5XksCuXq++uFRsnUd7Ovu1XenbeuIuNRJxYWjgQbPuFhT14lAvsWfqfAmnwluf1OwMjz39HjfLPci0Q==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "aproba": "^1.0.3 || ^2.0.0",
+        "color-support": "^1.1.2",
+        "console-control-strings": "^1.0.0",
+        "has-unicode": "^2.0.1",
+        "object-assign": "^4.1.1",
+        "signal-exit": "^3.0.0",
+        "string-width": "^4.2.3",
+        "strip-ansi": "^6.0.1",
+        "wide-align": "^1.1.2"
+      },
+      "dependencies": {
+        "ansi-regex": {
+          "version": "5.0.1",
+          "resolved": "https://registry.npmjs.org/ansi-regex/-/ansi-regex-5.0.1.tgz",
+          "integrity": "sha512-quJQXlTSUGL2LH9SUXo8VwsY4soanhgo6LNSm84E1LBcE8s3O0wpdiRzyR9z/ZZJMlMWv37qOOb9pdJlMUEKFQ==",
+          "dev": true,
+          "optional": true
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+        "is-fullwidth-code-point": {
+          "version": "3.0.0",
+          "resolved": "https://registry.npmjs.org/is-fullwidth-code-point/-/is-fullwidth-code-point-3.0.0.tgz",
+          "integrity": "sha512-zymm5+u+sCsSWyD9qNaejV3DFvhCKclKdizYaJUuHA83RLjb7nSuGnddCHGv0hk+KY7BMAlsWeK4Ueg6EV6XQg==",
+          "dev": true,
+          "optional": true
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+        "string-width": {
+          "version": "4.2.3",
+          "resolved": "https://registry.npmjs.org/string-width/-/string-width-4.2.3.tgz",
+          "integrity": "sha512-wKyQRQpjJ0sIp62ErSZdGsjMJWsap5oRNihHhu6G7JVO/9jIB6UyevL+tXuOqrng8j/cxKTWyWUwvSTriiZz/g==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "emoji-regex": "^8.0.0",
+            "is-fullwidth-code-point": "^3.0.0",
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+        "strip-ansi": {
+          "version": "6.0.1",
+          "resolved": "https://registry.npmjs.org/strip-ansi/-/strip-ansi-6.0.1.tgz",
+          "integrity": "sha512-Y38VPSHcqkFrCpFnQ9vuSXmquuv5oXOKpGeT6aGrr3o3Gc9AlVa6JBfUSOCnbxGGZF+/0ooI7KrPuUSztUdU5A==",
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+          "optional": true,
+          "requires": {
+            "ansi-regex": "^5.0.1"
+          }
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+    },
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@@ -2033,6 +2346,13 @@
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       "dev": true
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+    "has-unicode": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/has-unicode/-/has-unicode-2.0.1.tgz",
+      "integrity": "sha512-8Rf9Y83NBReMnx0gFzA8JImQACstCYWUplepDa9xprwwtmgEZUF0h/i5xSA625zB/I37EtrswSST6OXxwaaIJQ==",
+      "dev": true,
+      "optional": true
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       "resolved": "https://registry.npmjs.org/has-value/-/has-value-1.0.0.tgz",
@@ -2102,6 +2422,36 @@
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       "dev": true
     },
+    "https-proxy-agent": {
+      "version": "5.0.1",
+      "resolved": "https://registry.npmjs.org/https-proxy-agent/-/https-proxy-agent-5.0.1.tgz",
+      "integrity": "sha512-dFcAjpTQFgoLMzC2VwU+C/CbS7uRL0lWmxDITmqm7C+7F0Odmj6s9l6alZc6AELXhrnggM2CeWSXHGOdX2YtwA==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "agent-base": "6",
+        "debug": "4"
+      },
+      "dependencies": {
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+          "version": "4.3.4",
+          "resolved": "https://registry.npmjs.org/debug/-/debug-4.3.4.tgz",
+          "integrity": "sha512-PRWFHuSU3eDtQJPvnNY7Jcket1j0t5OuOsFzPPzsekD52Zl8qUfFIPEiswXqIvHWGVHOgX+7G/vCNNhehwxfkQ==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "ms": "2.1.2"
+          }
+        },
+        "ms": {
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+          "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.2.tgz",
+          "integrity": "sha512-sGkPx+VjMtmA6MX27oA4FBFELFCZZ4S4XqeGOXCv68tT+jb3vk/RyaKWP0PTKyWtmLSM0b+adUTEvbs1PEaH2w==",
+          "dev": true,
+          "optional": true
+        }
+      }
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     "iconv-lite": {
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@@ -2544,6 +2894,13 @@
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       "dev": true
     },
+    "mimic-response": {
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/mimic-response/-/mimic-response-2.1.0.tgz",
+      "integrity": "sha512-wXqjST+SLt7R009ySCglWBCFpjUygmCIfD790/kVbiGmUgfYGuB14PiTd5DwVxSV4NcYHjzMkoj5LjQZwTQLEA==",
+      "dev": true,
+      "optional": true
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       "resolved": "https://registry.npmjs.org/minimalistic-assert/-/minimalistic-assert-1.0.1.tgz",
@@ -2571,6 +2928,43 @@
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       "dev": true
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+    "minipass": {
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/minipass/-/minipass-5.0.0.tgz",
+      "integrity": "sha512-3FnjYuehv9k6ovOEbyOswadCDPX1piCfhV8ncmYtHOjuPwylVWsghTLo7rabjC3Rx5xD4HDx8Wm1xnMF7S5qFQ==",
+      "dev": true,
+      "optional": true
+    },
+    "minizlib": {
+      "version": "2.1.2",
+      "resolved": "https://registry.npmjs.org/minizlib/-/minizlib-2.1.2.tgz",
+      "integrity": "sha512-bAxsR8BVfj60DWXHE3u30oHzfl4G7khkSuPW+qvpd7jFRHm7dLxOjUk1EHACJ/hxLY8phGJ0YhYHZo7jil7Qdg==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "minipass": "^3.0.0",
+        "yallist": "^4.0.0"
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+        "minipass": {
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+          "resolved": "https://registry.npmjs.org/minipass/-/minipass-3.3.6.tgz",
+          "integrity": "sha512-DxiNidxSEK+tHG6zOIklvNOwm3hvCrbUrdtzY74U6HKTJxvIDfOUL5W5P2Ghd3DTkhhKPYGqeNUIh5qcM4YBfw==",
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "yallist": "^4.0.0"
+          }
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+        "yallist": {
+          "version": "4.0.0",
+          "resolved": "https://registry.npmjs.org/yallist/-/yallist-4.0.0.tgz",
+          "integrity": "sha512-3wdGidZyq5PB084XLES5TpOSRA3wjXAlIWMhum2kRcv/41Sn2emQ0dycQW4uZXLejwKvg6EsvbdlVL+FYEct7A==",
+          "dev": true,
+          "optional": true
+        }
+      }
+    },
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       "resolved": "https://registry.npmjs.org/mississippi/-/mississippi-2.0.0.tgz",
@@ -2683,11 +3077,15 @@
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-      "resolved": "https://registry.npmjs.org/node-ensure/-/node-ensure-0.0.0.tgz",
-      "integrity": "sha1-7K52QVDemYYexcgQ/V0Jaxg5Mqc=",
-      "dev": true
+    "node-fetch": {
+      "version": "2.7.0",
+      "resolved": "https://registry.npmjs.org/node-fetch/-/node-fetch-2.7.0.tgz",
+      "integrity": "sha512-c4FRfUm/dbcWZ7U+1Wq0AwCyFL+3nt2bEw05wfxSz+DWpWsitgmSgYmy2dQdWyKC1694ELPqMs/YzUSNozLt8A==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "whatwg-url": "^5.0.0"
+      }
     },
     "node-libs-browser": {
       "version": "2.1.0",
@@ -2728,6 +3126,16 @@
         }
       }
     },
+    "nopt": {
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/nopt/-/nopt-5.0.0.tgz",
+      "integrity": "sha512-Tbj67rffqceeLpcRXrT7vKAN8CwfPeIBgM7E6iBkmKLV7bEMwpGgYLGv0jACUsECaa/vuxP0IjEont6umdMgtQ==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "abbrev": "1"
+      }
+    },
     "normalize-path": {
       "version": "2.1.1",
       "resolved": "https://registry.npmjs.org/normalize-path/-/normalize-path-2.1.1.tgz",
@@ -2746,12 +3154,32 @@
         "path-key": "^2.0.0"
       }
     },
+    "npmlog": {
+      "version": "5.0.1",
+      "resolved": "https://registry.npmjs.org/npmlog/-/npmlog-5.0.1.tgz",
+      "integrity": "sha512-AqZtDUWOMKs1G/8lwylVjrdYgqA4d9nu8hc+0gzRxlDb1I10+FHBGMXs6aiQHFdCUUlqH99MUMuLfzWDNDtfxw==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "are-we-there-yet": "^2.0.0",
+        "console-control-strings": "^1.1.0",
+        "gauge": "^3.0.0",
+        "set-blocking": "^2.0.0"
+      }
+    },
     "number-is-nan": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/number-is-nan/-/number-is-nan-1.0.1.tgz",
       "integrity": "sha1-CXtgK1NCKlIsGvuHkDGDNpQaAR0=",
       "dev": true
     },
+    "object-assign": {
+      "version": "4.1.1",
+      "resolved": "https://registry.npmjs.org/object-assign/-/object-assign-4.1.1.tgz",
+      "integrity": "sha512-rJgTQnkUnH1sFw8yT6VSU3zD3sWmu6sZhIseY8VX+GRu3P6F7Fu+JNDoXfklElbLJSnc3FUQHVe4cU5hj+BcUg==",
+      "dev": true,
+      "optional": true
+    },
     "object-copy": {
       "version": "0.1.0",
       "resolved": "https://registry.npmjs.org/object-copy/-/object-copy-0.1.0.tgz",
@@ -2938,6 +3366,13 @@
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       "dev": true
     },
+    "path2d": {
+      "version": "0.2.0",
+      "resolved": "https://registry.npmjs.org/path2d/-/path2d-0.2.0.tgz",
+      "integrity": "sha512-KdPAykQX6kmLSOO6Jpu2KNcCED7CKjmaBNGGNuctOsG0hgYO1OdYQaan6cYXJiG0WmXOwZZPILPBimu5QAIw3A==",
+      "dev": true,
+      "optional": true
+    },
     "pbkdf2": {
       "version": "3.0.16",
       "resolved": "https://registry.npmjs.org/pbkdf2/-/pbkdf2-3.0.16.tgz",
@@ -2952,25 +3387,13 @@
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     "pdfjs-dist": {
-      "version": "2.0.489",
-      "resolved": "https://registry.npmjs.org/pdfjs-dist/-/pdfjs-dist-2.0.489.tgz",
-      "integrity": "sha1-Y+VLKSqGeQpFRpfrRNQ0e4+/rSc=",
+      "version": "4.2.67",
+      "resolved": "https://registry.npmjs.org/pdfjs-dist/-/pdfjs-dist-4.2.67.tgz",
+      "integrity": "sha512-rJmuBDFpD7cqC8WIkQUEClyB4UAH05K4AsyewToMTp2gSy3Rrx8c1ydAVqlJlGv3yZSOrhEERQU/4ScQQFlLHA==",
       "dev": true,
       "requires": {
-        "node-ensure": "^0.0.0",
-        "worker-loader": "^1.1.1"
-      },
-      "dependencies": {
-        "worker-loader": {
-          "version": "1.1.1",
-          "resolved": "https://registry.npmjs.org/worker-loader/-/worker-loader-1.1.1.tgz",
-          "integrity": "sha512-qJZLVS/jMCBITDzPo/RuweYSIG8VJP5P67mP/71alGyTZRe1LYJFdwLjLalY3T5ifx0bMDRD3OB6P2p1escvlg==",
-          "dev": true,
-          "requires": {
-            "loader-utils": "^1.0.0",
-            "schema-utils": "^0.4.0"
-          }
-        }
+        "canvas": "^2.11.2",
+        "path2d": "^0.2.0"
       }
     },
     "pify": {
@@ -3360,6 +3783,25 @@
       "integrity": "sha1-tf3AjxKH6hF4Yo5BXiUTK3NkbG0=",
       "dev": true
     },
+    "simple-concat": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/simple-concat/-/simple-concat-1.0.1.tgz",
+      "integrity": "sha512-cSFtAPtRhljv69IK0hTVZQ+OfE9nePi/rtJmw5UjHeVyVroEqJXP1sFztKUy1qU+xvz3u/sfYJLa947b7nAN2Q==",
+      "dev": true,
+      "optional": true
+    },
+    "simple-get": {
+      "version": "3.1.1",
+      "resolved": "https://registry.npmjs.org/simple-get/-/simple-get-3.1.1.tgz",
+      "integrity": "sha512-CQ5LTKGfCpvE1K0n2us+kuMPbk/q0EKl82s4aheV9oXjFEz6W/Y7oQFVJuU6QG77hRT4Ghb5RURteF5vnWjupA==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "decompress-response": "^4.2.0",
+        "once": "^1.3.1",
+        "simple-concat": "^1.0.0"
+      }
+    },
     "snapdragon": {
       "version": "0.8.2",
       "resolved": "https://registry.npmjs.org/snapdragon/-/snapdragon-0.8.2.tgz",
@@ -3634,6 +4076,44 @@
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       "dev": true
     },
+    "tar": {
+      "version": "6.2.1",
+      "resolved": "https://registry.npmjs.org/tar/-/tar-6.2.1.tgz",
+      "integrity": "sha512-DZ4yORTwrbTj/7MZYq2w+/ZFdI6OZ/f9SFHR+71gIVUZhOQPHzVCLpvRnPgyaMpfWxxk/4ONva3GQSyNIKRv6A==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "chownr": "^2.0.0",
+        "fs-minipass": "^2.0.0",
+        "minipass": "^5.0.0",
+        "minizlib": "^2.1.1",
+        "mkdirp": "^1.0.3",
+        "yallist": "^4.0.0"
+      },
+      "dependencies": {
+        "chownr": {
+          "version": "2.0.0",
+          "resolved": "https://registry.npmjs.org/chownr/-/chownr-2.0.0.tgz",
+          "integrity": "sha512-bIomtDF5KGpdogkLd9VspvFzk9KfpyyGlS8YFVZl7TGPBHL5snIOnxeshwVgPteQ9b4Eydl+pVbIyE1DcvCWgQ==",
+          "dev": true,
+          "optional": true
+        },
+        "mkdirp": {
+          "version": "1.0.4",
+          "resolved": "https://registry.npmjs.org/mkdirp/-/mkdirp-1.0.4.tgz",
+          "integrity": "sha512-vVqVZQyf3WLx2Shd0qJ9xuvqgAyKPLAiqITEtqW0oIUjzo3PePDd6fW9iFz30ef7Ysp/oiWqbhszeGWW2T6Gzw==",
+          "dev": true,
+          "optional": true
+        },
+        "yallist": {
+          "version": "4.0.0",
+          "resolved": "https://registry.npmjs.org/yallist/-/yallist-4.0.0.tgz",
+          "integrity": "sha512-3wdGidZyq5PB084XLES5TpOSRA3wjXAlIWMhum2kRcv/41Sn2emQ0dycQW4uZXLejwKvg6EsvbdlVL+FYEct7A==",
+          "dev": true,
+          "optional": true
+        }
+      }
+    },
     "through": {
       "version": "2.3.8",
       "resolved": "https://registry.npmjs.org/through/-/through-2.3.8.tgz",
@@ -3716,6 +4196,13 @@
         "repeat-string": "^1.6.1"
       }
     },
+    "tr46": {
+      "version": "0.0.3",
+      "resolved": "https://registry.npmjs.org/tr46/-/tr46-0.0.3.tgz",
+      "integrity": "sha512-N3WMsuqV66lT30CrXNbEjx4GEwlow3v6rr4mCcv6prnfwhS01rkgyFdjPNBYd9br7LpXV1+Emh01fHnq2Gdgrw==",
+      "dev": true,
+      "optional": true
+    },
     "tslib": {
       "version": "1.9.3",
       "resolved": "https://registry.npmjs.org/tslib/-/tslib-1.9.3.tgz",
@@ -3955,6 +4442,13 @@
         "neo-async": "^2.5.0"
       }
     },
+    "webidl-conversions": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/webidl-conversions/-/webidl-conversions-3.0.1.tgz",
+      "integrity": "sha512-2JAn3z8AR6rjK8Sm8orRC0h/bcl/DqL7tRPdGZ4I1CjdF+EaMLmYxBHyXuKL849eucPFhvBoxMsflfOb8kxaeQ==",
+      "dev": true,
+      "optional": true
+    },
     "webpack": {
       "version": "4.16.5",
       "resolved": "https://registry.npmjs.org/webpack/-/webpack-4.16.5.tgz",
@@ -4025,6 +4519,17 @@
         }
       }
     },
+    "whatwg-url": {
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/whatwg-url/-/whatwg-url-5.0.0.tgz",
+      "integrity": "sha512-saE57nupxk6v3HY35+jzBwYa0rKSy0XR8JSxZPwgLr7ys0IBzhGviA1/TUGJLmSVqs8pb9AnvICXEuOHLprYTw==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "tr46": "~0.0.3",
+        "webidl-conversions": "^3.0.0"
+      }
+    },
     "which": {
       "version": "1.3.1",
       "resolved": "https://registry.npmjs.org/which/-/which-1.3.1.tgz",
@@ -4040,6 +4545,16 @@
       "integrity": "sha1-2e8H3Od7mQK4o6j6SzHD4/fm6Ho=",
       "dev": true
     },
+    "wide-align": {
+      "version": "1.1.5",
+      "resolved": "https://registry.npmjs.org/wide-align/-/wide-align-1.1.5.tgz",
+      "integrity": "sha512-eDMORYaPNZ4sQIuuYPDHdQvf4gyCF9rEEV/yPxGfwPkRodwEgiMUUXTx/dex+Me0wxx53S+NgUHaP7y3MGlDmg==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "string-width": "^1.0.2 || 2 || 3 || 4"
+      }
+    },
     "worker-farm": {
       "version": "1.6.0",
       "resolved": "https://registry.npmjs.org/worker-farm/-/worker-farm-1.6.0.tgz",
diff --git a/example/package.json b/example/package.json
index 551f868..f85f546 100644
--- a/example/package.json
+++ b/example/package.json
@@ -13,7 +13,7 @@
   "author": " <ransixi@gmail.com>",
   "license": "MIT",
   "devDependencies": {
-    "pdfjs-dist": "^2.0.489",
+    "pdfjs-dist": "^4.2.67",
     "webpack": "^4.16.5",
     "webpack-cli": "^3.1.0",
     "worker-loader": "^2.0.0"