canvas.loadImage(src) got exception "Out of memory"

## Issue or Feature

Hi, I had trouble with load image by canvas that always got out of memory exception.
My device still can load image has size larger than 80MB without any problem except this image (16.8MB) `https://pbimg.btdmp.com/pbase/shop-id/10117363/artworks/2141699b41cb8b5b454ffbd0380e247b.png`

## Steps to Reproduce

```js
const _canvas = require('canvas')

_canvas.loadImage('https://pbimg.btdmp.com/pbase/shop-id/10117363/artworks/2141699b41cb8b5b454ffbd0380e247b.png')
.catch((e) => {
console.log(e)
})
```

Exception:

```
Error: out of memory
at setSource (/home/beeketing/code/front/print-2d-render/node_modules/canvas/lib/image.js:91:13)
at get.concat (/home/beeketing/code/front/print-2d-render/node_modules/canvas/lib/image.js:59:11)
at concat (/home/beeketing/code/front/print-2d-render/node_modules/simple-get/index.js:89:7)
at IncomingMessage. (/home/beeketing/code/front/print-2d-render/node_modules/simple-concat/index.js:8:13)
at Object.onceWrapper (events.js:273:13)
at IncomingMessage.emit (events.js:187:15)
at endReadableNT (_stream_readable.js:1094:12)
at process._tickCallback (internal/process/next_tick.js:63:19)
```

## Your Environment
* Version of node-canvas: 2.6.1
* Environment: Node v10.13, Ubuntu 18.04.4 LTS