Fabric.JS 与 Node.JS - 导出为 PNG/JPEG

所以我只是在玩 Fabric.JS适用于 Node.JS，不适用于 Web，我已经成功制作了一个静态画布，并在上面放置了一个矩形。出口的时间到了。这是我创建画布并添加矩形的代码：

var canvas = new fabric.StaticCanvas(null, {width: 200, height: 200})
var rect = new fabric.Rect({
  left: 100,
  top: 100,
  width: 100,
  height: 50,
  fill: "red"
})
canvas.add(rect)

这是我为导出图像所做的一切尝试：

//Creates a PNG file that isn't generated correctly. It's as if it's corrupt. No program can open it
canvas.createPNGStream().on("data", function (chunk) {
  fs.createWriteStream(__dirname + "/output.png").write(chunk)
})

//Causes a crash
canvas.createJPEGStream().on("data", function (chunk) {
  fs.createWriteStream(__dirname + "/output.jpeg").write(chunk)
})

Error:
C:\Users\me\Documents\my project\node_modules\canvas\lib\jpegstream.js:44
    canvas[method](options.bufsize, options.quality, options.progressive, function(err, chunk){
                  ^

TypeError: canvas[method] is not a function
    at C:\Users\me\Documents\my project\node_modules\canvas\lib\jpegstream.js:44:19
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

//Same thing as first try^^, except it's a JPEG
canvas.createJPEGStream({quality: 100}).pipe(fs.createWriteStream(__dirname + "/output.jpeg"))

//This one makes the PNG file, but when it's opened, its 100% transparent. That's it. The rectangle I added isn't there. Canvas size is correct, however
canvas.createPNGStream().pipe(fs.createWriteStream(__dirname + "/output.png"))

Note: fabric.Canvas(null, {width: 200, height: 200})似乎也完全一样的工作StaticCanvas， 在这种情况下

注2：这段代码：

var canvas = new fabric.createCanvasForNode(200, 200)

结果出现此错误：

var canvas = new fabric.createCanvasForNode(200, 200)
             ^

TypeError: fabric.createCanvasForNode is not a constructor
    at Client.client.on.message (C:\Users\me\Documents\my project\index.js:31:14)
    at emitOne (events.js:115:13)
    at Client.emit (events.js:210:7)
    at MessageCreateHandler.handle (C:\Users\me\Documents\my project\node_modules\discord.js\src\client\websocket\packets\handlers\MessageCreate.js:9:34)
    at WebSocketPacketManager.handle (C:\Users\me\Documents\my project\node_modules\discord.js\src\client\websocket\packets\WebSocketPacketManager.js:103:65)
    at WebSocketConnection.onPacket (C:\Users\me\Documents\my project\node_modules\discord.js\src\client\websocket\WebSocketConnection.js:330:35)
    at WebSocketConnection.onMessage (C:\Users\me\Documents\my project\node_modules\discord.js\src\client\websocket\WebSocketConnection.js:293:17)
    at WebSocketClient.internalOnMessage (C:\Users\me\Documents\my project\node_modules\uws\uws.js:103:17)
    at native.client.group.onMessage (C:\Users\me\Documents\my project\node_modules\uws\uws.js:57:15)

我在这里缺少什么吗？这些方法似乎都不起作用，这就是我在谷歌上能找到的所有方法。导出图像的正确方法是什么？它可以是 PNG 或 JPEG/JPG，最好是 PNG，但 JPEG/JPG 也可以。确实是任何常见的格式。

找到了答案。canvas.createPNGStream().pipe(fs.createWriteStream(__dirname + "/output.png"))确实有效。它完全是空的，因为它看起来像canvas.add()不是一个瞬时动作。我所做的就是解决这个问题setTimeout()在输出文件之前。希望这对某人有帮助！