支持 mac

npm-packages/mac-v2.4.x/canvas/lib/pngstream.js

@@ -0,0 +1,42 @@
+'use strict'
+
+/*!
+ * Canvas - PNGStream
+ * Copyright (c) 2010 LearnBoost <tj@learnboost.com>
+ * MIT Licensed
+ */
+
+const { Readable } = require('stream')
+function noop () {}
+
+class PNGStream extends Readable {
+  constructor (canvas, options) {
+    super()
+
+    if (options &&
+      options.palette instanceof Uint8ClampedArray &&
+      options.palette.length % 4 !== 0) {
+      throw new Error('Palette length must be a multiple of 4.')
+    }
+    this.canvas = canvas
+    this.options = options || {}
+  }
+
+  _read () {
+    // For now we're not controlling the c++ code's data emission, so we only
+    // call canvas.streamPNGSync once and let it emit data at will.
+    this._read = noop
+
+    this.canvas.streamPNGSync((err, chunk, len) => {
+      if (err) {
+        this.emit('error', err)
+      } else if (len) {
+        this.push(chunk)
+      } else {
+        this.push(null)
+      }
+    }, this.options)
+  }
+}
+
+module.exports = PNGStream