Added new test case covering issue #2.

Author: dmester

tests/expected-truecolor.png

@@ -0,0 +1,67 @@
+/**
+ * canvas-renderer
+ * https://github.com/dmester/canvas-renderer
+ * 
+ * Copyright (c) 2017-2018 Daniel Mester Pirttijärvi
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the 
+ * "Software"), to deal in the Software without restriction, including 
+ * without limitation the rights to use, copy, modify, merge, publish, 
+ * distribute, sublicense, and/or sell copies of the Software, and to 
+ * permit persons to whom the Software is furnished to do so, subject to 
+ * the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+ 
+"use strict";
+
+
+/**
+ * canvas-renderer will use a palette when possible. To force it to produce
+ * a truecolor PNG we need to ensure the image contains more than 256 colors.
+ * This is done by rendering large circles, leading to a lot of different
+ * colors.
+ *
+ * A mix of light and dark colors are used to ensure we test colors that
+ * are represented as integers where the sign bit is set and unset.
+ */
+
+const fs = require("fs");
+const tap = require("tap");
+const canvasRenderer = require("../index");
+
+var canvas = canvasRenderer.createCanvas(1000, 1000);
+canvas.backColor = "#abcdefff";
+
+var ctx = canvas.getContext("2d");
+
+var radius = 250;
+
+ctx.beginPath();
+ctx.fillStyle = "#ffffffff";
+ctx.moveTo(100 + radius, 250 + radius);
+ctx.arc(100 + radius, 250 + radius, radius, 0, Math.PI * 2, true); // last argument should have no effect
+ctx.closePath();
+ctx.fill();
+
+ctx.beginPath();
+ctx.fillStyle = "#000000ff";
+ctx.moveTo(400 + radius, 250 + radius);
+ctx.arc(400 + radius, 250 + radius, radius, 0, Math.PI * 2, false); // last argument should have no effect
+ctx.closePath();
+ctx.fill();
+
+var expected = fs.readFileSync(__dirname + "/expected-truecolor.png");
+var expectedB64 = Buffer.from(expected).toString("base64");
+tap.equal("data:image/png;base64," + expectedB64, canvas.toDataURL());