From 9a832a200d270c3f79e5220f69a2498d559ad010 Mon Sep 17 00:00:00 2001
From: Nayuki Minase <nayuki@eigenstate.org>
Date: Fri, 22 Apr 2016 16:10:35 +0000
Subject: [PATCH] Added QrCode.drawCanvas() to JavaScript version of the
 library, by moving it from the demo program.

---
 javascript/qrcodegen-demo.js | 12 +-----------
 javascript/qrcodegen.js      | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/javascript/qrcodegen-demo.js b/javascript/qrcodegen-demo.js
index ee07226..e4fedf3 100644
--- a/javascript/qrcodegen-demo.js
+++ b/javascript/qrcodegen-demo.js
@@ -76,17 +76,7 @@ function redrawQrCode() {
 		var scale = parseInt(document.getElementById("scale-input").value, 10);
 		if (scale <= 0 || scale > 30)
 			return;
-		// Draw QR Code onto canvas
-		var width = (qr.size + border * 2) * scale;
-		canvas.width = width;
-		canvas.height = width;
-		var ctx = canvas.getContext("2d");
-		for (var y = -border; y < qr.size + border; y++) {
-			for (var x = -border; x < qr.size + border; x++) {
-				ctx.fillStyle = qr.getModule(x, y) == 1 ? "#000000" : "#FFFFFF";
-				ctx.fillRect((x + border) * scale, (y + border) * scale, scale, scale);
-			}
-		}
+		qr.drawCanvas(scale, border, canvas);
 		canvas.style.removeProperty("display");
 	} else {
 		var code = qr.toSvgString(border);
diff --git a/javascript/qrcodegen.js b/javascript/qrcodegen.js
index 5a40e4e..10d46a6 100644
--- a/javascript/qrcodegen.js
+++ b/javascript/qrcodegen.js
@@ -37,6 +37,7 @@
  *   - Fields int version, size, mask
  *   - Field QrCode.Ecc errorCorrectionLevel
  *   - Method getModule(int x, int y) -> int
+ *   - Method drawCanvas(int scale, int border, HTMLCanvasElement canvas) -> void
  *   - Method toSvgString(int border) -> str
  *   - Enum Ecc:
  *     - Constants LOW, MEDIUM, QUARTILE, HIGH
@@ -185,6 +186,24 @@ var qrcodegen = new function() {
 		
 		/*---- Public instance methods ----*/
 		
+		// Draws this QR Code symbol with the given module scale and number of modules onto the given HTML canvas element.
+		// The canvas will be resized to a width and height of (this.size + border * 2) * scale. The painted image will be purely
+		// black and white with no transparent regions. The scale must be a positive integer, and the border must be a non-negative integer.
+		this.drawCanvas = function(scale, border, canvas) {
+			if (scale <= 0 || border < 0)
+				throw "Value out of range";
+			var width = (size + border * 2) * scale;
+			canvas.width = width;
+			canvas.height = width;
+			var ctx = canvas.getContext("2d");
+			for (var y = -border; y < size + border; y++) {
+				for (var x = -border; x < size + border; x++) {
+					ctx.fillStyle = this.getModule(x, y) == 1 ? "#000000" : "#FFFFFF";
+					ctx.fillRect((x + border) * scale, (y + border) * scale, scale, scale);
+				}
+			}
+		};
+		
 		// Based on the given number of border modules to add as padding, this returns a
 		// string whose contents represents an SVG XML file that depicts this QR Code symbol.
 		this.toSvgString = function(border) {