From 198fc0210ecdcf43a126ae7efb9893bca6b2b2a1 Mon Sep 17 00:00:00 2001
From: Peter Beard <peter.b.beard+github@gmail.com>
Date: Wed, 19 Nov 2014 02:16:06 -0500
Subject: [PATCH] Added support for drawing directly to <canvas> tags.

---
 js/qrcode.js | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/js/qrcode.js b/js/qrcode.js
index 8732a64..713a788 100644
--- a/js/qrcode.js
+++ b/js/qrcode.js
@@ -464,9 +464,30 @@ var qrcode = function() {
       } );
     };
 
+    _this.drawOnCanvas = function(canvas, cellSize, margin) {
+
+      cellSize = cellSize || 2;
+      margin = (typeof margin == 'undefined')? cellSize * 4 : margin;
+
+      var size = _this.getModuleCount() * cellSize + margin * 2;
+      var min = margin;
+      var max = size - margin;
+
+      drawOnCanvas(canvas, size, size, function(x, y) {
+        if (min <= x && x < max && min <= y && y < max) {
+          var c = Math.floor( (x - min) / cellSize);
+          var r = Math.floor( (y - min) / cellSize);
+          return _this.isDark(r, c)? 0 : 1;
+        } else {
+          return 1;
+        }
+      } );
+    };
+
     return _this;
   };
 
+
   //---------------------------------------------------------------------
   // qrcode.stringToBytes
   //---------------------------------------------------------------------
@@ -1627,6 +1648,27 @@ var qrcode = function() {
     return img;
   };
 
+  var drawOnCanvas = function(canvas, width, height, getPixel) {
+    // Set the canvas size
+    canvas.width = width;
+    canvas.height = height;
+    // Get a drawing context
+    var ctx = canvas.getContext("2d");
+    // Fill the background with black
+    ctx.fillStyle = "#000";
+    ctx.fillRect(0,0,width,height);
+    // Draw the white pixels
+    ctx.fillStyle = "#fff";
+    for(var x = 0; x < width; x++)
+    {
+      for(var y = 0; y < height; y++)
+      {
+        if(getPixel(x,y))
+          ctx.fillRect(x,y,1,1);
+      }
+    }
+  };
+
   //---------------------------------------------------------------------
   // returns qrcode function.