Added PNGStream test

lib/canvas.js

@@ -14,7 +14,8 @@ var canvas = require('../build/default/canvas')
   , Canvas = canvas.Canvas
   , Context2d = canvas.CanvasRenderingContext2d
   , CanvasGradient = canvas.CanvasGradient
-  , cairoVersion = canvas.cairoVersion;
+  , cairoVersion = canvas.cairoVersion
+  , PNGStream = require('./pngstream');
 
 /**
  * Export `Canvas` as the module.
@@ -126,6 +127,17 @@ Canvas.prototype.getContext = function(contextId){
   }
 };
 
+/**
+ * Create a `PNGStream` for `this` canvas.
+ *
+ * @return {PNGStream}
+ * @api public
+ */
+
+Canvas.prototype.createPNGStream = function(){
+  return new PNGStream(this);
+};
+
 /**
  * Add `color` stop at the given `offset`.
  *

src/canvas.cc

@@ -72,6 +72,7 @@ Handle<Value>
 Canvas::StreamPNG(const Arguments &args) {
   HandleScope scope;
   // TODO: error handling
+  // TODO: nonblocking
   if (!args[0]->IsFunction())
     return ThrowException(Exception::TypeError(String::New("callback function required")));
   Canvas *canvas = ObjectWrap::Unwrap<Canvas>(args.This());

test/canvas.test.js

@@ -14,6 +14,10 @@ function hash(val) {
 
 function assertChecksum(canvas, path, checksum, msg) {
   canvas.savePNG(path);
+  assertChecksumOf(canvas, path, checksum, msg);
+}
+
+function assertChecksumOf(canvas, path, checksum, msg) {
   fs.readFile(path, function(err, buf){
     assert.equal(hash(buf), checksum, msg);  
   });
@@ -499,5 +503,47 @@ module.exports = {
     assert.ok(ctx.isPointInPath(60,110));
     assert.ok(!ctx.isPointInPath(70,110));
     assert.ok(!ctx.isPointInPath(50,120));
+  },
+  
+  'test PNGStream': function(assert, beforeExit){
+    var canvas = new Canvas(320, 320)
+      , ctx = canvas.getContext('2d')
+      , path = __dirname + '/images/pngstream.png'
+      , called = 0;
+
+    ctx.strokeStyle = 'rgba(0,0,0,0.5)';
+    ctx.strokeRect(0,0,320,320);
+    
+    ctx.fillStyle = 'rgba(0,0,0,0.02)';
+    var steps = 200;
+    while (steps--) {
+      ctx.fillRect(
+          160 - (steps / 2)
+        , 160 - (steps / 2)
+        , steps
+        , steps
+        );
+    }
+    
+    var out = fs.createWriteStream(path)
+      , stream = canvas.createPNGStream();
+
+    out.on('close', function(){
+      assertChecksumOf(
+          canvas
+        , path
+        , '04f2e1b4338de2d7451194cba7d29970'
+        , 'PNGStream failed');
+    });
+
+    stream.on('data', function(chunk){ out.write(chunk); });
+    stream.on('end', function(){
+      ++called;
+      out.end();
+    });
+
+    beforeExit(function(){
+      assert.equal(1, called);
+    });
   }
 }