From 916871365fad339280f9608f804c43b941bb46d1 Mon Sep 17 00:00:00 2001
From: Raul Ochoa <rochoaf@gmail.com>
Date: Wed, 4 Mar 2015 18:53:06 +0100
Subject: [PATCH] image.compare returns the % difference against the reference
 image As canvas can differ from one implementation to another make tests to
 have a tolerance to differences.

---
 test/acceptance/renderer/point.js | 6 ++++--
 test/support/image.js             | 2 +-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/test/acceptance/renderer/point.js b/test/acceptance/renderer/point.js
index d1ad220..e37f576 100644
--- a/test/acceptance/renderer/point.js
+++ b/test/acceptance/renderer/point.js
@@ -3,6 +3,8 @@ var image = require('../../support/image');
 
 QUnit.module('renderer/point');
 
+var IMAGE_DIFF_TOLERANCE = 4 / 100;
+
 asyncTest('navy example', function(assert) {
     var cartocss = [
         'Map {',
@@ -33,7 +35,7 @@ asyncTest('navy example', function(assert) {
     pointRenderer.getTile('default_navy_3-3-2.torque.json', cartocss, 3, 3, 2, step, function(err, canvas) {
         assert.ok(!err, 'no error while getting tile');
         var imageDiff = image.compare(canvas.toBuffer(), 'default_navy_3-3-2.png');
-        assert.equal(imageDiff, 0, 'navy tile is ok');
+        assert.ok(imageDiff < IMAGE_DIFF_TOLERANCE, 'navy tile is ok');
         QUnit.start();
     });
 });
@@ -58,7 +60,7 @@ asyncTest('basic heatmap', function(assert) {
     pointRenderer.getTile('heatmap_navy_3-2-3.torque.json', cartocss, 3, 2, 3, step, function(err, canvas) {
         assert.ok(!err, 'no error while getting tile');
         var imageDiff = image.compare(canvas.toBuffer(), 'heatmap_navy_3-2-3.png');
-        assert.equal(imageDiff, 0, 'heatmap tile is ok');
+        assert.ok(imageDiff < IMAGE_DIFF_TOLERANCE, 'heatmap tile is ok');
         QUnit.start();
     });
 });
\ No newline at end of file
diff --git a/test/support/image.js b/test/support/image.js
index 91964e5..062508d 100644
--- a/test/support/image.js
+++ b/test/support/image.js
@@ -5,7 +5,7 @@ function compare(buffer, fixtureRelPath) {
 
     var img = new mapnik.Image.fromBytesSync(buffer);
     var reference = new mapnik.Image.openSync(__dirname + '/../fixtures/image/' + fixtureRelPath);
-    return img.compare(reference);
+    return img.compare(reference) / (reference.width() * reference.height());
 }
 
 function save(path, buffer) {