New rule: similar colors

lib/metadata/policies.js

@@ -463,7 +463,7 @@ var policies = {
     },
     "cssColors": {
         "tool": "phantomas",
-        "label": "Different colors",
+        "label": "Colors count",
         "message": "<p>This is the number of different colors defined in CSS.</p><p>Your CSS project will be easier to maintain if you keep a small color set.</p>",
         "isOkThreshold": 30,
         "isBadThreshold": 150,
@@ -507,6 +507,21 @@ var policies = {
             };
         }
     },
+    "similarColors": {
+        "tool": "colorDiff",
+        "label": "Similar colors",
+        "message": "<p>This is the list of colors found in the stylesheets, that are very close to each other. The eye can barely see the difference.</p><p>Use this list to reduce the number of colors in your palette, it will be easier to maintain.</p>",
+        "isOkThreshold": 0,
+        "isBadThreshold": 40,
+        "isAbnormalThreshold": 80,
+        "hasOffenders": true,
+        "offendersTransformFn": function(offenders) {
+            return {
+                count: offenders.length,
+                list: offenders
+            };
+        }
+    },
     "cssImports": {
         "tool": "phantomas",
         "label": "Uses of @import",
@@ -970,7 +985,7 @@ var policies = {
         "tool": "phantomas",
         "label": "Hidden images",
         "message": "<p>List of all images that have a display:none property, or one of their parents. These images are loaded by the browser even if they're not visible. You might be able to find a way to lazy-load them, only when they get visible.</p><p>Trackers are an exception, you'd better hide them.</p>",
-        "isOkThreshold": 3,
+        "isOkThreshold": 1,
         "isBadThreshold": 12,
         "isAbnormalThreshold": 30,
         "hasOffenders": true

lib/metadata/scoreProfileGeneric.json

@@ -70,7 +70,8 @@
                 "cssRules": 2,
                 "cssComplexSelectors": 2,
                 "cssComplexSelectorsByAttribute": 1.5,
-                "cssColors": 0.5
+                "cssColors": 0.5,
+                "similarColors": 0.5
             }
         },
         "badCSS": {

lib/runner.js

@@ -3,6 +3,7 @@ var debug                   = require('debug')('ylt:runner');
 
 var phantomasWrapper        = require('./tools/phantomas/phantomasWrapper');
 var jsExecutionTransformer  = require('./tools/jsExecutionTransformer');
+var colorDiff               = require('./tools/colorDiff');
 var weightChecker           = require('./tools/weightChecker/weightChecker');
 var rulesChecker            = require('./rulesChecker');
 var scoreCalculator         = require('./scoreCalculator');
@@ -28,6 +29,9 @@ var Runner = function(params) {
         // Treat the JS Execution Tree from offenders
         data = jsExecutionTransformer.transform(data);
 
+        // Compare colors
+        data = colorDiff.compareAllColors(data);
+
         // Redownload every file
         return weightChecker.recheckAllFiles(data);
 

lib/tools/colorDiff.js

@@ -0,0 +1,90 @@
+var debug   = require('debug')('ylt:colorDiff');
+var diff    = require('color-diff');
+var parse   = require('parse-color');
+
+
+var colorDiff = function() {
+
+    var COLOR_DIFF_THRESHOLD = 0.9;
+
+    this.compareAllColors = function(data) {
+        debug('Starting to compare all colors...');
+
+        var offenders = data.toolsResults.phantomas.offenders.cssColors;
+        var colors = (offenders) ? this.parseAllColors(offenders) : [];
+        var result = [];
+
+        // Compare colors to each other
+        for (var i = 0; i < colors.length - 1 ; i++) {
+            for (var j = i + 1; j < colors.length; j++) {
+                debug('Comparing color %s with color %s', colors[i].original, colors[j].original);
+                if (this.compareTwoColors(colors[i], colors[j])) {
+                    debug('Colors are similar!');
+                    result.push({
+                        color1: colors[i].original,
+                        color2: colors[j].original,
+                        isDark: (colors[i].Lab.L < 60)
+                    });
+                }
+            }
+        }
+
+        data.toolsResults.colorDiff = {
+            metrics: {
+                similarColors: result.length
+            },
+            offenders: {
+                similarColors: result
+            }
+        };
+
+        return data;
+    };
+
+    this.parseAllColors = function(offenders) {
+        var parsedOffenders = offenders.map(this.parseOffender);
+        var deduplicatedColors = {};
+
+        parsedOffenders.forEach(function(color) {
+            deduplicatedColors[color] = color;
+        });
+
+        return Object.keys(deduplicatedColors).map(this.parseColor);
+    };
+
+    this.parseOffender = function(offender) {
+        var regexResult = /^(.*) \(\d+ times\)$/.exec(offender);
+        return regexResult[1];
+    };
+
+    this.parseColor = function(color) {
+        var colorArray = parse(color).rgba;
+
+        var obj = {
+            R: colorArray[0],
+            G: colorArray[1],
+            B: colorArray[2],
+            A: colorArray[3]
+        };
+
+        obj.Lab = diff.rgb_to_lab(obj);
+        obj.original = color;
+
+        return obj;
+    };
+
+    this.compareTwoColors = function(color1, color2) {
+        if (color1.A !== color2.A) {
+            debug('Comparison not possible, because the alpha channel is different');
+            return false;
+        }
+
+        var delta = diff.diff(color1.Lab, color2.Lab);
+        debug('Delta is %d', delta);
+        
+        return delta <= COLOR_DIFF_THRESHOLD;
+    };
+
+};
+
+module.exports = new colorDiff();