Added setting for minimal colors

Fixes #162

_locales/de/messages.json

@@ -311,6 +311,15 @@
 		"description": ""
 	},
 	
+	"minColors_title": {
+		"message": "Minimale Anzahl an Farben",
+		"description": ""
+	},
+	"minColors_description": {
+		"message": "Anzahl der Farben, die ein Canvas aufweisen muss, damit es vorgetäuscht wird. Dies ist ein Parameter, der die Detektion des Addons erschweren soll.\nACHTUNG: Dies kann die Sicherheit des Addons beeinträchtigen. Deswegen wird stark empfohlen, diesen Wert nicht über 10 zu setzen.",
+		"description": ""
+	},
+	
 	"fakeAlphaChannel_title": {
 		"message": "Alpha-Kanal auch vortäuschen",
 		"description": ""

_locales/en/messages.json

@@ -311,6 +311,15 @@
 		"description": ""
 	},
 	
+	"minColors_title": {
+		"message": "Minimal number of colors",
+		"description": ""
+	},
+	"minColors_description": {
+		"message": "Number of colors that a canvas must have to be faked.\nCAUTION: This can lower the safety of the addon, therefore it is highly recommended not to set this value above 10.",
+		"description": ""
+	},
+	
 	"fakeAlphaChannel_title": {
 		"message": "Fake the alpha channel",
 		"description": ""

lib/colorStatistics.js

@@ -82,4 +82,29 @@
 		}
 		return statistic;
 	};
+	scope.hasMoreColors = function hasMoreColors(rawData, threshold, statistic){
+		if (statistic){
+			return statistic.numberOfColors > threshold;
+		}
+		else {
+			var colors = Object.create(null);
+			var count = 0;
+			for (var i = 0, l = rawData.length; i < l; i += 4){
+				var index = String.fromCharCode(
+					rawData[i + 0],
+					rawData[i + 1],
+					rawData[i + 2],
+					rawData[i + 3]
+				);
+				if (!Object.prototype.hasOwnProperty.call(colors, index)){
+					colors[index] = true;
+					count += 1;
+					if (count > threshold){
+						return true;
+					}
+				}
+			}
+			return count > threshold;
+		}
+	};
 }());

lib/modifiedAPI.js

@@ -79,10 +79,16 @@
 			var l = desc.length;
 			
 			var ignoredColors = {};
+			var statistic;
 			if (prefs("ignoreFrequentColors")){
-				var statistic = colorStatistics.compute(source);
+				statistic = colorStatistics.compute(source);
 				ignoredColors = statistic.getMaxColors(prefs("ignoreFrequentColors"));
 			}
+			if (prefs("minColors")){
+				if (!colorStatistics.hasMoreColors(source, prefs("minColors"), statistic)){
+					return original;
+				}
+			}
 			
 			var rng = randomSupply.getPixelRng(l, window, ignoredColors);
 			var fakeAlphaChannel = prefs("fakeAlphaChannel");

lib/settingDefinitions.js

@@ -67,6 +67,10 @@
 			name: "ignoreFrequentColors",
 			defaultValue: 0
 		},
+		{
+			name: "minColors",
+			defaultValue: 0
+		},
 		{
 			name: "fakeAlphaChannel",
 			defaultValue: false

options/settingsDisplay.js

@@ -143,6 +143,20 @@
 				}
 			]
 		},
+		{
+			"name": "minColors",
+			"displayDependencies": [
+				{
+					"blockMode": ["fakeReadout"],
+					"displayAdvancedSettings": [true]
+				},
+				{
+					"blockMode": ["askReadout", "ask"],
+					"askDenyMode": ["fake"],
+					"displayAdvancedSettings": [true]
+				}
+			]
+		},
 		{
 			"name": "fakeAlphaChannel",
 			"displayDependencies": [

releaseNotes.txt

@@ -8,7 +8,8 @@ Version 0.4.3:
 	new features:
 		- reset settings
 		- new white random generator - creates output similar to Tor browser
-		- blockMode and showNotifications can now be chosen url specific 
+		- blockMode and showNotifications can now be chosen url specific
+		- new setting to ignore canvas with only few colors
 	
 	fixes:
 		- page action was not always showing