diff --git a/tools/colorchecker.py b/tools/colorchecker.py
--- a/tools/colorchecker.py
+++ b/tools/colorchecker.py
@@ -31,67 +31,84 @@
 	path = sys.argv[fileIndex]
 	print("Processing " + path)
 	xmlFile = QtCore.QFile(path)
-	
-	if xmlFile.exists():
-		if (xmlFile.open(QtCore.QIODevice.ReadOnly)):
+
+	if not xmlFile.exists():
+		print("Error: File {} does not exist".format(path))
+	else:
+		if not xmlFile.open(QtCore.QIODevice.ReadOnly):
+			print("Error: Could not open {} for reading".format(path))
+		else:
 			doc = QtXml.QDomDocument()
 			doc.setContent(xmlFile.readAll())
 			root = doc.documentElement()
-			if (root.tagName() == "map"):
+			if root.tagName() != "map":
+				print("Error: The map description file should begin with the map tag")
+			else:
 				imagePath = QtCore.QFileInfo(path).absolutePath() + "/" + root.firstChildElement("mapFile").text()
-				
+
 				if not QtCore.QFile.exists(imagePath):
 					print ("Error: Map file {} does not exist".format(imagePath))
 					sys.exit(2)
-				
+
 				colorList = [];
 				divisionTag = root.firstChildElement("division");
-				while (not divisionTag.isNull()):
+				while not divisionTag.isNull():
 					colorTag = divisionTag.firstChildElement("color");
 					red = int(colorTag.firstChildElement("red").text())
 					green = int(colorTag.firstChildElement("green").text())
 					blue = int(colorTag.firstChildElement("blue").text())
-					contains = colorList.count(QtGui.qRgb(red, green, blue))
-					if (contains == 0):
-						colorList.append(QtGui.qRgb(red, green, blue))
+					rgba = QtGui.qRgba(red, green, blue, 255)
+					if rgba not in colorList:
+						colorList.append(rgba)
 					else:
 						print("Error: The color {},{},{} is used more than once in the kgm file".format(red, green, blue))
-					
+
 					divisionTag = divisionTag.nextSiblingElement("division");
-				
+
 				image = QtGui.QImage(imagePath)
-				error = False
+				ct = image.colorTable()
+				error = len(image.colorTable()) == 0
+				if error:
+					print("Error: The PNG file should be in indexed color mode")
+				ac = image.convertToFormat(QtGui.QImage.Format_Alpha8)
+				act = ac.colorTable()
 				usedColors = set()
+				notfoundcolors = {}
 				for x in range(0, image.width()):
 					for y in range(0, image.height()):
-						rgbcolor = image.pixel(x,y)
-						qcolor = QtGui.qRgb(QtGui.qRed(rgbcolor), QtGui.qGreen(rgbcolor), QtGui.qBlue(rgbcolor))
-						contains = colorList.count(qcolor)
-						usedColors.add(qcolor)
-						if contains == 0:
-							qcolor = QtGui.QColor(rgbcolor)
-							print("Error: The pixel ({},{}) has color {},{},{} that is not defined in the kgm file".format(x, y, qcolor.red(), qcolor.green(), qcolor.blue()))
-							error = True
-				
+						rgbcolor = image.pixel(x, y)
+						ipix = image.pixelIndex(x, y)
+						c = ct[ipix]
+						al0 = ac.pixel(x, y)
+						al = QtGui.qAlpha(al0)
+						rgba = QtGui.qRgba(QtGui.qRed(rgbcolor), QtGui.qGreen(rgbcolor), QtGui.qBlue(rgbcolor), al)
+						usedColors.add(rgba)
+						if rgbcolor not in colorList:
+							tri = notfoundcolors.get(rgba)
+							if tri is None:
+								notfoundcolors[rgba] = [(x, y), 1, (x, y)]
+							else:
+								tri[1] += 1
+								tri[2] = (x, y)
+
+				error |= len(notfoundcolors) > 0
+				for rgba, tri in notfoundcolors.items():
+					qcolor = QtGui.QColor.fromRgba(rgba)
+					first, c, last = tri
+					x, y = first
+					print ("Error: The pixel (%d ,%d) has color rgba %d,%d,%d,%d that is not defined in the kgm file" % (
+						x, y, qcolor.red(), qcolor.green(), qcolor.blue(), qcolor.alpha()))
+
+				nonUsedColors = set(colorList)
+				nonUsedColors.difference_update(usedColors)
+				error |= len(nonUsedColors) > 0
+				for rgba in nonUsedColors:
+					qcolor = QtGui.QColor.fromRgba(rgba)
+					print("Error: the rgb(a) color {},{},{},({}) is absent from the png pixels".format(
+						qcolor.red(), qcolor.green(), qcolor.blue(), qcolor.alpha()))
+
 				if not error:
-					if len(colorList) == len(usedColors):
-						if (len(image.colorTable()) > 0):
-							print("The map is correctly formed")
-						else:
-							print("Error: The PNG file should be in indexed color mode")
-					else:
-						nonUsedColors = set(colorList)
-						nonUsedColors.difference_update(usedColors)
-						print("Warning: There are colors defined that are not used in the map file")
-						for color in nonUsedColors:
-							qcolor = QtGui.QColor(color)
-							print("{},{},{}".format(qcolor.red(), qcolor.green(), qcolor.blue()))
-			else:
-				print("Error: The map description file should begin with the map tag")
+					print("The map is correctly formed")
 			xmlFile.close();
-		else:
-			print("Error: Could not open {} for reading".format(path))
-	else:
-		print("Error: File {} does not exist".format(path))
 
 sys.exit(0)