from feature_extraction import FEATURE_DATATYPE
import numpy
import cv2

CLASS_DATATYPE=     numpy.uint16
CLASS_SIZE=         1
CLASSES_DIRECTION=  0 #vertical - a classes COLUMN

BLANK_CLASS=        chr(10) #marks unclassified elements

def classes_to_numpy( classes ):
    '''given a list of unicode chars, transforms it into a numpy array'''
    import array
    #utf-32 starts with constant ''\xff\xfe\x00\x00', then has little endian 32 bits chars
    #this assumes little endian architecture!
    assert unichr(15).encode('utf-32')=='\xff\xfe\x00\x00\x0f\x00\x00\x00'
    int_classes= array.array( "L", "".join(classes).encode('utf-32')[4:])
    assert len(int_classes) == len(classes)
    classes=  numpy.array( int_classes,  dtype=CLASS_DATATYPE, ndmin=2) #each class in a column. numpy is strange :(
    classes= classes if CLASSES_DIRECTION==1 else numpy.transpose(classes)
    return classes

def classes_from_numpy(classes):
    '''reverses classes_to_numpy'''
    classes= classes if CLASSES_DIRECTION==0 else classes.tranpose()
    classes= map(unichr, classes)
    return classes

class Classifier( object ):
    def train( self, features, classes ):
        '''trains the classifier with the classified feature vectors'''
        raise NotImplementedError()

    @staticmethod
    def _filter_unclassified( features, classes ):
        classified= (classes != classes_to_numpy(BLANK_CLASS)).reshape(-1)
        return features[classified], classes[classified]
        
    def classify( self, features):
        '''returns the classes of the feature vectors'''
        raise NotImplementedError

class KNNClassifier( Classifier ):
    def __init__(self, k=1, debug=False):
        self.knn= cv2.KNearest()
        self.k=k
        self.debug= debug

    def train( self, features, classes ):
        if FEATURE_DATATYPE!=numpy.float32:
            features= numpy.asarray( features, dtype=numpy.float32 )
        if CLASS_DATATYPE!=numpy.float32:
            classes= numpy.asarray( classes, dtype=numpy.float32 )
        features, classes= Classifier._filter_unclassified( features, classes )
        self.knn.train( features, classes )
        
    def classify( self, features):
        if FEATURE_DATATYPE!=numpy.float32:
            features= numpy.asarray( features, dtype=numpy.float32 )
        retval, result_classes, neigh_resp, dists= self.knn.find_nearest(features, k= 1)
        return result_classes

@@ -201,10 +201,10 @@
 chr(
-10
+35
 ) #m

change BLANK_CLASS to # to avoid tesseract file serialization problems