test/ocr/words.py

# -*- coding: utf-8 -*-
"""
Detect words on the page
return array of words' bounding boxes
"""
import numpy as np
import matplotlib.pyplot as plt
import cv2

from .helpers import *


def detection(image, join=False):
    """Detecting the words bounding boxes.
    Return: numpy array of bounding boxes [x, y, x+w, y+h]
    """
    # Preprocess image for word detection
    blurred = cv2.GaussianBlur(image, (5, 5), 18)
    edge_img = _edge_detect(blurred)
    ret, edge_img = cv2.threshold(edge_img, 50, 255, cv2.THRESH_BINARY)
    bw_img = cv2.morphologyEx(edge_img, cv2.MORPH_CLOSE,
                              np.ones((15,15), np.uint8))

    return _text_detect(bw_img, image, join)


def sort_words(boxes):
    """Sort boxes - (x, y, x+w, y+h) from left to right, top to bottom."""
    mean_height = sum([y2 - y1 for _, y1, _, y2 in boxes]) / len(boxes)
    
    boxes.view('i8,i8,i8,i8').sort(order=['f1'], axis=0)
    current_line = boxes[0][1]
    lines = []
    tmp_line = []
    for box in boxes:
        if box[1] > current_line + mean_height:
            lines.append(tmp_line)
            tmp_line = [box]
            current_line = box[1]            
            continue
        tmp_line.append(box)
    lines.append(tmp_line)
        
    for line in lines:
        line.sort(key=lambda box: box[0])
        
    return lines


def _edge_detect(im):
    """ 
    Edge detection using sobel operator on each layer individually.
    Sobel operator is applied for each image layer (RGB)
    """
    return np.max(np.array([_sobel_detect(im[:,:, 0]),
                            _sobel_detect(im[:,:, 1]),
                            _sobel_detect(im[:,:, 2])]), axis=0)


def _sobel_detect(channel):
    """Sobel operator."""
    sobelX = cv2.Sobel(channel, cv2.CV_16S, 1, 0)
    sobelY = cv2.Sobel(channel, cv2.CV_16S, 0, 1)
    sobel = np.hypot(sobelX, sobelY)
    sobel[sobel > 255] = 255
    return np.uint8(sobel)


def union(a,b):
    x = min(a[0], b[0])
    y = min(a[1], b[1])
    w = max(a[0]+a[2], b[0]+b[2]) - x
    h = max(a[1]+a[3], b[1]+b[3]) - y
    return [x, y, w, h]

def _intersect(a,b):
    x = max(a[0], b[0])
    y = max(a[1], b[1])
    w = min(a[0]+a[2], b[0]+b[2]) - x
    h = min(a[1]+a[3], b[1]+b[3]) - y
    if w<0 or h<0:
        return False
    return True

def _group_rectangles(rec):
    """
    Uion intersecting rectangles.
    Args:
        rec - list of rectangles in form [x, y, w, h]
    Return:
        list of grouped ractangles 
    """
    tested = [False for i in range(len(rec))]
    final = []
    i = 0
    while i < len(rec):
        if not tested[i]:
            j = i+1
            while j < len(rec):
                if not tested[j] and _intersect(rec[i], rec[j]):
                    rec[i] = union(rec[i], rec[j])
                    tested[j] = True
                    j = i
                j += 1
            final += [rec[i]]
        i += 1
            
    return final


def _text_detect(img, image, join=False):
    """Text detection using contours."""
    small = resize(img, 2000)
    
    # Finding contours
    mask = np.zeros(small.shape, np.uint8)
    cnt, hierarchy = cv2.findContours(np.copy(small),
                                           cv2.RETR_CCOMP,
                                           cv2.CHAIN_APPROX_SIMPLE)
    
    index = 0    
    boxes = []
    # Go through all contours in top level
    while (index >= 0):
        x,y,w,h = cv2.boundingRect(cnt[index])
        cv2.drawContours(mask, cnt, index, (255, 255, 255), cv2.FILLED)
        maskROI = mask[y:y+h, x:x+w]
        # Ratio of white pixels to area of bounding rectangle
        r = cv2.countNonZero(maskROI) / (w * h)
        
        # Limits for text
        if (r > 0.1
            and 1600 > w > 10
            and 1600 > h > 10
            and h/w < 3
            and w/h < 10
            and (60 // h) * w < 1000):
            boxes += [[x, y, w, h]]
            
        index = hierarchy[0][index][0]

    if join:
        # Need more work
        boxes = _group_rectangles(boxes)

    # image for drawing bounding boxes
    small = cv2.cvtColor(small, cv2.COLOR_GRAY2RGB)
    bounding_boxes = np.array([0,0,0,0])
    for (x, y, w, h) in boxes:
        cv2.rectangle(small, (x, y),(x+w,y+h), (0, 255, 0), 2)
        bounding_boxes = np.vstack((bounding_boxes,
                                    np.array([x, y, x+w, y+h])))
        
    implt(small, t='Bounding rectangles')
    
    boxes = bounding_boxes.dot(ratio(image, small.shape[0])).astype(np.int64)
    return boxes[1:]  
    

def textDetectWatershed(thresh):
    """NOT IN USE - Text detection using watershed algorithm.
    Based on: http://docs.opencv.org/trunk/d3/db4/tutorial_py_watershed.html
    """
    img = cv2.cvtColor(cv2.imread("data/textdet/%s.jpg" % IMG),
                       cv2.COLOR_BGR2RGB)
    img = resize(img, 3000)
    thresh = resize(thresh, 3000)
    # noise removal
    kernel = np.ones((3,3),np.uint8)
    opening = cv2.morphologyEx(thresh,cv2.MORPH_OPEN,kernel, iterations = 3)
    
    # sure background area
    sure_bg = cv2.dilate(opening,kernel,iterations=3)

    # Finding sure foreground area
    dist_transform = cv2.distanceTransform(opening,cv2.DIST_L2,5)
    ret, sure_fg = cv2.threshold(dist_transform,
                                 0.01*dist_transform.max(), 255, 0)

    # Finding unknown region
    sure_fg = np.uint8(sure_fg)
    unknown = cv2.subtract(sure_bg,sure_fg)
    
    # Marker labelling
    ret, markers = cv2.connectedComponents(sure_fg)

    # Add one to all labels so that sure background is not 0, but 1
    markers += 1

    # Now, mark the region of unknown with zero
    markers[unknown == 255] = 0
    
    markers = cv2.watershed(img, markers)
    implt(markers, t='Markers')
    image = img.copy()
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    
    for mark in np.unique(markers):
        # mark == 0 --> background
        if mark == 0:
            continue

        # Draw it on mask and detect biggest contour
        mask = np.zeros(gray.shape, dtype="uint8")
        mask[markers == mark] = 255

        cnts = cv2.findContours(mask.copy(),
                                cv2.RETR_EXTERNAL,
                                cv2.CHAIN_APPROX_SIMPLE)[-2]
        c = max(cnts, key=cv2.contourArea)
        
        # Draw a bounding rectangle if it contains text
        x,y,w,h = cv2.boundingRect(c)
        cv2.drawContours(mask, c, 0, (255, 255, 255), cv2.FILLED)
        maskROI = mask[y:y+h, x:x+w]
        # Ratio of white pixels to area of bounding rectangle
        r = cv2.countNonZero(maskROI) / (w * h)
        
        # Limits for text
        if r > 0.2 and 2000 > w > 15 and 1500 > h > 15:
            cv2.rectangle(image, (x, y),(x+w,y+h), (0, 255, 0), 2)
        
    implt(image)