textdeskew.py

import numpy as np
import cv2

def textdeskew(image):
	"""
	Function that calculates a the rotation angle for documents that are 
	already properly scanned. Using the angle, it tries to deskew. Useful in 
	cases where there is no difference between foreground and background, and
	the document is properly scanned. 
	"""
	gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
	gray = cv2.bitwise_not(gray)
	thresh = cv2.threshold(gray, 0, 255,
		cv2.THRESH_BINARY | cv2.THRESH_OTSU)[1]


	coords = np.column_stack(np.where(thresh > 0))
	angle = cv2.minAreaRect(coords)[-1]
	if angle < -45:
		angle = -(90 + angle)

	else:
		angle = -angle

	(h, w) = image.shape[:2]
	center = (w // 2, h // 2)
	M = cv2.getRotationMatrix2D(center, angle, 1.0)
	rotated = cv2.warpAffine(image, M, (w, h),
		flags=cv2.INTER_CUBIC, borderMode=cv2.BORDER_REPLICATE)

	print("[INFO] angle: {:.3f}".format(angle))
	# cv2.namedWindow("Input", cv2.WINDOW_NORMAL)
	# cv2.namedWindow("Final", cv2.WINDOW_NORMAL)
	# cv2.imshow("Input", image)
	# cv2.imshow("Final", rotated)
	# cv2.waitKey(0)
	return rotated