Commit 5e58ce50 authored by Mickaël Desfrênes's avatar Mickaël Desfrênes
Browse files

add skew detection in rpc.methods

parent a307ff57

requirements.txt

+3 −1
Original line number Diff line number Diff line
@@ -11,3 +11,5 @@ django-ranged-fileresponse 
pyvips

huey

pre-commit

numpy

opencv-python-headless
 
 No newline at end of file

rpc/methods.py

+64 −0
Original line number Diff line number Diff line
@@ -33,6 +33,8 @@ from rpc.const import * 
import logging

import pyvips

import tempfile

import cv2

import numpy

from resources.helpers import handle_local_file as _handle_local_file
@@ -49,6 +51,52 @@ class ServiceException(Exception): 
        self.message = args[0]





def _deskew(image_path: str, max_skew: int = 10) -> float:

    im = cv2.imread(image_path)

    height, width, _ = im.shape

    im_gs = cv2.cvtColor(im, cv2.COLOR_BGR2GRAY)

    im_gs = cv2.fastNlMeansDenoising(im_gs, h=3)

    im_bw = cv2.threshold(im_gs, 0, 255, cv2.THRESH_BINARY_INV | cv2.THRESH_OTSU)[1]

    lines = cv2.HoughLinesP(

        im_bw, 1, numpy.pi / 180, 200, minLineLength=width / 12, maxLineGap=width / 150

    )

    # Collect the angles of these lines (in radians)

    angles = []

    for line in lines:

        x1, y1, x2, y2 = line[0]

        angles.append(numpy.arctan2(y2 - y1, x2 - x1))



    # If the majority of our lines are vertical, this is probably a landscape image

    landscape = (

        numpy.sum([abs(angle) > numpy.pi / 4 for angle in angles]) > len(angles) / 2

    )



    # Filter the angles to remove outliers based on max_skew

    if landscape:

        angles = [

            angle

            for angle in angles

            if numpy.deg2rad(90 - max_skew) < abs(angle) < numpy.deg2rad(90 + max_skew)

        ]

    else:

        angles = [angle for angle in angles if abs(angle) < numpy.deg2rad(max_skew)]



    if len(angles) < 5:

        # Insufficient data to deskew

        return 0



    # Average the angles to a degree offset

    angle_deg = numpy.rad2deg(numpy.median(angles))



    # If this is landscape image, rotate the entire canvas appropriately

    if landscape:

        if angle_deg < 0:

            angle_deg += 90

        elif angle_deg > 0:

            angle_deg -= 90

    return angle_deg * -1





def _validate_limits(limit_from: int, limit_to: int) -> Tuple[int, int]:

    try:

        limit_from = int(limit_from)
@@ -3060,3 +3108,19 @@ def remove_meta_value_from_selection( 
            user, collection_instance.pk, meta_value_id, True

        )

    return True





@_log_call

@_rpc_groups(["Resources"])

def auto_find_rotate_angle(user: User, resource_id: int) -> float:

    """

    Tries to determine skew angle of image with text.

    """

    resource_instance = Resource.objects.filter(pk=resource_id).first()

    if not resource_instance:

        raise ServiceException(NO_SUCH_RESOURCE)

    if not resource_instance.file:

        raise ServiceException(NOT_A_FILE)

    if not resource_instance.file.should_have_iiif():

        raise ServiceException(NOT_AN_IMAGE)

    return _deskew(resource_instance.file.local_path())