[cv2] contour 사용해서 이미지 내 외부 패딩 삭제

https://aihints.com/how-to-draw-bounding-box-in-opencv-python/

How to Draw Bounding Box in OpenCV Python - AiHints

 

이미지 내 특정 그림을 포함하는 bbox만을 남겨두고, 나머지는 crop해버리는 코드

 

def make_inner_crop():    
    # target_lst is list of cropped image,
    # we're going to remove the padding area, only remain the inner text(figure) area.
    # save the result to remove padding area.
    target_lst = glob.glob("./crop/*")
    result_dir = "./double_crop"
    os.makedirs(result_dir, exist_ok=True)
    
    # Crop inner image, remove white padding area
    for file in target_lst:
        # load image
        target = cv2.imread(file)
        # convert to gray
        target_gray = cv2.cvtColor(target, cv2.COLOR_BGR2GRAY)
        thresh = cv2.threshold(target_gray, 0, 255, cv2.THRESH_BINARY_INV + cv2.THRESH_OTSU)[1]
        
        contours = cv2.findContours(thresh, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
        contours = contours[0] if len(contours) == 2 else contours[1]
        
        for i in contours:
            x,y,w,h = cv2.boundingRect(i)
            #cv2.rectangle(target, (x, y), (x + w, y + h), (255,0,0), 1)
            #cv2.imwrite("./vis/{}_inner.jpg".format(os.path.splitext(os.path.basename(file))[0]), target)
        
        crop = target[y:y+h, x:x+w]
        # save
        basename = os.path.splitext(os.path.basename(file))[0]
        cv2.imwrite(os.path.join(result_dir, "{}_inner.jpg".format(basename)), crop)