comic_panels.py

import imageio    
import cv2                                                    
import numpy as np    
                                         
# Load GIF                
gif = imageio.mimread('calvin.gif')                                                                                                                        
frames = [cv2.cvtColor(np.array(frame), cv2.COLOR_RGBA2BGR) for frame in gif]                                                                              
    
def is_panel(box, w_thresh=200, h_thresh=200):    
    x, y, w, h = box           
    return w > w_thresh and h > h_thresh              
                                                   
def hidden_panel(box1, box2, dist_thresh=100):    
    if edge_distance(box1, box2) > dist_thresh:                                          
        x1, y1, w1, h1 = box1                                               
        x2, y2, w2, h2 = box2    
        right_edge = x1+w1                             
        left_edge = x2                                           
        x3 = right_edge    
        y3 = y1                                
        w3 = left_edge - right_edge                      
        h3 = h1    
        return (x3, y3, w3, h3)                                                                                      
    else:                                      
        return    
                             
                                        
def edge_distance(box1, box2):    
    x1, y1, w1, h1 = box1                      
    x2, y2, w2, h2 = box2    
    right_edge = x1+w1       
    left_edge = x2                      
    return left_edge - right_edge    
                                                                   
green = (0, 255, 0)                                    
red = (0, 0, 255)    
yellow = (0, 255, 255)              
black = (0, 0, 0)                                   
    
                                        
# green by default                                                            
def draw_box(box, frame, color=(0, 255, 0)):
    x, y, w, h = box
    print(box)
    cv2.rectangle(frame, (x, y), (x + w, y + h), color, 2)

def extract_image(idx, panel, frame):
    x, y, w, h = panel
    extracted = frame[y:y+h, x:x+w]
    cv2.imwrite(f'panel_{idx}.png', extracted)

for idx, frame in enumerate(frames):
    # find edged panels
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    blurred = cv2.GaussianBlur(gray, (5, 5), 0)
    edged = cv2.Canny(blurred, 50, 150)
    contours, _ = cv2.findContours(edged, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
    bounding_boxes = [cv2.boundingRect(contour) for contour in contours]

    # many false positive panels.. apply threshold
    panels = [box for box in bounding_boxes if is_panel(box)]

    # outline opencv found panels in green
    # [draw_box(box, frame, green) for box in panels]

    # between each panel, check if distance is about panel sized.. i.e. there's an unboredered panel between
    hp = hidden_panel(panels[0], panels[1])
    if hp:
        panels.append(hp)
        #draw_box(hp, frame, yellow)

    hp = hidden_panel(panels[1], panels[2])
    if hp:
        panels.append(hp)
        #draw_box(hp, frame, yellow)

    # save comic w/ panels highlighted, for visual sanity check
    # cv2.imwrite(f'highlighted_panels.png', frame)

    # sort by x position
    panels = sorted(panels, key=lambda x: x[0])

    # save panels as separate images
    [extract_image(idx, panel, frame) for idx, panel in enumerate(panels)]