Inter-panel cropping method. (#810)

* Inter-panel cropping method.

* 1. Save interpanelcrop option.
2. Update readme with the the new interpanelcrop argument.
3. Add a tooltip to the inter-panel crop box.

kindlecomicconverter/inter_panel_crop_alg.py

@@ -0,0 +1,76 @@
+from PIL import Image, ImageFilter, ImageOps
+import numpy as np
+from typing import Literal
+from .common_crop import threshold_from_power, group_close_values
+
+
+'''
+Crops inter-panel empty spaces (ignores empty spaces near borders - for that use crop margins).
+
+    Parameters:
+            img (PIL image): A PIL image.
+            direction (horizontal or vertical or both): To crop rows (horizontal), cols (vertical) or both.
+            keep (float): Distance to keep between panels after cropping (in percentage relative to the original distance).
+            background_color (string): 'white' for white background, anything else for black.
+    Returns:
+            img (PIL image): A PIL image after cropping empty sections.
+'''
+def crop_empty_inter_panel(img, direction: Literal["horizontal", "vertical", "both"], keep=0.04, background_color='white'):
+    img_temp = img
+    
+    if img.mode != 'L':
+        img_temp = ImageOps.grayscale(img)
+        
+    if background_color != 'white':
+        img_temp = ImageOps.invert(img)
+        
+    img_mat = np.array(img)
+    
+    power = 1
+    img_temp = ImageOps.autocontrast(img_temp, 1).filter(ImageFilter.BoxBlur(1))
+    img_temp = img_temp.point(lambda p: 255 if p <= threshold_from_power(power) else 0)
+    
+    if direction in ["horizontal", "both"]:
+        rows_idx_to_remove = empty_sections(img_temp, keep, horizontal=True)
+        img_mat = np.delete(img_mat, rows_idx_to_remove, 0)
+        
+    if direction in ["vertical", "both"]:
+        cols_idx_to_remove = empty_sections(img_temp, keep, horizontal=False)
+        img_mat = np.delete(img_mat, cols_idx_to_remove, 1)
+
+    return Image.fromarray(img_mat)
+
+
+'''
+Finds empty sections (excluding near borders).
+
+    Parameters:
+            img (PIL image): A PIL image.
+            keep (float): Distance to keep between panels after cropping (in percentage relative to the original distance).
+            horizontal (boolean): True to find empty rows, False to find empty columns.
+    Returns:
+            Itertable (list or NumPy array): indices of rows or columns to remove.
+'''
+def empty_sections(img, keep, horizontal=True):
+    axis = 1 if horizontal else 0
+    
+    img_mat = np.array(img)
+    img_mat_max = np.max(img_mat, axis=axis)
+    img_mat_empty_idx = np.where(img_mat_max == 0)[0]
+        
+    empty_sections = group_close_values(img_mat_empty_idx, 1)
+    sections_to_remove = []
+    for section in empty_sections:
+        if section[1] < img.size[1] * 0.99 and section[0] > img.size[1] * 0.01: # if not near borders
+            sections_to_remove.append(section)
+        
+    if len(sections_to_remove) != 0:
+        sections_to_remove_after_keep = [(int(x1+(keep/2)*(x2-x1)), int(x2-(keep/2)*(x2-x1))) for x1,x2 in sections_to_remove]
+        idx_to_remove = np.concatenate([np.arange(x1, x2) for x1,x2 in sections_to_remove_after_keep])
+
+        return idx_to_remove
+    
+    return []
+
+
+