added image aspect ratio fixing

src/recrop.py

@@ -0,0 +1,31 @@
+import cv2
+from math import ceil
+
+# [3/4 --> 16/9]
+def fix_aspect_ratio(img_file):
+    """Returns path to new image that better fits the aspect ratio of a single-image post."""
+    img = cv2.imread(img_file)
+    img_ratio = img.shape[1]/img.shape[0]
+    print(f'{img_file}: {img_ratio}')
+
+    if img_ratio > 16/9:
+        print('too wide; add height')
+        x, y = img.shape[1], (img.shape[1]*9)/16
+    elif img_ratio < 3/4:
+        print('too skinny; add width')
+        x, y = (img.shape[0]*3)/4, img.shape[0]
+    else:
+        print('ratio is good; no need to readjust')
+        return img_file
+    
+    img_adjusted = cv2.copyMakeBorder(
+        img,
+        top=ceil((y-img.shape[0])/2),
+        bottom=ceil((y-img.shape[0])/2),
+        left=ceil((x-img.shape[1])/2),
+        right=ceil((x-img.shape[1])/2),
+        borderType=cv2.BORDER_REPLICATE
+    )
+    adjusted_file = f'{img_file.rsplit(".", 1)[0]}_adjusted.png'
+    cv2.imwrite(filename=adjusted_file, img=img_adjusted)
+    return adjusted_file