custom grayscale is now mostly working

.vscode/settings.json

@@ -1,5 +1,5 @@
 {
-    "python.pythonPath": "/home/evyhaan/.local/share/virtualenvs/bitmap-cli-transformer-T-wSHdGM/bin/python",
+    "python.pythonPath": "/home/milo/.local/share/virtualenvs/bitmap-cli-transformer-g2MSi3y4/bin/python",
     "python.linting.pylintEnabled": false,
     "python.linting.pep8Enabled": false,
     "python.linting.enabled": true

cli.py

@@ -25,4 +25,7 @@
 bitmap.make_grayscale()
 for transform in transforms:
     method = getattr(bitmap, transform)
-    bitmap.save_new(method())
+    if transform == 'custom_grayscale':
+        bitmap.save_custom(method())
+    else:
+        bitmap.save_new(method())

modify.py

@@ -9,6 +9,8 @@ def __init__(self, file_path):
         """
         self.file_path = file_path
         self.img = Image.open(self.file_path)
+        with open(file_path, 'rb') as file:
+            self.bin_img = bytearray(file.read())
 
     def new_file_path(self, mod_type):
         """
@@ -26,6 +28,42 @@ def make_grayscale(self, img='self.img'):
         img = self.img.convert('L')
         return [new_path, img]
 
+    def _make_bi_int(self, byts):
+        return int.from_bytes(byts, byteorder='little')
+
+    def custom_grayscale(self, img='self.img'):
+        new_path = self.new_file_path('_grayscale')
+
+        file_header = self.bin_img[:14]
+        img_header_size = self._make_bi_int(self.bin_img[14:18])
+        img_header = self.bin_img[14:14 + img_header_size]
+        img_pix_location = self._make_bi_int(file_header[10:])
+        img_pix = self.bin_img[img_pix_location:]
+        img_width = self._make_bi_int(img_header[4:6])
+        img_height = self._make_bi_int(img_header[8:10])
+        img_bpp = self._make_bi_int(img_header[14:16])
+        img_cols = img_width * 3
+        img_cols_pad = ((img_cols + 3) & ~0x03) - img_cols
+
+        counter = 0
+        for i in range(0, len(img_pix) - 1):
+            if counter < img_cols and counter % 3 == 0:
+                b = img_pix[i]
+                g = img_pix[i + 1]
+                r = img_pix[i + 2]
+                avg = int(round((r + g + b) / 3))
+                img_pix[i] = avg
+                img_pix[i + 1] = avg
+                img_pix[i + 2] = avg
+            if counter == img_cols + img_cols_pad:
+                counter = 0
+            else:
+                counter += 1
+
+        new_bitmap = file_header + img_header + img_pix
+        return [new_bitmap, new_path]
+
+
     def flip_horizontal(self, img='self.img'):
         """
         Modify the input image with flip horizontal  and returns the new path with the new image
@@ -66,12 +104,11 @@ def save_new(self, lst):
         """
         lst[1].save(lst[0], 'bmp')
 
-if __name__ == "__main__":
+    def save_custom(self, img_path):
+        with open(img_path[1], 'wb') as file:
+            file.write(img_path[0])
 
-    tiger = Bitmap('./assets/tiger.bmp')
+if __name__ == "__main__":
 
-    tiger.save_new(tiger.make_grayscale())
-    tiger.save_new(tiger.flip_horizontal())
-    tiger.save_new(tiger.flip_vertical())
-    tiger.save_new(tiger.make_thumbnail())
-    tiger.save_new(tiger.invert_colors())
+    test = Bitmap('./assets/spock.bmp')
+    test.custom_grayscale()