Support arbitrary gamma correction of input image

convert.py

@@ -65,6 +65,10 @@ def main():
     parser.add_argument(
         '--verbose', action=argparse.BooleanOptionalAction,
         default=False, help="Show progress during conversion")
+    parser.add_argument(
+        '--gamma_correct', type=float, default=2.4,
+        help='Gamma-correct image by this value (default: 2.4)'
+    )
     args = parser.parse_args()
 
     palette = palette_py.PALETTES[args.palette]()
@@ -88,7 +92,9 @@ def main():
         image_py.resize(image, screen.NATIVE_X_RES, screen.NATIVE_Y_RES * 2,
                         srgb_output=True).show()
     resized = np.array(image_py.resize(image, screen.X_RES,
-                                       screen.Y_RES)).astype(np.float32)
+                                       screen.Y_RES,
+                                       gamma=args.gamma_correct)).astype(
+        np.float32)
 
     # convert from sRGB1-linear to CAM02UCS perceptually uniform colour space
     cam16ucs = colour.convert(

image.py

@@ -13,8 +13,8 @@ def linear_to_srgb_array(a: np.ndarray, gamma=2.4) -> np.ndarray:
                     0.055)
 
 
-def srgb_to_linear(im: np.ndarray) -> np.ndarray:
-    rgb_linear = srgb_to_linear_array(im / 255.0, gamma=2.4)
+def srgb_to_linear(im: np.ndarray, gamma=2.4) -> np.ndarray:
+    rgb_linear = srgb_to_linear_array(im / 255.0, gamma=gamma)
     return (np.clip(rgb_linear, 0.0, 1.0) * 255).astype(np.float32)
 
 
@@ -32,13 +32,16 @@ def open(filename: str) -> np.ndarray:
     return im
 
 
-def resize(image: Image, x_res, y_res, srgb_output: bool = False) -> Image:
+def resize(
+        image: Image, x_res, y_res, gamma: float = 2.4,
+        srgb_output: bool = False) -> Image:
     # Convert to linear RGB before rescaling so that colour interpolation is
     # in linear space
-    linear = srgb_to_linear(np.asarray(image)).astype(np.uint8)
+    linear = srgb_to_linear(np.asarray(image), gamma=gamma).astype(np.uint8)
     res = Image.fromarray(linear).resize((x_res, y_res), Image.LANCZOS)
     if srgb_output:
         return Image.fromarray(
-            linear_to_srgb(np.array(res, dtype=np.float32)).astype(np.uint8))
+            linear_to_srgb(np.array(res, dtype=np.float32), gamma=gamma).astype(
+                np.uint8))
     else:
         return res