Remove unnecessary alpha channels for loaded DDS files (#2293)

backend/src/packages/chaiNNer_standard/image/io/load_image.py

@@ -35,6 +35,25 @@ def get_ext(path: str) -> str:
     return split_file_path(path)[2].lower()
 
 
+def remove_unnecessary_alpha(img: np.ndarray) -> np.ndarray:
+    """
+    Removes the alpha channel from an image if it is not used.
+    """
+    if get_h_w_c(img)[2] != 4:
+        return img
+
+    unnecessary = (
+        (img.dtype == np.uint8 and np.all(img[:, :, 3] == 255))
+        or (img.dtype == np.uint16 and np.all(img[:, :, 3] == 65536))
+        or (img.dtype == np.float32 and np.all(img[:, :, 3] == 1.0))
+        or (img.dtype == np.float64 and np.all(img[:, :, 3] == 1.0))
+    )
+
+    if unnecessary:
+        return img[:, :, :3]
+    return img
+
+
 def _read_cv(path: str) -> np.ndarray | None:
     if get_ext(path) not in get_opencv_formats():
         # not supported
@@ -88,7 +107,10 @@ def _read_dds(path: str) -> np.ndarray | None:
 
     png = dds_to_png_texconv(path)
     try:
-        return _read_cv(png)
+        img = _read_cv(png)
+        if img is not None:
+            img = remove_unnecessary_alpha(img)
+        return img
     finally:
         os.remove(png)