Fix alpha premultiplication being used when generating mipmaps

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 All notable changes to this project will be documented in this file
 
+## Unreleased
+
+### Fixed
+
+- Fixed alpha premultiplication when generating mipmaps
+
+
 ## 0.1.0 - 2021-05-10
 
 ### Added

quicktex/dds.py

@@ -256,7 +256,7 @@ def encode(image: Image.Image, encoder, four_cc: str, mip_count: typing.Optional
         image = image.convert(mode)
 
     sizes = quicktex.image_utils.mip_sizes(image.size, mip_count)
-    images = [image] + [image.resize(size, Image.BILINEAR) for size in sizes[1:]]
+    images = [image] + [quicktex.image_utils.resize_no_premultiply(image, size) for size in sizes[1:]]
     dds = DDSFile()
 
     for i in images:

quicktex/image_utils.py

@@ -32,3 +32,20 @@ def mip_sizes(dimensions: Tuple[int, int], mip_count: Optional[int] = None) -> L
         dimensions = tuple([max(dim // 2, 1) for dim in dimensions])
 
     return chain
+
+
+def resize_no_premultiply(image: Image.Image, size: Tuple[int, int]) -> Image.Image:
+    """
+    Resize an image without premulitplying the alpha. Required due to a quick in Pillow
+
+    :param image: Image to resize
+    :param size: Size to resize to
+    :return: The resized image
+    """
+    if image.mode == 'RGBA':
+        rgb = image.convert('RGB').resize(size, Image.BILINEAR)
+        a = image.getchannel('A').resize(size, Image.BILINEAR)
+        rgb.putalpha(a)
+        return rgb
+    else:
+        return image.resize(size, Image.BILINEAR)