From e36774617c6e6cac2540678b28858f9ed6783e1d Mon Sep 17 00:00:00 2001
From: Andrew Murray <radarhere@users.noreply.github.com>
Date: Fri, 25 Feb 2022 23:58:13 +1100
Subject: [PATCH] Added BLP1 saving

---
 Tests/test_file_blp.py               | 20 +++++++++++---------
 docs/handbook/image-file-formats.rst | 21 ++++++++++++++-------
 src/PIL/BlpImagePlugin.py            | 13 +++++++++----
 3 files changed, 34 insertions(+), 20 deletions(-)

diff --git a/Tests/test_file_blp.py b/Tests/test_file_blp.py
index 86f208729f7..c1fae44ca35 100644
--- a/Tests/test_file_blp.py
+++ b/Tests/test_file_blp.py
@@ -31,19 +31,21 @@ def test_load_blp2_dxt1a():
 
 
 def test_save(tmp_path):
-    im = hopper("P")
     f = str(tmp_path / "temp.blp")
-    im.save(f)
 
-    with Image.open(f) as reloaded:
-        assert_image_equal(im.convert("RGB"), reloaded)
-
-    with Image.open("Tests/images/transparent.png") as im:
-        f = str(tmp_path / "temp.blp")
-        im.convert("P").save(f)
+    for version in ("BLP1", "BLP2"):
+        im = hopper("P")
+        im.save(f, blp_version=version)
 
         with Image.open(f) as reloaded:
-            assert_image_similar(im, reloaded, 8)
+            assert_image_equal(im.convert("RGB"), reloaded)
+
+        with Image.open("Tests/images/transparent.png") as im:
+            f = str(tmp_path / "temp.blp")
+            im.convert("P").save(f, blp_version=version)
+
+            with Image.open(f) as reloaded:
+                assert_image_similar(im, reloaded, 8)
 
     im = hopper()
     with pytest.raises(ValueError):
diff --git a/docs/handbook/image-file-formats.rst b/docs/handbook/image-file-formats.rst
index d1a5ba33982..17808dbc463 100644
--- a/docs/handbook/image-file-formats.rst
+++ b/docs/handbook/image-file-formats.rst
@@ -26,6 +26,20 @@ Fully supported formats
 
 .. contents::
 
+BLP
+^^^
+
+BLP is the Blizzard Mipmap Format, a texture format used in World of
+Warcraft. Pillow supports reading ``JPEG`` Compressed or raw ``BLP1``
+images, and all types of ``BLP2`` images.
+
+Pillow supports writing BLP images. The :py:meth:`~PIL.Image.Image.save` method
+can take the following keyword arguments:
+
+**blp_version**
+    If present and set to "BLP1", images will be saved as BLP1. Otherwise, images
+    will be saved as BLP2.
+
 BMP
 ^^^
 
@@ -1042,13 +1056,6 @@ Pillow reads and writes X bitmap files (mode ``1``).
 Read-only formats
 -----------------
 
-BLP
-^^^
-
-BLP is the Blizzard Mipmap Format, a texture format used in World of
-Warcraft. Pillow supports reading ``JPEG`` Compressed or raw ``BLP1``
-images, and all types of ``BLP2`` images.
-
 CUR
 ^^^
 
diff --git a/src/PIL/BlpImagePlugin.py b/src/PIL/BlpImagePlugin.py
index ffd0412e91c..779fddea860 100644
--- a/src/PIL/BlpImagePlugin.py
+++ b/src/PIL/BlpImagePlugin.py
@@ -439,7 +439,7 @@ def _load(self):
         self.set_as_raw(bytes(data))
 
 
-class BLP2Encoder(ImageFile.PyEncoder):
+class BLPEncoder(ImageFile.PyEncoder):
     _pushes_fd = True
 
     def _write_palette(self):
@@ -472,15 +472,20 @@ def _save(im, fp, filename, save_all=False):
     if im.mode != "P":
         raise ValueError("Unsupported BLP image mode")
 
-    fp.write(b"BLP2")
+    magic = b"BLP1" if im.encoderinfo.get("blp_version") == "BLP1" else b"BLP2"
+    fp.write(magic)
+
     fp.write(struct.pack("<i", 1))  # Uncompressed or DirectX compression
     fp.write(struct.pack("<b", Encoding.UNCOMPRESSED))
     fp.write(struct.pack("<b", 1 if im.palette.mode == "RGBA" else 0))
     fp.write(struct.pack("<b", 0))  # alpha encoding
     fp.write(struct.pack("<b", 0))  # mips
     fp.write(struct.pack("<II", *im.size))
+    if magic == b"BLP1":
+        fp.write(struct.pack("<i", 5))
+        fp.write(struct.pack("<i", 0))
 
-    ImageFile._save(im, fp, [("BLP2", (0, 0) + im.size, 0, im.mode)])
+    ImageFile._save(im, fp, [("BLP", (0, 0) + im.size, 0, im.mode)])
 
 
 Image.register_open(BlpImageFile.format, BlpImageFile, _accept)
@@ -489,4 +494,4 @@ def _save(im, fp, filename, save_all=False):
 Image.register_decoder("BLP2", BLP2Decoder)
 
 Image.register_save(BlpImageFile.format, _save)
-Image.register_encoder("BLP2", BLP2Encoder)
+Image.register_encoder("BLP", BLPEncoder)