From 4b7b07de701d210dbc65d7814eb2eda440b9dfe4 Mon Sep 17 00:00:00 2001
From: Andrew Murray <radarhere@users.noreply.github.com>
Date: Wed, 22 Dec 2021 10:32:53 +1100
Subject: [PATCH] Fixed JPEG2000 I;16 images on big endian

---
 Tests/test_file_jpeg2k.py     |  3 ---
 src/libImaging/Jpeg2KDecode.c |  6 ++++--
 src/libImaging/Jpeg2KEncode.c | 19 ++++++++++---------
 3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/Tests/test_file_jpeg2k.py b/Tests/test_file_jpeg2k.py
index 2ef262e3e..ca410162a 100644
--- a/Tests/test_file_jpeg2k.py
+++ b/Tests/test_file_jpeg2k.py
@@ -10,7 +10,6 @@ from .helper import (
     assert_image_equal,
     assert_image_similar,
     assert_image_similar_tofile,
-    is_big_endian,
     skip_unless_feature,
 )
 
@@ -234,13 +233,11 @@ def test_16bit_monochrome_has_correct_mode():
         assert jp2.mode == "I;16"
 
 
-@pytest.mark.xfail(is_big_endian(), reason="Fails on big-endian")
 def test_16bit_monochrome_jp2_like_tiff():
     with Image.open("Tests/images/16bit.cropped.tif") as tiff_16bit:
         assert_image_similar_tofile(tiff_16bit, "Tests/images/16bit.cropped.jp2", 1e-3)
 
 
-@pytest.mark.xfail(is_big_endian(), reason="Fails on big-endian")
 def test_16bit_monochrome_j2k_like_tiff():
     with Image.open("Tests/images/16bit.cropped.tif") as tiff_16bit:
         assert_image_similar_tofile(tiff_16bit, "Tests/images/16bit.cropped.j2k", 1e-3)
diff --git a/src/libImaging/Jpeg2KDecode.c b/src/libImaging/Jpeg2KDecode.c
index 601bd4b62..8f27d87d8 100644
--- a/src/libImaging/Jpeg2KDecode.c
+++ b/src/libImaging/Jpeg2KDecode.c
@@ -180,9 +180,11 @@ j2ku_gray_i(
         case 2:
             for (y = 0; y < h; ++y) {
                 const UINT16 *data = (const UINT16 *)&tiledata[2 * y * w];
-                UINT16 *row = (UINT16 *)im->image[y0 + y] + x0;
+                UINT8 *row = (UINT8 *)im->image[y0 + y] + x0;
                 for (x = 0; x < w; ++x) {
-                    *row++ = j2ku_shift(offset + *data++, shift);
+                    UINT16 pixel = j2ku_shift(offset + *data++, shift);
+                    *row++ = pixel;
+                    *row++ = pixel >> 8;
                 }
             }
             break;
diff --git a/src/libImaging/Jpeg2KEncode.c b/src/libImaging/Jpeg2KEncode.c
index 701853159..86cd7d5af 100644
--- a/src/libImaging/Jpeg2KEncode.c
+++ b/src/libImaging/Jpeg2KEncode.c
@@ -110,8 +110,15 @@ j2k_pack_i16(Imaging im, UINT8 *buf, unsigned x0, unsigned y0, unsigned w, unsig
     for (y = 0; y < h; ++y) {
         UINT8 *data = (UINT8 *)(im->image[y + y0] + x0);
         for (x = 0; x < w; ++x) {
-            *ptr++ = *data++;
-            *ptr++ = *data++;
+#ifdef WORDS_BIGENDIAN
+            ptr[0] = data[1];
+            ptr[1] = data[0];
+#else
+            ptr[0] = data[0];
+            ptr[1] = data[1];
+#endif
+            ptr += 2;
+            data += 2;
         }
     }
 }
@@ -301,13 +308,7 @@ j2k_encode_entry(Imaging im, ImagingCodecState state) {
         components = 1;
         color_space = OPJ_CLRSPC_GRAY;
         pack = j2k_pack_l;
-    } else if (strcmp(im->mode, "I;16") == 0) {
-        components = 1;
-        color_space = OPJ_CLRSPC_GRAY;
-        pack = j2k_pack_i16;
-        prec = 16;
-        bpp = 12;
-    } else if (strcmp(im->mode, "I;16B") == 0) {
+    } else if (strcmp(im->mode, "I;16") == 0 || strcmp(im->mode, "I;16B") == 0) {
         components = 1;
         color_space = OPJ_CLRSPC_GRAY;
         pack = j2k_pack_i16;