Inconsistency with BGR packing

Reposting in plain text:

---------- Forwarded message ----------
From: Alexey Borzenkov <snaurygmail.com>
Date: Feb 3, 2007 2:08 PM
Subject: Inconsistency with BGR packing
To: image-sigpython.org


Hi everyone,

Yesterday I've tried using PIL to load and save .bmp files
that
contain alpha channel. Well, loading was easy to do without
even
modifying the library:

from PIL import BmpImagePlugin
BmpImagePlugin.BIT2MODE [32] = ("RGBA",
"BGRA")
BmpImagePlugin.SAVE["RGBA"] = ("BGRA",
32, 0)

However when I tried to save bitmap after loading it I
suddenly found
that packing into BGRA is not supported. I wonder if this
was decided
some time ago as "the right thing", or if this was
just accidentally
left out? (as it seems inconsistent to me that it can
unpack
BGRA/ABGR, but can't pack it back) Fix for this is pretty
trivial, but
as it contains tabulation characters in addition to seeing
it below
you can download it here:
http://snaury.googlepages.com/Imaging-1.1.6-df-bgr.patch


I hope here is the right place to submit a patch, as PIL
site told to
do so. And if what's done below is in any way wrong, I'd
like to hear
your reasons.

diff -druN Imaging-1.1.6-orig/libImaging/Pack.c
Imaging-1.1.6/libImaging/Pack.c
--- Imaging-1.1.6-orig/libImaging/Pack.c    Sun Dec  3
14:37:25 2006
+++ Imaging-1.1.6/libImaging/Pack.c    Sat Feb  3 09:56:20
2007
 -287,6
+287,34 
     }
 }

+void
+ImagingPackBGRA(UINT8* out, const UINT8* in, int pixels)
+{
+    int i;
+    /* BGRX, reversed bytes with right padding */
+    for (i = 0; i < pixels; i++) {
+    out[0] = in[B];
+    out[1] = in[G];
+    out[2] = in[R];
+    out[3] = in[A];
+    out += 4; in += 4;
+    }
+}
+
+void
+ImagingPackABGR(UINT8* out, const UINT8* in, int pixels)
+{
 +    int i;
+    /* XBGR, reversed bytes with left padding */
+    for (i = 0; i < pixels; i++) {
+    out[0] = in[A];
+    out[1] = in[B];
+    out[2] = in[G];
+    out[3] = in[R];
+    out += 4; in += 4;
+    }
+}
+
 static void
 packRGBL(UINT8* out, const UINT8* in, int pixels)
 {
 -460,6
+488,9 
     {"RGBA",    "RGBA",        32,   
copy4},
     {"RGBA",    "RGBA;L",    32,   
packRGBXL},
     {"RGBA",    "RGB",        24,   
ImagingPackRGB},
+    {"RGBA",    "BGR",        24,   
ImagingPackBGR},
+    {"RGBA",    "BGRA",        32,   
ImagingPackBGRA},
+    {"RGBA",    "ABGR",        32,   
ImagingPackABGR},
     {"RGBA",       "R",            8,  
   band0},
     {"RGBA",       "G",            8,  
   band1},
     {"RGBA",       "B",            8,  
   band2},
 -469,6
+500,9 
     {"RGBX",    "RGBX",        32,   
copy4},
     {"RGBX",    "RGBX;L",    32,   
packRGBXL},
     {"RGBX",    "RGB",        32,   
ImagingPackRGB},
+    {"RGBX",    "BGR",        32,   
ImagingPackBGR},
+    {"RGBX",    "BGRX",        32,   
ImagingPackBGRX},
+    {"RGBX",    "XBGR",        32,   
ImagingPackXBGR},
     {"RGBX",       "R",            8,  
   band0},
     {"RGBX",       "G",            8,  
   band1},
     {"RGBX",       "B",            8,  
   band2},
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