[gdk-pixbuf] bmp: Add support for BMP headers with bitmask

[Bastien Nocera <hadess src gnome org>]

commit cd302dd3005733e235292711a6e5763711cf5895
Author: Gokul Krishnan <gk7huki gmail com>
Date:   Wed May 25 22:24:00 2016 +0000

    bmp: Add support for BMP headers with bitmask
    
    Header size 52 and 56 failed to load before this patch.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=766890

 gdk-pixbuf/io-bmp.c |   21 +++++++++++++++++----
 1 files changed, 17 insertions(+), 4 deletions(-)
---
diff --git a/gdk-pixbuf/io-bmp.c b/gdk-pixbuf/io-bmp.c
index b896a03..f78c092 100644
--- a/gdk-pixbuf/io-bmp.c
+++ b/gdk-pixbuf/io-bmp.c
@@ -298,6 +298,18 @@ static gboolean DecodeHeader(unsigned char *BFH, unsigned char *BIH,
                State->Header.height = lsb_32 (&BIH[8]);
                State->Header.depth = lsb_16 (&BIH[14]);
                State->Compressed = lsb_32 (&BIH[16]);
+       } else if (State->Header.size == 56) {
+                /* BMP v3 with RGBA bitmasks */
+               State->Header.width = lsb_32 (&BIH[4]);
+               State->Header.height = lsb_32 (&BIH[8]);
+               State->Header.depth = lsb_16 (&BIH[14]);
+               State->Compressed = lsb_32 (&BIH[16]);
+       } else if (State->Header.size == 52) {
+                /* BMP v3 with RGB bitmasks */
+               State->Header.width = lsb_32 (&BIH[4]);
+               State->Header.height = lsb_32 (&BIH[8]);
+               State->Header.depth = lsb_16 (&BIH[14]);
+               State->Compressed = lsb_32 (&BIH[16]);
        } else if (State->Header.size == 40) {
                 /* BMP v3 */ 
                State->Header.width = lsb_32 (&BIH[4]);
@@ -495,9 +507,10 @@ static gboolean DecodeHeader(unsigned char *BFH, unsigned char *BIH,
                        State->BufferSize = State->LineWidth;
                }
        } else if (State->Compressed == BI_BITFIELDS) {
-               if (State->Header.size == 108 || State->Header.size == 124) 
+               if (State->Header.size == 52  || State->Header.size == 56 ||
+                   State->Header.size == 108 || State->Header.size == 124)
                {
-                       /* v4 and v5 have the bitmasks in the header */
+                       /* extended v3, v4 and v5 have the bitmasks in the header */
                        if (!decode_bitmasks (&BIH[40], State, error)) {
                               State->read_state = READ_STATE_ERROR;
                               return FALSE;
@@ -607,8 +620,8 @@ decode_bitmasks (guchar *buf,
        find_bits (State->g_mask, &State->g_shift, &State->g_bits);
        find_bits (State->b_mask, &State->b_shift, &State->b_bits);
 
-        /* v4 and v5 have an alpha mask */
-        if (State->Header.size == 108 || State->Header.size == 124) {
+        /* extended v3, v4 and v5 have an alpha mask */
+        if (State->Header.size == 56 || State->Header.size == 108 || State->Header.size == 124) {
              buf += 4;
              State->a_mask = buf[0] | (buf[1] << 8) | (buf[2] << 16) | (buf[3] << 24);
              find_bits (State->a_mask, &State->a_shift, &State->a_bits);