[vlc-commits] Automatically orient JPEG image based on orientation flag, if present
Wayne McDougall
git at videolan.org
Wed Apr 20 13:21:28 CEST 2016
vlc | branch: master | Wayne McDougall <waynemcdougall at gmail.com> | Wed Apr 20 22:39:11 2016 +1200| [16b5785805eba9e778ede9deda08d76635b9e710] | committer: Jean-Baptiste Kempf
Automatically orient JPEG image based on orientation flag, if present
Signed-off-by: Jean-Baptiste Kempf <jb at videolan.org>
> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=16b5785805eba9e778ede9deda08d76635b9e710
---
NEWS | 1 +
modules/codec/jpeg.c | 225 +++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 225 insertions(+), 1 deletion(-)
diff --git a/NEWS b/NEWS
index 5233b81..dd37984 100644
--- a/NEWS
+++ b/NEWS
@@ -67,6 +67,7 @@ Decoder:
supporting H.263, H.264/MPEG-4 AVC, MPEG-4 Part 2, and DV depending on device
and OS version
* Support for the OggSpots video codec
+ * JPEG images correctly oriented using embedded orientation tag, if present
Demuxers:
* Support HD-DVD .evo (H.264, VC-1, MPEG-2, PCM, AC-3, E-AC3, MLP, DTS)
diff --git a/modules/codec/jpeg.c b/modules/codec/jpeg.c
index fdb91c7..981d077 100644
--- a/modules/codec/jpeg.c
+++ b/modules/codec/jpeg.c
@@ -1,7 +1,7 @@
/*****************************************************************************
* jpeg.c: jpeg decoder module making use of libjpeg.
*****************************************************************************
- * Copyright (C) 2013-2014 VLC authors and VideoLAN
+ * Copyright (C) 2013-2014,2016 VLC authors and VideoLAN
*
* Authors: Maxim Bublis <b at codemonkey.ru>
*
@@ -182,6 +182,220 @@ static int OpenDecoder(vlc_object_t *p_this)
}
/*
+ * The following two functions are used to return 16 and 32 bit values from
+ * the EXIF tag structure. That structure is borrowed from TIFF files and may be
+ * in big endian or little endian format. The endian parameter tells us which.
+ * Case Little Endian EXIF tag / Little Endian machine
+ * - just memcpy the tag structure into the value to return
+ * Case Little Endian EXIF tag / Big Endian machine
+ * - memcpy the tag structure into value, and bswap it
+ * Case Little Endian EXIF tag / Big Endian machine
+ * - memcpy the tag structure into value, and bswap it
+ * Case Big Endian EXIF tag / Big Endian machine
+ * - just memcpy the tag structure into the value to return
+ *
+ * While there are byte manipulation functions in vlc_common.h, none of them
+ * address that format of the data supplied may be either big or little endian.
+ *
+ * The claim is made that this is the best way to do it. Can you do better?
+*/
+
+#define G_LITTLE_ENDIAN 1234
+#define G_BIG_ENDIAN 4321
+
+LOCAL( unsigned short )
+de_get16( void * ptr, uint endian ) {
+ unsigned short val;
+
+ memcpy( &val, ptr, sizeof( val ) );
+ if ( endian == G_BIG_ENDIAN )
+ {
+ #ifndef WORDS_BIGENDIAN
+ val = bswap16( val );
+ #endif
+ }
+ else
+ {
+ #ifdef WORDS_BIGENDIAN
+ val = bswap16( val );
+ #endif
+ }
+ return val;
+}
+
+LOCAL( unsigned int )
+de_get32( void * ptr, uint endian ) {
+ unsigned int val;
+
+ memcpy( &val, ptr, sizeof( val ) );
+ if ( endian == G_BIG_ENDIAN )
+ {
+ #ifndef WORDS_BIGENDIAN
+ val = bswap32( val );
+ #endif
+ }
+ else
+ {
+ #ifdef WORDS_BIGENDIAN
+ val = bswap32( val );
+ #endif
+ }
+ return val;
+}
+
+/*
+ * Look through the meta data in the libjpeg decompress structure to determine
+ * if an EXIF Orientation tag is present. If so return its value (1-8),
+ * otherwise return 0
+ *
+ * This function is based on the function get_orientation in io-jpeg.c, part of
+ * the GdkPixbuf library, licensed under LGPLv2+.
+ * Copyright (C) 1999 Michael Zucchi, The Free Software Foundation
+*/
+LOCAL( int )
+jpeg_GetOrientation( j_decompress_ptr cinfo )
+{
+
+ uint i; /* index into working buffer */
+ ushort tag_type; /* endianed tag type extracted from tiff header */
+ uint ret; /* Return value */
+ uint offset; /* de-endianed offset in various situations */
+ uint tags; /* number of tags in current ifd */
+ uint type; /* de-endianed type of tag */
+ uint count; /* de-endianed count of elements in a tag */
+ uint tiff = 0; /* offset to active tiff header */
+ uint endian = 0; /* detected endian of data */
+
+ jpeg_saved_marker_ptr exif_marker; /* Location of the Exif APP1 marker */
+ jpeg_saved_marker_ptr cmarker; /* Location to check for Exif APP1 marker */
+
+ const char leth[] = { 0x49, 0x49, 0x2a, 0x00 }; /* Little endian TIFF header */
+ const char beth[] = { 0x4d, 0x4d, 0x00, 0x2a }; /* Big endian TIFF header */
+
+ #define EXIF_JPEG_MARKER 0xE1
+ #define EXIF_IDENT_STRING "Exif\000\000"
+ #define EXIF_ORIENT_TAGID 0x112
+
+ /* check for Exif marker (also called the APP1 marker) */
+ exif_marker = NULL;
+ cmarker = cinfo->marker_list;
+
+ while ( cmarker )
+ {
+ if ( cmarker->marker == EXIF_JPEG_MARKER )
+ {
+ /* The Exif APP1 marker should contain a unique
+ identification string ("Exif\0\0"). Check for it. */
+ if ( !memcmp( cmarker->data, EXIF_IDENT_STRING, 6 ) )
+ {
+ exif_marker = cmarker;
+ }
+ }
+ cmarker = cmarker->next;
+ }
+
+ /* Did we find the Exif APP1 marker? */
+ if ( exif_marker == NULL )
+ return 0;
+
+ /* Do we have enough data? */
+ if ( exif_marker->data_length < 32 )
+ return 0;
+
+ /* Check for TIFF header and catch endianess */
+ i = 0;
+
+ /* Just skip data until TIFF header - it should be within 16 bytes from marker start.
+ Normal structure relative to APP1 marker -
+ 0x0000: APP1 marker entry = 2 bytes
+ 0x0002: APP1 length entry = 2 bytes
+ 0x0004: Exif Identifier entry = 6 bytes
+ 0x000A: Start of TIFF header (Byte order entry) - 4 bytes
+ - This is what we look for, to determine endianess.
+ 0x000E: 0th IFD offset pointer - 4 bytes
+
+ exif_marker->data points to the first data after the APP1 marker
+ and length entries, which is the exif identification string.
+ The TIFF header should thus normally be found at i=6, below,
+ and the pointer to IFD0 will be at 6+4 = 10.
+ */
+
+ while ( i < 16 )
+ {
+ /* Little endian TIFF header */
+ if ( memcmp( &exif_marker->data[i], leth, 4 ) == 0 )
+ {
+ endian = G_LITTLE_ENDIAN;
+ }
+ /* Big endian TIFF header */
+ else
+ if ( memcmp( &exif_marker->data[i], beth, 4 ) == 0 )
+ {
+ endian = G_BIG_ENDIAN;
+ }
+ /* Keep looking through buffer */
+ else
+ {
+ i++;
+ continue;
+ }
+ /* We have found either big or little endian TIFF header */
+ tiff = i;
+ break;
+ }
+
+ /* So did we find a TIFF header or did we just hit end of buffer? */
+ if ( tiff == 0 )
+ return 0;
+
+ /* Read out the offset pointer to IFD0 */
+ offset = de_get32( &exif_marker->data[i] + 4, endian );
+ i = i + offset;
+
+ /* Check that we still are within the buffer and can read the tag count */
+
+ if ( ( i + 2 ) > exif_marker->data_length )
+ return 0;
+
+ /* Find out how many tags we have in IFD0. As per the TIFF spec, the first
+ two bytes of the IFD contain a count of the number of tags. */
+ tags = de_get16( &exif_marker->data[i], endian );
+ i = i + 2;
+
+ /* Check that we still have enough data for all tags to check. The tags
+ are listed in consecutive 12-byte blocks. The tag ID, type, size, and
+ a pointer to the actual value, are packed into these 12 byte entries. */
+ if ( ( i + tags * 12 ) > exif_marker->data_length )
+ return 0;
+
+ /* Check through IFD0 for tags of interest */
+ while ( tags-- )
+ {
+ tag_type = de_get16( &exif_marker->data[i], endian );
+ /* Is this the orientation tag? */
+ if ( tag_type == EXIF_ORIENT_TAGID )
+ {
+ type = de_get16( &exif_marker->data[i + 2], endian );
+ count = de_get32( &exif_marker->data[i + 4], endian );
+
+ /* Check that type and count fields are OK. The orientation field
+ will consist of a single (count=1) 2-byte integer (type=3). */
+ if ( type != 3 || count != 1 )
+ return 0;
+
+ /* Return the orientation value. Within the 12-byte block, the
+ pointer to the actual data is at offset 8. */
+ ret = de_get16( &exif_marker->data[i + 8], endian );
+ return ( ret <= 8 ) ? ret : 0;
+ }
+ /* move the pointer to the next 12-byte tag field. */
+ i = i + 12;
+ }
+
+ return 0; /* No EXIF Orientation tag found */
+}
+
+/*
* This function must be fed with a complete compressed frame.
*/
static picture_t *DecodeBlock(decoder_t *p_dec, block_t **pp_block)
@@ -214,6 +428,7 @@ static picture_t *DecodeBlock(decoder_t *p_dec, block_t **pp_block)
jpeg_create_decompress(&p_sys->p_jpeg);
jpeg_mem_src(&p_sys->p_jpeg, p_block->p_buffer, p_block->i_buffer);
+ jpeg_save_markers( &p_sys->p_jpeg, EXIF_JPEG_MARKER, 0xffff );
jpeg_read_header(&p_sys->p_jpeg, TRUE);
p_sys->p_jpeg.out_color_space = JCS_RGB;
@@ -230,6 +445,14 @@ static picture_t *DecodeBlock(decoder_t *p_dec, block_t **pp_block)
p_dec->fmt_out.video.i_gmask = 0x0000ff00;
p_dec->fmt_out.video.i_bmask = 0x00ff0000;
+ int i_otag; /* Orientation tag has valid range of 1-8. 1 is normal orientation, 0 = unspecified = normal */
+ i_otag = jpeg_GetOrientation( &p_sys->p_jpeg );
+ if ( i_otag > 1 )
+ {
+ msg_Dbg( p_dec, "Jpeg orientation is %d", i_otag );
+ p_dec->fmt_out.video.orientation = ORIENT_FROM_EXIF( i_otag );
+ }
+
/* Get a new picture */
p_pic = decoder_NewPicture(p_dec);
if (!p_pic)
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