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fix ASCII exif tag write

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sigh libexif has three different types of string write
This commit is contained in:
John Cupitt 2018-07-04 08:50:14 +01:00
parent 3a9adbcea9
commit 63bb380569
1 changed files with 55 additions and 14 deletions
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69
libvips/foreign/exif.c
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@ -709,13 +709,26 @@ typedef void (*write_fn)( ExifData *ed,
ExifEntry *entry, unsigned long component, void *data ); ExifEntry *entry, unsigned long component, void *data );
/* String-valued tags need special treatment, sadly. /* String-valued tags need special treatment, sadly.
*
* Strings are written in three ways:
*
* 1. As ASCII, but with an 8-byte preamble giving the encoding (it's always
* ASCII though) and the format undefined.
* 2. As plain ASCII, with the format giving the encoding.
* 3. As UTF16 in the MS tags.
*/ */
static gboolean
tag_is_encoding( ExifTag tag )
{
return( tag == EXIF_TAG_USER_COMMENT );
}
static gboolean static gboolean
tag_is_ascii( ExifTag tag ) tag_is_ascii( ExifTag tag )
{ {
return( tag == EXIF_TAG_MAKE || return( tag == EXIF_TAG_MAKE ||
tag == EXIF_TAG_MODEL || tag == EXIF_TAG_MODEL ||
tag == EXIF_TAG_USER_COMMENT ||
tag == EXIF_TAG_IMAGE_DESCRIPTION || tag == EXIF_TAG_IMAGE_DESCRIPTION ||
tag == EXIF_TAG_ARTIST ); tag == EXIF_TAG_ARTIST );
} }
@ -730,10 +743,6 @@ tag_is_utf16( ExifTag tag )
tag == EXIF_TAG_XP_SUBJECT ); tag == EXIF_TAG_XP_SUBJECT );
} }
/* special header required for EXIF_TAG_USER_COMMENT.
*/
#define ASCII_COMMENT "ASCII\0\0\0"
/* Set a libexif-formatted string entry. /* Set a libexif-formatted string entry.
*/ */
static void static void
@ -786,11 +795,15 @@ drop_tail( const char *data )
return( str ); return( str );
} }
/* Write a libvips NULL-terminated utf-8 string into an ASCII entry. Tags like /* special header required for EXIF_TAG_USER_COMMENT.
* UserComment are really ASCII-only. */
#define ASCII_COMMENT "ASCII\0\0\0"
/* Write a libvips NULL-terminated utf-8 string into a entry tagged with a
* encoding. UserComment is like this, for example.
*/ */
static void static void
vips_exif_set_string_ascii( ExifData *ed, vips_exif_set_string_encoding( ExifData *ed,
ExifEntry *entry, unsigned long component, const char *data ) ExifEntry *entry, unsigned long component, const char *data )
{ {
char *str; char *str;
@ -815,7 +828,32 @@ vips_exif_set_string_ascii( ExifData *ed,
g_free( str ); g_free( str );
} }
/* Write a libvips NULL-terminated utf-8 string into an entry. /* Write a libvips NULL-terminated utf-8 string into an ASCII entry. Tags like
* ImageDescription work like this.
*/
static void
vips_exif_set_string_ascii( ExifData *ed,
ExifEntry *entry, unsigned long component, const char *data )
{
char *str;
char *ascii;
int len;
str = drop_tail( data );
ascii = g_str_to_ascii( str, NULL );
/* ASCII strings are NULL-terminated.
*/
len = strlen( ascii );
vips_exif_alloc_string( entry, len + 1 );
memcpy( entry->data, ascii, len + 1 );
entry->format = EXIF_FORMAT_ASCII;
g_free( ascii );
g_free( str );
}
/* Write a libvips NULL-terminated utf-8 string into a utf16 entry.
*/ */
static void static void
vips_exif_set_string_utf16( ExifData *ed, vips_exif_set_string_utf16( ExifData *ed,
@ -829,10 +867,10 @@ vips_exif_set_string_utf16( ExifData *ed,
utf16 = g_utf8_to_utf16( str, -1, NULL, &len, NULL ); utf16 = g_utf8_to_utf16( str, -1, NULL, &len, NULL );
/* libexif utf16 strings are not NULL-terminated. /* libexif utf16 strings are NULL-terminated.
*/ */
vips_exif_alloc_string( entry, len * 2 ); vips_exif_alloc_string( entry, (len + 1) * 2 );
memcpy( entry->data, utf16, len * 2 ); memcpy( entry->data, utf16, (len + 1) * 2 );
entry->format = EXIF_FORMAT_BYTE; entry->format = EXIF_FORMAT_BYTE;
g_free( utf16 ); g_free( utf16 );
@ -861,7 +899,9 @@ vips_exif_set_tag( ExifData *ed, int ifd, ExifTag tag, write_fn fn, void *data )
/* libexif makes us have a special path for string-valued /* libexif makes us have a special path for string-valued
* fields :( * fields :(
*/ */
if( tag_is_ascii( tag ) ) if( tag_is_encoding( tag ) )
vips_exif_set_string_encoding( ed, entry, 0, data );
else if( tag_is_ascii( tag ) )
vips_exif_set_string_ascii( ed, entry, 0, data ); vips_exif_set_string_ascii( ed, entry, 0, data );
else if( tag_is_utf16( tag ) ) else if( tag_is_utf16( tag ) )
vips_exif_set_string_utf16( ed, entry, 0, data ); vips_exif_set_string_utf16( ed, entry, 0, data );
@ -1166,7 +1206,8 @@ vips_exif_exif_entry( ExifEntry *entry, VipsExifRemove *ve )
/* If this is a string tag, we must also remove it ready for /* If this is a string tag, we must also remove it ready for
* recreation, see the comment below. * recreation, see the comment below.
*/ */
if( tag_is_ascii( entry->tag ) || if( tag_is_encoding( entry->tag ) ||
tag_is_ascii( entry->tag ) ||
tag_is_utf16( entry->tag ) ) tag_is_utf16( entry->tag ) )
ve->to_remove = g_slist_prepend( ve->to_remove, entry ); ve->to_remove = g_slist_prepend( ve->to_remove, entry );
} }