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seems to work 

could probably add some more fields
This commit is contained in:
John Cupitt 2018-07-03 16:36:39 +01:00
parent c12cd6d2cb
commit 3a9adbcea9
2 changed files with 123 additions and 50 deletions
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1
ChangeLog
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@ -31,6 +31,7 @@
- add Mitchell kernel
- pyramid builders have a choice of 2x2 shrinkers [harukizaemon]
- add `palette` option to pngsave [felixbuenemann]
- support writing string-valued fields via libexif
12/3/18 started 8.6.4
- better fitting of fonts with overhanging edges [Adrià]

172
libvips/foreign/exif.c
View File

@ -7,6 +7,8 @@
* - only read orientation from ifd0
* 1/2/18
* - remove exif thumbnail if "jpeg-thumbnail-data" has been removed
* 3/7/18
* - add support for writing string-valued fields
*/
/*
@ -706,69 +708,137 @@ vips_exif_set_double( ExifData *ed,
typedef void (*write_fn)( ExifData *ed,
ExifEntry *entry, unsigned long component, void *data );
/* String-valued tags need special treatment, sadly.
*/
static gboolean
tag_is_ascii( ExifTag tag )
{
return( tag == EXIF_TAG_MAKE ||
tag == EXIF_TAG_MODEL ||
tag == EXIF_TAG_USER_COMMENT ||
tag == EXIF_TAG_IMAGE_DESCRIPTION ||
tag == EXIF_TAG_ARTIST );
}
static gboolean
tag_is_utf16( ExifTag tag )
{
return( tag == EXIF_TAG_XP_TITLE ||
tag == EXIF_TAG_XP_COMMENT ||
tag == EXIF_TAG_XP_AUTHOR ||
tag == EXIF_TAG_XP_KEYWORDS ||
tag == EXIF_TAG_XP_SUBJECT );
}
/* special header required for EXIF_TAG_USER_COMMENT.
*/
#define ASCII_COMMENT "ASCII\0\0\0"
/* data is a null-terminated utf-8 string.
/* Set a libexif-formatted string entry.
*/
static void
vips_exif_set_string( ExifData *ed,
ExifEntry *entry, unsigned long component, const char *data )
vips_exif_alloc_string( ExifEntry *entry, unsigned long components )
{
ExifMem *mem = exif_mem_new_default();
ExifMem *mem;
void *buf;
int len;
const char *p;
char *q;
/* A copy of data which we may have to free.
*/
q = NULL;
/* The final " (xx, ASCII, yy, zz)" part of the string (if present) was
* added by us in _to_s(), we must remove it before setting the string
* back again.
*
* It may not be there if the user has changed the string.
*
* Leave p pointing to the trimmed string.
*/
len = strlen( data );
if( len > 0 &&
data[len - 1] == ')' &&
(p = strrchr( data, '(' )) &&
p - data > 0 &&
p[-1] == ' ' ) {
q = g_strdup( data );
q[p - data - 1] = '\0';
p = q;
}
else
p = data;
len = strlen( p );
g_assert( !entry->data );
/* The string in the entry must be allocated with the same allocator
* that was used to allocate the entry itself. We assume the entry was
* that was used to allocate the entry itself. We can't do this
* because the allocator is private :( so we must assume the entry was
* created with the default one.
*
* We have to write the ASCII charset tag and not write a
* null-terminator.
*/
buf = exif_mem_alloc( mem, len + sizeof( ASCII_COMMENT ) - 1 );
entry->data = buf;
entry->size = len;
entry->components = len;
entry->format = EXIF_FORMAT_ASCII;
mem = exif_mem_new_default();
memcpy( entry->data, ASCII_COMMENT, sizeof( ASCII_COMMENT ) - 1 );
memcpy( entry->data + sizeof(ASCII_COMMENT) - 1, p, len - 1 );
/* EXIF_FORMAT_UNDEFINED is correct for EXIF_TAG_USER_COMMENT, our
* caller should change this if it wishes.
*/
entry->data = exif_mem_alloc( mem, components );
entry->size = components;
entry->components = components;
entry->format = EXIF_FORMAT_UNDEFINED;
VIPS_FREEF( g_free, q );
VIPS_FREEF( exif_mem_unref, mem );
}
/* The final " (xx, yy, zz, kk)" part of the string (if present) was
* added by us in _to_s(), we must remove it before setting the string
* back again.
*
* It may not be there if the user has changed the string.
*/
static char *
drop_tail( const char *data )
{
char *str;
char *p;
str = g_strdup( data );
p = str + strlen( str );
if( p > str &&
*(p = g_utf8_prev_char( p )) == ')' &&
(p = g_utf8_strrchr( p, -1, (gunichar) '(')) &&
p > str &&
*(p = g_utf8_prev_char( p )) == ' ' )
*p = '\0';
return( str );
}
/* Write a libvips NULL-terminated utf-8 string into an ASCII entry. Tags like
* UserComment are really ASCII-only.
*/
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 );
/* libexif can only really save ASCII to things like UserComment.
*/
ascii = g_str_to_ascii( str, NULL );
/* libexif comment strings are not NULL-terminated, and have an
* encoding tag (always ASCII) in the first 8 bytes.
*/
len = strlen( ascii );
vips_exif_alloc_string( entry, sizeof( ASCII_COMMENT ) - 1 + len );
memcpy( entry->data, ASCII_COMMENT, sizeof( ASCII_COMMENT ) - 1 );
memcpy( entry->data + sizeof( ASCII_COMMENT ) - 1, ascii, len );
g_free( ascii );
g_free( str );
}
/* Write a libvips NULL-terminated utf-8 string into an entry.
*/
static void
vips_exif_set_string_utf16( ExifData *ed,
ExifEntry *entry, unsigned long component, const char *data )
{
char *str;
gunichar2 *utf16;
glong len;
str = drop_tail( data );
utf16 = g_utf8_to_utf16( str, -1, NULL, &len, NULL );
/* libexif utf16 strings are not NULL-terminated.
*/
vips_exif_alloc_string( entry, len * 2 );
memcpy( entry->data, utf16, len * 2 );
entry->format = EXIF_FORMAT_BYTE;
g_free( utf16 );
g_free( str );
}
/* Write a tag. Update what's there, or make a new one.
*/
static void
@ -791,9 +861,10 @@ 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
* fields :(
*/
if( tag == EXIF_TAG_USER_COMMENT ) {
vips_exif_set_string( ed, entry, 0, data );
}
if( tag_is_ascii( tag ) )
vips_exif_set_string_ascii( ed, entry, 0, data );
else if( tag_is_utf16( tag ) )
vips_exif_set_string_utf16( ed, entry, 0, data );
else {
exif_entry_initialize( entry, tag );
fn( ed, entry, 0, data );
@ -1095,7 +1166,8 @@ vips_exif_exif_entry( ExifEntry *entry, VipsExifRemove *ve )
/* If this is a string tag, we must also remove it ready for
* recreation, see the comment below.
*/
if( entry->format == EXIF_FORMAT_ASCII )
if( tag_is_ascii( entry->tag ) ||
tag_is_utf16( entry->tag ) )
ve->to_remove = g_slist_prepend( ve->to_remove, entry );
}