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better exif string value change detection

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see https://github.com/libvips/libvips/pull/2518
This commit is contained in:
John Cupitt 2021-11-09 19:28:55 +00:00
parent 296fd99925
commit 8195b67d83
1 changed files with 42 additions and 15 deletions
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53
libvips/foreign/exif.c
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@ -1228,18 +1228,32 @@ vips_exif_exif_entry( ExifEntry *entry, VipsExifRemove *ve )
{ {
const char *tag_name; const char *tag_name;
char vips_name_txt[256]; char vips_name_txt[256];
VipsBuf vips_name = VIPS_BUF_STATIC( vips_name_txt ); VipsBuf vips_name_buf = VIPS_BUF_STATIC( vips_name_txt );
const char *vips_name;
const char *vips_value;
if( !(tag_name = vips_exif_entry_get_name( entry )) ) if( !(tag_name = vips_exif_entry_get_name( entry )) )
return; return;
vips_buf_appendf( &vips_name, "exif-ifd%d-%s", vips_buf_appendf( &vips_name_buf, "exif-ifd%d-%s",
exif_entry_get_ifd( entry ), tag_name ); exif_entry_get_ifd( entry ), tag_name );
vips_name = vips_buf_all( &vips_name_buf );
/* Is there a image metadata item for this tag?
*/
vips_value = NULL;
if( vips_image_get_typeof( ve->image, vips_name ) ) {
/* No easy way to return an error code from here, sadly.
*/
if( vips_image_get_string( ve->image, vips_name, &vips_value ) )
g_warning( _( "bad exif meta \"%s\"" ), vips_name );
}
/* Does this field exist on the image? If not, schedule it for /* Does this field exist on the image? If not, schedule it for
* removal. * removal.
*/ */
if( !vips_image_get_typeof( ve->image, vips_buf_all( &vips_name ) ) ) if( !vips_value )
ve->to_remove = g_slist_prepend( ve->to_remove, entry ); ve->to_remove = g_slist_prepend( ve->to_remove, entry );
/* Orientation is really set from the vips /* Orientation is really set from the vips
@ -1247,16 +1261,29 @@ vips_exif_exif_entry( ExifEntry *entry, VipsExifRemove *ve )
* any matching EXIF tags too. * any matching EXIF tags too.
*/ */
if( strcmp( tag_name, "Orientation" ) == 0 && if( strcmp( tag_name, "Orientation" ) == 0 &&
vips_image_get_typeof( ve->image, VIPS_META_ORIENTATION ) ) vips_value )
ve->to_remove = g_slist_prepend( ve->to_remove, entry ); ve->to_remove = g_slist_prepend( ve->to_remove, entry );
/* If this is a string tag, we must also remove it ready for /* If this is a string tag with a new value, we must also remove it
* recreation, see the comment below. * ready for recreation, see the comment below.
*/ */
if( tag_is_encoding( entry->tag ) || if( vips_value &&
(tag_is_encoding( entry->tag ) ||
tag_is_ascii( entry->tag ) || tag_is_ascii( entry->tag ) ||
tag_is_utf16( entry->tag ) ) tag_is_utf16( entry->tag )) ) {
char value_txt[256];
VipsBuf value = VIPS_BUF_STATIC( value_txt );
/* Render the original exif-data value to a string and see
* if the user has changed it. If they have, remove it ready
* for re-adding.
*
* Leaving it there prevents it being recreated.
*/
vips_exif_to_s( ve->ed, entry, &value );
if( strcmp( vips_buf_all( &value ), vips_value ) != 0 )
ve->to_remove = g_slist_prepend( ve->to_remove, entry ); ve->to_remove = g_slist_prepend( ve->to_remove, entry );
}
} }
static void * static void *
@ -1305,12 +1332,12 @@ vips_exif_update( ExifData *ed, VipsImage *image )
* the image must have been deliberately removed. Remove them from the * the image must have been deliberately removed. Remove them from the
* block as well. * block as well.
* *
* If there are any string-valued fields (eg. comment etc.) which * Any string-valued fields (eg. comment etc.) which exist as libvips
* exist as libvips metadata tags, we must also remove those from the * metadata tags with changed whose values have changed must also be
* exif block. * removed.
* *
* libexif does not allow you to change string lengths, you must make * libexif does not allow you to change string lengths (you must make
* new tags, so we have to remove ready to re-add. * new tags) so we have to remove ready to re-add.
*/ */
if( vips_image_get_typeof( image, VIPS_META_EXIF_NAME ) ) { if( vips_image_get_typeof( image, VIPS_META_EXIF_NAME ) ) {
ve.image = image; ve.image = image;