copy photoshop data in tiff load/save

well, try anyway, it might work

see https://github.com/jcupitt/libvips/issues/332

ChangeLog

@@ -19,7 +19,7 @@
 - vips_log(), vips_log10() are zero-avoiding
 - better overlap handling for dzsave, thanks robclouth
 - add @spacing option to vips_text()
-- tiff loads and saves IPCT data
+- tiff loads and saves IPCT and Photoshop data
 
 7/5/15 started 8.0.3
 - dzsave and tif pyr write could fail for some image dimensions, thanks Jonas

libvips/foreign/tiff2vips.c

@@ -159,6 +159,7 @@
  * 	  fd during file read, handy for large numbers of input images 
  * 29/9/15
  * 	- load IPCT metadata
+ * 	- load photoshop metadata
  */
 
 /*
@@ -1202,6 +1203,19 @@ parse_header( ReadTiff *rtiff, VipsImage *out )
 			(VipsCallbackFn) vips_free, data_copy, data_length );
 	}
 
+	/* Read any photoshop metadata.
+	 */
+	if( TIFFGetField( rtiff->tiff, 
+		TIFFTAG_PHOTOSHOP, &data_length, &data ) ) {
+		void *data_copy;
+
+		if( !(data_copy = vips_malloc( NULL, data_length )) ) 
+			return( -1 );
+		memcpy( data_copy, data, data_length );
+		vips_image_set_blob( out, VIPS_META_PHOTOSHOP_NAME, 
+			(VipsCallbackFn) vips_free, data_copy, data_length );
+	}
+
 	return( 0 );
 }
 

libvips/foreign/vips2tiff.c

@@ -155,6 +155,7 @@
  * 	- add miniswhite option
  * 29/9/15
  * 	- try to write IPCT metadata
+ * 	- try to write photoshop metadata
  */
 
 /*
@@ -473,7 +474,29 @@ write_embed_ipct( Write *write, TIFF *tif )
 	TIFFSetField( tif, TIFFTAG_RICHTIFFIPTC, data_length, data );
 
 #ifdef DEBUG
-	printf( "vips2tiff: attached XMP from meta\n" );
+	printf( "vips2tiff: attached IPCT from meta\n" );
+#endif /*DEBUG*/
+
+	return( 0 );
+}
+
+/* Embed any XMP metadata. 
+ */
+static int
+write_embed_photoshop( Write *write, TIFF *tif )
+{
+	void *data;
+	size_t data_length;
+
+	if( !vips_image_get_typeof( write->im, VIPS_META_PHOTOSHOP_NAME ) )
+		return( 0 );
+	if( vips_image_get_blob( write->im, VIPS_META_PHOTOSHOP_NAME, 
+		&data, &data_length ) )
+		return( -1 );
+	TIFFSetField( tif, TIFFTAG_PHOTOSHOP, data_length, data );
+
+#ifdef DEBUG
+	printf( "vips2tiff: attached photoshop data from meta\n" );
 #endif /*DEBUG*/
 
 	return( 0 );
@@ -514,7 +537,8 @@ write_tiff_header( Write *write, Layer *layer )
 
 	if( write_embed_profile( write, tif ) ||
 		write_embed_xmp( write, tif ) ||
-		write_embed_ipct( write, tif ) )
+		write_embed_ipct( write, tif ) ||
+		write_embed_photoshop( write, tif ) )
 		return( -1 ); 
 
 	/* And colour fields.
@@ -1461,7 +1485,8 @@ write_copy_tiff( Write *write, TIFF *out, TIFF *in )
 	 */
 	if( write_embed_profile( write, out ) ||
 		write_embed_xmp( write, out ) ||
-		write_embed_ipct( write, out ) )
+		write_embed_ipct( write, out ) ||
+		write_embed_photoshop( write, out ) )
 		return( -1 );
 
 	buf = vips_malloc( NULL, TIFFTileSize( in ) );

libvips/include/vips/header.h

@@ -48,17 +48,25 @@ extern "C" {
 /**
  * VIPS_META_XMP_NAME:
  *
- * The name that JPEG read and write operations use for the image's XMP data.
+ * The name that read and write operations use for the image's XMP data.
  */
 #define VIPS_META_XMP_NAME "xmp-data"
 
 /**
  * VIPS_META_IPCT_NAME:
  *
- * The name that JPEG read and write operations use for the image's IPCT data.
+ * The name that read and write operations use for the image's IPCT data.
  */
 #define VIPS_META_IPCT_NAME "ipct-data"
 
+/**
+ * VIPS_META_PHOTOSHOP_NAME:
+ *
+ * The name that TIFF read and write operations use for the image's
+ * TIFFTAG_PHOTOSHOP data.
+ */
+#define VIPS_META_PHOTOSHOP_NAME "photoshop-data"
+
 /**
  * VIPS_META_ICC_NAME:
  *