add an intent option to thumbnail

"intent" lets you set the rendering intent for any ICC conversions --
the default is the (more correct) relative, but "perceptual" can look
better

see https://github.com/jcupitt/libvips/issues/714

ChangeLog

@@ -14,6 +14,7 @@
 - remove lcms1 support, it had bitrotted
 - `join` tagged as seq
 - support tiffsave_buffer for pyramids, thanks bubba
+- thumbnail and vipsthumbnail have an option for rendering intent, thanks kleisauke 
 
 29/8/17 started 8.5.9
 - make --fail stop jpeg read on any libjpeg warning, thanks @mceachen

libvips/resample/thumbnail.c

@@ -9,6 +9,8 @@
  * 	- add FORCE
  * 29/5/17
  * 	- don't cache (thanks tomasc)
+ * 30/8/17
+ * 	- add intent option, thanks kleisauke
  */
 
 /*
@@ -81,6 +83,7 @@ typedef struct _VipsThumbnail {
 	gboolean linear;
 	char *export_profile;
 	char *import_profile;
+	VipsIntent intent;
 
 	/* Set by subclasses to the input image.
 	 */
@@ -375,6 +378,7 @@ vips_thumbnail_build( VipsObject *object )
 		if( vips_icc_import( in, &t[1], 
 			"input_profile", thumbnail->import_profile,
 			"embedded", TRUE,
+			"intent", thumbnail->intent,
 			"pcs", VIPS_PCS_XYZ,
 			NULL ) )  
 			return( -1 );
@@ -442,6 +446,7 @@ vips_thumbnail_build( VipsObject *object )
 			g_info( "exporting to device space with a profile" );
 			if( vips_icc_export( in, &t[7], 
 				"output_profile", thumbnail->export_profile,
+				"intent", thumbnail->intent,
 				NULL ) )  
 				return( -1 );
 			in = t[7];
@@ -470,6 +475,7 @@ vips_thumbnail_build( VipsObject *object )
 
 			if( vips_icc_transform( in, &t[7], 
 				thumbnail->export_profile,
+				"intent", thumbnail->intent,
 				"embedded", TRUE,
 				NULL ) ) {
 				g_warning( _( "unable to import with "
@@ -489,6 +495,7 @@ vips_thumbnail_build( VipsObject *object )
 			if( vips_icc_transform( in, &t[7], 
 				thumbnail->export_profile,
 				"input_profile", thumbnail->import_profile,
+				"intent", thumbnail->intent,
 				"embedded", FALSE,
 				NULL ) )  
 				return( -1 );
@@ -630,6 +637,13 @@ vips_thumbnail_class_init( VipsThumbnailClass *class )
 		G_STRUCT_OFFSET( VipsThumbnail, export_profile ),
 		NULL ); 
 
+	VIPS_ARG_ENUM( class, "intent", 120, 
+		_( "Intent" ), 
+		_( "Rendering intent" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsThumbnail, intent ),
+		VIPS_TYPE_INTENT, VIPS_INTENT_RELATIVE );
+
 }
 
 static void
@@ -638,6 +652,7 @@ vips_thumbnail_init( VipsThumbnail *thumbnail )
 	thumbnail->width = 1;
 	thumbnail->height = 1;
 	thumbnail->auto_rotate = TRUE;
+	thumbnail->intent = VIPS_INTENT_RELATIVE;
 }
 
 typedef struct _VipsThumbnailFile {
@@ -745,6 +760,7 @@ vips_thumbnail_file_init( VipsThumbnailFile *file )
  * * @linear: %gboolean, perform shrink in linear light
  * * @import_profile: %gchararray, fallback import ICC profile
  * * @export_profile: %gchararray, export ICC profile
+ * * @intent: #VipsIntent, rendering intent
  *
  * Make a thumbnail from a file. Shrinking is done in three stages: using any
  * shrink-on-load features available in the file import library, using a block
@@ -786,6 +802,9 @@ vips_thumbnail_file_init( VipsThumbnailFile *file )
  * input image has no ICC profile, or if the profile embedded in the 
  * input image is broken.
  *
+ * Use @intent to set the rendering intent for any ICC transform. The default
+ * is #VIPS_INTENT_RELATIVE.
+ *
  * See also: vips_thumbnail_buffer().
  *
  * Returns: 0 on success, -1 on error.
@@ -917,6 +936,7 @@ vips_thumbnail_buffer_init( VipsThumbnailBuffer *buffer )
  * * @linear: %gboolean, perform shrink in linear light
  * * @import_profile: %gchararray, fallback import ICC profile
  * * @export_profile: %gchararray, export ICC profile
+ * * @intent: #VipsIntent, rendering intent
  *
  * Exacty as vips_thumbnail(), but read from a memory buffer. 
  *
@@ -1031,6 +1051,7 @@ vips_thumbnail_image_init( VipsThumbnailImage *image )
  * * @linear: %gboolean, perform shrink in linear light
  * * @import_profile: %gchararray, fallback import ICC profile
  * * @export_profile: %gchararray, export ICC profile
+ * * @intent: #VipsIntent, rendering intent
  *
  * Exacty as vips_thumbnail(), but read from an existing image.
  *

tools/vipsthumbnail.c

@@ -92,6 +92,8 @@
  * 	- support VipSize restrictions
  * 4/5/17
  * 	- add ! geo modifier
+ * 30/8/17
+ * 	- add --intent
  */
 
 #ifdef HAVE_CONFIG_H
@@ -125,6 +127,7 @@ static gboolean linear_processing = FALSE;
 static gboolean crop_image = FALSE;
 static char *smartcrop_image = NULL;
 static gboolean rotate_image = FALSE;
+static char *thumbnail_intent = NULL;
 
 /* Deprecated and unused.
  */
@@ -162,6 +165,10 @@ static GOptionEntry options[] = {
 		G_OPTION_ARG_STRING, &smartcrop_image, 
 		N_( "shrink and crop to fill SIZE using STRATEGY" ), 
 		N_( "STRATEGY" ) },
+	{ "intent", 'n', 0, 
+		G_OPTION_ARG_STRING, &thumbnail_intent, 
+		N_( "ICC transform with INTENT" ), 
+		N_( "INTENT" ) },
 	{ "rotate", 't', 0, 
 		G_OPTION_ARG_NONE, &rotate_image, 
 		N_( "auto-rotate" ), NULL },
@@ -245,18 +252,28 @@ thumbnail_process( VipsObject *process, const char *filename )
 {
 	VipsInteresting interesting;
 	VipsImage *image;
+	VipsIntent intent;
 
 	interesting = VIPS_INTERESTING_NONE;
 	if( crop_image )
 		interesting = VIPS_INTERESTING_CENTRE;
 	if( smartcrop_image ) {
 		int n;
-		
+
 		if( (n = vips_enum_from_nick( "vipsthumbnail", 
 			VIPS_TYPE_INTERESTING, smartcrop_image )) < 0 ) 
 			return( -1 ); 
 		interesting = n;
 	}
+	intent = VIPS_INTENT_RELATIVE;
+	if( thumbnail_intent ) {
+		int n;
+
+		if( (n = vips_enum_from_nick( "vipsthumbnail", 
+			VIPS_TYPE_INTENT, thumbnail_intent )) < 0 ) 
+			return( -1 ); 
+		intent = n;
+	}
 
 	if( vips_thumbnail( filename, &image, thumbnail_width, 
 		"height", thumbnail_height, 
@@ -266,6 +283,7 @@ thumbnail_process( VipsObject *process, const char *filename )
 		"linear", linear_processing, 
 		"import_profile", import_profile, 
 		"export_profile", export_profile, 
+		"intent", intent, 
 		NULL ) )
 		return( -1 );