images: move rowstride to the images vocab because it will be used by

gdi too

basis/images/images-docs.factor

@@ -0,0 +1,6 @@
+USING: help.markup help.syntax math ;
+IN: images
+
+HELP: rowstride
+{ $values { "image" image } { "n" integer } }
+{ $description "Returns an images rowstride metric." } ;

basis/images/images-tests.factor

@@ -27,3 +27,8 @@ IN: images.tests
     0 0 0 0
     0 0 0 0
 } } [ set-pixel-at ] keep bitmap>> ] unit-test
+
+{ 40 30 } [
+    T{ image f { 10 3 } RGBA ubyte-components f f } rowstride
+    T{ image f { 10 3 } RGB ubyte-components f f } rowstride
+] unit-test

basis/images/images.factor

@@ -135,6 +135,9 @@ TUPLE: image
 : bytes-per-image ( image -- n )
     [ dim>> product ] [ bytes-per-pixel ] bi * ;
 
+: rowstride ( image -- n )
+    [ dim>> first ] [ bytes-per-pixel ] bi * ;
+
 <PRIVATE
 
 :: pixel@ ( x y w image -- start end bitmap )
@@ -164,4 +167,3 @@ PRIVATE>
 
 : set-pixel-at ( pixel x y image -- )
     [ 1 ] dip set-pixel-row-at ; inline
-

basis/images/loader/gtk/gtk.factor

@@ -60,18 +60,12 @@ CONSTANT: bits>components {
         f >>premultiplied-alpha?
         f >>upside-down? ;
 
-: bits-per-sample ( image -- bits )
-    component-type>> bits>components value-at ;
-
-: rowstride ( image -- rowstride )
-    [ dim>> first ] [ bits-per-sample 8 / ] [ has-alpha? 4 3 ? ] tri * * ;
-
 : image>GdkPixbuf ( image -- GdkPixbuf )
     {
         [ bitmap>> ]
         [ drop GDK_COLORSPACE_RGB ]
         [ has-alpha? ]
-        [ bits-per-sample ]
+        [ bytes-per-component 8 * ]
         [ dim>> first2 ]
         [ rowstride ]
     } cleave f f gdk_pixbuf_new_from_data ;