improve scRGB alpha handling

since it's now 0-1

Author: jcupitt

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## master
 
 - fix ctrl/shift detect on windows
+- add menu pin button
 
 ## 9.0.6 2025/04/16
 

TODO

@@ -1,12 +1,3 @@
-- toolkit menu: return to home by default, have a temp "pin in place" toggle
-  at the top right to stop it
-
-        - pin in place disables if you click "back"
-
-- ctrl-drag / ctrl-click to make region / mark does not work on windows
-
-- fix scRGB with alpha
-
 - "reset" in display bar resets the position of scale/offset widgets, but does
   not reset the menu items (eg. tick on falsecolour)
 
@@ -33,6 +24,8 @@
 
 	we've implemented #separator
 
+- the nip4 menus need reworking to use max_alpha 255 for scrgb
+
 - add something to find unresolved symbols
 
 - get rid of im_copy_set etc.
@@ -44,15 +37,6 @@
 
 - rename Image_type as Image_interpretation
 
-- add
-
-	minpair
-	maxpair
-	clamp
-	sdf
-
-  to stdenv
-
 - try:
 
 	Matrix_build_item.Matrix_laplacian_item.action

src/tilesource.c

@@ -654,7 +654,18 @@ tilesource_rgb_image(Tilesource *tilesource, VipsImage *in)
 
 	// reattach alpha
 	if (alpha) {
-		if (vips_cast(alpha, &x, image->BandFmt, "shift", TRUE, NULL))
+		double max_alpha_before = vips_interpretation_max_alpha(alpha->Type);
+		double max_alpha_after = vips_interpretation_max_alpha(image->Type);
+
+		if (max_alpha_before != max_alpha_after) {
+			if (vips_linear1(alpha, &x,
+				max_alpha_after / max_alpha_before, 0.0, NULL))
+				return NULL;
+			VIPS_UNREF(alpha);
+			alpha = x;
+		}
+
+		if (vips_cast(alpha, &x, image->BandFmt, NULL))
 			return NULL;
 		VIPS_UNREF(alpha);
 		alpha = x;

src/workspaceview.c

@@ -1259,9 +1259,9 @@ workspaceview_key_pressed(GtkEventControllerKey *self,
 	gboolean handled;
 
 #ifdef DEBUG_VERBOSE
-#endif /*DEBUG_VERBOSE*/
 	printf("workspaceview_key_pressed: keyval = %d, state = %d\n",
 		keyval, state);
+#endif /*DEBUG_VERBOSE*/
 
 	handled = FALSE;