Wrap get_gainmap

Author: rolandlo

src/vips/Image_methods.lua

@@ -497,6 +497,16 @@ function Image_method:remove(name)
     return vips_lib.vips_image_remove(self.vimage, name) ~= 0
 end
 
+function Image_method:get_gainmap()
+    collectgarbage("stop")
+    local vimage = vips_lib.vips_image_get_gainmap(self.vimage)
+    if vimage == ffi.NULL then
+        return nil
+    end
+
+    collectgarbage("restart")
+    return Image.new(vimage)
+end
 -- standard header fields
 
 function Image_method:width()

src/vips/cdefs.lua

@@ -166,6 +166,8 @@ ffi.cdef [[
         // opaque
     } VipsImage;
 
+    VipsImage *vips_image_get_gainmap(VipsImage *image);
+
     typedef struct _VipsConnection {
         VipsObject parent_instance;