feat: set_image_gray

src/wand/magick.rs

@@ -715,6 +715,14 @@ impl MagickWand {
         Ok(bytes)
     }
 
+    pub fn set_image_gray (&self) -> Result<(), &'static str> {
+        let result = unsafe { bindings::SetImageGray(self.wand) };
+        match result {
+            MagickBooleanType_MagickTrue => Ok(()),
+            _ => Err("Couldn't set image to gray")
+        }
+    }
+
     mutations!(
         /// Set the image colorspace, transforming (unlike `set_image_colorspace`) image data in
         /// the process.