refactor: pointer sensor image resizing

Cache resized pointer image instead of resizing it every time when the
sensor is rendered.
Change sensor.width and .height fields to u32.

src/cfg.rs

@@ -322,9 +322,9 @@ pub struct Sensor {
     #[serde(deserialize_with = "f32_as_rounded_i32")]
     pub y: i32,
     /// Used for pointer type
-    pub width: Option<i32>,
+    pub width: Option<u32>,
     /// Used for pointer type
-    pub height: Option<i32>,
+    pub height: Option<u32>,
     /// Sensor graphic orientation
     pub direction: Option<SensorDirection>,
 

src/render.rs

@@ -430,27 +430,20 @@ impl PanelRenderer {
             ImageProcessingError::ImageLoadError("No picture specified".to_string())
         })?;
 
-        // TODO combine get image with resize
+        // Resize if dimensions specified
-        let mut pic = self
+        let size = if let (Some(width), Some(height)) = (sensor.width, sensor.height) {
+            Some((width, height))
+        } else {
+            None
+        };
+        let pic = self
             .image_cache
-            .get(pic_path, None)
+            .get(pic_path, size)
             .ok_or_else(|| {
                 ImageProcessingError::ImageLoadError(format!("Failed to load: {:?}", pic_path))
             })?
             .clone();
 
-        // Resize if dimensions specified
-        if let (Some(width), Some(height)) = (sensor.width, sensor.height) {
-            let item_width = width as u32;
-            let item_height = height as u32;
-            pic = image::imageops::resize(
-                &pic,
-                item_width,
-                item_height,
-                image::imageops::FilterType::Lanczos3,
-            );
-        }
-
         let min_val = sensor.min_value.unwrap_or(0.0);
         let max_val = sensor.max_value.unwrap_or(100.0);
         let current_value = value