Depth scale

It turns out that this is basically just 1000, but I wasn't sure.

Topic: depth-scale

Author: wolfd

src/frame.rs

@@ -69,6 +69,16 @@ pub struct DepthFrame {
 }
 impl_video_frame!(DepthFrame);
 
+impl DepthFrame {
+    /// Get the scale (pixel value * scale = distance in millimeters) of the depth frame
+    pub fn depth_scale(&self) -> f32 {
+        // Unwrap is safe here because internal pointer is guaranteed to be valid and a depth frame
+        // SDK only returns error for this function if pointer is NULL or not a depth frame
+        // Ref: https://github.com/orbbec/OrbbecSDK_v2/blob/815ae047cc977a1f7edd2b97b69ff6cd29f510b3/src/impl/Frame.cpp#L198
+        self.inner.get_depth_scale().unwrap()
+    }
+}
+
 /// Point Cloud frame
 pub struct PointCloudFrame {
     inner: OBFrame,

src/sys/frame.rs

@@ -150,4 +150,16 @@ impl OBFrame {
 
         Ok(scale)
     }
+
+    /// Get the depth frame scale.
+    /// Only valid for depth frames.
+    pub fn get_depth_scale(&self) -> Result<f32, OBError> {
+        let mut err_ptr = std::ptr::null_mut();
+
+        let scale = unsafe { orb::ob_depth_frame_get_value_scale(self.inner, &mut err_ptr) };
+
+        OBError::consume(err_ptr)?;
+
+        Ok(scale)
+    }
 }