# bb_avg_edge_length_68_euclidean_error¶

menpofit.error.bb_avg_edge_length_68_euclidean_error(shape, gt_shape)[source]

Computes the Euclidean error based on 68 points normalised by the average edge length of the 68-point ground truth shape’s bounding box, i.e.

$\frac{\mathcal{F}(s,s^*)}{\mathcal{N}(s^*)}$

where

$\mathcal{F}(s,s^*) = \frac{1}{68}\sum_{i=1}^{68}\sqrt{(s_{i,x}-s^*_{i,x})^2 + (s_{i,y}-s^*_{i,y})^2}$

where $$s$$ and $$s^*$$ are the final and ground truth shapes, respectively. $$(s_{i,x}, s_{i,y})$$ are the x and y coordinates of the $$i$$’th point of the final shape, $$(s^*_{i,x}, s^*_{i,y})$$ are the x and y coordinates of the $$i$$’th point of the ground truth shape. Finally, $$\mathcal{N}(s^*)$$ is a normalising function that returns the average edge length of the bounding box of the 68-point ground truth shape (bb_avg_edge_length).

Parameters
• shape (menpo.shape.PointCloud) – The input shape (e.g. the final shape of a fitting procedure). It must have 68 points.

• gt_shape (menpo.shape.PointCloud) – The ground truth shape. It must have 68 points.

Returns

normalised_error (float) – The computed Euclidean normalised error.

Raises
• ValueError – Final shape must have 68 points

• ValueError – Ground truth shape must have 68 points