def center(self, loc=None):
"""Center the image foreground
This function shifts the center of mass (CoM) to the image center.
Parameters
----------
loc : (col, row), optional
The pixel location at which to center the CoM. By default, shifts
the CoM to the image center.
Returns
-------
stim : `ImageStimulus`
A copy of the stimulus object containing the centered image
"""
# Calculate center of mass:
img = self.data.reshape(self.img_shape)
m = img_moments(img, order=1)
# No area found:
if np.isclose(m[0, 0], 0):
return img
# Center location:
if loc is None:
loc = np.array(self.img_shape[::-1]) / 2.0 - 0.5
# Shift the image by -centroid, +image center:
transl = (loc[0] - m[0, 1] / m[0, 0], loc[1] - m[1, 0] / m[0, 0])
tf_shift = SimilarityTransform(translation=transl)
img = img_warp(img, tf_shift.inverse)
return ImageStimulus(img,
electrodes=self.electrodes,
metadata=self.metadata)
def scale(self, scaling_factor):
"""Scale the image foreground
This function scales the image foreground (excluding black pixels)
by a factor.
Parameters
----------
scaling_factor : float
Factory by which to scale the image
Returns
-------
stim : `ImageStimulus`
A copy of the stimulus object containing the scaled image
"""
if scaling_factor <= 0:
raise ValueError("Scaling factor must be greater than zero")
# Calculate center of mass:
img = self.data.reshape(self.img_shape)
m = img_moments(img, order=1)
# No area found:
if np.isclose(m[0, 0], 0):
return img
# Shift the phosphene to (0, 0):
center_mass = np.array([m[0, 1] / m[0, 0], m[1, 0] / m[0, 0]])
tf_shift = SimilarityTransform(translation=-center_mass)
# Scale the phosphene:
tf_scale = SimilarityTransform(scale=scaling_factor)
# Shift the phosphene back to where it was:
tf_shift_inv = SimilarityTransform(translation=center_mass)
# Combine all three transforms:
tf = tf_shift + tf_scale + tf_shift_inv
img = img_warp(img, tf.inverse)
return ImageStimulus(img,
electrodes=self.electrodes,
metadata=self.metadata)