def for_subimage(self, bbox: Box2I) -> ImageSectionTransform:
"""Return the transform that maps a subimage to the same coordinate
system.
Parameters
----------
bbox : `Box2I`
Bounding box of the subimage that the new transform will operate
on. Must satisfy ``self.input_bbox.contains(bbox)``.
Returns
-------
subimage_transform : `ImageSectionTransform`
A transform whose ``input_bbox`` is the given ``bbox`` that maps it
to the appropriate location within ``self.output_bbox`` and applies
the same flips.
"""
# Distances (defined to be positive) between minimum points of both
# boxes and maximum points of both boxes.
lower_dist_x, lower_dist_y = bbox.getMin() - self.input_bbox.getMin()
upper_dist_x, upper_dist_y = self.input_bbox.getMax() - bbox.getMax()
if self.flip_x:
lower_dist_x, upper_dist_x = upper_dist_x, lower_dist_x
if self.flip_y:
lower_dist_y, upper_dist_y = upper_dist_y, lower_dist_y
output_bbox = Box2I(
minimum=self.output_bbox.getMin() + ExtentI(lower_dist_x, lower_dist_y),
maximum=self.output_bbox.getMax() - ExtentI(upper_dist_x, upper_dist_y),
)
return ImageSectionTransform(
input_bbox=bbox,
output_bbox=output_bbox,
flip_x=self.flip_x,
flip_y=self.flip_y,
)
def subimage(self, bbox: Box2I) -> NumPyImageSection:
# Docstring inherited.
start = bbox.getMin() - self._bbox_min
stop = start + bbox.getSize()
return NumPyImageSection(
self._array[start.getY():stop.getY(),
start.getX():stop.getX(), ...], # noqa:E203
bbox,
)
