def get_view_box(self):
"""Calculate shown portion of image and image units per pixel
This method utilizes a precomputed "mesh" of relatively evenly
spaced points over the entire image space. This mesh is transformed
to the canvas space (-1 to 1 user-viewed space) to figure out which
portions of the image are currently being viewed and which portions
can actually be projected on the viewed projection.
While the result of the chosen method may not always be completely
accurate, it should work for all possible viewing cases.
"""
if self._viewable_mesh_mask is None or self.canvas.size[
0] == 0 or self.canvas.size[1] == 0:
raise ValueError("Image '%s' is not viewable in this projection" %
(self.name, ))
# Image points transformed to canvas coordinates
img_cmesh = self.transforms.get_transform().map(self.calc.image_mesh)
# The image mesh projected to canvas coordinates (valid only)
img_cmesh = img_cmesh[self._viewable_mesh_mask]
# The image mesh of only valid "viewable" projected coordinates
img_vbox = self.calc.image_mesh[self._viewable_mesh_mask]
ref_idx_1, ref_idx_2 = get_reference_points(img_cmesh, img_vbox)
dx, dy = calc_pixel_size(img_cmesh[(self._ref1, self._ref2), :],
img_vbox[(self._ref1, self._ref2), :],
self.canvas.size)
view_extents = self.calc.calc_view_extents(img_cmesh[ref_idx_1],
img_vbox[ref_idx_1],
self.canvas.size, dx, dy)
return ViewBox(*view_extents, dx=dx, dy=dy)
def determine_reference_points(self):
# Image points transformed to canvas coordinates
img_cmesh = self.transforms.get_transform().map(self.calc.image_mesh)
# Mask any points that are really far off screen (can't be transformed)
valid_mask = (np.abs(img_cmesh[:, 0]) < CANVAS_EPSILON) & (np.abs(
img_cmesh[:, 1]) < CANVAS_EPSILON)
# The image mesh projected to canvas coordinates (valid only)
img_cmesh = img_cmesh[valid_mask]
# The image mesh of only valid "viewable" projected coordinates
img_vbox = self.calc.image_mesh[valid_mask]
if not img_cmesh[:, 0].size or not img_cmesh[:, 1].size:
self._viewable_mesh_mask = None
self._ref1, self._ref2 = None, None
return
x_cmin, x_cmax = img_cmesh[:, 0].min(), img_cmesh[:, 0].max()
y_cmin, y_cmax = img_cmesh[:, 1].min(), img_cmesh[:, 1].max()
center_x = (x_cmax - x_cmin) / 2. + x_cmin
center_y = (y_cmax - y_cmin) / 2. + y_cmin
dist = img_cmesh.copy()
dist[:, 0] = center_x - img_cmesh[:, 0]
dist[:, 1] = center_y - img_cmesh[:, 1]
self._viewable_mesh_mask = valid_mask
self._ref1, self._ref2 = get_reference_points(dist, img_vbox)
def test_get_reference_points_bad_points(ic, iv):
"""Test that error is thrown if given invalid mesh points."""
with pytest.raises(ValueError):
get_reference_points(np.array(ic), np.array(iv))
def test_get_reference_points(ic, iv, exp):
"""Test returned image reference point indexes are correct."""
res = get_reference_points(np.array(ic), np.array(iv))
assert res == exp