Curved surface (#45)

* Initial curved surface function. Parameters need more thought.

src/ttmask/__init__.py

@@ -18,4 +18,5 @@
 from .ellipsoid import ellipsoid
 from .map2mask import map2mask
 from .tube import tube
+from .curved_surface import curved_surface
 

src/ttmask/curved_surface.py

@@ -0,0 +1,45 @@
+from pathlib import Path
+
+
+import numpy as np
+import typer
+import mrcfile
+
+from ._cli import cli
+from .soft_edge import add_soft_edge
+from .box_setup import box_setup
+
+@cli.command(name='curved_surface')
+def curved_surface(
+    sidelength: int = typer.Option(...),
+    fit_sphere_diameter: float = typer.Option(...),
+    soft_edge_width: int = typer.Option(0),
+    pixel_size: float = typer.Option(1),
+    output: Path = typer.Option(Path("curved_surface.mrc")),
+    surface_thickness: float = typer.Option(...),
+):
+    sphere_radius = fit_sphere_diameter / 2
+
+    # establish our coordinate system and empty mask
+    coordinates_centered, mask = box_setup(sidelength)
+    coordinates_shifted = coordinates_centered - ([0, sphere_radius, 0])
+
+
+    #determine distances of each pixel to the center
+    distance_to_center = np.linalg.norm(coordinates_shifted, axis=-1)
+
+
+    # set up criteria for which pixels are inside the sphere and modify values to 1.
+    inside_sphere = distance_to_center < (sphere_radius / pixel_size)
+    mask[inside_sphere] = 1
+
+    # if requested, criteria set up for pixels within the hollowed area and these values changed to zero
+    if surface_thickness != 0:
+        within_hollowing = distance_to_center < ((sphere_radius - surface_thickness) / pixel_size)
+        mask[within_hollowing] = 0
+
+    # if requested, a soft edge is added to the mask
+    mask = add_soft_edge(mask, soft_edge_width)
+
+    # output created with desired pixel size.
+    mrcfile.write(output, mask, voxel_size=pixel_size, overwrite=True)

src/ttmask/sphere.py

@@ -9,7 +9,6 @@
 from .soft_edge import add_soft_edge
 from .box_setup import box_setup
 
-
 @cli.command(name='sphere')
 def sphere(
     sidelength: int = typer.Option(...),