add module for filter applied to the reconstruction

mu_map/recon/filter.py

+from mu_map.file.interfile import Interfile, InterfileKeys
+
+TEMPLATE_FILTER_GAUSSIAN_PARAMS = """
+post-filter type := Separable Gaussian
+separable gaussian filter parameters :=
+  x-dir filter fwhm (in mm) := {FWHM_X}
+  y-dir filter fwhm (in mm) := {FWHM_Y}
+  z-dir filter fwhm (in mm) := {FWHM_Z}
+  x-dir maximum kernel size := {SIZE_X}
+  y-dir maximum kernel size := {SIZE_Y}
+  z-dir maximum kernel size := {SIZE_Z}
+  Normalise filter to 1 := 1
+end separable gaussian filter parameters :=
+"""
+
+class GaussianFilter:
+
+    def __init__(self, projection: Interfile, width_scale: int = 1.0):
+        header, _ = projection
+
+        self.params = TEMPLATE_FILTER_GAUSSIAN_PARAMS
+
+        spacing_x = float(header[InterfileKeys.spacing(1)]) * width_scale
+        spacing_y = float(header[InterfileKeys.spacing(1)]) * width_scale
+        spacing_z = float(header[InterfileKeys.spacing(2)]) * width_scale
+        self.params = self.params.replace("{FWHM_X}", f"{spacing_x:.4f}")
+        self.params = self.params.replace("{FWHM_Y}", f"{spacing_y:.4f}")
+        self.params = self.params.replace("{FWHM_Z}", f"{spacing_z:.4f}")
+
+        self.params = self.params.replace("{SIZE_X}", header[InterfileKeys.dim(1)])
+        self.params = self.params.replace("{SIZE_Y}", header[InterfileKeys.dim(1)])
+        self.params = self.params.replace("{SIZE_Z}", header[InterfileKeys.dim(2)])
+
+    def insert(self, osem_params: str):
+        lines = self.params.strip().split("\n")
+        lines = list(map(lambda line: "  " + line, lines))
+        lines.append("\n")
+
+        osem_lines = osem_params.strip().split("\n")
+        res = osem_lines[:-1] + lines + osem_lines[-1:]
+        return "\n".join(res)
+
+    def __repr__(self):
+        return self.params