measure stars background level

src/vstarstack/library/photometry/star_background.py

@@ -0,0 +1,75 @@
+#
+# Copyright (c) 2025 Vladislav Tsendrovskii
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3 of the License.
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the GNU General Public License for more details.
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <https://www.gnu.org/licenses/>.
+#
+
+from typing import Tuple
+import numpy as np
+import cv2
+from vstarstack.library.data import DataFrame
+
+def calculate_bg(image : np.ndarray, x : int, y : int, star_r : int, bg_r_big : int, bg_r_small : int) -> dict:
+    star_mask = np.zeros(image.shape)
+    cv2.circle(star_mask, (x,y), star_r, 1, -1)
+    bg_mask = np.zeros(image.shape)
+    cv2.circle(bg_mask, (x,y), bg_r_big, 1, -1)
+    cv2.circle(bg_mask, (x,y), bg_r_small, 0, -1)
+
+    bg_pixels = image * bg_mask
+    bg_sum = np.sum(bg_pixels)
+    bg_npix = np.sum(bg_mask)
+    bg_mean = bg_sum / bg_npix
+
+    star_pixels = (image - bg_mean) * star_mask
+    star_sum = np.sum(star_pixels)
+    star_npix = np.sum(star_mask)
+    return {
+        "star" : star_sum,
+        "star_npix" : star_npix,
+        "bg" : bg_sum,
+        "bg_npix" : bg_npix
+    }
+
+def calculate_bgs(image : np.ndarray, stars : list) -> list:
+    bgs = []
+    for star in stars:
+        x = star["x"]
+        y = star["y"]
+        r = int(star["radius"])
+        bg = calculate_bg(image, x, y, r, 2*r, 4*r)
+        bgs.append(bg)
+    return bgs
+
+def calculate_bgs_df(df : DataFrame, stars : list) -> Tuple[list, set]:
+    values = []
+    all_channels = set()
+    for star in stars:
+        channels = {
+            "x" : star["x"],
+            "y" : star["y"],
+            "radius" : star["radius"],
+            "channels" : {},
+        }
+        for channel in df.get_channels():
+            if not df.get_channel_option(channel, "brightness"):
+                continue
+            all_channels.add(channel)
+            image, _ = df.get_channel(channel)
+            x = star["x"]
+            y = star["y"]
+            sr = int(star["radius"]+0.5)
+            bgr_small = sr * 2
+            bgr_big = sr * 3
+            bg = calculate_bg(image, x, y, sr, bgr_big, bgr_small)
+            channels["channels"][channel] = bg
+        values.append(channels)
+    return values, all_channels

src/vstarstack/tool/photometry/measure_pollution.py

@@ -0,0 +1,75 @@
+#
+# Copyright (c) 2025 Vladislav Tsendrovskii
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3 of the License.
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the GNU General Public License for more details.
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <https://www.gnu.org/licenses/>.
+#
+
+import json
+import csv
+
+from vstarstack.library.photometry.star_background import calculate_bgs_df
+from vstarstack.library.data import DataFrame
+
+
+def process_image(project, argv : list):
+    image_path = argv[0]
+    stars_path = argv[1]
+    report_fname = argv[2]
+    with open(stars_path) as f:
+        stars = json.load(f)
+    stars = [{"x" : star["keypoint"]["x"], "y" : star["keypoint"]["y"], "radius" : star["keypoint"]["radius"]} for star in stars["points"]]
+
+    df = DataFrame.load(image_path)
+    backgrounds, channels = calculate_bgs_df(df, stars)
+    with open(report_fname, "w", encoding="utf-8") as f:
+        writer = csv.writer(f)
+        header1 = ["x", "y", "radius","","name","mag","lum","", "star pixels", "background pixels",""]
+        header2 = ["","","","","","","","","","",""]
+        for channel in channels:
+            header2.append(channel)
+            header2.append("")
+            header2.append("")
+            header1 += ["star value", "background value", ""]
+        header2 += ["Total", "", "", ""]
+        header1 += ["star value", "background value", "mean star pixel", "mean background pixel"]
+        writer.writerow(header2)
+        writer.writerow(header1)
+
+        for item in backgrounds:
+            bg_npix = 0
+            star_npix = 0
+            row = None
+            sum_star = 0
+            sum_bg = 0
+            for channel in channels:
+                if row is None:
+                    mag = ""
+                    lum = ""
+                    name = ""
+                    row = [item["x"], item["y"], int(item["radius"]+0.5), "", name, mag, lum, ""]
+                    star_npix = int(item["channels"][channel]["star_npix"])
+                    bg_npix = int(item["channels"][channel]["bg_npix"])
+                    row += [star_npix, bg_npix, ""]
+                row += [int(item["channels"][channel]["star"])]
+                row += [int(item["channels"][channel]["bg"])]
+                row += [""]
+
+                sum_star += int(item["channels"][channel]["star"])
+                sum_bg += int(item["channels"][channel]["bg"])
+
+            row += [sum_star, sum_bg, int(sum_star/star_npix), int(sum_bg/bg_npix)]
+            writer.writerow(row)
+
+commands = {
+    "image": (process_image,
+             "build report for clusters",
+             "image.zip stars.json report.csv"),
+}

src/vstarstack/tool/photometry/photometry.py

@@ -15,4 +15,5 @@
 commands = {
     "measure-mag" : ("vstarstack.tool.photometry.measure_mag", "measure star magnitude"),
     "measure-fwhm" : ("vstarstack.tool.photometry.measure_fwhm", "measure full width at half maximum"),
+    "measure-background" : ("vstarstack.tool.photometry.measure_pollution", "measure background light level"),
 }