Fix star detection

src/vstarstack/library/stars/detect.py

@@ -26,6 +26,7 @@
     "BORDER_WIDTH" : 10,
     "MIN_STAR_R" : 2,
     "MAX_STAR_R" : 20,
+    "SAFETY_THRESHOLD" : 1e-4,
 }
 
 def calculate_brightness(image : np.ndarray, x : int, y : int, r : int):
@@ -36,27 +37,25 @@ def calculate_brightness(image : np.ndarray, x : int, y : int, r : int):
     pos_mask = np.zeros(patch.shape)
     cv2.circle(pos_mask, (r, r), r, 1, -1)
     masked = patch * pos_mask
+    masked = np.clip(masked, 0, None)
     brightness = math.sqrt(np.sum(masked) / math.pi)
     return brightness
 
-def _threshold(image, radius, ratio):
-    kernel = np.zeros((2*radius+1, 2*radius+1))
-    cv2.circle(kernel, (radius, radius), radius, 1, -1)
-    kernel = kernel / np.sum(kernel)
-    filtered = cv2.filter2D(image, ddepth=-1, kernel=kernel)
-    mask = (image > filtered*ratio).astype('uint8')
+def _threshold(image, radius, ratio, safety_threshold):
+    filtered = cv2.GaussianBlur(image, (2*radius+1, 2*radius+1), 0)
+    mask = (image > filtered*ratio + safety_threshold).astype('uint8')
     return mask
 
 def _find_stars(gray_image : np.ndarray):
     """Find stars on image"""
     shape = gray_image.shape
 
     gray_image = cv2.GaussianBlur(gray_image, (3, 3), 0)
-    gray_image = (gray_image / np.amax(gray_image) * 255).astype('uint8')
 
     thresh = _threshold(gray_image, _detector_cfg["THRESHOLD_BLOCK_SIZE"],
-                                    _detector_cfg["THRESHOLD_COEFF"])
-
+                                    _detector_cfg["THRESHOLD_COEFF"],
+                                    _detector_cfg["SAFETY_THRESHOLD"])
+
     kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (3,3))
     blob = cv2.morphologyEx(thresh, cv2.MORPH_OPEN, kernel)
     kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (5,5))
@@ -112,7 +111,8 @@ def configure_detector(*,
                        max_r = None,
                        border = None,
                        thresh_block_size = None,
-                       thresh_coeff = None):
+                       thresh_coeff = None,
+                       safety_threshold = None):
     """Configure detector parameters"""
     global _detector_cfg
     if min_r is not None:
@@ -125,3 +125,5 @@ def configure_detector(*,
         _detector_cfg["THRESHOLD_BLOCK_SIZE"] = thresh_block_size
     if thresh_coeff is not None:
         _detector_cfg["THRESHOLD_COEFF"] = thresh_coeff
+    if safety_threshold is not None:
+        _detector_cfg["SAFETY_THRESHOLD"] = safety_threshold

tests/test_stars_pipeline.py

@@ -122,5 +122,7 @@ def test_1():
     merged = vstarstack.library.merge.simple_add(source)
     layer,_ = merged.get_channel("L")
 
+    import matplotlib.pyplot as plt
+
     merged_stars = vstarstack.library.stars.detect.detect_stars(layer)
     assert len(merged_stars) == 4