Splittend in several files

src/river_annotation_tool/mask_canvas.py

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+import numpy as np
+from matplotlib.backends.backend_qtagg import FigureCanvasQTAgg as FigureCanvas
+from matplotlib.figure import Figure
+from PySide6.QtCore import Qt
+from PySide6.QtWidgets import QPushButton, QSlider
+
+
+class MaskCanvas:
+    """Matplotlib canvas with brush-based mask drawing, undo, and erase."""
+
+    def __init__(self, frames, dh: int, dw: int):
+        self.dh = dh
+        self.dw = dw
+
+        self.mask = np.zeros((dh, dw), dtype=np.uint8)
+        self.history: list[np.ndarray] = []
+        self.erase_mode = False
+        self.drawing = False
+
+        self._build_figure(frames)
+        self._build_controls()
+        self._connect_events()
+
+    def _build_figure(self, frames):
+        self.fig = Figure()
+        self.canvas = FigureCanvas(self.fig)
+        self.ax = self.fig.add_subplot(111)
+        self.ax.axis("off")
+        self.img_artist = self.ax.imshow(frames[0])
+        self.mask_artist = self.ax.imshow(np.zeros((self.dh, self.dw, 4)))
+        self.title_text = self.ax.set_title("", fontsize=10, pad=4)
+
+    def _build_controls(self):
+        self.btn_erase = QPushButton("Eraser")
+        self.brush_slider = QSlider(Qt.Horizontal)
+        self.brush_slider.setRange(2, 50)
+        self.brush_slider.setValue(5)
+
+    def _connect_events(self):
+        self.canvas.mpl_connect("button_press_event", self._on_press)
+        self.canvas.mpl_connect("motion_notify_event", self._on_move)
+        self.canvas.mpl_connect("button_release_event", self._on_release)
+        self.btn_erase.clicked.connect(self.toggle_erase)
+
+    # ── clip transition ────────────────────────────────────────────
+    def load_clip(self, frames, dh: int, dw: int, mask=None, title: str = ""):
+        self.dh = dh
+        self.dw = dw
+        self.mask = mask if mask is not None else np.zeros((dh, dw), dtype=np.uint8)
+        self.history = []
+        self.img_artist.set_data(frames[0])
+        self.set_title(title)
+        self.redraw()
+
+    # ── frame / title ──────────────────────────────────────────────
+    def set_frame(self, frame):
+        self.img_artist.set_data(frame)
+        self.canvas.draw_idle()
+
+    def set_title(self, text: str):
+        self.title_text.set_text(text)
+
+    # ── mask ops ───────────────────────────────────────────────────
+    def reset(self, mask=None):
+        self.mask = mask if mask is not None else np.zeros((self.dh, self.dw), dtype=np.uint8)
+        self.history = []
+        self.redraw()
+
+    def redraw(self):
+        rgba = np.zeros((self.dh, self.dw, 4))
+        rgba[..., 1] = self.mask * 0.7
+        rgba[..., 3] = self.mask * 0.4
+        self.mask_artist.set_data(rgba)
+        self.canvas.draw_idle()
+
+    def clear(self):
+        self.mask[:] = 0
+        self.redraw()
+
+    def undo(self):
+        if self.history:
+            self.mask = self.history.pop()
+            self.redraw()
+
+    def toggle_erase(self):
+        self.erase_mode = not self.erase_mode
+        self.btn_erase.setText("Eraser ON" if self.erase_mode else "Eraser")
+
+    def stamp(self, x, y):
+        if x is None or y is None:
+            return
+        self.history.append(self.mask.copy())
+        r = self.brush_slider.value()
+        ix, iy = int(x), int(y)
+        y0, y1 = max(0, iy - r), min(self.dh, iy + r + 1)
+        x0, x1 = max(0, ix - r), min(self.dw, ix + r + 1)
+        Y, X = np.ogrid[y0:y1, x0:x1]
+        circle = (X - ix) ** 2 + (Y - iy) ** 2 <= r**2
+        self.mask[y0:y1, x0:x1][circle] = 0 if self.erase_mode else 1
+        self.redraw()
+
+    # ── mouse events ───────────────────────────────────────────────
+    def _on_press(self, e):
+        if e.xdata is None:
+            return
+        self.drawing = True
+        self.stamp(e.xdata, e.ydata)
+
+    def _on_move(self, e):
+        if self.drawing:
+            self.stamp(e.xdata, e.ydata)
+
+    def _on_release(self, _):
+        self.drawing = False