Reintroduce translations and theme handling

app/qt/app.py

@@ -7,6 +7,7 @@ from pathlib import Path
 
 from PySide6 import QtGui, QtWidgets
 
+from app.logic import DEFAULTS, LANGUAGE, RESET_EXCLUSIONS_ON_IMAGE_CHANGE
 from .main_window import MainWindow
 
 
@@ -45,6 +46,10 @@ def create_application() -> QtWidgets.QApplication:
 def run() -> int:
     """Run the PySide6 GUI."""
     app = create_application()
-    window = MainWindow()
+    window = MainWindow(
+        language=LANGUAGE,
+        defaults=DEFAULTS.copy(),
+        reset_exclusions=RESET_EXCLUSIONS_ON_IMAGE_CHANGE,
+    )
     window.show()
     return app.exec()

app/qt/image_processor.py

@@ -5,7 +5,7 @@ from __future__ import annotations
 import colorsys
 from dataclasses import dataclass
 from pathlib import Path
-from typing import Iterable, Tuple
+from typing import Dict, Iterable, Tuple
 
 from PIL import Image, ImageDraw
 from PySide6 import QtGui
@@ -20,15 +20,12 @@ class Stats:
     matches_keep: int = 0
     total_keep: int = 0
 
-    def summary(self) -> str:
+    def summary(self, translate) -> str:
         if self.total_all == 0:
-            return "Matches with exclusions: —"
+            return translate("stats.placeholder")
         with_pct = (self.matches_keep / self.total_keep * 100) if self.total_keep else 0.0
         without_pct = (self.matches_all / self.total_all * 100) if self.total_all else 0.0
-        return (
-            f"Matches with exclusions: {with_pct:.1f}%   ·   "
-            f"Matches overall: {without_pct:.1f}%"
-        )
+        return translate("stats.summary", with_pct=with_pct, without_pct=without_pct, excluded_pct=0.0, excluded_match_pct=0.0)
 
 
 class QtImageProcessor:
@@ -42,16 +39,30 @@ class QtImageProcessor:
         self.current_index: int = -1
         self.stats = Stats()
 
-        # HSV thresholds and overlay alpha
-        self.hue_min = 0
-        self.hue_max = 360
-        self.sat_min = 25
-        self.val_min = 15
-        self.val_max = 100
-        self.alpha = 120
+        self.defaults: Dict[str, int] = {
+            "hue_min": 0,
+            "hue_max": 360,
+            "sat_min": 25,
+            "val_min": 15,
+            "val_max": 100,
+            "alpha": 120,
+        }
+        self.hue_min = self.defaults["hue_min"]
+        self.hue_max = self.defaults["hue_max"]
+        self.sat_min = self.defaults["sat_min"]
+        self.val_min = self.defaults["val_min"]
+        self.val_max = self.defaults["val_max"]
+        self.alpha = self.defaults["alpha"]
 
         self.exclude_shapes: list[dict[str, object]] = []
 
+    def set_defaults(self, defaults: dict) -> None:
+        for key in self.defaults:
+            if key in defaults:
+                self.defaults[key] = int(defaults[key])
+        for key, value in self.defaults.items():
+            setattr(self, key, value)
+
     # thresholds -------------------------------------------------------------
 
     def set_threshold(self, key: str, value: int) -> None:

app/qt/main_window.py

@@ -1,4 +1,4 @@
-"""Main PySide6 window emulating the legacy Tk interface."""
+"""Main PySide6 window emulating the legacy Tk interface with translations and themes."""
 
 from __future__ import annotations
 
@@ -7,33 +7,62 @@ from typing import Callable, Dict, List, Tuple
 
 from PySide6 import QtCore, QtGui, QtWidgets
 
+from app.i18n import I18nMixin
 from app.logic import SUPPORTED_IMAGE_EXTENSIONS
 from .image_processor import QtImageProcessor
 
 DEFAULT_COLOUR = "#763e92"
+
 PRESET_COLOURS: List[Tuple[str, str]] = [
-    ("Red", "#ff3b30"),
-    ("Orange", "#ff9500"),
-    ("Yellow", "#ffd60a"),
-    ("Green", "#34c759"),
-    ("Teal", "#5ac8fa"),
-    ("Blue", "#0a84ff"),
-    ("Violet", "#af52de"),
-    ("Magenta", "#ff2d55"),
-    ("White", "#ffffff"),
-    ("Grey", "#8e8e93"),
-    ("Black", "#000000"),
+    ("palette.swatch.red", "#ff3b30"),
+    ("palette.swatch.orange", "#ff9500"),
+    ("palette.swatch.yellow", "#ffd60a"),
+    ("palette.swatch.green", "#34c759"),
+    ("palette.swatch.teal", "#5ac8fa"),
+    ("palette.swatch.blue", "#0a84ff"),
+    ("palette.swatch.violet", "#af52de"),
+    ("palette.swatch.magenta", "#ff2d55"),
+    ("palette.swatch.white", "#ffffff"),
+    ("palette.swatch.grey", "#8e8e93"),
+    ("palette.swatch.black", "#000000"),
 ]
 
-SLIDER_SPECS: List[Tuple[str, str, int, int, int]] = [
-    ("Hue min", "hue_min", 0, 360, 0),
-    ("Hue max", "hue_max", 0, 360, 360),
-    ("Sat min", "sat_min", 0, 100, 25),
-    ("Value min", "val_min", 0, 100, 15),
-    ("Value max", "val_max", 0, 100, 100),
-    ("Overlay alpha", "alpha", 0, 255, 120),
+SLIDER_SPECS: List[Tuple[str, str, int, int]] = [
+    ("sliders.hue_min", "hue_min", 0, 360),
+    ("sliders.hue_max", "hue_max", 0, 360),
+    ("sliders.sat_min", "sat_min", 0, 100),
+    ("sliders.val_min", "val_min", 0, 100),
+    ("sliders.val_max", "val_max", 0, 100),
+    ("sliders.alpha", "alpha", 0, 255),
 ]
 
+THEMES: Dict[str, Dict[str, str]] = {
+    "dark": {
+        "window_bg": "#111216",
+        "panel_bg": "#16171d",
+        "text": "#f7f7fb",
+        "text_muted": "rgba(255,255,255,0.68)",
+        "text_dim": "rgba(255,255,255,0.45)",
+        "accent": "#5168ff",
+        "accent_secondary": "#9a4dff",
+        "titlebar_bg": "#16171d",
+        "border": "rgba(255,255,255,0.08)",
+        "highlight": "#e6b84b",
+    },
+    "light": {
+        "window_bg": "#f3f4fb",
+        "panel_bg": "#ffffff",
+        "text": "#1d1e24",
+        "text_muted": "rgba(29,30,36,0.78)",
+        "text_dim": "rgba(29,30,36,0.55)",
+        "accent": "#5168ff",
+        "accent_secondary": "#9a4dff",
+        "titlebar_bg": "#e9ebf5",
+        "border": "rgba(29,30,36,0.12)",
+        "highlight": "#c56217",
+    },
+}
+
 
 class ToolbarButton(QtWidgets.QPushButton):
     """Rounded toolbar button inspired by the legacy design."""
@@ -62,6 +91,26 @@ class ToolbarButton(QtWidgets.QPushButton):
         )
         self.clicked.connect(callback)
 
+    def apply_theme(self, colours: Dict[str, str]) -> None:
+        self.setStyleSheet(
+            f"""
+            QPushButton {{
+                padding: 8px 16px;
+                border-radius: 10px;
+                border: 1px solid {colours['border']};
+                background-color: rgba(255, 255, 255, 0.04);
+                color: {colours['text']};
+                font-weight: 600;
+            }}
+            QPushButton:hover {{
+                background-color: rgba(255, 255, 255, 0.12);
+            }}
+            QPushButton:pressed {{
+                background-color: rgba(255, 255, 255, 0.18);
+            }}
+            """
+        )
+
 
 class ColourSwatch(QtWidgets.QPushButton):
     """Clickable palette swatch."""
@@ -69,10 +118,14 @@ class ColourSwatch(QtWidgets.QPushButton):
     def __init__(self, name: str, hex_code: str, callback: Callable[[str, str], None], parent: QtWidgets.QWidget | None = None):
         super().__init__(parent)
         self.hex_code = hex_code
-        self.name = name
-        self.setToolTip(f"{name} ({hex_code})")
+        self.name_key = name
+        self.callback = callback
         self.setCursor(QtCore.Qt.PointingHandCursor)
         self.setFixedSize(28, 28)
+        self._apply_colour(hex_code)
+        self.clicked.connect(lambda: callback(hex_code, self.name_key))
+
+    def _apply_colour(self, hex_code: str) -> None:
         self.setStyleSheet(
             f"""
             QPushButton {{
@@ -85,7 +138,20 @@ class ColourSwatch(QtWidgets.QPushButton):
             }}
             """
         )
-        self.clicked.connect(lambda: callback(hex_code, name))
+
+    def apply_theme(self, colours: Dict[str, str]) -> None:
+        self.setStyleSheet(
+            f"""
+            QPushButton {{
+                background-color: {self.hex_code};
+                border: 2px solid {colours['border']};
+                border-radius: 6px;
+            }}
+            QPushButton:hover {{
+                border-color: {colours['accent']};
+            }}
+            """
+        )
 
 
 class SliderControl(QtWidgets.QWidget):
@@ -103,12 +169,10 @@ class SliderControl(QtWidgets.QWidget):
 
         header = QtWidgets.QHBoxLayout()
         header.setContentsMargins(0, 0, 0, 0)
-        title_label = QtWidgets.QLabel(title)
-        title_label.setStyleSheet("color: rgba(255,255,255,0.85); font-weight: 500;")
-        header.addWidget(title_label)
+        self.title_label = QtWidgets.QLabel(title)
+        header.addWidget(self.title_label)
         header.addStretch(1)
         self.value_label = QtWidgets.QLabel(str(initial))
-        self.value_label.setStyleSheet("color: rgba(255,255,255,0.6);")
         header.addWidget(self.value_label)
         layout.addLayout(header)
 
@@ -146,36 +210,26 @@ class SliderControl(QtWidgets.QWidget):
         self.slider.blockSignals(False)
         self.value_label.setText(str(value))
 
-
-class ImageView(QtWidgets.QLabel):
-    """Aspect-ratio aware image view."""
-
-    def __init__(self) -> None:
-        super().__init__()
-        self.setAlignment(QtCore.Qt.AlignCenter)
-        self._pixmap: QtGui.QPixmap | None = None
-
-    def set_image(self, pixmap: QtGui.QPixmap | None) -> None:
-        self._pixmap = pixmap
-        self._rescale()
-
-    def resizeEvent(self, event: QtGui.QResizeEvent) -> None:
-        super().resizeEvent(event)
-        self._rescale()
-
-    def _rescale(self) -> None:
-        if self._pixmap is None:
-            self.setPixmap(QtGui.QPixmap())
-            self.setText("<No image loaded>")
-            self.setStyleSheet("color: rgba(255,255,255,0.45); font-size: 14px;")
-            return
-        target = self._pixmap.scaled(
-            self.size(),
-            QtCore.Qt.KeepAspectRatio,
-            QtCore.Qt.SmoothTransformation,
+    def apply_theme(self, colours: Dict[str, str]) -> None:
+        self.title_label.setStyleSheet(f"color: {colours['text_muted']}; font-weight: 500;")
+        self.value_label.setStyleSheet(f"color: {colours['text_dim']};")
+        self.slider.setStyleSheet(
+            f"""
+            QSlider::groove:horizontal {{
+                border: 1px solid {colours['border']};
+                height: 6px;
+                background: rgba(255,255,255,0.14);
+                border-radius: 4px;
+            }}
+            QSlider::handle:horizontal {{
+                background: {colours['accent_secondary']};
+                border: 1px solid rgba(255,255,255,0.2);
+                width: 14px;
+                margin: -5px 0;
+                border-radius: 7px;
+            }}
+            """
         )
-        self.setPixmap(target)
-        self.setStyleSheet("")
 
 
 class TitleBar(QtWidgets.QWidget):
@@ -190,10 +244,6 @@ class TitleBar(QtWidgets.QWidget):
         self.setCursor(QtCore.Qt.ArrowCursor)
         self.setAutoFillBackground(True)
 
-        palette = self.palette()
-        palette.setColor(QtGui.QPalette.Window, QtGui.QColor("#16171d"))
-        self.setPalette(palette)
-
         layout = QtWidgets.QHBoxLayout(self)
         layout.setContentsMargins(12, 8, 12, 8)
         layout.setSpacing(8)
@@ -201,16 +251,17 @@ class TitleBar(QtWidgets.QWidget):
         logo_path = Path(__file__).resolve().parents[1] / "assets" / "logo.png"
         if logo_path.exists():
             pixmap = QtGui.QPixmap(str(logo_path))
-            logo_label = QtWidgets.QLabel()
-            logo_label.setPixmap(pixmap.scaled(26, 26, QtCore.Qt.KeepAspectRatio, QtCore.Qt.SmoothTransformation))
-            layout.addWidget(logo_label)
+            self.logo_label = QtWidgets.QLabel()
+            self.logo_label.setPixmap(pixmap.scaled(26, 26, QtCore.Qt.KeepAspectRatio, QtCore.Qt.SmoothTransformation))
+            layout.addWidget(self.logo_label)
+        else:
+            self.logo_label = None
 
-        title_label = QtWidgets.QLabel("Interactive Color Range Analyzer")
-        title_label.setStyleSheet("color: #f7f7fb; font-weight: 600;")
-        layout.addWidget(title_label)
+        self.title_label = QtWidgets.QLabel()
+        layout.addWidget(self.title_label)
         layout.addStretch(1)
 
-        self.min_btn = self._create_button("–", "Minimise window")
+        self.min_btn = self._create_button("–", "Minimise")
         self.min_btn.clicked.connect(window.showMinimized)
         layout.addWidget(self.min_btn)
 
@@ -218,15 +269,9 @@ class TitleBar(QtWidgets.QWidget):
         self.max_btn.clicked.connect(window.toggle_maximise)
         layout.addWidget(self.max_btn)
 
-        close_btn = self._create_button("✕", "Close")
-        close_btn.clicked.connect(window.close)
-        close_btn.setStyleSheet(
-            """
-            QPushButton { background: transparent; color: #f7f7fb; border: none; padding: 4px 10px; }
-            QPushButton:hover { background-color: #d0342c; }
-            """
-        )
-        layout.addWidget(close_btn)
+        self.close_btn = self._create_button("✕", "Close")
+        self.close_btn.clicked.connect(window.close)
+        layout.addWidget(self.close_btn)
 
     def _create_button(self, text: str, tooltip: str) -> QtWidgets.QPushButton:
         btn = QtWidgets.QPushButton(text)
@@ -248,6 +293,41 @@ class TitleBar(QtWidgets.QWidget):
         )
         return btn
 
+    def apply_theme(self, colours: Dict[str, str]) -> None:
+        palette = self.palette()
+        palette.setColor(QtGui.QPalette.Window, QtGui.QColor(colours["titlebar_bg"]))
+        self.setPalette(palette)
+        self.title_label.setStyleSheet(f"color: {colours['text']}; font-weight: 600;")
+        hover_bg = "#d0342c" if colours["titlebar_bg"] != "#e9ebf5" else "#e6675a"
+        self.close_btn.setStyleSheet(
+            f"""
+            QPushButton {{
+                background-color: transparent;
+                color: {colours['text']};
+                border: none;
+                padding: 4px 10px;
+            }}
+            QPushButton:hover {{
+                background-color: {hover_bg};
+                color: #ffffff;
+            }}
+            """
+        )
+        for btn in (self.min_btn, self.max_btn):
+            btn.setStyleSheet(
+                f"""
+                QPushButton {{
+                    background-color: transparent;
+                    color: {colours['text']};
+                    border: none;
+                    padding: 4px 10px;
+                }}
+                QPushButton:hover {{
+                    background-color: rgba(0, 0, 0, 0.1);
+                }}
+                """
+            )
+
     def mouseDoubleClickEvent(self, event: QtGui.QMouseEvent) -> None:
         if event.button() == QtCore.Qt.LeftButton:
             self.window.toggle_maximise()
@@ -260,11 +340,13 @@ class TitleBar(QtWidgets.QWidget):
         super().mousePressEvent(event)
 
 
-class MainWindow(QtWidgets.QMainWindow):
+class MainWindow(QtWidgets.QMainWindow, I18nMixin):
     """Main application window containing all controls."""
 
-    def __init__(self) -> None:
+    def __init__(self, language: str, defaults: dict, reset_exclusions: bool) -> None:
         super().__init__()
+        self.init_i18n(language)
+        self.setWindowTitle(self._t("app.title"))
         self.setWindowFlag(QtCore.Qt.FramelessWindowHint)
         self.setWindowFlag(QtCore.Qt.Window)
         self.setAttribute(QtCore.Qt.WA_TranslucentBackground, False)
@@ -276,19 +358,19 @@ class MainWindow(QtWidgets.QMainWindow):
         container_layout.setSpacing(0)
 
         self.title_bar = TitleBar(self)
+        self.title_bar.title_label.setText(self._t("app.title"))
         container_layout.addWidget(self.title_bar)
 
         self.content = QtWidgets.QWidget()
-        self.content.setStyleSheet("background-color: #111216;")
-        content_layout = QtWidgets.QVBoxLayout(self.content)
-        content_layout.setContentsMargins(24, 24, 24, 24)
-        content_layout.setSpacing(18)
+        self.content_layout = QtWidgets.QVBoxLayout(self.content)
+        self.content_layout.setContentsMargins(24, 24, 24, 24)
+        self.content_layout.setSpacing(18)
 
-        content_layout.addLayout(self._build_toolbar())
-        content_layout.addLayout(self._build_palette())
-        content_layout.addLayout(self._build_sliders())
-        content_layout.addWidget(self._build_previews(), 1)
-        content_layout.addLayout(self._build_status_section())
+        self.content_layout.addLayout(self._build_toolbar())
+        self.content_layout.addLayout(self._build_palette())
+        self.content_layout.addLayout(self._build_sliders())
+        self.content_layout.addWidget(self._build_previews(), 1)
+        self.content_layout.addLayout(self._build_status_section())
 
         container_layout.addWidget(self.content, 1)
         self.setCentralWidget(container)
@@ -297,11 +379,16 @@ class MainWindow(QtWidgets.QMainWindow):
         self._current_image_path: Path | None = None
         self._current_colour = DEFAULT_COLOUR
         self._toolbar_actions: Dict[str, Callable[[], None]] = {}
-        self._slider_controls: Dict[str, SliderControl] = {}
         self._register_default_actions()
-        self._update_colour_display(DEFAULT_COLOUR, "Default colour")
 
         self.processor = QtImageProcessor()
+        self.processor.set_defaults(defaults)
+        self.processor.reset_exclusions_on_switch = reset_exclusions
+        self._sync_sliders_from_processor()
+        self._update_colour_display(DEFAULT_COLOUR, self._t("palette.current"))
+
+        self.current_theme = "dark"
+        self._apply_theme(self.current_theme)
 
     # Window control helpers -------------------------------------------------
 
@@ -330,26 +417,26 @@ class MainWindow(QtWidgets.QMainWindow):
         layout.setSpacing(12)
 
         buttons = [
-            ("open_image", "🖼", "Open image…"),
-            ("open_folder", "📂", "Open folder…"),
-            ("choose_color", "🎨", "Choose colour"),
-            ("pick_from_image", "🖱", "Pick from image"),
-            ("save_overlay", "💾", "Save overlay"),
-            ("toggle_free_draw", "△", "Toggle free-draw"),
-            ("clear_excludes", "🧹", "Clear exclusions"),
-            ("undo_exclude", "↩", "Undo last exclusion"),
-            ("reset_sliders", "🔄", "Reset sliders"),
-            ("toggle_theme", "🌓", "Toggle theme"),
+            ("open_image", "🖼", "toolbar.open_image"),
+            ("open_folder", "📂", "toolbar.open_folder"),
+            ("choose_color", "🎨", "toolbar.choose_color"),
+            ("pick_from_image", "🖱", "toolbar.pick_from_image"),
+            ("save_overlay", "💾", "toolbar.save_overlay"),
+            ("toggle_free_draw", "△", "toolbar.toggle_free_draw"),
+            ("clear_excludes", "🧹", "toolbar.clear_excludes"),
+            ("undo_exclude", "↩", "toolbar.undo_exclude"),
+            ("reset_sliders", "🔄", "toolbar.reset_sliders"),
+            ("toggle_theme", "🌓", "toolbar.toggle_theme"),
         ]
         self._toolbar_buttons: Dict[str, ToolbarButton] = {}
-        for key, icon_txt, label in buttons:
+        for key, icon_txt, text_key in buttons:
+            label = self._t(text_key)
             button = ToolbarButton(icon_txt, label, lambda k=key: self._invoke_action(k))
             layout.addWidget(button)
             self._toolbar_buttons[key] = button
 
         layout.addStretch(1)
-        self.status_label = QtWidgets.QLabel("No image loaded")
-        self.status_label.setStyleSheet("color: rgba(255,255,255,0.7); font-weight: 500;")
+        self.status_label = QtWidgets.QLabel(self._t("status.no_file"))
         layout.addWidget(self.status_label, 0, QtCore.Qt.AlignRight)
         return layout
 
@@ -360,9 +447,8 @@ class MainWindow(QtWidgets.QMainWindow):
 
         current_group = QtWidgets.QHBoxLayout()
         current_group.setSpacing(8)
-        current_label = QtWidgets.QLabel("Current colour")
-        current_label.setStyleSheet("color: rgba(255,255,255,0.75); font-weight: 500;")
-        current_group.addWidget(current_label)
+        self.current_label = QtWidgets.QLabel(self._t("palette.current"))
+        current_group.addWidget(self.current_label)
 
         self.current_colour_swatch = QtWidgets.QLabel()
         self.current_colour_swatch.setFixedSize(28, 28)
@@ -370,19 +456,19 @@ class MainWindow(QtWidgets.QMainWindow):
         current_group.addWidget(self.current_colour_swatch)
 
         self.current_colour_label = QtWidgets.QLabel(f"({DEFAULT_COLOUR})")
-        self.current_colour_label.setStyleSheet("color: rgba(255,255,255,0.65);")
         current_group.addWidget(self.current_colour_label)
         layout.addLayout(current_group)
 
-        more_label = QtWidgets.QLabel("More colours")
-        more_label.setStyleSheet("color: rgba(255,255,255,0.65); font-weight: 500;")
-        layout.addWidget(more_label)
+        self.more_label = QtWidgets.QLabel(self._t("palette.more"))
+        layout.addWidget(self.more_label)
 
         swatch_container = QtWidgets.QHBoxLayout()
         swatch_container.setSpacing(8)
-        for name, hex_code in PRESET_COLOURS:
-            swatch = ColourSwatch(name, hex_code, self._update_colour_display)
+        self.swatch_buttons: List[ColourSwatch] = []
+        for name_key, hex_code in PRESET_COLOURS:
+            swatch = ColourSwatch(self._t(name_key), hex_code, self._update_colour_display)
             swatch_container.addWidget(swatch)
+            self.swatch_buttons.append(swatch)
         layout.addLayout(swatch_container)
         layout.addStretch(1)
         return layout
@@ -390,12 +476,13 @@ class MainWindow(QtWidgets.QMainWindow):
     def _build_sliders(self) -> QtWidgets.QHBoxLayout:
         layout = QtWidgets.QHBoxLayout()
         layout.setSpacing(16)
-        self._slider_controls.clear()
-        for title, key, minimum, maximum, initial in SLIDER_SPECS:
-            control = SliderControl(title, key, minimum, maximum, initial)
+        self._slider_controls: Dict[str, SliderControl] = {}
+        for key, attr, minimum, maximum in SLIDER_SPECS:
+            initial = int(getattr(self.processor, attr))
+            control = SliderControl(self._t(key), attr, minimum, maximum, initial)
             control.value_changed.connect(self._on_slider_change)
             layout.addWidget(control)
-            self._slider_controls[key] = control
+            self._slider_controls[attr] = control
         return layout
 
     def _build_previews(self) -> QtWidgets.QWidget:
@@ -403,41 +490,26 @@ class MainWindow(QtWidgets.QMainWindow):
         layout = QtWidgets.QGridLayout(container)
         layout.setContentsMargins(0, 0, 0, 0)
         layout.setHorizontalSpacing(16)
-        layout.setVerticalSpacing(0)
 
         self.prev_button = QtWidgets.QToolButton()
         self.prev_button.setText("◀")
         self.prev_button.setCursor(QtCore.Qt.PointingHandCursor)
         self.prev_button.setFixedSize(44, 44)
-        self.prev_button.setStyleSheet(
-            """
-            QToolButton {
-                border-radius: 22px;
-                background-color: rgba(255, 255, 255, 0.08);
-                color: #f7f7fb;
-                font-size: 18px;
-            }
-            QToolButton:hover {
-                background-color: rgba(255, 255, 255, 0.16);
-            }
-            """
-        )
         self.prev_button.clicked.connect(lambda: self._invoke_action("show_previous_image"))
         layout.addWidget(self.prev_button, 0, 0, QtCore.Qt.AlignVCenter)
 
-        self.image_view = ImageView()
-        self.image_view.setStyleSheet("border: 1px solid rgba(255,255,255,0.08); border-radius: 12px;")
+        self.image_view = QtWidgets.QLabel("<No image loaded>")
+        self.image_view.setAlignment(QtCore.Qt.AlignCenter)
         layout.addWidget(self.image_view, 0, 1)
 
-        self.overlay_view = ImageView()
-        self.overlay_view.setStyleSheet("border: 1px solid rgba(255,255,255,0.08); border-radius: 12px;")
+        self.overlay_view = QtWidgets.QLabel("<No image loaded>")
+        self.overlay_view.setAlignment(QtCore.Qt.AlignCenter)
         layout.addWidget(self.overlay_view, 0, 2)
 
         self.next_button = QtWidgets.QToolButton()
         self.next_button.setText("▶")
         self.next_button.setCursor(QtCore.Qt.PointingHandCursor)
         self.next_button.setFixedSize(44, 44)
-        self.next_button.setStyleSheet(self.prev_button.styleSheet())
         self.next_button.clicked.connect(lambda: self._invoke_action("show_next_image"))
         layout.addWidget(self.next_button, 0, 3, QtCore.Qt.AlignVCenter)
         layout.setColumnStretch(1, 1)
@@ -451,12 +523,10 @@ class MainWindow(QtWidgets.QMainWindow):
 
         self.filename_label = QtWidgets.QLabel("—")
         self.filename_label.setAlignment(QtCore.Qt.AlignCenter)
-        self.filename_label.setStyleSheet("color: rgba(255,255,255,0.85); font-weight: 600;")
         layout.addWidget(self.filename_label)
 
-        self.ratio_label = QtWidgets.QLabel("Matches with exclusions: —")
+        self.ratio_label = QtWidgets.QLabel(self._t("stats.placeholder"))
         self.ratio_label.setAlignment(QtCore.Qt.AlignCenter)
-        self.ratio_label.setStyleSheet("color: #e6b84b; font-weight: 600;")
         layout.addWidget(self.ratio_label)
         return layout
 
@@ -473,7 +543,7 @@ class MainWindow(QtWidgets.QMainWindow):
             "clear_excludes": self._coming_soon,
             "undo_exclude": self._coming_soon,
             "reset_sliders": self._reset_sliders,
-            "toggle_theme": self._coming_soon,
+            "toggle_theme": self.toggle_theme,
             "show_previous_image": self.show_previous_image,
             "show_next_image": self.show_next_image,
         }
@@ -487,20 +557,20 @@ class MainWindow(QtWidgets.QMainWindow):
 
     def open_image(self) -> None:
         filters = "Images (*.png *.jpg *.jpeg *.bmp *.webp)"
-        path_str, _ = QtWidgets.QFileDialog.getOpenFileName(self, "Select image", "", filters)
+        path_str, _ = QtWidgets.QFileDialog.getOpenFileName(self, self._t("dialog.open_image_title"), "", filters)
         if not path_str:
             return
         path = Path(path_str)
         try:
             self.processor.load_single_image(path)
-        except Exception as exc:
-            QtWidgets.QMessageBox.warning(self, "ICRA", f"Unable to open the selected image.\n{exc}")
+        except Exception as exc:  # pragma: no cover - user feedback
+            QtWidgets.QMessageBox.warning(self, self._t("dialog.error_title"), str(exc))
             return
         self._current_image_path = path
         self._refresh_views()
 
     def open_folder(self) -> None:
-        directory = QtWidgets.QFileDialog.getExistingDirectory(self, "Select image folder")
+        directory = QtWidgets.QFileDialog.getExistingDirectory(self, self._t("dialog.open_folder_title"))
         if not directory:
             return
         folder = Path(directory)
@@ -509,19 +579,19 @@ class MainWindow(QtWidgets.QMainWindow):
             key=lambda p: p.name.lower(),
         )
         if not paths:
-            QtWidgets.QMessageBox.information(self, "ICRA", "No supported image files found in the selected folder.")
+            QtWidgets.QMessageBox.information(self, self._t("dialog.info_title"), self._t("dialog.folder_empty"))
             return
         try:
             self.processor.load_folder(paths)
         except ValueError as exc:
-            QtWidgets.QMessageBox.information(self, "ICRA", str(exc))
+            QtWidgets.QMessageBox.information(self, self._t("dialog.info_title"), str(exc))
             return
         self._current_image_path = paths[0]
         self._refresh_views()
 
     def show_previous_image(self) -> None:
         if not self.processor.preview_paths:
-            self._coming_soon()
+            QtWidgets.QMessageBox.information(self, self._t("dialog.info_title"), self._t("dialog.no_image_loaded"))
             return
         self.processor.previous_image()
         self._current_image_path = self.processor.preview_paths[self.processor.current_index]
@@ -529,7 +599,7 @@ class MainWindow(QtWidgets.QMainWindow):
 
     def show_next_image(self) -> None:
         if not self.processor.preview_paths:
-            self._coming_soon()
+            QtWidgets.QMessageBox.information(self, self._t("dialog.info_title"), self._t("dialog.no_image_loaded"))
             return
         self.processor.next_image()
         self._current_image_path = self.processor.preview_paths[self.processor.current_index]
@@ -544,46 +614,87 @@ class MainWindow(QtWidgets.QMainWindow):
         self.status_label.setText(f"{label}: {hex_code}")
 
     def _on_slider_change(self, key: str, value: int) -> None:
-        formatted = key.replace("_", " ").title()
         self.processor.set_threshold(key, value)
-        self.status_label.setText(f"{formatted} → {value}")
+        formatted = self._t("status.defaults_restored")
+        self.status_label.setText(f"{formatted} ({key} → {value})")
         self._refresh_overlay_only()
 
     def _reset_sliders(self) -> None:
-        for _, key, _, _, initial in SLIDER_SPECS:
-            control = self._slider_controls.get(key)
+        for _, attr, _, _ in SLIDER_SPECS:
+            control = self._slider_controls.get(attr)
             if control:
-                control.set_value(initial)
-                self.processor.set_threshold(key, initial)
-        self.status_label.setText("Sliders reset to defaults")
+                default_value = int(getattr(self.processor, attr))
+                control.set_value(default_value)
+        self.status_label.setText(self._t("status.defaults_restored"))
         self._refresh_overlay_only()
 
     def _coming_soon(self) -> None:
         QtWidgets.QMessageBox.information(
             self,
-            "Coming soon",
-            "This action is not yet wired up in the PySide6 migration prototype.",
+            self._t("dialog.info_title"),
+            "Feature coming soon in the PySide6 migration.",
         )
 
-    # view refresh -----------------------------------------------------------
+    def toggle_theme(self) -> None:
+        self.current_theme = "light" if self.current_theme == "dark" else "dark"
+        self._apply_theme(self.current_theme)
+
+    def _apply_theme(self, mode: str) -> None:
+        colours = THEMES[mode]
+        self.content.setStyleSheet(f"background-color: {colours['window_bg']};")
+        self.image_view.setStyleSheet(f"border: 1px solid {colours['border']}; border-radius: 12px; color: {colours['text_dim']};")
+        self.overlay_view.setStyleSheet(f"border: 1px solid {colours['border']}; border-radius: 12px; color: {colours['text_dim']};")
+
+        self.status_label.setStyleSheet(f"color: {colours['text_muted']}; font-weight: 500;")
+        self.current_label.setStyleSheet(f"color: {colours['text_muted']}; font-weight: 500;")
+        self.current_colour_label.setStyleSheet(f"color: {colours['text_dim']};")
+        self.more_label.setStyleSheet(f"color: {colours['text_muted']}; font-weight: 500;")
+        self.filename_label.setStyleSheet(f"color: {colours['text']}; font-weight: 600;")
+        self.ratio_label.setStyleSheet(f"color: {colours['highlight']}; font-weight: 600;")
+
+        for button in self._toolbar_buttons.values():
+            button.apply_theme(colours)
+        for swatch in self.swatch_buttons:
+            swatch.apply_theme(colours)
+        for control in self._slider_controls.values():
+            control.apply_theme(colours)
+
+        style_button = (
+            f"QToolButton {{ border-radius: 22px; background-color: {colours['panel_bg']}; "
+            f"border: 1px solid {colours['border']}; color: {colours['text']}; }}"
+            f"QToolButton:hover {{ background-color: {colours['accent_secondary']}; color: white; }}"
+        )
+        self.prev_button.setStyleSheet(style_button)
+        self.next_button.setStyleSheet(style_button)
+
+        self.title_bar.apply_theme(colours)
+
+    def _sync_sliders_from_processor(self) -> None:
+        for _, attr, _, _ in SLIDER_SPECS:
+            control = self._slider_controls.get(attr)
+            if control:
+                control.set_value(int(getattr(self.processor, attr)))
 
     def _refresh_views(self) -> None:
         preview_pix = self.processor.preview_pixmap()
         overlay_pix = self.processor.overlay_pixmap()
-        self.image_view.set_image(preview_pix)
-        self.overlay_view.set_image(overlay_pix)
+        self.image_view.setPixmap(preview_pix)
+        self.overlay_view.setPixmap(overlay_pix)
         if self._current_image_path and self.processor.preview_img:
             width, height = self.processor.preview_img.size
+            total = len(self.processor.preview_paths)
+            position = f" [{self.processor.current_index + 1}/{total}]" if total > 1 else ""
+            dimensions = f"{width}×{height}"
             self.status_label.setText(
-                f"{self._current_image_path.name}  ·  {width}×{height}"
+                self._t("status.loaded", name=self._current_image_path.name, dimensions=dimensions, position=position)
             )
             self.filename_label.setText(
-                f"{self._current_image_path.name}  ({width}×{height})"
+                self._t("status.filename_label", name=self._current_image_path.name, dimensions=dimensions, position=position)
             )
-        self.ratio_label.setText(self.processor.stats.summary())
+        self.ratio_label.setText(self.processor.stats.summary(self._t))
 
     def _refresh_overlay_only(self) -> None:
         if self.processor.preview_img is None:
             return
-        self.overlay_view.set_image(self.processor.overlay_pixmap())
-        self.ratio_label.setText(self.processor.stats.summary())
+        self.overlay_view.setPixmap(self.processor.overlay_pixmap())
+        self.ratio_label.setText(self.processor.stats.summary(self._t))