feat(gui): add shared zoomable image preview

tests/test_gui.py

@@ -54,8 +54,10 @@ from app.gui import (
     GenerateWorker,
     GenerateTab,
     ForcedUpdateDialog,
+    ImageStudioPreviewDialog,
     ImageStudioTab,
     MainWindow,
+    ProductSuitePreviewDialog,
     ProductSuiteTab,
     SettingsTab,
     TAB_STYLE,
@@ -4515,6 +4517,121 @@ class GuiTests(TempDirMixin, unittest.TestCase):
 
         self.assert_removed(temp_dir)
 
+    def test_shared_image_preview_defaults_to_fit_and_keeps_fixed_zoom_on_resize(self):
+        with self.make_temp_dir() as temp_dir:
+            image_path = self.write_test_image(
+                os.path.join(temp_dir, "suite-large.jpg"),
+                width=1200,
+                height=800,
+            )
+            dialog = ProductSuitePreviewDialog(image_path, "商品原图预览")
+            self.addCleanup(dialog.close)
+            dialog.resize(600, 450)
+            dialog.show()
+            QApplication.processEvents()
+            dialog._resize_timer.stop()
+            dialog._render()
+
+            fit_pixmap = dialog.image_label.pixmap()
+            viewport = dialog.scroll.viewport().size()
+            self.assertTrue(dialog.fit_to_window)
+            self.assertEqual("适应窗口", dialog.zoom_label.text())
+            self.assertIn("1200x800", dialog.windowTitle())
+            self.assertLessEqual(fit_pixmap.width(), viewport.width())
+            self.assertLessEqual(fit_pixmap.height(), viewport.height())
+            self.assertAlmostEqual(1.5, fit_pixmap.width() / fit_pixmap.height(), places=1)
+
+            dialog.show_actual_size()
+            QApplication.processEvents()
+            self.assertFalse(dialog.fit_to_window)
+            self.assertEqual("100%", dialog.zoom_label.text())
+            self.assertEqual(QSize(1200, 800), dialog.image_label.pixmap().size())
+            self.assertEqual(QSize(1200, 800), dialog.image_label.size())
+            self.assertGreater(dialog.scroll.horizontalScrollBar().maximum(), 0)
+            self.assertGreater(dialog.scroll.verticalScrollBar().maximum(), 0)
+
+            dialog.resize(520, 360)
+            QApplication.processEvents()
+            dialog._resize_timer.stop()
+            dialog._render()
+            self.assertEqual(QSize(1200, 800), dialog.image_label.pixmap().size())
+
+            dialog.show_fit()
+            self.assertTrue(dialog.fit_to_window)
+            self.assertEqual("适应窗口", dialog.zoom_label.text())
+            self.assertLessEqual(
+                dialog.image_label.pixmap().width(),
+                dialog.scroll.viewport().width(),
+            )
+            self.assertLessEqual(
+                dialog.image_label.pixmap().height(),
+                dialog.scroll.viewport().height(),
+            )
+
+        self.assert_removed(temp_dir)
+
+    def test_shared_image_preview_bounds_zoom_and_does_not_enlarge_small_fit_image(self):
+        with self.make_temp_dir() as temp_dir:
+            image_path = self.write_test_image(
+                os.path.join(temp_dir, "suite-small.jpg"),
+                width=200,
+                height=100,
+            )
+            dialog = ProductSuitePreviewDialog(image_path, "图片预览")
+            self.addCleanup(dialog.close)
+            dialog.resize(700, 500)
+            dialog.show()
+            QApplication.processEvents()
+            dialog._resize_timer.stop()
+            dialog._render()
+
+            self.assertEqual(QSize(200, 100), dialog.image_label.pixmap().size())
+            for _index in range(20):
+                dialog.zoom_out()
+            self.assertEqual(0.25, dialog.zoom_factor)
+            self.assertEqual("25%", dialog.zoom_label.text())
+            self.assertFalse(dialog.zoom_out_button.isEnabled())
+
+            for _index in range(20):
+                dialog.zoom_in()
+            self.assertEqual(4.0, dialog.zoom_factor)
+            self.assertEqual("400%", dialog.zoom_label.text())
+            self.assertFalse(dialog.zoom_in_button.isEnabled())
+            self.assertEqual(QSize(800, 400), dialog.image_label.pixmap().size())
+
+        self.assert_removed(temp_dir)
+
+    def test_shared_image_preview_legacy_wrapper_and_missing_file_state(self):
+        with self.make_temp_dir() as temp_dir:
+            image_path = self.write_test_image(
+                os.path.join(temp_dir, "legacy.jpg"),
+                width=320,
+                height=240,
+            )
+            asset = SimpleNamespace(id=7, kind="original", local_path=image_path)
+            legacy = ImageStudioPreviewDialog(asset)
+            self.addCleanup(legacy.close)
+            legacy.show()
+            QApplication.processEvents()
+            legacy._resize_timer.stop()
+            legacy._render()
+
+            self.assertIn("AI工场图片预览", legacy.windowTitle())
+            self.assertIn("320x240", legacy.windowTitle())
+            self.assertEqual("适应窗口", legacy.zoom_label.text())
+
+            missing_path = os.path.join(temp_dir, "missing-private-name.jpg")
+            missing = ProductSuitePreviewDialog(missing_path, "商品原图预览")
+            self.addCleanup(missing.close)
+            missing._render()
+            self.assertEqual("图片文件不存在或无法读取", missing.image_label.text())
+            self.assertEqual("无法预览", missing.zoom_label.text())
+            self.assertFalse(missing.fit_button.isEnabled())
+            self.assertFalse(missing.actual_size_button.isEnabled())
+            self.assertNotIn(missing_path, missing.windowTitle())
+
+        self.assert_removed(temp_dir)
+
     def test_cover_gallery_previous_next_switch_visible_tasks_without_resizing(self):
         with self.make_temp_dir() as temp_dir:
             cfg, account, tasks, canonicals, _archives = self._cover_gallery_task_set(temp_dir, count=3)