Add linear interpolation support and tests

Read and honor IMIV_IMGUI_TEST_ENGINE_LINEAR_INTERPOLATION in the UI (imiv_frame.cpp), and parse/emit a linear_interpolation attribute in the test engine (imiv_test_engine.cpp) so test scenarios can control sampling mode via env. Update sampling and OCIO regression tools: sampling scenario steps now set linear_interpolation explicitly instead of using the preferences step (imiv_sampling_regression.py), and the OCIO live-update tool picks a preferred target view (avoiding raw/video when possible) and clarifies failure messages to include the switch mode (imiv_ocio_live_update_regression.py). These changes allow deterministic regression runs that toggle linear/nearest sampling and improve target-view selection for live OCIO tests.

Author: ssh4net

src/imiv/imiv_frame.cpp

@@ -130,6 +130,20 @@ namespace {
             ui_state.ocio_image_color_space = std::string(
                 Strutil::strip(value));
         }
+
+        if (read_env_value("IMIV_IMGUI_TEST_ENGINE_LINEAR_INTERPOLATION",
+                           value)) {
+            const string_view trimmed = Strutil::strip(value);
+            if (trimmed == "1" || Strutil::iequals(trimmed, "true")
+                || Strutil::iequals(trimmed, "yes")
+                || Strutil::iequals(trimmed, "on")) {
+                ui_state.linear_interpolation = true;
+            } else if (trimmed == "0" || Strutil::iequals(trimmed, "false")
+                       || Strutil::iequals(trimmed, "no")
+                       || Strutil::iequals(trimmed, "off")) {
+                ui_state.linear_interpolation = false;
+            }
+        }
     }
 
     void begin_developer_screenshot_request(DeveloperUiState& developer_ui,

src/imiv/imiv_test_engine.cpp

@@ -159,6 +159,8 @@ namespace {
         bool has_display           = false;
         bool has_view              = false;
         bool has_image_color_space = false;
+        bool has_linear_interpolation = false;
+        bool linear_interpolation     = false;
         std::string display;
         std::string view;
         std::string image_color_space;
@@ -376,6 +378,10 @@ namespace {
                 step.ocio.has_image_color_space = true;
                 step.ocio.image_color_space     = ocio_cs_attr.as_string();
             }
+            if (parse_bool_attr(step_node.attribute("linear_interpolation"),
+                                step.ocio.linear_interpolation)) {
+                step.ocio.has_linear_interpolation = true;
+            }
 
             parse_bool_attr(step_node.attribute("screenshot"),
                             step.capture.screenshot);
@@ -909,6 +915,11 @@ namespace {
                 "IMIV_IMGUI_TEST_ENGINE_OCIO_IMAGE_COLOR_SPACE",
                 &ocio.image_color_space);
         }
+        if (ocio.has_linear_interpolation) {
+            const std::string value = ocio.linear_interpolation ? "1" : "0";
+            set_process_env_value(
+                "IMIV_IMGUI_TEST_ENGINE_LINEAR_INTERPOLATION", &value);
+        }
     }
 
     bool write_test_engine_scenario_step_outputs(

src/imiv/tools/imiv_ocio_live_update_regression.py

@@ -177,6 +177,24 @@ def _pick_first_other(values: list[str], current: str) -> str:
     return ""
 
 
+def _pick_preferred_target_view(values: list[str], current: str) -> str:
+    ranked: list[str] = []
+    for value in values:
+        if value == current:
+            continue
+        lowered = value.lower()
+        penalty = 0
+        if "raw" in lowered:
+            penalty += 100
+        if "video" in lowered:
+            penalty += 40
+        ranked.append((penalty, value))
+    if not ranked:
+        return ""
+    ranked.sort(key=lambda item: (item[0], item[1]))
+    return ranked[0][1]
+
+
 def _display_priority(display_name: str, current_display: str) -> tuple[int, str]:
     name = display_name.lower()
     score = 100
@@ -285,7 +303,13 @@ def _resolve_live_targets(
         target_views = display_views.get(target_display, [])
         target_view = args.target_view.strip()
         if not target_view:
-            target_view = initial_view if initial_view in target_views else "default"
+            target_view = _pick_preferred_target_view(target_views, initial_view)
+            if not target_view:
+                target_view = (
+                    target_views[0]
+                    if target_views
+                    else ("default" if initial_view != "default" else initial_view)
+                )
     else:
         raise RuntimeError(f"unsupported switch mode: {switch_mode}")
 
@@ -881,7 +905,7 @@ def main() -> int:
     )
     if static_switch_diff <= 4.0:
         return _fail(
-            "live OCIO view switch did not update the image region "
+            f"live OCIO {switch_mode} switch did not update the image region "
             f"(mean abs RGB diff={static_switch_diff:.4f})"
         )
 
@@ -890,7 +914,7 @@ def main() -> int:
     )
     if target_switch_diff > 2.0:
         return _fail(
-            "live OCIO view switch does not match the settled target view "
+            f"live OCIO {switch_mode} switch does not match the settled target state "
             f"(mean abs RGB diff={target_switch_diff:.4f})"
         )
 

src/imiv/tools/imiv_sampling_regression.py

@@ -129,24 +129,18 @@ def _write_scenario(path: Path, runtime_dir_rel: str) -> None:
     root.set("out_dir", runtime_dir_rel)
     root.set("layout_items", "true")
 
-    _scenario_step(root, "nearest", delay_frames=3, screenshot=True, layout=True)
     _scenario_step(
         root,
-        "open_preferences",
-        key_chord="ctrl+comma",
-        post_action_delay_frames=2,
-    )
-    _scenario_step(
-        root,
-        "enable_linear",
-        set_ref="iv Preferences",
-        item_click="Linear interpolation",
-        post_action_delay_frames=2,
+        "nearest",
+        delay_frames=3,
+        linear_interpolation=False,
+        screenshot=True,
+        layout=True,
     )
     _scenario_step(
         root,
         "linear",
-        key_chord="ctrl+comma",
+        linear_interpolation=True,
         post_action_delay_frames=2,
         screenshot=True,
         layout=True,