diff --git a/viewer/JFJochImageReadingWorker.cpp b/viewer/JFJochImageReadingWorker.cpp
index a86e4619..0e8de2c5 100644
--- a/viewer/JFJochImageReadingWorker.cpp
+++ b/viewer/JFJochImageReadingWorker.cpp
@@ -90,6 +90,7 @@ JFJochImageReadingWorker::JFJochImageReadingWorker(const SpotFindingSettings &se
       azint_settings(experiment.GetAzimuthalIntegrationSettings()) {
     qRegisterMetaType<QVector<QRect>>("QVector<QRect>");
     qRegisterMetaType<BrokerStatus>("BrokerStatus");
+    qRegisterMetaType<ROIDefinition>("ROIDefinition");
     spot_finding_settings = settings;
 
     indexing = std::make_unique<IndexerThreadPool>(indexing_settings);
@@ -382,8 +383,16 @@ void JFJochImageReadingWorker::LoadImage_i(int64_t image_number, int64_t summati
 
         auto end = std::chrono::high_resolution_clock::now();
 
-        if (auto_reanalyze)
+        if (auto_reanalyze) {
             ReanalyzeImage_i();
+        } else if (image_analysis && !curr_experiment.ROI().empty()) {
+            // ROIs are wanted even when a full re-analysis is not; compute only those.
+            try {
+                image_analysis->AnalyzeROIOnly(current_image_ptr->ImageData());
+            } catch (const std::exception &e) {
+                logger.Error("ROI-only analysis failed: {}", e.what());
+            }
+        }
 
         auto end_analysis = std::chrono::high_resolution_clock::now();
 
@@ -580,6 +589,40 @@ void JFJochImageReadingWorker::UpdateAzintSettings(const AzimuthalIntegrationSet
     UpdateDataset_i(std::nullopt);
 }
 
+void JFJochImageReadingWorker::SetROIDefinition(const ROIDefinition &rois) {
+    QMutexLocker locker(&m);
+    SetROIDefinition_i(rois);
+}
+
+void JFJochImageReadingWorker::SetROIDefinition_i(const ROIDefinition &rois) {
+    // The worker experiment is the source of truth; the analysis ROI engine is rebuilt
+    // for it so newly loaded images pick up the change automatically.
+    curr_experiment.ROI().SetROI(rois);
+    if (image_analysis)
+        image_analysis->RebuildROI();
+
+    if (!current_image_ptr)
+        return;
+
+    // Mutate the dataset too, so the canvas (which draws image->Dataset().experiment.ROI())
+    // reflects the edit, then recompute only the ROIs for the current image.
+    auto mutable_dataset = current_image_ptr->CreateMutableDataset();
+    mutable_dataset->experiment.ROI().SetROI(rois);
+    std::shared_ptr<const JFJochReaderDataset> dataset = mutable_dataset;
+    current_image_ptr = std::make_shared<JFJochReaderImage>(current_image_ptr->ImageData(), dataset);
+
+    if (image_analysis) {
+        try {
+            image_analysis->RunROIOnly(current_image_ptr->ImageData());
+        } catch (const std::exception &e) {
+            logger.Error("ROI-only analysis failed: {}", e.what());
+        }
+    }
+
+    emit datasetLoaded(dataset);
+    emit imageLoaded(current_image_ptr);
+}
+
 void JFJochImageReadingWorker::UpdateUserMask_i(const std::vector<uint32_t> &mask) {
     std::shared_ptr<const JFJochReaderDataset> dataset;
     if (http_mode) {
diff --git a/viewer/JFJochImageReadingWorker.h b/viewer/JFJochImageReadingWorker.h
index 07144f52..3db9e495 100644
--- a/viewer/JFJochImageReadingWorker.h
+++ b/viewer/JFJochImageReadingWorker.h
@@ -31,6 +31,7 @@ Q_DECLARE_METATYPE(AzimuthalIntegrationSettings)
 Q_DECLARE_METATYPE(UnitCell)
 Q_DECLARE_METATYPE(std::shared_ptr<const SimpleImage>)
 Q_DECLARE_METATYPE(BrokerStatus)
+Q_DECLARE_METATYPE(ROIDefinition)
 
 class JFJochImageReadingWorker : public QObject {
     Q_OBJECT
@@ -117,6 +118,7 @@ private:
     void UpdateDataset_i(const std::optional<DiffractionExperiment>& experiment);
     void UpdateAzint_i(const JFJochReaderDataset *dataset);
     void UpdateUserMask_i(const std::vector<uint32_t> &mask);
+    void SetROIDefinition_i(const ROIDefinition &rois);
     void setAutoLoadMode_i(AutoloadMode mode);
 
 signals:
@@ -164,6 +166,8 @@ public slots:
     void AddROIToUserMask();
     void SubtractROIFromUserMask();
 
+    void SetROIDefinition(const ROIDefinition &rois);
+
     void SaveUserMaskTIFF(QString filename);
     void UploadUserMask();
     void ClearUserMask();