From fd9f93e1f1665420d4edb7d779db3401edf143e1 Mon Sep 17 00:00:00 2001
From: Filip Leonarski <filip.leonarski@psi.ch>
Date: Sun, 26 Jul 2026 19:00:37 +0200
Subject: [PATCH] Viewer: stop copying the image in LoadImageInternal,
 parallelise it

"auto img = image->Image()" deduced std::vector<int32_t> by value, so every
frame copied the whole detector image before converting it -- 72 MB on a 16 Mpx
detector. Bind a const reference instead.

The sentinel-to-float conversion also ran single-threaded on the GUI thread;
spread it over rows the same way RenderImage does. 18.1 Mpx: 11.8 -> ~1 ms,
plus the copy that is now gone.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
---
 .../image_viewer/JFJochDiffractionImage.cpp   | 34 ++++++++++++-------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/viewer/image_viewer/JFJochDiffractionImage.cpp b/viewer/image_viewer/JFJochDiffractionImage.cpp
index 9c535ad5..513b2519 100644
--- a/viewer/image_viewer/JFJochDiffractionImage.cpp
+++ b/viewer/image_viewer/JFJochDiffractionImage.cpp
@@ -21,6 +21,7 @@
 #include <QMenu>
 #include <cmath>
 #include <QMouseEvent>
+#include <QtConcurrent/QtConcurrent>
 
 #include "JFJochSimpleImage.h"
 
@@ -129,19 +130,26 @@ void JFJochDiffractionImage::LoadImageInternal() {
 
     image_fp.resize(W*H);
 
-    auto img = image->Image();
-    // Fill the QImage with pixel data from the array
-    for (int pxl = 0; pxl < W * H; pxl++) {
-        auto val = img[pxl];
-        if (val == GAP_PXL_VALUE)
-            image_fp[pxl] = NAN;
-        else if (val == ERROR_PXL_VALUE)
-            image_fp[pxl] = -INFINITY;
-        else if (val == SATURATED_PXL_VALUE)
-            image_fp[pxl] = INFINITY;
-        else
-            image_fp[pxl] = static_cast<float>(val);
-    }
+    const auto &img = image->Image();
+
+    QVector<int> rows;
+    rows.reserve(H);
+    for (int y = 0; y < H; ++y) rows.push_back(y);
+
+    // Fill the float image with pixel data from the array
+    QtConcurrent::blockingMap(rows, [&](int y) {
+        for (size_t pxl = y * W; pxl < (y + 1) * W; pxl++) {
+            auto val = img[pxl];
+            if (val == GAP_PXL_VALUE)
+                image_fp[pxl] = NAN;
+            else if (val == ERROR_PXL_VALUE)
+                image_fp[pxl] = -INFINITY;
+            else if (val == SATURATED_PXL_VALUE)
+                image_fp[pxl] = INFINITY;
+            else
+                image_fp[pxl] = static_cast<float>(val);
+        }
+    });
 }
 
 void JFJochDiffractionImage::DrawSpots() {