From 332816779c42e8a3fed34e9295c09338bc9b4945 Mon Sep 17 00:00:00 2001
From: Allan Sandfeld Jensen <allan.jensen@qt.io>
Date: Fri, 22 Nov 2019 13:02:31 +0100
Subject: Multithread some QImage routines

Use QThreadPool to process QImage smooth-scaling, format conversions,
and colorspace transforms multithreaded.

Change-Id: Ic142b1fa899f56e7e5099d36ca713701a47b681b
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
---
 src/gui/image/qimage.cpp | 46 ++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 38 insertions(+), 8 deletions(-)

(limited to 'src/gui/image/qimage.cpp')

diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index ec72180f0d..2646d298e9 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -69,6 +69,11 @@
 #include <private/qimage_p.h>
 #include <private/qfont_p.h>
 
+#if QT_CONFIG(thread)
+#include "qsemaphore.h"
+#include "qthreadpool.h"
+#endif
+
 QT_BEGIN_NAMESPACE
 
 static inline bool isLocked(QImageData *data)
@@ -5024,18 +5029,43 @@ void QImage::applyColorTransform(const QColorTransform &transform)
         Q_UNREACHABLE();
     }
 
+    std::function<void(int,int)> transformSegment;
+
     if (depth() > 32) {
-        for (int i = 0; i < height(); ++i) {
-            QRgba64 *scanline = reinterpret_cast<QRgba64 *>(scanLine(i));
-            transform.d->apply(scanline, scanline, width(), flags);
-        }
+        transformSegment = [&](int yStart, int yEnd) {
+            for (int y = yStart; y < yEnd; ++y) {
+                QRgba64 *scanline = reinterpret_cast<QRgba64 *>(scanLine(y));
+                transform.d->apply(scanline, scanline, width(), flags);
+            }
+        };
     } else {
-        for (int i = 0; i < height(); ++i) {
-            QRgb *scanline = reinterpret_cast<QRgb *>(scanLine(i));
-            transform.d->apply(scanline, scanline, width(), flags);
-        }
+        transformSegment = [&](int yStart, int yEnd) {
+            for (int y = yStart; y < yEnd; ++y) {
+                QRgb *scanline = reinterpret_cast<QRgb *>(scanLine(y));
+                transform.d->apply(scanline, scanline, width(), flags);
+            }
+        };
     }
 
+#if QT_CONFIG(thread)
+    int segments = sizeInBytes() / (1<<16);
+    segments = std::min(segments, height());
+    if (segments > 1) {
+        QSemaphore semaphore;
+        int y = 0;
+        for (int i = 0; i < segments; ++i) {
+            int yn = (height() - y) / (segments - i);
+            QThreadPool::globalInstance()->start([&, y, yn]() {
+                transformSegment(y, y + yn);
+                semaphore.release(1);
+            });
+            y += yn;
+        }
+        semaphore.acquire(segments);
+    } else
+#endif
+        transformSegment(0, height());
+
     if (oldFormat != format())
         *this = std::move(*this).convertToFormat(oldFormat);
 }
-- 
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