From 1206598337ca40ecfcee6e10d00f3d4abb827a7c Mon Sep 17 00:00:00 2001
From: Mirco Miranda <mirco.miranda@systemceramics.com>
Date: Thu, 7 May 2026 08:41:10 +0200
Subject: [PATCH] imageAlloc: add image initialization support

---
 src/imageformats/jxr.cpp  |  2 +-
 src/imageformats/util_p.h | 41 ++++++++++++++++++++++++++++++++++-----
 2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/src/imageformats/jxr.cpp b/src/imageformats/jxr.cpp
index 5b09390..01a12d6 100644
--- a/src/imageformats/jxr.cpp
+++ b/src/imageformats/jxr.cpp
@@ -1031,7 +1031,7 @@ bool JXRHandler::read(QImage *outImage)
 
     PKPixelFormatGUID convFmt;
     auto imageFmt = d->imageFormat(&convFmt);
-    auto img = imageAlloc(d->imageSize(), imageFmt);
+    auto img = imageAlloc(d->imageSize(), imageFmt, ImageInitToZero::FPOnly);
     if (img.isNull()) {
         return false;
     }
diff --git a/src/imageformats/util_p.h b/src/imageformats/util_p.h
index 85d1ef6..4dc02ac 100644
--- a/src/imageformats/util_p.h
+++ b/src/imageformats/util_p.h
@@ -13,6 +13,7 @@
 #include <QImage>
 #include <QImageIOHandler>
 #include <QIODevice>
+#include <QPixelFormat>
 
 // Default maximum width and height for the large image plugins.
 #ifndef KIF_LARGE_IMAGE_PIXEL_LIMIT
@@ -63,20 +64,50 @@
 // QList uses some extra space for stuff, hence the 32 here suggested by Thiago Macieira
 static constexpr int kMaxQVectorSize = std::numeric_limits<int>::max() - 32;
 
-// On Qt 6 to make the plugins fail to allocate if the image size is greater than QImageReader::allocationLimit()
-// it is necessary to allocate the image with QImageIOHandler::allocateImage().
-inline QImage imageAlloc(const QSize &size, const QImage::Format &format)
+/*!
+ * \brief The ImageInitToZero enum
+ */
+enum class ImageInitToZero
+{
+    None, /**< Do not initialize the image. */
+    All, /**< Initialize all images. */
+    PremulOnly, /**< Initialize only images with premultiplied alpha. */
+    FPOnly, /**< Initialize only images with floating point format. */
+    FPAndPremul /**< Initialize floating point and premultiplied formats. */
+};
+
+/*!
+ * \brief imageAlloc
+ * Helper function to initialize framework images.
+ * \param size The image size.
+ * \param format The image format,
+ * \param init Whether and which images should be initialized to zero.
+ * \return The allocated image or a null image on error.
+ */
+inline QImage imageAlloc(const QSize &size, const QImage::Format &format, const ImageInitToZero& init = ImageInitToZero::None)
 {
     QImage img;
     if (!QImageIOHandler::allocateImage(size, format, &img)) {
         img = QImage(); // paranoia
     }
+    if (init != ImageInitToZero::None && !img.isNull()) {
+        auto pixelFormat = img.pixelFormat();
+        auto isFloat = pixelFormat.typeInterpretation() == QPixelFormat::FloatingPoint;
+        auto isPremul = pixelFormat.premultiplied();
+        if (init == ImageInitToZero::All) {
+            img.fill(0);
+        } else if (isFloat && (init == ImageInitToZero::FPOnly || init == ImageInitToZero::FPAndPremul)) {
+            img.fill(0);
+        } else if (isPremul && (init == ImageInitToZero::PremulOnly || init == ImageInitToZero::FPAndPremul)) {
+            img.fill(0);
+        }
+    }
     return img;
 }
 
-inline QImage imageAlloc(qint32 width, qint32 height, const QImage::Format &format)
+inline QImage imageAlloc(qint32 width, qint32 height, const QImage::Format &format, const ImageInitToZero& init = ImageInitToZero::None)
 {
-    return imageAlloc(QSize(width, height), format);
+    return imageAlloc(QSize(width, height), format, init);
 }
 
 template<class TI, class SF> // SF = source FP, TI = target INT