From 9f7b1b8deee59354e0683e041953997ac9350afc Mon Sep 17 00:00:00 2001
From: Mirco Miranda <mirco.miranda@systemceramics.com>
Date: Sat, 6 Jan 2024 09:04:06 +0100
Subject: [PATCH] ScanlineConverter: fix indexed conversion and support for
 source depth less than 24 bits

---
 autotests/read/exr/gray.exr            | Bin 0 -> 3022 bytes
 autotests/read/exr/gray.png            | Bin 0 -> 1654 bytes
 src/imageformats/scanlineconverter.cpp |  14 ++++++++------
 3 files changed, 8 insertions(+), 6 deletions(-)
 create mode 100644 autotests/read/exr/gray.exr
 create mode 100644 autotests/read/exr/gray.png

diff --git a/autotests/read/exr/gray.exr b/autotests/read/exr/gray.exr
new file mode 100644
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diff --git a/autotests/read/exr/gray.png b/autotests/read/exr/gray.png
new file mode 100644
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diff --git a/src/imageformats/scanlineconverter.cpp b/src/imageformats/scanlineconverter.cpp
index a797818..f949900 100644
--- a/src/imageformats/scanlineconverter.cpp
+++ b/src/imageformats/scanlineconverter.cpp
@@ -60,20 +60,25 @@ const uchar *ScanLineConverter::convertedScanLine(const QImage &image, qint32 y)
     }
     if (image.width() != _tmpBuffer.width() || image.format() != _tmpBuffer.format()) {
         _tmpBuffer = QImage(image.width(), 1, image.format());
+        _tmpBuffer.setColorTable(image.colorTable());
     }
     if (_tmpBuffer.isNull()) {
         return nullptr;
     }
     std::memcpy(_tmpBuffer.bits(), image.constScanLine(y), std::min(_tmpBuffer.bytesPerLine(), image.bytesPerLine()));
+    auto tmp = _tmpBuffer;
     if (colorSpaceConversion) {
         auto cs = image.colorSpace();
         if (!cs.isValid()) {
             cs = _defaultColorSpace;
         }
-        _tmpBuffer.setColorSpace(cs);
-        _tmpBuffer.convertToColorSpace(_colorSpace);
+        if (tmp.depth() < 24) {
+            tmp = tmp.convertToFormat(tmp.hasAlphaChannel() ? QImage::Format_ARGB32 : QImage::Format_RGB32);
+        }
+        tmp.setColorSpace(cs);
+        tmp.convertToColorSpace(_colorSpace);
     }
-    _convBuffer = _tmpBuffer.convertToFormat(_targetFormat);
+    _convBuffer = tmp.convertToFormat(_targetFormat);
     if (_convBuffer.isNull()) {
         return nullptr;
     }
@@ -90,9 +95,6 @@ qsizetype ScanLineConverter::bytesPerLine() const
 
 bool ScanLineConverter::isColorSpaceConversionNeeded(const QImage &image, const QColorSpace &targetColorSpace, const QColorSpace &defaultColorSpace)
 {
-    if (image.depth() < 24) { // RGB 8 bit or grater only
-        return false;
-    }
     auto sourceColorSpace = image.colorSpace();
     if (!sourceColorSpace.isValid()) {
         sourceColorSpace = defaultColorSpace;