exr: write support and more

- Added support for writing EXR files
- Large image support (tested with 32GiB 16-bit image)
- OpenEXR multithreaded read/write support through the use of line blocks
- Build option to enable conversion to sRGB when read (disabled by default)
- Multi-view image reading support
- Options support: Size, ImageFormat, Quality, CompressRatio
- Metadata write/read support via EXR attributes

The plugin is now quite complete. It should also work on KF5 (not tested): if there is the will to include this MR also on KF5, let me know and I will do all the necessary tests.

README.md

@@ -17,7 +17,6 @@ The following image formats have read-only support:
 - Camera RAW images (arw, cr2, cr3, dcs, dng, ...)
 - Gimp (xcf)
 - Krita (kra)
-- OpenEXR (exr)
 - OpenRaster (ora)
 - Photoshop documents (psd, psb, pdd, psdt)
 - Radiance HDR (hdr)
@@ -29,6 +28,7 @@ The following image formats have read and write support:
 - Encapsulated PostScript (eps)
 - High Efficiency Image File Format (heif). Can be enabled with the KIMAGEFORMATS_HEIF build option.
 - JPEG XL (jxl)
+- OpenEXR (exr)
 - Personal Computer Exchange (pcx)
 - Quite OK Image format (qoi)
 - SGI images (rgb, rgba, sgi, bw)
@@ -45,10 +45,6 @@ of Qt is the license.  As such, if you write an imageformat plugin and
 you are willing to sign the Qt Project contributor agreement, it may be
 better to submit the plugin directly to the Qt Project.
 
-Note that the imageformat plugins provided by this module also provide a
-desktop file.  This is for the benefit of KImageIO in the KDE4 Support
-framework.
-
 ## Duplicated Plugins
 
 The TGA plugin supports more formats than Qt's own TGA plugin;

autotests/CMakeLists.txt

@@ -138,6 +138,11 @@ if (OpenEXR_FOUND)
     kimageformats_read_tests(
         exr
     )
+    # Color space conversions from sRGB to linear on saving and
+    # from linear to sRGB on loading result in some rounding errors.
+    kimageformats_write_tests(FUZZ 5
+        exr-nodatacheck-lossless
+    )
 endif()
 
 if (LibRaw_FOUND)

autotests/writetest.cpp

@@ -7,6 +7,7 @@
 #include <stdio.h>
 
 #include <QBuffer>
+#include <QColorSpace>
 #include <QCommandLineParser>
 #include <QCoreApplication>
 #include <QDir>
@@ -23,8 +24,8 @@ int main(int argc, char **argv)
     QCoreApplication app(argc, argv);
     QCoreApplication::removeLibraryPath(QStringLiteral(PLUGIN_DIR));
     QCoreApplication::addLibraryPath(QStringLiteral(PLUGIN_DIR));
-    QCoreApplication::setApplicationName(QStringLiteral("readtest"));
+    QCoreApplication::setApplicationName(QStringLiteral("writetest"));
-    QCoreApplication::setApplicationVersion(QStringLiteral("1.0.0"));
+    QCoreApplication::setApplicationVersion(QStringLiteral("1.1.0"));
 
     QCommandLineParser parser;
     parser.setApplicationDescription(QStringLiteral("Performs basic image conversion checking."));
@@ -148,6 +149,14 @@ int main(int argc, char **argv)
                 ++failed;
                 continue;
             }
+            if (reReadImage.colorSpace().isValid()) {
+                QColorSpace toColorSpace;
+                if (pngImage.colorSpace().isValid()) {
+                    reReadImage.convertToColorSpace(pngImage.colorSpace());
+                } else {
+                    reReadImage.convertToColorSpace(QColorSpace(QColorSpace::SRgb));
+                }
+            }
             reReadImage = reReadImage.convertToFormat(pngImage.format());
         }
 

src/imageformats/CMakeLists.txt

@@ -41,7 +41,7 @@ endif()
 ##################################
 
 if(OpenEXR_FOUND)
-    kimageformats_add_plugin(kimg_exr SOURCES exr.cpp)
+    kimageformats_add_plugin(kimg_exr SOURCES exr.cpp scanlineconverter.cpp)
     if(TARGET OpenEXR::OpenEXR)
         target_link_libraries(kimg_exr PRIVATE OpenEXR::OpenEXR)
     else()

src/imageformats/exr.cpp

@@ -1,6 +1,5 @@
 /*
-    KImageIO Routines to read (and perhaps in the future, write) images
+    The high dynamic range EXR format support for QImage.
-    in the high dynamic range EXR format.
 
     SPDX-FileCopyrightText: 2003 Brad Hards <bradh@frogmouth.net>
     SPDX-FileCopyrightText: 2023 Mirco Miranda <mircomir@outlook.com>
@@ -16,15 +15,52 @@
  */
 //#define EXR_USE_LEGACY_CONVERSIONS // default commented -> you should define it in your cmake file
 
-/* *** EXR_ALLOW_LINEAR_COLORSPACE ***
+/* *** EXR_CONVERT_TO_SRGB ***
- * If defined, the linear data is kept and it is the display program that
+ * If defined, the linear data is converted to sRGB on read to accommodate
- * must convert to the monitor profile. Otherwise the data is converted to sRGB
+ * programs that do not support color profiles.
- * to accommodate programs that do not support color profiles.
+ * Otherwise the data are kept as is and it is the display program that
+ * must convert to the monitor profile.
  * NOTE: If EXR_USE_LEGACY_CONVERSIONS is active, this is ignored.
  */
-//#define EXR_ALLOW_LINEAR_COLORSPACE // default: commented -> you should define it in your cmake file
+//#define EXR_CONVERT_TO_SRGB // default: commented -> you should define it in your cmake file
+
+/* *** EXR_STORE_XMP_ATTRIBUTE ***
+ * If defined, disables the stores XMP values in a non-standard attribute named "xmp".
+ * The QImage metadata used is "XML:com.adobe.xmp".
+ * NOTE: The use of non-standard attributes is possible but discouraged by the specification. However,
+ *       metadata is essential for good image management and programs like darktable also set this
+ *       attribute. Gimp reads the "xmp" attribute and Darktable writes it as well.
+ */
+//#define EXR_DISABLE_XMP_ATTRIBUTE // default: commented -> you should define it in your cmake file
+
+/* *** EXR_MAX_IMAGE_WIDTH and EXR_MAX_IMAGE_HEIGHT ***
+ * The maximum size in pixel allowed by the plugin.
+ */
+#ifndef EXR_MAX_IMAGE_WIDTH
+#define EXR_MAX_IMAGE_WIDTH 300000
+#endif
+#ifndef EXR_MAX_IMAGE_HEIGHT
+#define EXR_MAX_IMAGE_HEIGHT EXR_MAX_IMAGE_WIDTH
+#endif
+
+/* *** EXR_LINES_PER_BLOCK ***
+ * Allows certain compression schemes to work in multithreading
+ * Requires up to "LINES_PER_BLOCK * MAX_IMAGE_WIDTH * 8"
+ * additional RAM (e.g. if 128, up to 307MiB of RAM).
+ * There is a performance gain with the following parameters (based on empirical tests):
+ * - PIZ compression needs 64+ lines
+ * - ZIPS compression needs 8+ lines
+ * - ZIP compression needs 32+ lines
+ * - Others not tested
+ *
+ * NOTE: The OpenEXR documentation states that the higher the better :)
+ */
+#ifndef EXR_LINES_PER_BLOCK
+#define EXR_LINES_PER_BLOCK 128
+#endif
 
 #include "exr_p.h"
+#include "scanlineconverter_p.h"
 #include "util_p.h"
 
 #include <IexThrowErrnoExc.h>
@@ -39,10 +75,9 @@
 #include <ImfInt64.h>
 #include <ImfIntAttribute.h>
 #include <ImfLineOrderAttribute.h>
+#include <ImfPreviewImage.h>
 #include <ImfRgbaFile.h>
 #include <ImfStandardAttributes.h>
-#include <ImfStringAttribute.h>
-#include <ImfVecAttribute.h>
 #include <ImfVersion.h>
 
 #include <iostream>
@@ -53,8 +88,12 @@
 #include <QFloat16>
 #include <QImage>
 #include <QImageIOPlugin>
+#include <QLocale>
+#include <QThread>
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
 #include <QTimeZone>
+#endif
 
 // Allow the code to works on all QT versions supported by KDE
 // project (Qt 5.15 and Qt 6.x) to easy backports fixes.
@@ -122,6 +161,57 @@ void K_IStream::clear()
     // TODO
 }
 
+class K_OStream : public Imf::OStream
+{
+public:
+    K_OStream(QIODevice *dev, const QByteArray &fileName)
+        : OStream(fileName.data())
+        , m_dev(dev)
+    {
+    }
+
+    void write(const char c[/*n*/], int n) override;
+#if OPENEXR_VERSION_MAJOR > 2
+    uint64_t tellp() override;
+    void seekp(uint64_t pos) override;
+#else
+    Imf::Int64 tellp() override;
+    void seekp(Imf::Int64 pos) override;
+#endif
+
+private:
+    QIODevice *m_dev;
+};
+
+void K_OStream::write(const char c[], int n)
+{
+    qint64 result = m_dev->write(c, n);
+    if (result > 0) {
+        return;
+    } else { // negative value {
+        Iex::throwErrnoExc("Error in write", result);
+    }
+    return;
+}
+
+#if OPENEXR_VERSION_MAJOR > 2
+uint64_t K_OStream::tellp()
+#else
+Imf::Int64 K_OStream::tellg()
+#endif
+{
+    return m_dev->pos();
+}
+
+#if OPENEXR_VERSION_MAJOR > 2
+void K_OStream::seekp(uint64_t pos)
+#else
+void K_OStream::seekg(Imf::Int64 pos)
+#endif
+{
+    m_dev->seek(pos);
+}
+
 #ifdef EXR_USE_LEGACY_CONVERSIONS
 // source: https://openexr.com/en/latest/ReadingAndWritingImageFiles.html
 inline unsigned char gamma(float x)
@@ -139,7 +229,14 @@ inline QRgb RgbaToQrgba(struct Imf::Rgba &imagePixel)
 #endif
 
 EXRHandler::EXRHandler()
+    : m_compressionRatio(-1)
+    , m_quality(-1)
+    , m_imageNumber(-1)
+    , m_imageCount(0)
+    , m_startPos(-1)
 {
+    // Set the number of threads to use (0 is allowed)
+    Imf::setGlobalThreadCount(QThread::idealThreadCount() / 2);
 }
 
 bool EXRHandler::canRead() const
@@ -151,113 +248,571 @@ bool EXRHandler::canRead() const
     return false;
 }
 
+static QImage::Format imageFormat(const Imf::RgbaInputFile &file)
+{
+    auto isRgba = file.channels() & Imf::RgbaChannels::WRITE_A;
+#if defined(EXR_USE_LEGACY_CONVERSIONS)
+    return (isRgba ? QImage::Format_ARGB32 : QImage::Format_RGB32);
+#elif defined(EXR_USE_QT6_FLOAT_IMAGE)
+    return (isRgba ? QImage::Format_RGBA16FPx4 : QImage::Format_RGBX16FPx4);
+#else
+    return (isRgba ? QImage::Format_RGBA64 : QImage::Format_RGBX64);
+#endif
+}
+
+/*!
+ * \brief viewList
+ * \param header
+ * \return The list of available views.
+ */
+static QStringList viewList(const Imf::Header &h)
+{
+    QStringList l;
+    if (auto views = h.findTypedAttribute<Imf::StringVectorAttribute>("multiView")) {
+        for (auto &&v : views->value()) {
+            l << QString::fromStdString(v);
+        }
+    }
+    return l;
+}
+
+#ifdef QT_DEBUG
+void printAttributes(const Imf::Header &h)
+{
+    for (auto i = h.begin(); i != h.end(); ++i) {
+        qDebug() << i.name();
+    }
+}
+#endif
+
+/*!
+ * \brief readMetadata
+ * Reads EXR attributes from the \a header and set its as metadata in the \a image.
+ */
+static void readMetadata(const Imf::Header &header, QImage &image)
+{
+    // set some useful metadata
+    if (auto comments = header.findTypedAttribute<Imf::StringAttribute>("comments")) {
+        image.setText(QStringLiteral("Comment"), QString::fromStdString(comments->value()));
+    }
+
+    if (auto owner = header.findTypedAttribute<Imf::StringAttribute>("owner")) {
+        image.setText(QStringLiteral("Owner"), QString::fromStdString(owner->value()));
+    }
+
+    if (auto lat = header.findTypedAttribute<Imf::FloatAttribute>("latitude")) {
+        image.setText(QStringLiteral("Latitude"), QLocale::c().toString(lat->value()));
+    }
+
+    if (auto lon = header.findTypedAttribute<Imf::FloatAttribute>("longitude")) {
+        image.setText(QStringLiteral("Longitude"), QLocale::c().toString(lon->value()));
+    }
+
+    if (auto alt = header.findTypedAttribute<Imf::FloatAttribute>("altitude")) {
+        image.setText(QStringLiteral("Altitude"), QLocale::c().toString(alt->value()));
+    }
+
+    if (auto capDate = header.findTypedAttribute<Imf::StringAttribute>("capDate")) {
+        float off = 0;
+        if (auto utcOffset = header.findTypedAttribute<Imf::FloatAttribute>("utcOffset")) {
+            off = utcOffset->value();
+        }
+        auto dateTime = QDateTime::fromString(QString::fromStdString(capDate->value()), QStringLiteral("yyyy:MM:dd HH:mm:ss"));
+        if (dateTime.isValid()) {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
+            dateTime.setTimeZone(QTimeZone::fromSecondsAheadOfUtc(off));
+#else
+            dateTime.setOffsetFromUtc(off);
+#endif
+            image.setText(QStringLiteral("CreationDate"), dateTime.toString(Qt::ISODate));
+        }
+    }
+
+    if (auto xDensity = header.findTypedAttribute<Imf::FloatAttribute>("xDensity")) {
+        float par = 1;
+        if (auto pixelAspectRatio = header.findTypedAttribute<Imf::FloatAttribute>("pixelAspectRatio")) {
+            par = pixelAspectRatio->value();
+        }
+        image.setDotsPerMeterX(qRound(xDensity->value() * 100.0 / 2.54));
+        image.setDotsPerMeterY(qRound(xDensity->value() * par * 100.0 / 2.54));
+    }
+
+    // Non-standard attribute
+    if (auto xmp = header.findTypedAttribute<Imf::StringAttribute>("xmp")) {
+        image.setText(QStringLiteral("XML:com.adobe.xmp"), QString::fromStdString(xmp->value()));
+    }
+
+    /* TODO: OpenEXR 3.2 metadata
+     *
+     * New Optional Standard Attributes:
+     * - Support automated editorial workflow:
+     *   reelName, imageCounter, ascFramingDecisionList
+     *
+     * - Support forensics (“which other shots used that camera and lens before the camera firmware was updated?”):
+     *   cameraMake, cameraModel, cameraSerialNumber, cameraFirmware, cameraUuid, cameraLabel, lensMake, lensModel,
+     *   lensSerialNumber, lensFirmware, cameraColorBalance
+     *
+     * -Support pickup shots (reproduce critical camera settings):
+     *   shutterAngle, cameraCCTSetting, cameraTintSetting
+     *
+     * - Support metadata-driven match move:
+     *   sensorCenterOffset, sensorOverallDimensions, sensorPhotositePitch, sensorAcquisitionRectanglenominalFocalLength,
+     *   effectiveFocalLength, pinholeFocalLength, entrancePupilOffset, tStop(complementing existing 'aperture')
+     */
+}
+
+/*!
+ * \brief readColorSpace
+ * Reads EXR chromaticities from the \a header and set its as color profile in the \a image.
+ */
+static void readColorSpace(const Imf::Header &header, QImage &image)
+{
+    // final color operations
+#ifndef EXR_USE_LEGACY_CONVERSIONS
+
+    QColorSpace cs;
+    if (auto chroma = header.findTypedAttribute<Imf::ChromaticitiesAttribute>("chromaticities")) {
+        auto &&v = chroma->value();
+        cs = QColorSpace(QPointF(v.white.x, v.white.y),
+                         QPointF(v.red.x, v.red.y),
+                         QPointF(v.green.x, v.green.y),
+                         QPointF(v.blue.x, v.blue.y),
+                         QColorSpace::TransferFunction::Linear);
+    }
+    if (!cs.isValid()) {
+        cs = QColorSpace(QColorSpace::SRgbLinear);
+    }
+    image.setColorSpace(cs);
+
+#ifdef EXR_CONVERT_TO_SRGB
+    image.convertToColorSpace(QColorSpace(QColorSpace::SRgb));
+#endif
+
+#endif // !EXR_USE_LEGACY_CONVERSIONS
+}
+
 bool EXRHandler::read(QImage *outImage)
 {
     try {
-        int width;
+        auto d = device();
-        int height;
 
-        K_IStream istr(device(), QByteArray());
+        // set the image position after the first run.
+        if (!d->isSequential()) {
+            if (m_startPos < 0) {
+                m_startPos = d->pos();
+            } else {
+                d->seek(m_startPos);
+            }
+        }
+
+        K_IStream istr(d, QByteArray());
         Imf::RgbaInputFile file(istr);
+        auto &&header = file.header();
+
+        // set the image to load
+        if (m_imageNumber > -1) {
+            auto views = viewList(header);
+            if (m_imageNumber < views.count()) {
+                file.setLayerName(views.at(m_imageNumber).toStdString());
+            }
+        }
+
+        // get image info
         Imath::Box2i dw = file.dataWindow();
-        bool isRgba = file.channels() & Imf::RgbaChannels::WRITE_A;
+        qint32 width = dw.max.x - dw.min.x + 1;
+        qint32 height = dw.max.y - dw.min.y + 1;
 
-        width = dw.max.x - dw.min.x + 1;
+        // limiting the maximum image size on a reasonable size (as done in other plugins)
-        height = dw.max.y - dw.min.y + 1;
+        if (width > EXR_MAX_IMAGE_WIDTH || height > EXR_MAX_IMAGE_HEIGHT) {
+            qWarning() << "The maximum image size is limited to" << EXR_MAX_IMAGE_WIDTH << "x" << EXR_MAX_IMAGE_HEIGHT << "px";
+            return false;
+        }
 
-#if defined(EXR_USE_LEGACY_CONVERSIONS)
+        // creating the image
-        QImage image = imageAlloc(width, height, isRgba ? QImage::Format_ARGB32 : QImage::Format_RGB32);
+        QImage image = imageAlloc(width, height, imageFormat(file));
-#elif defined(EXR_USE_QT6_FLOAT_IMAGE)
-        QImage image = imageAlloc(width, height, isRgba ? QImage::Format_RGBA16FPx4 : QImage::Format_RGBX16FPx4);
-#else
-        QImage image = imageAlloc(width, height, isRgba ? QImage::Format_RGBA64 : QImage::Format_RGBX64);
-#endif
         if (image.isNull()) {
             qWarning() << "Failed to allocate image, invalid size?" << QSize(width, height);
             return false;
         }
 
-        // set some useful metadata
+        Imf::Array2D<Imf::Rgba> pixels;
-        auto &&h = file.header();
+        pixels.resizeErase(EXR_LINES_PER_BLOCK, width);
-        if (auto comments = h.findTypedAttribute<Imf::StringAttribute>("comments")) {
+        bool isRgba = image.hasAlphaChannel();
-            image.setText(QStringLiteral("Comment"), QString::fromStdString(comments->value()));
-        }
-        if (auto owner = h.findTypedAttribute<Imf::StringAttribute>("owner")) {
-            image.setText(QStringLiteral("Owner"), QString::fromStdString(owner->value()));
-        }
-        if (auto capDate = h.findTypedAttribute<Imf::StringAttribute>("capDate")) {
-            float off = 0;
-            if (auto utcOffset = h.findTypedAttribute<Imf::FloatAttribute>("utcOffset")) {
-                off = utcOffset->value();
-            }
-            auto dateTime = QDateTime::fromString(QString::fromStdString(capDate->value()), QStringLiteral("yyyy:MM:dd HH:mm:ss"));
-            if (dateTime.isValid()) {
-                dateTime.setTimeZone(QTimeZone::fromSecondsAheadOfUtc(off));
-                image.setText(QStringLiteral("Date"), dateTime.toString(Qt::ISODate));
-            }
-        }
-        if (auto xDensity = h.findTypedAttribute<Imf::FloatAttribute>("xDensity")) {
-            float par = 1;
-            if (auto pixelAspectRatio = h.findTypedAttribute<Imf::FloatAttribute>("pixelAspectRatio")) {
-                par = pixelAspectRatio->value();
-            }
-            image.setDotsPerMeterX(qRound(xDensity->value() * 100.0 / 2.54));
-            image.setDotsPerMeterY(qRound(xDensity->value() * par * 100.0 / 2.54));
-        }
-
-        Imf::Array<Imf::Rgba> pixels;
-        pixels.resizeErase(width);
 
         // somehow copy pixels into image
-        for (int y = 0; y < height; ++y) {
+        for (int y = 0, n = 0; y < height; y += n) {
             auto my = dw.min.y + y;
-            if (my <= dw.max.y) { // paranoia check
+            if (my > dw.max.y) { // paranoia check
-                file.setFrameBuffer(&pixels[0] - dw.min.x - qint64(my) * width, 1, width);
+                break;
-                file.readPixels(my, my);
+            }
 
+            file.setFrameBuffer(&pixels[0][0] - dw.min.x - qint64(my) * width, 1, width);
+            file.readPixels(my, std::min(my + EXR_LINES_PER_BLOCK - 1, dw.max.y));
+
+            for (n = 0; n < std::min(EXR_LINES_PER_BLOCK, height - y); ++n) {
 #if defined(EXR_USE_LEGACY_CONVERSIONS)
-                auto scanLine = reinterpret_cast<QRgb *>(image.scanLine(y));
+                Q_UNUSED(isRgba)
+                auto scanLine = reinterpret_cast<QRgb *>(image.scanLine(y + n));
                 for (int x = 0; x < width; ++x) {
-                    *(scanLine + x) = RgbaToQrgba(pixels[x]);
+                    *(scanLine + x) = RgbaToQrgba(pixels[n][x]);
                 }
 #elif defined(EXR_USE_QT6_FLOAT_IMAGE)
-                auto scanLine = reinterpret_cast<qfloat16 *>(image.scanLine(y));
+                auto scanLine = reinterpret_cast<qfloat16 *>(image.scanLine(y + n));
                 for (int x = 0; x < width; ++x) {
                     auto xcs = x * 4;
-                    *(scanLine + xcs) = qfloat16(qBound(0.f, float(pixels[x].r), 1.f));
+                    *(scanLine + xcs) = qfloat16(qBound(0.f, float(pixels[n][x].r), 1.f));
-                    *(scanLine + xcs + 1) = qfloat16(qBound(0.f, float(pixels[x].g), 1.f));
+                    *(scanLine + xcs + 1) = qfloat16(qBound(0.f, float(pixels[n][x].g), 1.f));
-                    *(scanLine + xcs + 2) = qfloat16(qBound(0.f, float(pixels[x].b), 1.f));
+                    *(scanLine + xcs + 2) = qfloat16(qBound(0.f, float(pixels[n][x].b), 1.f));
-                    *(scanLine + xcs + 3) = qfloat16(isRgba ? qBound(0.f, float(pixels[x].a), 1.f) : 1.f);
+                    *(scanLine + xcs + 3) = qfloat16(isRgba ? qBound(0.f, float(pixels[n][x].a), 1.f) : 1.f);
                 }
 #else
-                auto scanLine = reinterpret_cast<QRgba64 *>(image.scanLine(y));
+                auto scanLine = reinterpret_cast<QRgba64 *>(image.scanLine(y + n));
                 for (int x = 0; x < width; ++x) {
-                    *(scanLine + x) = QRgba64::fromRgba64(quint16(qBound(0.f, float(pixels[x].r) * 65535.f + 0.5f, 65535.f)),
+                    *(scanLine + x) = QRgba64::fromRgba64(quint16(qBound(0.f, float(pixels[n][x].r) * 65535.f + 0.5f, 65535.f)),
-                                                          quint16(qBound(0.f, float(pixels[x].g) * 65535.f + 0.5f, 65535.f)),
+                                                          quint16(qBound(0.f, float(pixels[n][x].g) * 65535.f + 0.5f, 65535.f)),
-                                                          quint16(qBound(0.f, float(pixels[x].b) * 65535.f + 0.5f, 65535.f)),
+                                                          quint16(qBound(0.f, float(pixels[n][x].b) * 65535.f + 0.5f, 65535.f)),
-                                                          isRgba ? quint16(qBound(0.f, float(pixels[x].a) * 65535.f + 0.5f, 65535.f)) : quint16(65535));
+                                                          isRgba ? quint16(qBound(0.f, float(pixels[n][x].a) * 65535.f + 0.5f, 65535.f)) : quint16(65535));
                 }
 #endif
             }
         }
 
+        // set some useful metadata
+        readMetadata(header, image);
         // final color operations
-#ifndef EXR_USE_LEGACY_CONVERSIONS
+        readColorSpace(header, image);
-        image.setColorSpace(QColorSpace(QColorSpace::SRgbLinear));
-#ifndef EXR_ALLOW_LINEAR_COLORSPACE
-        image.convertToColorSpace(QColorSpace(QColorSpace::SRgb));
-#endif // !EXR_ALLOW_LINEAR_COLORSPACE
-#endif // !EXR_USE_LEGACY_CONVERSIONS
 
         *outImage = image;
 
         return true;
-    } catch (const std::exception &exc) {
+    } catch (const std::exception &) {
-        //      qDebug() << exc.what();
         return false;
     }
 }
 
+/*!
+ * \brief makePreview
+ * Creates a preview of maximum 256 x 256 pixels from the \a image.
+ */
+bool makePreview(const QImage &image, Imf::Array2D<Imf::PreviewRgba> &pixels)
+{
+    auto w = image.width();
+    auto h = image.height();
+
+    QImage preview;
+    if (w > h) {
+        preview = image.scaledToWidth(256).convertToFormat(QImage::Format_ARGB32);
+    } else {
+        preview = image.scaledToHeight(256).convertToFormat(QImage::Format_ARGB32);
+    }
+    if (preview.isNull()) {
+        return false;
+    }
+
+    w = preview.width();
+    h = preview.height();
+    pixels.resizeErase(h, w);
+    preview.convertToColorSpace(QColorSpace(QColorSpace::SRgb));
+
+    for (int y = 0; y < h; ++y) {
+        auto scanLine = reinterpret_cast<const QRgb *>(preview.constScanLine(y));
+        for (int x = 0; x < w; ++x) {
+            auto &&out = pixels[y][x];
+            out.r = qRed(*(scanLine + x));
+            out.g = qGreen(*(scanLine + x));
+            out.b = qBlue(*(scanLine + x));
+            out.a = qAlpha(*(scanLine + x));
+        }
+    }
+
+    return true;
+}
+
+/*!
+ * \brief setMetadata
+ * Reades the metadata from \a image and set its as attributes in the \a header.
+ */
+static void setMetadata(const QImage &image, Imf::Header &header)
+{
+    auto dateTime = QDateTime::currentDateTime();
+    for (auto &&key : image.textKeys()) {
+        auto text = image.text(key);
+        if (!key.compare(QStringLiteral("Comment"), Qt::CaseInsensitive)) {
+            header.insert("comments", Imf::StringAttribute(text.toStdString()));
+        }
+
+        if (!key.compare(QStringLiteral("Owner"), Qt::CaseInsensitive)) {
+            header.insert("owner", Imf::StringAttribute(text.toStdString()));
+        }
+
+        // clang-format off
+        if (!key.compare(QStringLiteral("Latitude"), Qt::CaseInsensitive) ||
+            !key.compare(QStringLiteral("Longitude"), Qt::CaseInsensitive) ||
+            !key.compare(QStringLiteral("Altitude"), Qt::CaseInsensitive)) {
+            // clang-format on
+            auto ok = false;
+            auto value = QLocale::c().toFloat(text, &ok);
+            if (ok) {
+                header.insert(qPrintable(key.toLower()), Imf::FloatAttribute(value));
+            }
+        }
+
+        if (!key.compare(QStringLiteral("CreationDate"), Qt::CaseInsensitive)) {
+            auto dt = QDateTime::fromString(text, Qt::ISODate);
+            if (dt.isValid()) {
+                dateTime = dt;
+            }
+        }
+
+#ifndef EXR_DISABLE_XMP_ATTRIBUTE // warning: Non-standard attribute!
+        if (!key.compare(QStringLiteral("XML:com.adobe.xmp"), Qt::CaseInsensitive)) {
+            header.insert("xmp", Imf::StringAttribute(text.toStdString()));
+        }
+#endif
+    }
+    if (dateTime.isValid()) {
+        header.insert("capDate", Imf::StringAttribute(dateTime.toString(QStringLiteral("yyyy:MM:dd HH:mm:ss")).toStdString()));
+        header.insert("utcOffset", Imf::FloatAttribute(dateTime.offsetFromUtc()));
+    }
+
+    if (image.dotsPerMeterX() && image.dotsPerMeterY()) {
+        header.insert("xDensity", Imf::FloatAttribute(image.dotsPerMeterX() * 2.54f / 100.f));
+        header.insert("pixelAspectRatio", Imf::FloatAttribute(float(image.dotsPerMeterX()) / float(image.dotsPerMeterY())));
+    }
+
+    // set default chroma (default constructor ITU-R BT.709-3 -> sRGB)
+    // The image is converted to Linear sRGB so, the chroma is the default EXR value.
+    // If a file doesn’t have a chromaticities attribute, display software should assume that the
+    // file’s primaries and the white point match Rec. ITU-R BT.709-3.
+    // header.insert("chromaticities", Imf::ChromaticitiesAttribute(Imf::Chromaticities()));
+
+    // TODO: EXR 3.2 attributes (see readMetadata())
+}
+
+bool EXRHandler::write(const QImage &image)
+{
+    try {
+        // create EXR header
+        qint32 width = image.width();
+        qint32 height = image.height();
+
+        // limiting the maximum image size on a reasonable size (as done in other plugins)
+        if (width > EXR_MAX_IMAGE_WIDTH || height > EXR_MAX_IMAGE_HEIGHT) {
+            qWarning() << "The maximum image size is limited to" << EXR_MAX_IMAGE_WIDTH << "x" << EXR_MAX_IMAGE_HEIGHT << "px";
+            return false;
+        }
+
+        Imf::Header header(width, height);
+        // set compression scheme (forcing PIZ as default)
+        header.compression() = Imf::Compression::PIZ_COMPRESSION;
+        if (m_compressionRatio >= qint32(Imf::Compression::NO_COMPRESSION) && m_compressionRatio < qint32(Imf::Compression::NUM_COMPRESSION_METHODS)) {
+            header.compression() = Imf::Compression(m_compressionRatio);
+        }
+        // set the DCT quality (used by DCT compressions only)
+        if (m_quality > -1 && m_quality <= 100) {
+            header.dwaCompressionLevel() = float(m_quality);
+        }
+        // make ZIP compression fast (used by ZIP compressions)
+        header.zipCompressionLevel() = 1;
+
+        // set preview (don't set it for small images)
+        if (width > 1024 || height > 1024) {
+            Imf::Array2D<Imf::PreviewRgba> previewPixels;
+            if (makePreview(image, previewPixels)) {
+                header.setPreviewImage(Imf::PreviewImage(previewPixels.width(), previewPixels.height(), &previewPixels[0][0]));
+            }
+        }
+
+        // set metadata (EXR attributes)
+        setMetadata(image, header);
+
+        // write the EXR
+        K_OStream ostr(device(), QByteArray());
+        Imf::RgbaOutputFile file(ostr, header, image.hasAlphaChannel() ? Imf::RgbaChannels::WRITE_RGBA : Imf::RgbaChannels::WRITE_RGB);
+        Imf::Array2D<Imf::Rgba> pixels;
+        pixels.resizeErase(EXR_LINES_PER_BLOCK, width);
+
+        // convert the image and write into the stream
+#if defined(EXR_USE_QT6_FLOAT_IMAGE)
+        auto convFormat = image.hasAlphaChannel() ? QImage::Format_RGBA16FPx4 : QImage::Format_RGBX16FPx4;
+#else
+        auto convFormat = image.hasAlphaChannel() ? QImage::Format_RGBA64 : QImage::Format_RGBX64;
+#endif
+        ScanLineConverter slc(convFormat);
+        slc.setDefaultSourceColorSpace(QColorSpace(QColorSpace::SRgb));
+        slc.setTargetColorSpace(QColorSpace(QColorSpace::SRgbLinear));
+        for (int y = 0, n = 0; y < height; y += n) {
+            for (n = 0; n < std::min(EXR_LINES_PER_BLOCK, height - y); ++n) {
+#if defined(EXR_USE_QT6_FLOAT_IMAGE)
+                auto scanLine = reinterpret_cast<const qfloat16 *>(slc.convertedScanLine(image, y + n));
+                if (scanLine == nullptr) {
+                    return false;
+                }
+                for (int x = 0; x < width; ++x) {
+                    auto xcs = x * 4;
+                    pixels[n][x].r = float(*(scanLine + xcs));
+                    pixels[n][x].g = float(*(scanLine + xcs + 1));
+                    pixels[n][x].b = float(*(scanLine + xcs + 2));
+                    pixels[n][x].a = float(*(scanLine + xcs + 3));
+                }
+#else
+                auto scanLine = reinterpret_cast<const QRgba64 *>(slc.convertedScanLine(image, y + n));
+                if (scanLine == nullptr) {
+                    return false;
+                }
+                for (int x = 0; x < width; ++x) {
+                    pixels[n][x].r = float((scanLine + x)->red() / 65535.f);
+                    pixels[n][x].g = float((scanLine + x)->green() / 65535.f);
+                    pixels[n][x].b = float((scanLine + x)->blue() / 65535.f);
+                    pixels[n][x].a = float((scanLine + x)->alpha() / 65535.f);
+                }
+#endif
+            }
+            file.setFrameBuffer(&pixels[0][0] - qint64(y) * width, 1, width);
+            file.writePixels(n);
+        }
+    } catch (const std::exception &) {
+        return false;
+    }
+
+    return true;
+}
+
+void EXRHandler::setOption(ImageOption option, const QVariant &value)
+{
+    if (option == QImageIOHandler::CompressionRatio) {
+        auto ok = false;
+        auto cr = value.toInt(&ok);
+        if (ok) {
+            m_compressionRatio = cr;
+        }
+    }
+    if (option == QImageIOHandler::Quality) {
+        auto ok = false;
+        auto q = value.toInt(&ok);
+        if (ok) {
+            m_quality = q;
+        }
+    }
+}
+
+bool EXRHandler::supportsOption(ImageOption option) const
+{
+    if (option == QImageIOHandler::Size) {
+        return true;
+    }
+    if (option == QImageIOHandler::ImageFormat) {
+        return true;
+    }
+    if (option == QImageIOHandler::CompressionRatio) {
+        return true;
+    }
+    if (option == QImageIOHandler::Quality) {
+        return true;
+    }
+    return false;
+}
+
+QVariant EXRHandler::option(ImageOption option) const
+{
+    QVariant v;
+
+    if (option == QImageIOHandler::Size) {
+        if (auto d = device()) {
+            // transactions works on both random and sequential devices
+            d->startTransaction();
+            try {
+                K_IStream istr(d, QByteArray());
+                Imf::RgbaInputFile file(istr);
+                if (m_imageNumber > -1) { // set the image to read
+                    auto views = viewList(file.header());
+                    if (m_imageNumber < views.count()) {
+                        file.setLayerName(views.at(m_imageNumber).toStdString());
+                    }
+                }
+                Imath::Box2i dw = file.dataWindow();
+                v = QVariant(QSize(dw.max.x - dw.min.x + 1, dw.max.y - dw.min.y + 1));
+            } catch (const std::exception &) {
+                // broken file or unsupported version
+            }
+            d->rollbackTransaction();
+        }
+    }
+
+    if (option == QImageIOHandler::ImageFormat) {
+        if (auto d = device()) {
+            // transactions works on both random and sequential devices
+            d->startTransaction();
+            try {
+                K_IStream istr(d, QByteArray());
+                Imf::RgbaInputFile file(istr);
+                v = QVariant::fromValue(imageFormat(file));
+            } catch (const std::exception &) {
+                // broken file or unsupported version
+            }
+            d->rollbackTransaction();
+        }
+    }
+
+    if (option == QImageIOHandler::CompressionRatio) {
+        v = QVariant(m_compressionRatio);
+    }
+
+    if (option == QImageIOHandler::Quality) {
+        v = QVariant(m_quality);
+    }
+
+    return v;
+}
+
+bool EXRHandler::jumpToNextImage()
+{
+    return jumpToImage(m_imageNumber + 1);
+}
+
+bool EXRHandler::jumpToImage(int imageNumber)
+{
+    if (imageNumber >= imageCount()) {
+        return false;
+    }
+    m_imageNumber = imageNumber;
+    return true;
+}
+
+int EXRHandler::imageCount() const
+{
+    // NOTE: image count is cached for performance reason
+    auto &&count = m_imageCount;
+    if (count > 0) {
+        return count;
+    }
+
+    count = QImageIOHandler::imageCount();
+
+    auto d = device();
+    d->startTransaction();
+
+    try {
+        K_IStream istr(d, QByteArray());
+        Imf::RgbaInputFile file(istr);
+        auto views = viewList(file.header());
+        if (!views.isEmpty()) {
+            count = views.size();
+        }
+    } catch (const std::exception &) {
+        // do nothing
+    }
+
+    d->rollbackTransaction();
+
+    return count;
+}
+
+int EXRHandler::currentImageNumber() const
+{
+    return m_imageNumber;
+}
+
 bool EXRHandler::canRead(QIODevice *device)
 {
     if (!device) {
@@ -273,7 +828,7 @@ bool EXRHandler::canRead(QIODevice *device)
 QImageIOPlugin::Capabilities EXRPlugin::capabilities(QIODevice *device, const QByteArray &format) const
 {
     if (format == "exr") {
-        return Capabilities(CanRead);
+        return Capabilities(CanRead | CanWrite);
     }
     if (!format.isEmpty()) {
         return {};
@@ -286,6 +841,9 @@ QImageIOPlugin::Capabilities EXRPlugin::capabilities(QIODevice *device, const QB
     if (device->isReadable() && EXRHandler::canRead(device)) {
         cap |= CanRead;
     }
+    if (device->isWritable()) {
+        cap |= CanWrite;
+    }
     return cap;
 }
 

src/imageformats/exr_p.h

@@ -1,8 +1,8 @@
 /*
-    QImageIO Routines to read (and perhaps in the future, write) images
+    The high dynamic range EXR format support for QImage.
-    in the high definition EXR format.
 
     SPDX-FileCopyrightText: 2003 Brad Hards <bradh@frogmouth.net>
+    SPDX-FileCopyrightText: 2023 Mirco Miranda <mircomir@outlook.com>
 
     SPDX-License-Identifier: LGPL-2.0-or-later
 */
@@ -12,6 +12,44 @@
 
 #include <QImageIOPlugin>
 
+/*!
+ * \brief The EXRHandler class
+ * The handler uses the OpenEXR reference implementation of the EXR file format.
+ *
+ * The purpose of EXR format is to accurately and efficiently represent high-dynamic-range scene-linear
+ * image data and associated metadata.
+ *
+ * Both reading and writing of EXR files is supported. When saving, the image is converted to 16-bit
+ * and sRGB Linear color space (if not already so). If no color space is set in the image, sRGB is assumed.
+ * When the handler is compiled with the default compile options, the loaded image is a 16-bit image
+ * with linear color space.
+ * Multiview images are also supported (read only) via imageCount(), jumpToImage(), etc....
+ *
+ * The following QImageIOHandler options are supported:
+ * - ImageFormat: The image's data format returned by the handler.
+ * - Size: The size of the image.
+ * - CompressionRatio: The compression ratio of the image data (see OpenEXR compression schemes).
+ * - Quality: The quality level of the image (see OpenEXR compression level of lossy codecs).
+ *
+ * The following metadata are set/get via QImage::setText()/QImage::text() in both read/write (if any):
+ * - Latitude, Longitude, Altitude: Geographic coordinates (Float converted to string).
+ * - CreationDate: Date the image was captured/created (QDateTime converted to string using Qt::ISODate).
+ * - Comment: Additional image information in human-readable form, for example a verbal description of the image (QString).
+ * - Owner: Name of the owner of the image (QString).
+ *
+ * In addition, information about image resolution is preserved and the preview is written for images larger
+ * than 1024px.
+ *
+ * The following compile options are supported (defines):
+ * - EXR_MAX_IMAGE_WIDTH: Maximum image width supported (read/write, default: 300000 px).
+ * - EXR_MAX_IMAGE_HEIGHT: Maximum image height supported (read/write, default: 300000 px).
+ * - EXR_LINES_PER_BLOCK: The number of scanlines buffered on both read and write operations.\n
+ *                        The higher the value, the greater the parallelization but the RAM consumption increases (default: 128)
+ * - EXR_USE_LEGACY_CONVERSIONS: The result image is an 8-bit RGB(A) converted without icc profiles (read, default: undefined).
+ * - EXR_CONVERT_TO_SRGB: The resulting image is convertef in the sRGB color space (read, default: undefined).
+ * - EXR_DISABLE_XMP_ATTRIBUTE: Disable the stores of XMP values in a non-standard attribute named "xmp".\n
+ *                              The QImage metadata used is "XML:com.adobe.xmp" (write, default: undefined).
+ */
 class EXRHandler : public QImageIOHandler
 {
 public:
@@ -19,8 +57,65 @@ public:
 
     bool canRead() const override;
     bool read(QImage *outImage) override;
+    bool write(const QImage &image) override;
+
+    void setOption(ImageOption option, const QVariant &value) override;
+    bool supportsOption(QImageIOHandler::ImageOption option) const override;
+    QVariant option(QImageIOHandler::ImageOption option) const override;
+
+    bool jumpToNextImage() override;
+    bool jumpToImage(int imageNumber) override;
+    int imageCount() const override;
+    int currentImageNumber() const override;
 
     static bool canRead(QIODevice *device);
+
+private:
+    /*!
+     * \brief m_compressionRatio
+     * Value set by QImageWriter::setCompression().
+     *
+     * The compression scheme is the same as defined by OpenEXR library:
+     * - 0: no compression
+     * - 1: run length encoding
+     * - 2: zlib compression, one scan line at a time
+     * - 3: zlib compression, in blocks of 16 scan lines
+     * - 4: piz-based wavelet compression (default)
+     * - 5: lossy 24-bit float compression
+     * - 6: lossy 4-by-4 pixel block compression, fixed compression rate
+     * - 7: lossy 4-by-4 pixel block compression, fields are compressed more
+     * - 8: lossy DCT based compression, in blocks of 32 scanlines. More efficient for partial buffer access.
+     * - 9: lossy DCT based compression, in blocks of 256 scanlines. More efficient space wise and faster to decode full frames than DWAA_COMPRESSION.
+     */
+    qint32 m_compressionRatio;
+
+    /*!
+     * \brief m_quality
+     * Value set by QImageWriter::setQuality().
+     *
+     * The quality is used on DCT compression schemes only with a
+     * supposed value between 0 and 100 (default: 45).
+     */
+    qint32 m_quality;
+
+    /*!
+     * \brief m_imageNumber
+     * Value set by QImageReader::jumpToImage() or QImageReader::jumpToNextImage().
+     * The number of view selected in a multiview image.
+     */
+    qint32 m_imageNumber;
+
+    /*!
+     * \brief m_imageCount
+     * The total number of views (cache value)
+     */
+    mutable qint32 m_imageCount;
+
+    /*!
+     * \brief m_startPos
+     * The initial device position to allow multi image load (cache value).
+     */
+    qint64 m_startPos;
 };
 
 class EXRPlugin : public QImageIOPlugin

src/imageformats/scanlineconverter.cpp

@@ -15,13 +15,15 @@ ScanLineConverter::ScanLineConverter(const QImage::Format &targetFormat)
 ScanLineConverter::ScanLineConverter(const ScanLineConverter &other)
     : _targetFormat(other._targetFormat)
     , _colorSpace(other._colorSpace)
+    , _defaultColorSpace(other._defaultColorSpace)
 {
 }
 
 ScanLineConverter &ScanLineConverter::operator=(const ScanLineConverter &other)
 {
-    this->_targetFormat = other._targetFormat;
+    _targetFormat = other._targetFormat;
-    this->_colorSpace = other._colorSpace;
+    _colorSpace = other._colorSpace;
+    _defaultColorSpace = other._defaultColorSpace;
     return (*this);
 }
 
@@ -40,9 +42,19 @@ QColorSpace ScanLineConverter::targetColorSpace() const
     return _colorSpace;
 }
 
+void ScanLineConverter::setDefaultSourceColorSpace(const QColorSpace &colorSpace)
+{
+    _defaultColorSpace = colorSpace;
+}
+
+QColorSpace ScanLineConverter::defaultSourceColorSpace() const
+{
+    return _defaultColorSpace;
+}
+
 const uchar *ScanLineConverter::convertedScanLine(const QImage &image, qint32 y)
 {
-    auto colorSpaceConversion = isColorSpaceConversionNeeded(image, _colorSpace);
+    auto colorSpaceConversion = isColorSpaceConversionNeeded(image);
     if (image.format() == _targetFormat && !colorSpaceConversion) {
         return image.constScanLine(y);
     }
@@ -54,7 +66,11 @@ const uchar *ScanLineConverter::convertedScanLine(const QImage &image, qint32 y)
     }
     std::memcpy(_tmpBuffer.bits(), image.constScanLine(y), std::min(_tmpBuffer.bytesPerLine(), image.bytesPerLine()));
     if (colorSpaceConversion) {
-        _tmpBuffer.setColorSpace(image.colorSpace());
+        auto cs = image.colorSpace();
+        if (!cs.isValid()) {
+            cs = _defaultColorSpace;
+        }
+        _tmpBuffer.setColorSpace(cs);
         _tmpBuffer.convertToColorSpace(_colorSpace);
     }
     _convBuffer = _tmpBuffer.convertToFormat(_targetFormat);
@@ -72,12 +88,15 @@ qsizetype ScanLineConverter::bytesPerLine() const
     return _convBuffer.bytesPerLine();
 }
 
-bool ScanLineConverter::isColorSpaceConversionNeeded(const QImage &image, const QColorSpace &targetColorSpace) 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;
+    }
     if (!sourceColorSpace.isValid() || !targetColorSpace.isValid()) {
         return false;
     }

src/imageformats/scanlineconverter_p.h

@@ -42,6 +42,14 @@ public:
     void setTargetColorSpace(const QColorSpace &colorSpace);
     QColorSpace targetColorSpace() const;
 
+    /*!
+     * \brief setDefaultSourceColorSpace
+     * Set the source color space to use when the image does not have a color space.
+     * \param colorSpace
+     */
+    void setDefaultSourceColorSpace(const QColorSpace &colorSpace);
+    QColorSpace defaultSourceColorSpace() const;
+
     /*!
      * \brief convertedScanLine
      * Convert the scanline \a y.
@@ -62,14 +70,24 @@ public:
      * \note Only 24 bit or grater images.
      * \param image The source image.
      * \param targetColorSpace The target color space.
+     * \param defaultColorSpace The default color space to use it image does not contains one.
      * \return True if the conversion should be done otherwise false.
      */
-    bool isColorSpaceConversionNeeded(const QImage &image, const QColorSpace &targetColorSpace) const;
+    static bool isColorSpaceConversionNeeded(const QImage &image, const QColorSpace &targetColorSpace, const QColorSpace &defaultColorSpace = QColorSpace());
+
+    /*!
+     * \brief isColorSpaceConversionNeeded
+     */
+    inline bool isColorSpaceConversionNeeded(const QImage &image) const
+    {
+        return isColorSpaceConversionNeeded(image, _colorSpace, _defaultColorSpace);
+    }
 
 private:
     // data
     QImage::Format _targetFormat;
     QColorSpace _colorSpace;
+    QColorSpace _defaultColorSpace;
 
     // internal buffers
     QImage _tmpBuffer;