exr.cpp

/*
    The high dynamic range EXR format support for QImage.
 
    SPDX-FileCopyrightText: 2003 Brad Hards <bradh@frogmouth.net>
    SPDX-FileCopyrightText: 2023 Mirco Miranda <mircomir@outlook.com>
 
    SPDX-License-Identifier: LGPL-2.0-or-later
*/
 
/* *** EXR_CONVERT_TO_SRGB ***
 * If defined, the linear data is converted to sRGB on read 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.
 */
//#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>
#include <ImathBox.h>
#include <ImfArray.h>
#include <ImfBoxAttribute.h>
#include <ImfChannelListAttribute.h>
#include <ImfCompressionAttribute.h>
#include <ImfConvert.h>
#include <ImfFloatAttribute.h>
#include <ImfInputFile.h>
#include <ImfInt64.h>
#include <ImfIntAttribute.h>
#include <ImfLineOrderAttribute.h>
#include <ImfPreviewImage.h>
#include <ImfRgbaFile.h>
#include <ImfStandardAttributes.h>
#include <ImfVersion.h>
 
#include <iostream>
 
#include <QColorSpace>
#include <QDataStream>
#include <QDebug>
#include <QFloat16>
#include <QImage>
#include <QImageIOPlugin>
#include <QLocale>
#include <QThread>
#include <QTimeZone>
 
class K_IStream : public Imf::IStream
{
public:
    K_IStream(QIODevice *dev)
        : IStream("K_IStream")
        , m_dev(dev)
    {
    }
 
    bool read(char c[], int n) override;
#if OPENEXR_VERSION_MAJOR > 2
    uint64_t tellg() override;
    void seekg(uint64_t pos) override;
#else
    Imf::Int64 tellg() override;
    void seekg(Imf::Int64 pos) override;
#endif
    void clear() override;
 
private:
    QIODevice *m_dev;
};
 
bool K_IStream::read(char c[], int n)
{
    qint64 result = m_dev->read(c, n);
    if (result > 0) {
        return true;
    } else if (result == 0) {
        throw Iex::InputExc("Unexpected end of file");
    } else { // negative value {
        Iex::throwErrnoExc("Error in read", result);
    }
    return false;
}
 
#if OPENEXR_VERSION_MAJOR > 2
uint64_t K_IStream::tellg()
#else
Imf::Int64 K_IStream::tellg()
#endif
{
    return m_dev->pos();
}
 
#if OPENEXR_VERSION_MAJOR > 2
void K_IStream::seekg(uint64_t pos)
#else
void K_IStream::seekg(Imf::Int64 pos)
#endif
{
    m_dev->seek(pos);
}
 
void K_IStream::clear()
{
    // TODO
}
 
class K_OStream : public Imf::OStream
{
public:
    K_OStream(QIODevice *dev)
        : OStream("K_OStream")
        , 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);
}
 
EXRHandler::EXRHandler()
    : m_compressionRatio(-1)
    , m_quality(-1)
    , m_imageNumber(0)
    , 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
{
    if (canRead(device())) {
        setFormat("exr");
        return true;
    }
    return false;
}
 
static QImage::Format imageFormat(const Imf::RgbaInputFile &file)
{
    auto isRgba = file.channels() & Imf::RgbaChannels::WRITE_A;
    return (isRgba ? QImage::Format_RGBA16FPx4 : QImage::Format_RGBX16FPx4);
}
 
/*!
 * \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(META_KEY_COMMENT), QString::fromStdString(comments->value()));
    }
 
    if (auto owner = header.findTypedAttribute<Imf::StringAttribute>("owner")) {
        image.setText(QStringLiteral(META_KEY_OWNER), QString::fromStdString(owner->value()));
    }
 
    if (auto lat = header.findTypedAttribute<Imf::FloatAttribute>("latitude")) {
        image.setText(QStringLiteral(META_KEY_LATITUDE), QLocale::c().toString(lat->value()));
    }
 
    if (auto lon = header.findTypedAttribute<Imf::FloatAttribute>("longitude")) {
        image.setText(QStringLiteral(META_KEY_LONGITUDE), QLocale::c().toString(lon->value()));
    }
 
    if (auto alt = header.findTypedAttribute<Imf::FloatAttribute>("altitude")) {
        image.setText(QStringLiteral(META_KEY_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()) {
            dateTime.setTimeZone(QTimeZone::fromSecondsAheadOfUtc(off));
            image.setText(QStringLiteral(META_KEY_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(META_KEY_XMP_ADOBE), QString::fromStdString(xmp->value()));
    }
 
    // camera metadata
    if (auto manufacturer = header.findTypedAttribute<Imf::StringAttribute>("cameraMake")) {
        image.setText(QStringLiteral(META_KEY_MANUFACTURER), QString::fromStdString(manufacturer->value()));
    }
    if (auto model = header.findTypedAttribute<Imf::StringAttribute>("cameraModel")) {
        image.setText(QStringLiteral(META_KEY_MODEL), QString::fromStdString(model->value()));
    }
    if (auto serial = header.findTypedAttribute<Imf::StringAttribute>("cameraSerialNumber")) {
        image.setText(QStringLiteral(META_KEY_SERIALNUMBER), QString::fromStdString(serial->value()));
    }
 
    // lens metadata
    if (auto manufacturer = header.findTypedAttribute<Imf::StringAttribute>("lensMake")) {
        image.setText(QStringLiteral(META_KEY_LENS_MANUFACTURER), QString::fromStdString(manufacturer->value()));
    }
    if (auto model = header.findTypedAttribute<Imf::StringAttribute>("lensModel")) {
        image.setText(QStringLiteral(META_KEY_LENS_MODEL), QString::fromStdString(model->value()));
    }
    if (auto serial = header.findTypedAttribute<Imf::StringAttribute>("lensSerialNumber")) {
        image.setText(QStringLiteral(META_KEY_LENS_SERIALNUMBER), QString::fromStdString(serial->value()));
    }
}
 
/*!
 * \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
    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
}
 
bool EXRHandler::read(QImage *outImage)
{
    try {
        auto d = device();
 
        // 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);
        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();
        qint32 width = dw.max.x - dw.min.x + 1;
        qint32 height = dw.max.y - dw.min.y + 1;
 
        // 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;
        }
 
        // creating the image
        QImage image = imageAlloc(width, height, imageFormat(file));
        if (image.isNull()) {
            qWarning() << "Failed to allocate image, invalid size?" << QSize(width, height);
            return false;
        }
 
        Imf::Array2D<Imf::Rgba> pixels;
        pixels.resizeErase(EXR_LINES_PER_BLOCK, width);
        bool isRgba = image.hasAlphaChannel();
 
        for (int y = 0, n = 0; y < height; y += n) {
            auto my = dw.min.y + y;
            if (my > dw.max.y) { // paranoia check
                break;
            }
 
            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) {
                auto scanLine = reinterpret_cast<qfloat16 *>(image.scanLine(y + n));
                for (int x = 0; x < width; ++x) {
                    auto xcs = x * 4;
                    *(scanLine + xcs) = qfloat16(float(pixels[n][x].r));
                    *(scanLine + xcs + 1) = qfloat16(float(pixels[n][x].g));
                    *(scanLine + xcs + 2) = qfloat16(float(pixels[n][x].b));
                    *(scanLine + xcs + 3) = qfloat16(isRgba ? std::clamp(float(pixels[n][x].a), 0.f, 1.f) : 1.f);
                }
            }
        }
 
        // set some useful metadata
        readMetadata(header, image);
        // final color operations
        readColorSpace(header, image);
 
        *outImage = image;
 
        return true;
    } catch (const std::exception &) {
        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(META_KEY_COMMENT), Qt::CaseInsensitive)) {
            header.insert("comments", Imf::StringAttribute(text.toStdString()));
        }
 
        if (!key.compare(QStringLiteral(META_KEY_OWNER), Qt::CaseInsensitive)) {
            header.insert("owner", Imf::StringAttribute(text.toStdString()));
        }
 
        // clang-format off
        if (!key.compare(QStringLiteral(META_KEY_LATITUDE), Qt::CaseInsensitive) ||
            !key.compare(QStringLiteral(META_KEY_LONGITUDE), Qt::CaseInsensitive) ||
            !key.compare(QStringLiteral(META_KEY_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(META_KEY_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(META_KEY_XMP_ADOBE), Qt::CaseInsensitive)) {
            header.insert("xmp", Imf::StringAttribute(text.toStdString()));
        }
#endif
 
        if (!key.compare(QStringLiteral(META_KEY_MANUFACTURER), Qt::CaseInsensitive)) {
            header.insert("cameraMake", Imf::StringAttribute(text.toStdString()));
        }
        if (!key.compare(QStringLiteral(META_KEY_MODEL), Qt::CaseInsensitive)) {
            header.insert("cameraModel", Imf::StringAttribute(text.toStdString()));
        }
        if (!key.compare(QStringLiteral(META_KEY_SERIALNUMBER), Qt::CaseInsensitive)) {
            header.insert("cameraSerialNumber", Imf::StringAttribute(text.toStdString()));
        }
 
        if (!key.compare(QStringLiteral(META_KEY_LENS_MANUFACTURER), Qt::CaseInsensitive)) {
            header.insert("lensMake", Imf::StringAttribute(text.toStdString()));
        }
        if (!key.compare(QStringLiteral(META_KEY_LENS_MODEL), Qt::CaseInsensitive)) {
            header.insert("lensModel", Imf::StringAttribute(text.toStdString()));
        }
        if (!key.compare(QStringLiteral(META_KEY_LENS_SERIALNUMBER), Qt::CaseInsensitive)) {
            header.insert("lensSerialNumber", Imf::StringAttribute(text.toStdString()));
        }
    }
    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()));
}
 
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());
        auto channelsType = image.hasAlphaChannel() ? Imf::RgbaChannels::WRITE_RGBA : Imf::RgbaChannels::WRITE_RGB;
        if (image.format() == QImage::Format_Mono ||
            image.format() == QImage::Format_MonoLSB ||
            image.format() == QImage::Format_Grayscale16 ||
            image.format() == QImage::Format_Grayscale8) {
            channelsType = Imf::RgbaChannels::WRITE_Y;
        }
        Imf::RgbaOutputFile file(ostr, header, channelsType);
        Imf::Array2D<Imf::Rgba> pixels;
        pixels.resizeErase(EXR_LINES_PER_BLOCK, width);
 
        // convert the image and write into the stream
        auto convFormat = image.hasAlphaChannel() ? QImage::Format_RGBA16FPx4 : QImage::Format_RGBX16FPx4;
        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) {
                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));
                }
            }
            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) {
        if (auto d = device())
            return !d->isSequential();
    }
    if (option == QImageIOHandler::ImageFormat) {
        if (auto d = device())
            return !d->isSequential();
    }
    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();
            if (m_startPos > -1) {
                d->seek(m_startPos);
            }
            try {
                K_IStream istr(d);
                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();
            if (m_startPos > -1) {
                d->seek(m_startPos);
            }
            try {
                K_IStream istr(d);
                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 < 0 || 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);
        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) {
        qWarning("EXRHandler::canRead() called with no device");
        return false;
    }
 
#if OPENEXR_VERSION_MAJOR == 3 && OPENEXR_VERSION_MINOR > 2
    // openexpr >= 3.3 uses seek and tell extensively
    if (device->isSequential()) {
        return false;
    }
#endif
 
    const QByteArray head = device->peek(4);
 
    return Imf::isImfMagic(head.data());
}
 
QImageIOPlugin::Capabilities EXRPlugin::capabilities(QIODevice *device, const QByteArray &format) const
{
    if (format == "exr") {
        return Capabilities(CanRead | CanWrite);
    }
    if (!format.isEmpty()) {
        return {};
    }
    if (!device->isOpen()) {
        return {};
    }
 
    Capabilities cap;
    if (device->isReadable() && EXRHandler::canRead(device)) {
        cap |= CanRead;
    }
    if (device->isWritable()) {
        cap |= CanWrite;
    }
    return cap;
}
 
QImageIOHandler *EXRPlugin::create(QIODevice *device, const QByteArray &format) const
{
    QImageIOHandler *handler = new EXRHandler;
    handler->setDevice(device);
    handler->setFormat(format);
    return handler;
}
 
#include "moc_exr_p.cpp"