Add support for the QOI image format

This MR adds read-only QOI (https://qoiformat.org/) image format support for KImageFormats.

This format has received it's MIME type inclusion in shared-mime-info 4 months ago: ff51a0a9e3

The code is based on the reference QOI implementation at https://github.com/phoboslab/qoi/blob/master/qoi.h

Official test images: https://qoiformat.org/qoi_test_images.zip

![pngvsqoi](/uploads/e386aa5057641057106e21940c770d97/pngvsqoi.png)

Also: This is my first MR to KDE ;)

README.md

@@ -19,6 +19,7 @@ The following image formats have read-only support:
 - Photoshop documents (psd, psb, pdd, psdt)
 - Sun Raster (ras)
 - Camera RAW images (arw, cr2, cr3, dcs, dng, ...)
+- Quite OK Image format (qoi)
 
 The following image formats have read and write support:
 

autotests/CMakeLists.txt

@@ -68,6 +68,7 @@ kimageformats_read_tests(
     hdr
     pcx
     psd
+    qoi
     ras
     rgb
     tga

src/imageformats/AUTHORS

@@ -12,3 +12,4 @@ Ignacio Castaño <castano@ludicon.com> -- DDS and PDS format reader.
 Christoph Hormann <chris_hormann@gmx.de> -- HDR format read support.
 Michael Ritzert <kde@ritzert.de> -- JPEG 2000 format read/write support
 Troy Unrau <troy@kde.org> -- Sun RASter read support
+Ernest Gupik <ernestgupik@wp.pl> -- QOI format read support

src/imageformats/CMakeLists.txt

@@ -87,6 +87,10 @@ kimageformats_add_plugin(kimg_psd SOURCES psd.cpp)
 
 ##################################
 
+kimageformats_add_plugin(kimg_qoi SOURCES qoi.cpp)
+
+##################################
+
 kimageformats_add_plugin(kimg_ras SOURCES ras.cpp)
 
 ##################################

src/imageformats/qoi.cpp

@@ -0,0 +1,268 @@
+/*
+    This file is part of the KDE project
+    SPDX-FileCopyrightText: 2023 Ernest Gupik <ernestgupik@wp.pl>
+
+    SPDX-License-Identifier: LGPL-2.0-or-later
+*/
+
+#include "qoi.h"
+
+#include "util_p.h"
+#include <QColorSpace>
+#include <QFile>
+#include <QIODevice>
+#include <QImage>
+
+namespace // Private
+{
+
+#define QOI_OP_INDEX 0x00 /* 00xxxxxx */
+#define QOI_OP_DIFF 0x40 /* 01xxxxxx */
+#define QOI_OP_LUMA 0x80 /* 10xxxxxx */
+#define QOI_OP_RUN 0xc0 /* 11xxxxxx */
+#define QOI_OP_RGB 0xfe /* 11111110 */
+#define QOI_OP_RGBA 0xff /* 11111111 */
+#define QOI_MASK_2 0xc0 /* 11000000 */
+
+#define QOI_MAGIC (((unsigned int)'q') << 24 | ((unsigned int)'o') << 16 | ((unsigned int)'i') << 8 | ((unsigned int)'f'))
+#define QOI_HEADER_SIZE 14
+
+struct QoiHeader {
+    quint32 MagicNumber;
+    quint32 Width;
+    quint32 Height;
+    quint8 Channels;
+    quint8 Colorspace;
+};
+
+struct Px {
+    quint8 r;
+    quint8 g;
+    quint8 b;
+    quint8 a;
+};
+
+static QDataStream &operator>>(QDataStream &s, QoiHeader &head)
+{
+    s >> head.MagicNumber;
+    s >> head.Width;
+    s >> head.Height;
+    s >> head.Channels;
+    s >> head.Colorspace;
+    return s;
+}
+
+static bool IsSupported(const QoiHeader &head)
+{
+    // Check magic number
+    if (head.MagicNumber != QOI_MAGIC) {
+        return false;
+    }
+    // Check if the header is a valid QOI header
+    if (head.Width == 0 || head.Height == 0 || head.Channels < 3 || head.Colorspace > 1) {
+        return false;
+    }
+    return true;
+}
+
+static int QoiHash(const Px &px)
+{
+    return px.r * 3 + px.g * 5 + px.b * 7 + px.a * 11;
+}
+
+static bool LoadQOI(QDataStream &s, const QoiHeader &qoi, QImage &img)
+{
+    s.device()->seek(QOI_HEADER_SIZE);
+
+    Px index[64] = {Px{
+        0,
+        0,
+        0,
+        0,
+    }};
+
+    Px px = Px{
+        0,
+        0,
+        0,
+        255,
+    };
+
+    if (qoi.Width * qoi.Height > UINT64_MAX / qoi.Channels) {
+        return false;
+    }
+
+    quint64 px_len = quint64(qoi.Width) * qoi.Height * qoi.Channels;
+    quint32 chunks_len = s.device()->size() - 8; // 8 is the size of the QOI padding
+    quint32 run = 0;
+    quint32 p = 0;
+
+    if (px_len > kMaxQVectorSize) {
+        return false;
+    }
+
+    QVector<quint8> input(px_len);
+
+    int i = 0;
+    while (!s.atEnd() && i < input.size()) {
+        s >> input[i];
+        i++;
+    }
+
+    // Allocate image
+    img = QImage(qoi.Width, qoi.Height, QImage::Format_ARGB32);
+
+    if (img.isNull()) {
+        return false;
+    }
+
+    // Set the image colorspace based on the qoi.Colorspace value
+    // As per specification: 0 = sRGB with linear alpha, 1 = all channels linear
+    switch (qoi.Colorspace) {
+    case 0:
+        img.setColorSpace(QColorSpace(QColorSpace::SRgb));
+        break;
+    case 1: {
+        img.setColorSpace(QColorSpace(QColorSpace::SRgbLinear));
+        break;
+    }
+    }
+
+    // Handle the byte stream
+    for (quint32 y = 0; y < qoi.Height; y++) {
+        QRgb *scanline = (QRgb *)img.scanLine(y);
+
+        for (quint32 x = 0; x < qoi.Width; x++) {
+            if (run > 0) {
+                run--;
+            } else if (p < chunks_len) {
+                quint32 b1 = input[p++];
+
+                if (b1 == QOI_OP_RGB) {
+                    px.r = input[p++];
+                    px.g = input[p++];
+                    px.b = input[p++];
+                } else if (b1 == QOI_OP_RGBA) {
+                    px.r = input[p++];
+                    px.g = input[p++];
+                    px.b = input[p++];
+                    px.a = input[p++];
+                } else if ((b1 & QOI_MASK_2) == QOI_OP_INDEX) {
+                    px = index[b1];
+                } else if ((b1 & QOI_MASK_2) == QOI_OP_DIFF) {
+                    px.r += ((b1 >> 4) & 0x03) - 2;
+                    px.g += ((b1 >> 2) & 0x03) - 2;
+                    px.b += (b1 & 0x03) - 2;
+                } else if ((b1 & QOI_MASK_2) == QOI_OP_LUMA) {
+                    quint32 b2 = input[p++];
+                    quint32 vg = (b1 & 0x3f) - 32;
+                    px.r += vg - 8 + ((b2 >> 4) & 0x0f);
+                    px.g += vg;
+                    px.b += vg - 8 + (b2 & 0x0f);
+                } else if ((b1 & QOI_MASK_2) == QOI_OP_RUN) {
+                    run = (b1 & 0x3f);
+                }
+                index[QoiHash(px) % 64] = px;
+            }
+            // Set the values for the pixel at (x, y)
+            scanline[x] = qRgba(px.r, px.g, px.b, px.a);
+        }
+    }
+
+    return true;
+}
+
+} // namespace
+
+QOIHandler::QOIHandler()
+{
+}
+
+bool QOIHandler::canRead() const
+{
+    if (canRead(device())) {
+        setFormat("qoi");
+        return true;
+    }
+    return false;
+}
+
+bool QOIHandler::canRead(QIODevice *device)
+{
+    if (!device) {
+        qWarning("QOIHandler::canRead() called with no device");
+        return false;
+    }
+    if (device->isSequential()) {
+        return false;
+    }
+
+    qint64 oldPos = device->pos();
+    QByteArray head = device->read(QOI_HEADER_SIZE);
+    int readBytes = head.size();
+
+    device->seek(oldPos);
+
+    if (readBytes < QOI_HEADER_SIZE) {
+        return false;
+    }
+
+    QDataStream stream(head);
+    stream.setByteOrder(QDataStream::BigEndian);
+    QoiHeader qoi;
+    stream >> qoi;
+
+    return IsSupported(qoi);
+}
+
+bool QOIHandler::read(QImage *image)
+{
+    QDataStream s(device());
+    s.setByteOrder(QDataStream::BigEndian);
+
+    // Read image header
+    QoiHeader qoi;
+    s >> qoi;
+
+    // Check if file is supported
+    if (!IsSupported(qoi)) {
+        return false;
+    }
+
+    QImage img;
+    bool result = LoadQOI(s, qoi, img);
+
+    if (result == false) {
+        return false;
+    }
+
+    *image = img;
+    return true;
+}
+
+QImageIOPlugin::Capabilities QOIPlugin::capabilities(QIODevice *device, const QByteArray &format) const
+{
+    if (format == "qoi" || format == "QOI") {
+        return Capabilities(CanRead);
+    }
+    if (!format.isEmpty()) {
+        return {};
+    }
+    if (!device->isOpen()) {
+        return {};
+    }
+
+    Capabilities cap;
+    if (device->isReadable() && QOIHandler::canRead(device)) {
+        cap |= CanRead;
+    }
+    return cap;
+}
+
+QImageIOHandler *QOIPlugin::create(QIODevice *device, const QByteArray &format) const
+{
+    QImageIOHandler *handler = new QOIHandler;
+    handler->setDevice(device);
+    handler->setFormat(format);
+    return handler;
+}

src/imageformats/qoi.h

@@ -0,0 +1,34 @@
+/*
+    This file is part of the KDE project
+    SPDX-FileCopyrightText: 2023 Ernest Gupik <ernestgupik@wp.pl>
+
+    SPDX-License-Identifier: LGPL-2.0-or-later
+*/
+
+#ifndef KIMG_QOI_H
+#define KIMG_QOI_H
+
+#include <QImageIOPlugin>
+
+class QOIHandler : public QImageIOHandler
+{
+public:
+    QOIHandler();
+
+    bool canRead() const override;
+    bool read(QImage *image) override;
+
+    static bool canRead(QIODevice *device);
+};
+
+class QOIPlugin : public QImageIOPlugin
+{
+    Q_OBJECT
+    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QImageIOHandlerFactoryInterface" FILE "qoi.json")
+
+public:
+    Capabilities capabilities(QIODevice *device, const QByteArray &format) const override;
+    QImageIOHandler *create(QIODevice *device, const QByteArray &format = QByteArray()) const override;
+};
+
+#endif // KIMG_QOI_H

src/imageformats/qoi.json

@@ -0,0 +1,4 @@
+{
+    "Keys": [ "qoi" ],
+    "MimeTypes": [ "image/qoi" ]
+}