Add API for reading and decoding graphical texture files

Add a framework for reading and decoding stored graphical texture file
formats. Includes decoders for the PKM and KTX formats.

This is basically the same texture file reading that was added to
qtdeclarative for 5.11, but has been refactored to be independent of
the scenegraph and opengl.

Task-number: QTBUG-67026
Change-Id: I87d8117550d8a2112f4f58c03e9ac6b3249cbc5a
Reviewed-by: Kai Koehne <kai.koehne@qt.io>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

1 files changed, 126 insertions, 0 deletions

diff --git a/src/gui/util/qpkmhandler.cpp b/src/gui/util/qpkmhandler.cpp
new file mode 100644
index 0000000000..4481deaa8e
--- /dev/null
+++ b/src/gui/util/qpkmhandler.cpp
@@ -0,0 +1,126 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qpkmhandler_p.h"
+#include "qtexturefiledata_p.h"
+
+#include <QFile>
+#include <QDebug>
+#include <QSize>
+#include <qendian.h>
+
+//#define ETC_DEBUG
+
+QT_BEGIN_NAMESPACE
+
+static const int headerSize = 16;
+
+struct PkmType
+{
+    quint32 glFormat;
+    quint32 bytesPerBlock;
+};
+
+static PkmType typeMap[5] = {
+    { 0x8D64,  8 },   // GL_ETC1_RGB8_OES
+    { 0x9274,  8 },   // GL_COMPRESSED_RGB8_ETC2
+    { 0, 0 },         // unused (obsolete)
+    { 0x9278, 16},    // GL_COMPRESSED_RGBA8_ETC2_EAC
+    { 0x9276,  8 }    // GL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2
+};
+
+bool QPkmHandler::canRead(const QByteArray &suffix, const QByteArray &block)
+{
+    Q_UNUSED(suffix)
+
+    return block.startsWith("PKM ");
+}
+
+QTextureFileData QPkmHandler::read()
+{
+    QTextureFileData texData;
+
+    if (!device())
+        return texData;
+
+    QByteArray fileData = device()->readAll();
+    if (fileData.size() < headerSize || !canRead(QByteArray(), fileData)) {
+        qCDebug(lcQtGuiTextureIO, "Invalid PKM file %s", logName().constData());
+        return QTextureFileData();
+    }
+    texData.setData(fileData);
+
+    const char *rawData = fileData.constData();
+
+    // ignore version (rawData + 4 & 5)
+
+    // texture type
+    quint16 type = qFromBigEndian<quint16>(rawData + 6);
+    if (type > sizeof(typeMap)/sizeof(typeMap[0])) {
+        qCDebug(lcQtGuiTextureIO, "Unknown compression format in PKM file %s", logName().constData());
+        return QTextureFileData();
+    }
+    texData.setGLFormat(0);                    // 0 for compressed textures
+    texData.setGLInternalFormat(typeMap[type].glFormat);
+    //### setBaseInternalFormat
+
+    // texture size
+    texData.setNumLevels(1);
+    const int bpb = typeMap[type].bytesPerBlock;
+    QSize paddedSize(qFromBigEndian<quint16>(rawData + 8), qFromBigEndian<quint16>(rawData + 10));
+    texData.setDataLength((paddedSize.width() / 4) * (paddedSize.height() / 4) * bpb);
+    QSize texSize(qFromBigEndian<quint16>(rawData + 12), qFromBigEndian<quint16>(rawData + 14));
+    texData.setSize(texSize);
+
+    texData.setDataOffset(headerSize);
+
+    if (!texData.isValid()) {
+        qCDebug(lcQtGuiTextureIO, "Invalid values in header of PKM file %s", logName().constData());
+        return QTextureFileData();
+    }
+
+    texData.setLogName(logName());
+
+#ifdef ETC_DEBUG
+    qDebug() << "PKM file handler read" << texData;
+#endif
+    return texData;
+}
+
+QT_END_NAMESPACE