Replace QDrawHelperGammaTables with QColorProfile

Turns the two set of tables in QDrawHelperGammaTables into two
QColorProfile classes that use similar structures and can be reused for
other gamma correction.

At the same time clean-up and improve the comma-correct blending code
to use the new profiles and QRgba64 precision.

Change-Id: I302bd87a5c836e1010fff6d633eeb56fd4ae2ff0
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

1 files changed, 157 insertions, 0 deletions

diff --git a/src/gui/painting/qcolorprofile_p.h b/src/gui/painting/qcolorprofile_p.h
new file mode 100644
index 0000000000..ca1786ee6d
--- /dev/null
+++ b/src/gui/painting/qcolorprofile_p.h
@@ -0,0 +1,157 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QCOLORPROFILE_P_H
+#define QCOLORPROFILE_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtGui/private/qtguiglobal_p.h>
+#include <QtGui/qrgb.h>
+#include <QtGui/qrgba64.h>
+
+QT_BEGIN_NAMESPACE
+
+class Q_GUI_EXPORT QColorProfile
+{
+public:
+    static QColorProfile *fromGamma(qreal gamma);
+    static QColorProfile *fromSRgb();
+
+    // The following methods all convert opaque or unpremultiplied colors:
+
+    QRgba64 toLinear64(QRgb rgb32) const
+    {
+        ushort r = m_toLinear[qRed(rgb32) << 4];
+        ushort g = m_toLinear[qGreen(rgb32) << 4];
+        ushort b = m_toLinear[qBlue(rgb32) << 4];
+        r = r + (r >> 8);
+        g = g + (g >> 8);
+        b = b + (b >> 8);
+        return QRgba64::fromRgba64(r, g, b, qAlpha(rgb32) * 257);
+    }
+
+    QRgb toLinear(QRgb rgb32) const
+    {
+        uchar r = (m_toLinear[qRed(rgb32) << 4] + 0x80) >> 8;
+        uchar g = (m_toLinear[qGreen(rgb32) << 4] + 0x80) >> 8;
+        uchar b = (m_toLinear[qBlue(rgb32) << 4] + 0x80) >> 8;
+        return qRgba(r, g, b, qAlpha(rgb32));
+    }
+
+    QRgba64 toLinear(QRgba64 rgb64) const
+    {
+        ushort r = rgb64.red();
+        ushort g = rgb64.green();
+        ushort b = rgb64.blue();
+        r = r - (r >> 8);
+        g = g - (g >> 8);
+        b = b - (b >> 8);
+        r = m_toLinear[r >> 4];
+        g = m_toLinear[g >> 4];
+        b = m_toLinear[b >> 4];
+        r = r + (r >> 8);
+        g = g + (g >> 8);
+        b = b + (b >> 8);
+        return QRgba64::fromRgba64(r, g, b, rgb64.alpha());
+    }
+
+    QRgb fromLinear64(QRgba64 rgb64) const
+    {
+        ushort r = rgb64.red();
+        ushort g = rgb64.green();
+        ushort b = rgb64.blue();
+        r = r - (r >> 8);
+        g = g - (g >> 8);
+        b = b - (b >> 8);
+        r = (m_fromLinear[r >> 4] + 0x80) >> 8;
+        g = (m_fromLinear[g >> 4] + 0x80) >> 8;
+        b = (m_fromLinear[b >> 4] + 0x80) >> 8;
+        return qRgba(r, g, b, rgb64.alpha8());
+    }
+
+    QRgb fromLinear(QRgb rgb32) const
+    {
+        uchar r = (m_fromLinear[qRed(rgb32) << 4] + 0x80) >> 8;
+        uchar g = (m_fromLinear[qGreen(rgb32) << 4] + 0x80) >> 8;
+        uchar b = (m_fromLinear[qBlue(rgb32) << 4] + 0x80) >> 8;
+        return qRgba(r, g, b, qAlpha(rgb32));
+    }
+
+    QRgba64 fromLinear(QRgba64 rgb64) const
+    {
+        ushort r = rgb64.red();
+        ushort g = rgb64.green();
+        ushort b = rgb64.blue();
+        r = r - (r >> 8);
+        g = g - (g >> 8);
+        b = b - (b >> 8);
+        r = m_fromLinear[r >> 4];
+        g = m_fromLinear[g >> 4];
+        b = m_fromLinear[b >> 4];
+        r = r + (r >> 8);
+        g = g + (g >> 8);
+        b = b + (b >> 8);
+        return QRgba64::fromRgba64(r, g, b, rgb64.alpha());
+    }
+
+private:
+    QColorProfile() { }
+
+    // We translate to 0-65280 (255*256) instead to 0-65535 to make simple
+    // shifting an accurate conversion.
+    // We translate from 0-4080 (255*16) for the same speed up, and to keep
+    // the tables small enough to fit in most inner caches.
+    ushort m_toLinear[(255 * 16) + 1]; // [0-4080] -> [0-65280]
+    ushort m_fromLinear[(255 * 16) + 1]; // [0-4080] -> [0-65280]
+
+};
+
+QT_END_NAMESPACE
+
+#endif // QCOLORPROFILE_P_H