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/****************************************************************************
**
** Copyright (C) 2017 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Qt Virtual Keyboard module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:GPL$
** 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 General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 or (at your option) 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.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-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "handwritinggesturerecognizer.h"
#include <QtCore/qmath.h>
#include <QVector2D>
namespace QtVirtualKeyboard {
HandwritingGestureRecognizer::HandwritingGestureRecognizer(QObject *parent) :
GestureRecognizer(parent),
m_dpi(96)
{
}
void HandwritingGestureRecognizer::setDpi(int value)
{
m_dpi = value >= 0 ? value : 96;
}
int HandwritingGestureRecognizer::dpi() const
{
return m_dpi;
}
QVariantMap HandwritingGestureRecognizer::recognize(const QList<Trace *> traceList)
{
if (traceList.count() > 0 && traceList.count() < 3) {
// Swipe gesture detection
// =======================
//
// The following algorithm is based on the assumption that a
// vector composed of two arbitrary selected, but consecutive
// measuring points, and a vector composed of the first and last
// of the measuring points, are approximately in the same angle.
//
// If the measuring points are located very close to each other,
// the angle can fluctuate a lot. This has been taken into account
// by setting a minimum Euclidean distance between the measuring
// points.
//
// Minimum euclidean distance of a segment (in millimeters)
static const int MINIMUM_EUCLIDEAN_DISTANCE = 8;
// Maximum theta variance (in degrees)
static const qreal THETA_THRESHOLD = 25.0;
// Maximum width variance in multitouch swipe (+- in percent)
static const int MAXIMUM_WIDTH_VARIANCE = 20;
const qreal minimumEuclideanDistance = MINIMUM_EUCLIDEAN_DISTANCE / 25.4 * m_dpi;
static const qreal thetaThreshold = qDegreesToRadians(THETA_THRESHOLD);
QList<QVector2D> swipeVectors;
int traceIndex;
const int traceCount = traceList.size();
for (traceIndex = 0; traceIndex < traceCount; ++traceIndex) {
const Trace *trace = traceList.at(traceIndex);
const QVariantList &points = trace->points();
QVector2D swipeVector;
const int pointCount = points.count();
int pointIndex = 0;
if (pointCount >= 2) {
QPointF startPosition = points.first().toPointF();
swipeVector = QVector2D(points.last().toPointF() - startPosition);
const qreal swipeLength = swipeVector.length();
if (swipeLength >= minimumEuclideanDistance) {
QPointF previousPosition = startPosition;
qreal euclideanDistance = 0;
for (pointIndex = 1; pointIndex < pointCount; ++pointIndex) {
QPointF currentPosition(points.at(pointIndex).toPointF());
euclideanDistance += QVector2D(currentPosition - previousPosition).length();
if (euclideanDistance >= minimumEuclideanDistance) {
// Set the angle (theta) between the sample vector and the swipe vector
const QVector2D sampleVector(currentPosition - startPosition);
const qreal theta = qAcos(QVector2D::dotProduct(swipeVector, sampleVector) / (swipeLength * sampleVector.length()));
// Rejected when theta above threshold
if (theta >= thetaThreshold) {
swipeVector = QVector2D();
break;
}
startPosition = currentPosition;
euclideanDistance = 0;
}
previousPosition = currentPosition;
}
if (pointIndex < pointCount) {
swipeVector = QVector2D();
break;
}
// Check to see if angle and length matches to existing touch points
if (!swipeVectors.isEmpty()) {
bool matchesToExisting = true;
const qreal minimumSwipeLength = (swipeLength * (100.0 - MAXIMUM_WIDTH_VARIANCE) / 100.0);
const qreal maximumSwipeLength = (swipeLength * (100.0 + MAXIMUM_WIDTH_VARIANCE) / 100.0);
for (const QVector2D &otherSwipeVector : qAsConst(swipeVectors)) {
const qreal otherSwipeLength = otherSwipeVector.length();
const qreal theta = qAcos(QVector2D::dotProduct(swipeVector, otherSwipeVector) / (swipeLength * otherSwipeLength));
if (theta >= thetaThreshold) {
matchesToExisting = false;
break;
}
if (otherSwipeLength < minimumSwipeLength || otherSwipeLength > maximumSwipeLength) {
matchesToExisting = false;
break;
}
}
if (!matchesToExisting) {
swipeVector = QVector2D();
break;
}
}
} else {
swipeVector = QVector2D();
}
}
if (swipeVector.isNull())
break;
swipeVectors.append(swipeVector);
}
if (swipeVectors.size() == traceCount) {
QVariantMap swipeGesture;
// Get swipe angle from the first vector:
// 0 degrees == right
// 90 degrees == down
// 180 degrees == left
// 270 degrees == up
QList<QVector2D>::ConstIterator swipeVector = swipeVectors.constBegin();
qreal swipeLength = swipeVector->length();
qreal swipeAngle = qAcos(swipeVector->x() / swipeLength);
if (swipeVector->y() < 0)
swipeAngle = 2 * M_PI - swipeAngle;
// Calculate an average length of the vector
++swipeVector;
for (const auto cend = swipeVectors.cend(); swipeVector != cend; ++swipeVector)
swipeLength += swipeVector->length();
swipeLength /= traceCount;
swipeGesture[QLatin1String("type")] = QLatin1String("swipe");
swipeGesture[QLatin1String("angle")] = swipeAngle;
swipeGesture[QLatin1String("angle_degrees")] = qRadiansToDegrees(swipeAngle);
swipeGesture[QLatin1String("length")] = swipeLength;
swipeGesture[QLatin1String("length_mm")] = swipeLength / m_dpi * 25.4;
swipeGesture[QLatin1String("touch_count")] = traceCount;
return swipeGesture;
}
}
return QVariantMap();
}
}
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