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/****************************************************************************
**
** Copyright (C) 2017 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Qt Graphical Effects module.
**
** $QT_BEGIN_LICENSE:LGPL$
** 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.
**
** $QT_END_LICENSE$
**
****************************************************************************/
import QtQuick 2.12
import QtGraphicalEffects.private 1.12
/*!
\qmltype Displace
\inqmlmodule QtGraphicalEffects
\since QtGraphicalEffects 1.0
\inherits QtQuick2::Item
\ingroup qtgraphicaleffects-distortion
\brief Moves the pixels of the source item according to the given
displacement map.
\table
\header
\li Source
\li DisplacementSource
\li Effect applied
\row
\li \image Original_bug.png
\li \image Displace_map.png
\li \image Displace_bug.png
\endtable
\section1 Example
The following example shows how to apply the effect.
\snippet Displace-example.qml example
*/
Item {
id: rootItem
/*!
This property defines the source item for the pixels that are going to
be displaced according to the data from
\l{Displace::displacementSource}{displacementSource}.
\note It is not supported to let the effect include itself, for
instance by setting source to the effect's parent.
*/
property variant source
/*!
This property defines the item that is going to be used as the
displacement map. The displacementSource item gets rendered into the
intermediate pixel buffer. The red and green component values from the
result determine the displacement of the pixels from the source item.
The format for the displacement map is similar to the tangent space
normal maps, which can be created with most 3D-modeling tools. Many
image processing tools include the support for generating normal maps.
Alternatively, the displacement map for this effect can also be a QML
element which is colored appropriately. Like any QML element, it can be
animated. It is recommended that the size of the diplacement map matches
the size of the \l{Displace::source}{source}.
The displace data is interpreted in the RGBA format. For every pixel:
the red channel stores the x-axis displacement, and the green channel
stores the y-axis displacement. Blue and alpha channels are ignored for
this effect.
Assuming that red channel value 1.0 is fully red (0.0 having no red at
all), this effect considers pixel component value 0.5 to cause no
displacement at all. Values above 0.5 shift pixels to the left, values
below 0.5 do the shift to the right. In a similar way, green channel
values above 0.5 displace the pixels upwards, and values below 0.5 shift
the pixels downwards. The actual amount of displacement in pixels
depends on the \l displacement property.
*/
property variant displacementSource
/*!
This property defines the scale for the displacement. The bigger scale,
the bigger the displacement of the pixels. The value set to 0.0 causes
no displacement.
The value ranges from -1.0 (inverted maximum shift, according to
displacementSource) to 1.0 (maximum shift, according to
displacementSource). By default, the property is set to \c 0.0 (no
displacement).
\table
\header
\li Output examples with different displacement values
\li
\li
\row
\li \image Displace_displacement1.png
\li \image Displace_displacement2.png
\li \image Displace_displacement3.png
\row
\li \b { displacement: -0.2 }
\li \b { displacement: 0.0 }
\li \b { displacement: 0.2 }
\endtable
*/
property real displacement: 0.0
/*!
This property allows the effect output pixels to be cached in order to
improve the rendering performance.
Every time the source or effect properties are changed, the pixels in
the cache must be updated. Memory consumption is increased, because an
extra buffer of memory is required for storing the effect output.
It is recommended to disable the cache when the source or the effect
properties are animated.
By default, the property is set to \c false.
*/
property bool cached: false
SourceProxy {
id: sourceProxy
input: rootItem.source
}
SourceProxy {
id: displacementSourceProxy
input: rootItem.displacementSource
}
ShaderEffectSource {
id: cacheItem
anchors.fill: parent
visible: rootItem.cached
smooth: true
sourceItem: shaderItem
live: true
hideSource: visible
}
ShaderEffect {
id: shaderItem
property variant source: sourceProxy.output
property variant displacementSource: displacementSourceProxy.output
property real displacement: rootItem.displacement
property real xPixel: 1.0/width
property real yPixel: 1.0/height
anchors.fill: parent
fragmentShader: "qrc:/qt-project.org/imports/QtGraphicalEffects/shaders_ng/displace.frag.qsb"
}
}
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