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/****************************************************************************
**
** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the Qt Graphical Effects module.
**
** $QT_BEGIN_LICENSE:BSD$
** You may use this file under the terms of the BSD license as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
** * Redistributions of source code must retain the above copyright
** notice, this list of conditions and the following disclaimer.
** * Redistributions in binary form must reproduce the above copyright
** notice, this list of conditions and the following disclaimer in
** the documentation and/or other materials provided with the
** distribution.
** * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
** of its contributors may be used to endorse or promote products derived
** from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
** $QT_END_LICENSE$
**
****************************************************************************/
import QtQuick 2.0
import "private"
/*!
\qmltype GaussianBlur
\inqmlmodule QtGraphicalEffects 1.0
\since QtGraphicalEffects 1.0
\inherits QtQuick2::Item
\ingroup qtgraphicaleffects-blur
\brief Applies a higher quality blur effect.
GaussianBlur effect softens the image by blurring it with an algorithm that
uses the Gaussian function to calculate the effect. The effect produces
higher quality than \l{QtGraphicalEffects1::FastBlur}{FastBlur}, but is
slower to render.
\table
\header
\li Source
\li Effect applied
\row
\li \image Original_bug.png
\li \image GaussianBlur_bug.png
\endtable
\section1 Example
The following example shows how to apply the effect.
\snippet GaussianBlur-example.qml example
*/
Item {
id: rootItem
/*!
This property defines the source item that is going to be blurred.
\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 distance of the neighboring pixels which
affect the blurring of an individual pixel. A larger radius increases
the blur effect.
Depending on the radius value, value of the
\l{GaussianBlur::samples}{samples} should be set to sufficiently large
to ensure the visual quality.
The value ranges from 0.0 (no blur) to inf. By default, the property is
set to \c 0.0 (no blur).
\table
\header
\li Output examples with different radius values
\li
\li
\row
\li \image GaussianBlur_radius1.png
\li \image GaussianBlur_radius2.png
\li \image GaussianBlur_radius3.png
\row
\li \b { radius: 0 }
\li \b { radius: 4 }
\li \b { radius: 8 }
\row
\li \l samples: 16
\li \l samples: 16
\li \l samples: 16
\row
\li \l deviation: 3
\li \l deviation: 3
\li \l deviation: 3
\endtable
*/
property real radius: 0.0
/*!
This property defines how many samples are taken per pixel when blur
calculation is done. Larger value produces better quality, but is slower
to render.
Ideally, this value should be twice as large as the highest required
radius value, for example, if the radius is animated between 0.0 and
4.0, samples should be set to 8.
The value ranges from 0 to 32. By default, the property is set to \c 0.
This property is not intended to be animated. Changing this property may
cause the underlying OpenGL shaders to be recompiled.
*/
property int samples: 0
/*!
This property is a parameter to the gaussian function that is used when
calculating neighboring pixel weights for the blurring. A larger
deviation causes image to appear more blurry, but it also reduces the
quality of the blur. A very large deviation value causes the effect to
look a bit similar to what, for exmple, a box blur algorithm produces. A
too small deviation values makes the effect insignificant for the pixels
near the radius.
\inlineimage GaussianBlur_deviation_graph.png
\caption The image above shows the Gaussian function with two different
deviation values, yellow (1) and cyan (2.7). The y-axis shows the
weights, the x-axis shows the pixel distance.
The value ranges from 0.0 (no deviation) to inf (maximum deviation). By
default, devaition is binded to radius. When radius increases, deviation
is automatically increased linearly. With the radius value of 8, the
deviation default value becomes approximately 2.7034. This value
produces a compromise between the blur quality and overall blurriness.
\table
\header
\li Output examples with different deviation values
\li
\li
\row
\li \image GaussianBlur_deviation1.png
\li \image GaussianBlur_deviation2.png
\li \image GaussianBlur_deviation3.png
\row
\li \b { deviation: 1 }
\li \b { deviation: 2 }
\li \b { deviation: 4 }
\row
\li \l radius: 8
\li \l radius: 8
\li \l radius: 8
\row
\li \l samples: 16
\li \l samples: 16
\li \l samples: 16
\endtable
*/
property real deviation: (radius + 1) / 3.3333
/*!
This property defines the blur behavior near the edges of the item,
where the pixel blurring is affected by the pixels outside the source
edges.
If the property is set to \c true, the pixels outside the source are
interpreted to be transparent, which is similar to OpenGL
clamp-to-border extension. The blur is expanded slightly outside the
effect item area.
If the property is set to \c false, the pixels outside the source are
interpreted to contain the same color as the pixels at the edge of the
item, which is similar to OpenGL clamp-to-edge behavior. The blur does
not expand outside the effect item area.
By default, the property is set to \c false.
\table
\header
\li Output examples with different transparentBorder values
\li
\li
\row
\li \image GaussianBlur_transparentBorder1.png
\li \image GaussianBlur_transparentBorder2.png
\row
\li \b { transparentBorder: false }
\li \b { transparentBorder: true }
\row
\li \l radius: 8
\li \l radius: 8
\row
\li \l samples: 16
\li \l samples: 16
\row
\li \l deviation: 2.7
\li \l deviation: 2.7
\endtable
*/
property bool transparentBorder: false
/*!
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
sourceRect: rootItem.transparentBorder ? Qt.rect(-1, -1, parent.width + 2.0, parent.height + 2.0) : Qt.rect(0, 0, 0, 0)
}
ShaderEffectSource {
id: cacheItem
anchors.fill: verticalBlur
visible: rootItem.cached
smooth: true
sourceItem: verticalBlur
live: true
hideSource: visible
}
GaussianDirectionalBlur {
id: verticalBlur
x: transparentBorder ? -maximumRadius - 1 : 0
y: transparentBorder ? -maximumRadius - 1 : 0
width: horizontalBlur.width
height: horizontalBlur.height
horizontalStep: 0.0
verticalStep: 1.0 / parent.height
source: ShaderEffectSource {
id: horizontalBlurSource
sourceItem: horizontalBlur
hideSource: true
visible: false
smooth: true
}
deviation: rootItem.deviation
radius: rootItem.radius
maximumRadius: rootItem.samples * 0.5
transparentBorder: rootItem.transparentBorder
}
GaussianDirectionalBlur {
id: horizontalBlur
width: transparentBorder ? parent.width + 2 * maximumRadius + 2 : parent.width
height: transparentBorder ? parent.height + 2 * maximumRadius + 2 : parent.height
horizontalStep: 1.0 / parent.width
verticalStep: 0.0
source: sourceProxy.output
deviation: rootItem.deviation
radius: rootItem.radius
maximumRadius: rootItem.samples / 2.0
transparentBorder: rootItem.transparentBorder
}
}
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