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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
import QtQuick 2.0
import "private"
/*!
\qmltype DirectionalBlur
\inqmlmodule QtGraphicalEffects 1.0
\since QtGraphicalEffects 1.0
\inherits QtQuick2::Item
\ingroup qtgraphicaleffects-motion-blur
\brief Applies blur effect to the specified direction.
Effect creates perceived impression that the source item appears to be
moving in the direction of the blur. Blur is applied to both sides of
each pixel, therefore setting the direction to 0 and 180 provides the
same result.
Other available motionblur effects are \l{QtGraphicalEffects1::ZoomBlur}{ZoomBlur} and
\l{QtGraphicalEffects1::RadialBlur}{RadialBlur}.
\table
\header
\li Source
\li Effect applied
\row
\li \image Original_bug.png
\li \image DirectionalBlur_bug.png
\endtable
\section1 Example
The following example shows how to apply the effect.
\snippet DirectionalBlur-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 percieved amount of movement for each pixel.
The movement is divided evenly to both sides of each pixel.
The quality of the blur depends on \l{DirectionalBlur::samples}{samples}
property. If length value is large, more samples are needed to keep the
visual quality at high level.
The value ranges from 0.0 to inf.
By default the property is set to \c 0.0 (no blur).
\table
\header
\li Output examples with different length values
\li
\li
\row
\li \image DirectionalBlur_length1.png
\li \image DirectionalBlur_length2.png
\li \image DirectionalBlur_length3.png
\row
\li \b { length: 0.0 }
\li \b { length: 32.0 }
\li \b { length: 48.0 }
\row
\li \l samples: 24
\li \l samples: 24
\li \l samples: 24
\row
\li \l angle: 0
\li \l angle: 0
\li \l angle: 0
\endtable
*/
property real length: 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.
This property is not intended to be animated. Changing this property may
cause the underlying OpenGL shaders to be recompiled.
Allowed values are between 0 and inf (practical maximum depends on GPU).
By default the property is set to \c 0 (no samples).
*/
property int samples: 0
/*!
This property defines the direction for the blur. Blur is applied to
both sides of each pixel, therefore setting the direction to 0 and 180
produces the same result.
The value ranges from -180.0 to 180.0.
By default the property is set to \c 0.0.
\table
\header
\li Output examples with different angle values
\li
\li
\row
\li \image DirectionalBlur_angle1.png
\li \image DirectionalBlur_angle2.png
\li \image DirectionalBlur_angle3.png
\row
\li \b { angle: 0.0 }
\li \b { angle: 45.0 }
\li \b { angle: 90.0 }
\row
\li \l samples: 24
\li \l samples: 24
\li \l samples: 24
\row
\li \l length: 32
\li \l length: 32
\li \l length: 32
\endtable
*/
property real angle: 0.0
/*!
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.
*/
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: shaderItem
visible: rootItem.cached
smooth: true
sourceItem: shaderItem
live: true
hideSource: visible
}
ShaderEffect {
id: shaderItem
property variant source: sourceProxy.output
property real len: rootItem.length
property bool transparentBorder: rootItem.transparentBorder
property real samples: rootItem.samples
property real weight: 1.0 / Math.max(1.0, rootItem.samples)
property variant expandPixels: transparentBorder ? Qt.size(rootItem.samples, rootItem.samples) : Qt.size(0,0)
property variant expand: transparentBorder ? Qt.size(expandPixels.width / width, expandPixels.height / height) : Qt.size(0,0)
property variant delta: Qt.size(1.0 / rootItem.width * Math.cos((rootItem.angle + 90) * Math.PI/180), 1.0 / rootItem.height * Math.sin((rootItem.angle + 90) * Math.PI/180))
x: transparentBorder ? -expandPixels.width - 1: 0
y: transparentBorder ? -expandPixels.height - 1 : 0
width: transparentBorder ? parent.width + 2.0 * expandPixels.width + 2 : parent.width
height: transparentBorder ? parent.height + 2.0 * expandPixels.height + 2 : parent.height
property string fragmentShaderSkeleton: "
varying highp vec2 qt_TexCoord0;
uniform highp float qt_Opacity;
uniform lowp sampler2D source;
uniform highp float len;
uniform highp float samples;
uniform highp float weight;
uniform highp vec2 expand;
uniform highp vec2 delta;
void main(void) {
highp vec2 shift = delta * len / max(1.0, samples - 1.0);
mediump vec2 texCoord = qt_TexCoord0;
gl_FragColor = vec4(0.0);
PLACEHOLDER_EXPAND_STEPS
texCoord -= shift * max(0.0, samples - 1.0) * 0.5;
PLACEHOLDER_UNROLLED_LOOP
gl_FragColor *= weight * qt_Opacity;
}
"
function buildFragmentShader() {
var shader = fragmentShaderSkeleton
var expandSteps = ""
if (transparentBorder) {
expandSteps += "texCoord = (texCoord - expand) / (1.0 - 2.0 * expand);"
}
var unrolledLoop = "gl_FragColor += texture2D(source, texCoord);\n"
if (rootItem.samples > 1) {
unrolledLoop = ""
for (var i = 0; i < rootItem.samples; i++)
unrolledLoop += "gl_FragColor += texture2D(source, texCoord); texCoord += shift;\n"
}
shader = shader.replace("PLACEHOLDER_EXPAND_STEPS", expandSteps)
fragmentShader = shader.replace("PLACEHOLDER_UNROLLED_LOOP", unrolledLoop)
}
onFragmentShaderChanged: sourceChanged()
onSamplesChanged: buildFragmentShader()
onTransparentBorderChanged: buildFragmentShader()
Component.onCompleted: buildFragmentShader()
}
}
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