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diff --git a/doc/src/examples/qmlvideofx.qdoc b/doc/src/examples/qmlvideofx.qdoc new file mode 100644 index 0000000000..68a4e9df48 --- /dev/null +++ b/doc/src/examples/qmlvideofx.qdoc @@ -0,0 +1,221 @@ +/**************************************************************************** +** +** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:FDL$ +** GNU Free Documentation License +** Alternatively, this file may be used under the terms of the GNU Free +** Documentation License version 1.3 as published by the Free Software +** Foundation and appearing in the file included in the packaging of +** this file. +** +** Other Usage +** Alternatively, this file may be used in accordance with the terms +** and conditions contained in a signed written agreement between you +** and Nokia. +** +** +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! +\example video/qmlvideofx +\title QML Video Shader Effects Example + +\brief The QML Video Shader Effects Example shows how the \l {ShaderEffectItem} +element can be used to apply postprocessing effects, expressed in GLSL, to QML +\l {Video} and \l {Camera} items. + +\section1 Overview + +This example shows how the \l {ShaderEffectItem} element can be used to apply +postprocessing effects, expressed in GLSL, to QML \l {Video} and \l {Camera} items. + +It also shows how native code can be combined with QML to implement more +advanced functionality - in this case, C++ code is used to calculate the QML +frame rate and (on Symbian) the graphics memory consumption; these metrics +are rendered in QML as semi-transparent items overlaid on the video content. + +Finally, this application demonstrates the use of different top-level QML +files to handle different physical screen sizes. On small-screen devices, +menus are by default hidden, and only appear when summoned by a gesture. +Large-screen devices show a more traditional layout in which menus are +displayed around the video content pane. + +The following screenshots show shader effects being applied. In each case, +the effect is implemented using a fragment shader. + +Here we see an edge detection algorithm being applied to a video clip +(\l{http://orange.blender.org/}{Elephant's Dream from blender.org}). +\image qmlvideofx-video-edgedetection.png + +This image shows a page curl effect, applied to the same video clip. +\image qmlvideofx-video-pagecurl.png + +Here we see a 'glow' effect (edge detection plus colour quantization) being +applied to the camera viewfinder. +\image qmlvideofx-camera-glow.png + +This image shows a 'lens magnification' effect applied to the viewfinder. +\image qmlvideofx-camera-magnify.png + +The application includes many more effects than the ones shown here - look +for Effect*.qml files in the list above to see the full range. + +\section1 Application structure + +Shader effects can be applied to video or viewfinder content using the +\l{ShaderEffectItem} element, as shown in the following example, which applies +a wiggly effect to the content: + +\code +import QtQuick 1.0 +import Qt.labs.shaders 1.0 + +Rectangle { + width: 300 + height: 300 + color: "black" + + Video { + id: video + anchors.fill: parent + source: "test.mp4" + } + + ShaderEffectItem { + property variant source: ShaderEffectSource { sourceItem: video; hideSource: true } + property real wiggleAmount: 0.005 + anchors.fill: video + + fragmentShader: " + varying highp vec2 qt_TexCoord0; + uniform sampler2D source; + uniform highp float wiggleAmount; + void main(void) + { + highp vec2 wiggledTexCoord = qt_TexCoord0; + wiggledTexCoord.s += sin(4.0 * 3.141592653589 * wiggledTexCoord.t) * wiggleAmount; + gl_FragColor = texture2D(source, wiggledTexCoord.st); + } + " + } +} +\endcode + +In this application, the usage of the \l{ShaderEffectItem}, \l{Video} and +\l{Camera} elements is a bit more complicated, for the following reasons: + +\list + \o Each effect can be applied to either a \l{Video}, a \l{Camera} or a + \l{Image} item, so the type of the source item must be abstracted away + from the effect implementation + \o For some effects (such as the edge detection and glow examples shown in + the screenshots above), the transformation is applied only to pixels to + the left of a dividing line - this allows the effect to be easily + compared with the untransformed image on the right + \o Most effects have one or more parameters which can be modified by the + user - these are controlled by sliders in the UI which are connected + to uniform values passed into the GLSL code +\endlist + +The abstraction of source item type is achieved by the +\l{video/qmlvideofx/qml/qmlvideofx/Content.qml}{Content} element, which uses a +\l{Loader} to create either a \l{Video}, \l{Camera} or \l{Image} element: + +\quotefromfile video/qmlvideofx/qml/qmlvideofx/Content.qml +\skipto import +\printuntil { +\dots +\skipto Loader { +\printuntil } +\dots +\skipto function openImage +\printuntil "ContentImage.qml" +\skipto contentLoader.item.source +\printuntil path +\skipto } +\printuntil } +\skipto function openVideo +\printuntil "ContentVideo.qml" +\skipto contentLoader.item.source +\printuntil path +\skipto } +\printuntil } +\skipto function openCamera +\printuntil "ContentCamera.qml" +\skipto } +\printuntil } +\skipto /^\}/ +\printuntil } + +Each effect is implemented as a QML item which is based on the +\l{video/qmlvideofx/qml/qmlvideofx/Effect.qml}{Effect} element, which in turn +is based on the \l{ShaderEffectItem} element: + +\quotefromfile video/qmlvideofx/qml/qmlvideofx/Effect.qml +\skipto import +\printuntil /^\}/ + +The interface of the Effect element allows for derived effects to specify the +number of parameters which they support (and therefore the number of sliders +which should be displayed), and whether a vertical dividing line should be drawn +between transformed and untransformed image regions. As an example, here is the +implementation of the pixelation effect. As you can see, the pixelation effect +supports one parameter (which controls the pixelation granularity), and states +that the divider should be displayed. + +\quotefromfile video/qmlvideofx/qml/qmlvideofx/EffectPixelate.qml +\skipto import +\printuntil /^\}/ + +The main.qml file shows a +\l{video/qmlvideofx/qml/qmlvideofx/FileOpen.qml}{FileOpen} element which allows +the user to select the input source and an +\l{video/qmlvideofx/qml/qmlvideofx/EffectSelectionPanel.qml}{EffectSelectionPanel} +item, which lists each of the available shader effects. As described above, a +\l{video/qmlvideofx/qml/qmlvideofx/Content.qml}{Content} item is used to load the +appropriate input and effect element. A +\l{video/qmlvideofx/qml/qmlvideofx/Divider.qml}{Divider} item draws the +vertical dividing line, which can be dragged left / right by the user. Finally, +a \l{video/qmlvideofx/qml/qmlvideofx/ParameterPanel.qml}{ParameterPanel} item +renders the sliders corresponding to each effect parameter. + +Here is the source selection menu: +\image qmlvideofx-source-menu.png + +And here is the effect selection menu: +\image qmlvideofx-effects-menu.png + +\section1 Calculating and displaying QML painting rate + +\input examples/video-qml-paint-rate.qdocinc + +All that remains is to create a PaintEventMonitor in the C++ main() function, tell +it to monitor the QML viewport widget, and to connect its framePainted() signal to +a JavaScript function, which will eventually call frequencyItem.notify(): + +\quotefromfile video/qmlvideofx/main.cpp +\skipto QmlApplicationViewer +\printuntil ; +\dots +\skipto QGraphicsObject +\printuntil ; +\dots +\skipto PaintEventMonitor +\printuntil SLOT(qmlFramePainted())); + +\section1 Querying and displaying graphics memory consumption + +\input examples/video-graphics-memory.qdocinc + +*/ + + |