qmlcontrols/graphicaleffects/Lanczos.qml

0001 /*
0002     SPDX-FileCopyrightText: 2021 Arjen Hiemstra <ahiemstra@heimr.nl>
0003
0004     SPDX-License-Identifier: LGPL-2.0-or-later
0005 */
0006
0007 import QtQuick 2.15
0008
0009 /**
0010  * A ShaderEffect that makes use of the Lanczos resampling method for scaling textures.
0011  *
0012  * Lanczos resampling tries to preserve detail when scaling down images and
0013  * thus looks less blurry compared to a simple linear interpolation.
0014  *
0015  * This effect implements a single-pass Lanczos resampling filter using two
0016  * lobes. Everything is done in the shader, with some defaults set for
0017  * parameters. These defaults were designed to provide a good visual result when
0018  * scaling down window thumbnails.
0019  */
0020 ShaderEffect {
0021     /**
0022      * The source texture. Can be any QQuickTextureProvider.
0023      */
0024     required property var source
0025     /**
0026      * The size of the source texture. Used to perform aspect ratio correction.
0027      */
0028     required property size sourceSize
0029
0030     /**
0031      * The target size of the Lanczos effect.
0032      *
0033      * Defaults to the width and height of this effect.
0034      */
0035     property size targetSize: Qt.size(width, height)
0036
0037     /**
0038      * Lanczos window Sinc function factor.
0039      *
0040      * Defaults to 0.4
0041      */
0042     property real windowSinc: 0.4;
0043     /**
0044      * Lanczos Sinc function factor.
0045      *
0046      * Defaults to 1.0
0047      */
0048     property real sinc: 1.0;
0049
0050     /**
0051      * The amount of anti-ringing to apply.
0052      *
0053      * Defaults to 0.65
0054      */
0055     property real antiRingingStrength: 0.65;
0056     /**
0057      * The resolution of the Lanczos effect.
0058      *
0059      * Larger values mean reduced (more pixelated) results.
0060      * Defaults to 0.98 to achieve good results.
0061      */
0062     property real resolution: 0.98;
0063
0064     vertexShader: Qt.resolvedUrl("preserveaspect.vert")
0065     fragmentShader: Qt.resolvedUrl("lanczos2sharp.frag")
0066 }