GrayscaleEffect.qml Example File

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 import QtQuick 1.0
 import Qt.labs.shaders 1.0

 ShaderEffectItem {
     id: effect
     property real ratio: 1.0
     property variant source: 0

     fragmentShader:
         "
         varying highp vec2 qt_TexCoord0;
         uniform sampler2D source;
         uniform highp float ratio;
         void main(void)
         {
             lowp vec4 textureColor = texture2D(source, qt_TexCoord0.st);
             lowp float gray = dot(textureColor, vec4(0.299, 0.587, 0.114, 0.0));
             gl_FragColor = vec4(gray * ratio + textureColor.r * (1.0 - ratio), gray * ratio + textureColor.g * (1.0 - ratio), gray * ratio + textureColor.b * (1.0 - ratio), textureColor.a);
         }
         "
 }