The following example shows how to apply the effect. LinearGradient-example.qml example
*/ Item id: rootItem
/*! This property defines the starting point where the color at gradient position of 0.0 is rendered. Colors at larger position values are rendered linearly towards the end point. The point is given in pixels and the default value is Qt.point(0, 0). Setting the default values for the start and łLinearGradient::endend results in a full height linear gradient on the y-axis.
Output examples with different start values LinearGradient_start1.png LinearGradient_start2.png LinearGradient_start3.png s̱ tart: QPoint(0, 0) s̱ tart: QPoint(150, 150) s̱ tart: QPoint(300, 0) łend: QPoint(300, 300) łend: QPoint(300, 300) łend: QPoint(300, 300)
*/ property variant start: Qt.point(0, 0)
/*! This property defines the ending point where the color at gradient position of 1.0 is rendered. Colors at smaller position values are rendered linearly towards the start point. The point is given in pixels and the default value is Qt.point(0, height). Setting the default values for the łLinearGradient::startstart and end results in a full height linear gradient on the y-axis.
Output examples with different end values LinearGradient_end1.png LinearGradient_end2.png LinearGradient_end3.png e̱ nd: Qt.point(300, 300) e̱ nd: Qt.point(150, 150) e̱ nd: Qt.point(300, 0) łstart: Qt.point(0, 0) łstart: Qt.point(0, 0) łstart: Qt.point(0, 0)
*/ property variant end: Qt.point(0, height)
/*! 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 f̧alse. */ property bool cached: false
/*! This property defines the item that is going to be filled with gradient. Source item gets rendered into an intermediate pixel buffer and the alpha values from the result are used to determine the gradient's pixels visibility in the display. The default value for source is undefined and in that case whole effect area is filled with gradient.
Output examples with different source values LinearGradient_maskSource1.png LinearGradient_maskSource2.png s̱ ource: undefined s̱ ource: Image source: images/butterfly.png łstart: Qt.point(0, 0) łstart: Qt.point(0, 0) łend: Qt.point(300, 300) łend: Qt.point(300, 300)
It is not supported to let the effect include itself, for instance by setting source to the effect's parent. */ property variant source
/*! A gradient is defined by two or more colors, which are blended seamlessly. The colors are specified as a set of GradientStop child items, each of which defines a position on the gradient from 0.0 to 1.0 and a color. The position of each GradientStop is defined by the position property, and the color is definded by the color property.
Output examples with different gradient values LinearGradient_gradient1.png LinearGradient_gradient2.png LinearGradient_gradient3.png g̱radient: Gradient GradientStop position: 0.000 color: Qt.rgba(1, 0, 0, 1) GradientStop position: 0.167; color: Qt.rgba(1, 1, 0, 1) GradientStop position: 0.333; color: Qt.rgba(0, 1, 0, 1) GradientStop position: 0.500; color: Qt.rgba(0, 1, 1, 1) GradientStop position: 0.667; color: Qt.rgba(0, 0, 1, 1) GradientStop position: 0.833; color: Qt.rgba(1, 0, 1, 1) GradientStop position: 1.000; color: Qt.rgba(1, 0, 0, 1) g̱radient: Gradient GradientStop position: 0.0 color: "#F0F0F0" GradientStop position: 0.5 color: "#000000" GradientStop position: 1.0 color: "#F0F0F0" g̱radient: Gradient GradientStop position: 0.0 color: "#00000000" GradientStop position: 1.0 color: "#FF000000" łstart: Qt.point(0, 0) łstart: Qt.point(0, 0) łstart: Qt.point(0, 0) łend: Qt.point(300, 300) łend: Qt.point(300, 300) łend: Qt.point(300, 300)
*/ property Gradient gradient: Gradient GradientStop position: 0.0; color: "white" GradientStop position: 1.0; color: "black"
SourceProxy id: maskSourceProxy input: rootItem.source
ShaderEffectSource id: gradientSource sourceItem: Rectangle width: 16 height: 256 gradient: rootItem.gradient smooth: true smooth: true hideSource: true visible: false
ShaderEffectSource id: cacheItem anchors.fill: parent visible: rootItem.cached smooth: true sourceItem: shaderItem live: true hideSource: visible
ShaderEffect id: shaderItem
anchors.fill: parent
property variant source: gradientSource property variant maskSource: maskSourceProxy.output property variant startPoint: Qt.point(start.x / width, start.y / height) property real dx: end.x - start.x property real dy: end.y - start.y property real l: 1.0 / Math.sqrt(Math.pow(dx / width, 2.0) + Math.pow(dy / height, 2.0)) property real angle: Math.atan2(dx, dy) property variant matrixData: Qt.point(Math.sin(angle), Math.cos(angle))
vertexShader: " attribute highp vec4 qt_Vertex; attribute highp vec2 qt_MultiTexCoord0; uniform highp mat4 qt_Matrix; varying highp vec2 qt_TexCoord0; varying highp vec2 qt_TexCoord1; uniform highp vec2 startPoint; uniform highp float l; uniform highp vec2 matrixData;
void main() highp mat2 rot = mat2(matrixData.y, -matrixData.x, matrixData.x, matrixData.y);
qt_TexCoord0 = qt_MultiTexCoord0;
qt_TexCoord1 = qt_MultiTexCoord0 * l; qt_TexCoord1 -= startPoint * l; qt_TexCoord1 *= rot;
gl_Position = qt_Matrix * qt_Vertex; "
fragmentShader: maskSource == undefined ? noMaskShader : maskShader
onFragmentShaderChanged: lChanged()
property string maskShader: " uniform lowp sampler2D source; uniform lowp sampler2D maskSource; uniform lowp float qt_Opacity; varying highp vec2 qt_TexCoord0; varying highp vec2 qt_TexCoord1;
void main() lowp vec4 gradientColor = texture2D(source, qt_TexCoord1); lowp float maskAlpha = texture2D(maskSource, qt_TexCoord0).a; gl_FragColor = gradientColor * maskAlpha * qt_Opacity; "
property string noMaskShader: " uniform lowp sampler2D source; uniform lowp float qt_Opacity; varying highp vec2 qt_TexCoord1;
void main() gl_FragColor = texture2D(source, qt_TexCoord1) * qt_Opacity; "