如何在qml中绘制图像的梯形形状？

import QtQuick 2.0
import QtGraphicalEffects 1.0

Item {
    width: 400
    height: 400

    Image {
        id: image
        source: "image.png"
        anchors.centerIn: parent
        width: parent.width
        height: parent.height

        layer.enabled: true
        layer.effect: OpacityMask {
            maskSource: mask
            source: image
        }
    }

    Rectangle {
        id: mask
        width: parent.width
        height: parent.height
        gradient: Gradient {
            GradientStop { position: 0.0; color: "transparent" }
            GradientStop { position: 0.2; color: "transparent" }
            GradientStop { position: 0.8; color: "black" }
            GradientStop { position: 1.0; color: "black" }
        }
    }
}