QImage::pixel() in QML

guillaume.belz

For Qt exercise, I try tro write ColorPicker in QML. I have no problem to create gradients and mouse management : "image on forum":http://www.developpez.net/forums/d965869/c-cpp/bibliotheques/qt/contribuez/exercice-qt-color-picker-premiere-partie/#post5422837

I want to send signal on click with selected color. But I can't know color of pixel at given position.

Have you ideas to do this ?

PS : I have 2 solutions to do this : create specific QObject to store image and pick color and calcul RGBA parameters with x,y position. But I want to know if they are more simple solution

Thanks

DenisKormalev

AFAIK there is no other solution than calculate color from x,y pair

guillaume.belz

Thanks for reply

I do with x,y values

After the end of exercise, I send link with code here, those who would be interested.

Thanks

? Offline

yes, you could also add a howto wiki page for this

guillaume.belz

The code I had write :

@import Qt 4.7

Item
{
width: 256
height: 256

function updateSelectedColor()
{
    ColorPickerContext.selected_red =
            (1 - (cursor.y / height)) *
            (1 + (cursor.x / width) * (main_red - 1))
    ColorPickerContext.selected_green =
            (1 - (cursor.y / height)) *
            (1 + (cursor.x / width) * (main_green - 1))
    ColorPickerContext.selected_blue =
            (1 - (cursor.y / height)) *
            (1 + (cursor.x / width) * (main_blue - 1))
}

Rectangle
{
    width: parent.height
    height: parent.width
    transform: Rotation { angle: 90}
    x: parent.width
    y: 0
    gradient: Gradient
    {
        GradientStop { position: 0.0; color: 
                       Qt.rgba(main_red, main_green, main_blue, 1)}
        GradientStop { position: 1.0; color: "white" }
    }
}

Rectangle
{
    anchors.fill: parent
    gradient: Gradient
    {
        GradientStop { position: 0.0; color: Qt.rgba(0, 0, 0, 0) }
        GradientStop { position: 1.0; color: Qt.rgba(0, 0, 0, 1) }
    }
}

Image
{
    id: cursor
    x: width/2
    y: height/2
    source: "cursor.png"
}

MouseArea
{
    acceptedButtons: Qt.LeftButton
    anchors.fill: parent
    onPressed:
    {
        cursor.x = mouseX - 4
        cursor.y = mouseY - 4
        updateSelectedColor()
    }
    onPositionChanged:
    {
        cursor.x = mouseX - 4
        cursor.y = mouseY - 4
        updateSelectedColor()
    }
}

}@

I'm not expert in QML, so if someone have critics, I'm interessed.