Question

Say I have a liner gradient as shown:

QLinearGradient linearGrad(QPointF(0, 0), QPointF(0, 100));
linearGrad.setColorAt(1, Qt::red);
linearGrad.setColorAt(0.5, Qt::yellow);
linearGrad.setColorAt(0, Qt::green);

How to get the color of the point QPointF(0, 28.5) in this gradient?

Indeed I want to have this kind of color distribution to be able to choose intermediate colors. I don’t care if it is done by using QLinearGradient or something else.

Answer 1

There is only way to make it:

There is a static member in QPixmap class
QPixmap QPixmap::grabWindow( WId window, int x = 0, int y = 0, int width = -1, int height = -1 )

1) draw your gradient on your widget;

2) grab you widget’s surface into pixmap using that function; WId can be received from QWidget::effectiveWinId ();

3) convert token pixmap into QImage (there is an constructor available);

4) int QImage::pixelIndex( int x, int y ) returns the pixel index at (x, y) in QImage‘s color table. In your case you must calculate percentage value from widget’s height ( pWidget->height() / 100 * 28.5 ).

5) QRgb QImage::color( int i ) returns the color in the color table at index i.

So returned Color is the color you were seeking.