Colours for positive and negative values in a raster layer in QGIS

Question

I've got a raster layer in QGIS 3.10. It's statistics are the following (hopefully understandable although in Spanish):

Valor mínimo: -0.36928805708885193
Valor máximo: 0.6040433645248413
Intervalo: 0.9733314216136932
Suma: 14433.653211801786
Valor medio: 0.12369652924773997
Desviación estándar: 0.09271679256133081
Suma de cuadrados: 1003.0713567335182

I would like to represent it with a Red-to-Black colour ramp, but centered to zero, so values < 0 appear in the red palette and those > 0 in the grey one. Logically, my attempts with an automatic classification always set the central white color into the positive values. Is it possible to do what I want and how?

Answer 1

You have a range of values from -0.369288057 to 0.604043365, thus a difference of 0.973331422. You have a color ramp red-white-black and the "middle" value (white) is set to the middle of these values, thus at 0.117377654 - but you want it at 0. So your white value must be shifted to the left. To get the exact position, calculate the percentage of the value 0 in the range of your min/max values: (0-min) / (max-min) * 100 = 37.94%. Thus set the marker for the withe color to this value.

Apart from this, see also this solution: https://gis.stackexchange.com/a/385536/88814