private void scaleImage(double deltaScale, float focusX, float focusY, boolean stretchImageToSuper) {

        float lowerScale, upperScale;
        if (stretchImageToSuper) {
            lowerScale = superMinScale;
            upperScale = superMaxScale;

        } else {
            lowerScale = minScale;
            upperScale = maxScale;
        }

        float origScale = normalizedScale;
        normalizedScale *= deltaScale;
        if (normalizedScale > upperScale) {
            normalizedScale = upperScale;
            deltaScale = upperScale / origScale;
        } else if (normalizedScale < lowerScale) {
            normalizedScale = lowerScale;
            deltaScale = lowerScale / origScale;
        }

        matrix.postScale((float) deltaScale, (float) deltaScale, focusX, focusY);
        fixScaleTrans();
    }
ScaleListener detects user two finger scaling and scales image.

@author Ortiz
app/src/main/java/home/smart/fly/animations/customview/gallery/TouchImageView.java