First, check out the code in the dev branch. Next, check out a method in TouchImageView called setZoom()
. You can wire up this method to your zoom buttons like this:
zoomIn.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
float scale = image.getCurrentZoom();
PointF centerPoint = image.getCenterOfZoomedImage();
image.setZoom(scale * 1.25, centerPoint.x, centerPoint.y);
}
});