core: add Rescale utility function for straight linear rescaling

Signed-off-by: Ron Evans <ron@hybridgroup.com>

utils.go

@@ -57,6 +57,11 @@ func ToScale(input, min, max float64) float64 {
 	}
 }
 
+// Rescale performs a direct linear rescaling of a number from one scale to another.
+func Rescale(input, fromMin, fromMax, toMin, toMax float64) float64 {
+	return (input-fromMin)*(toMax-toMin)/(fromMax-fromMin) + toMin
+}
+
 // DefaultName returns a sensible random default name
 // for a robot, adaptor or driver
 func DefaultName(name string) string {

utils_test.go

@@ -73,6 +73,11 @@ func TestToScale(t *testing.T) {
 	gobottest.Assert(t, ToScale(0.5, 0, 10), 5.0)
 }
 
+func TestRescale(t *testing.T) {
+	gobottest.Assert(t, Rescale(500, 0, 1000, 0, 10), 5.0)
+	gobottest.Assert(t, Rescale(-1.0, -1, 0, 490, 350), 490.0)
+}
+
 func TestRand(t *testing.T) {
 	a := Rand(10000)
 	b := Rand(10000)