lepton: add Dev.Bounds()

This is in preparation to support the lepton 3 and refactor the driver to be in
better shape.

devices/lepton/lepton.go

@@ -113,6 +113,8 @@ func New(p spi.Port, i i2c.Bus, cs gpio.PinOut) (*Dev, error) {
 		Dev:        c,
 		s:          s,
 		cs:         cs,
+		w:          w,
+		h:          h,
 		prevImg:    image.NewGray16(image.Rect(0, 0, w, h)),
 		frameWidth: frameWidth,
 		frameLines: frameLines,
@@ -142,6 +144,8 @@ type Dev struct {
 	*cci.Dev
 	s              spi.Conn
 	cs             gpio.PinOut
+	w              int
+	h              int
 	prevImg        *image.Gray16
 	frameA, frameB []byte
 	frameWidth     int // in bytes
@@ -154,6 +158,11 @@ func (d *Dev) String() string {
 	return fmt.Sprintf("Lepton(%s/%s/%s)", d.Dev, d.s, d.cs)
 }
 
+// Bounds returns the device frame size.
+func (d *Dev) Bounds() image.Rectangle {
+	return image.Rect(0, 0, d.w, d.h)
+}
+
 // ReadImg reads an image.
 //
 // It is ok to call other functions concurrently to send commands to the

devices/lepton/lepton_test.go

@@ -163,6 +163,24 @@ func TestNew_cci_New_fail(t *testing.T) {
 	}
 }
 
+func TestBounds(t *testing.T) {
+	i := i2ctest.Playback{Ops: initSequence()}
+	s := spitest.Playback{CSPin: &gpiotest.Pin{N: "CS"}}
+	d, err := New(&s, &i, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if r := d.Bounds(); r != image.Rect(0, 0, 80, 60) {
+		t.Fatal(r)
+	}
+	if err := i.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := s.Close(); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestReadImg(t *testing.T) {
 	i := i2ctest.Playback{Ops: initSequence()}
 	s := spiStream{data: prepareFrame(t)}