Differential Optical Flow Rotation/Scale

# This work is licensed under the MIT license.
# Copyright (c) 2013-2023 OpenMV LLC. All rights reserved.
# https://github.com/openmv/openmv/blob/master/LICENSE
#
# Differential Optical Flow Rotation/Scale
#
# This example shows off using your OpenMV Cam to measure
# rotation/scale by comparing the current and the previous
# image against each other. Note that only rotation/scale is
# handled - not X and Y translation in this mode.
#
# To run this demo effectively please mount your OpenMV Cam on a steady
# base and SLOWLY rotate the camera around the lens and move the camera
# forward/backwards to see the numbers change.
# I.e. Z direction changes only.
#
# NOTE You have to use a small power of 2 resolution when using
# find_displacement(). This is because the algorithm is powered by
# something called phase correlation which does the image comparison
# using FFTs. A non-power of 2 resolution requires padding to a power
# of 2 which reduces the usefulness of the algorithm results. Please
# use a resolution like B64X64 or B64X32 (2x faster).
#
# Your OpenMV Cam supports power of 2 resolutions of 64x32, 64x64,
# 128x64, and 128x128. If you want a resolution of 32x32 you can create
# it by doing "img.scale(x_scale=0.5, y_scale=0.5, hint=image.AREA)" on a 64x64 image.

import csi
import image
import time
import math

csi0 = csi.CSI()
csi0.reset()  # Reset and initialize the sensor.
csi0.pixformat(csi.RGB565)  # Set pixel format to RGB565 (or GRAYSCALE)
csi0.framesize((64, 64))  # Set frame size to 64x64... (or 64x32)...
csi0.snapshot(time=2000)  # Wait for settings take effect.
clock = time.clock()  # Create a clock object to track the FPS.

# Create a second frame buffer on the heap.
extra_fb = image.Image(csi0.width(), csi0.height(), csi0.pixformat())
extra_fb.draw_image(csi0.snapshot())

while True:
    clock.tick()  # Track elapsed milliseconds between snapshots().
    img = csi0.snapshot()  # Take a picture and return the image.

    # This algorithm is hard to test without a perfect jig... So, here's a cheat to see it works.
    # Put in a z_rotation value below and you should see the r output be equal to that.
    if 0:
        expected_rotation = 20.0
        extra_fb.rotation_corr(z_rotation=(-expected_rotation))

    # This algorithm is hard to test without a perfect jig... So, here's a cheat to see it works.
    # Put in a zoom value below and you should see the z output be equal to that.
    if 0:
        expected_zoom = 0.8
        extra_fb.rotation_corr(zoom=(2.00 - expected_zoom))

    displacement = extra_fb.find_displacement(img, logpolar=True)
    extra_fb.draw_image(img)

    # Offset results are noisy without filtering so we drop some accuracy.
    rotation_change = int(math.degrees(displacement.rotation) * 5) / 5.0
    zoom_amount = displacement.scale

    if (
        displacement.response > 0.1
    ):  # Below 0.1 or so (YMMV) and the results are just noise.
        print(
            "{0:+f}r {1:+f}z {2} {3} FPS".format(
                rotation_change, zoom_amount, displacement.response, clock.fps()
            )
        )
    else:
        print(clock.fps())