Example: 01-Camera/02-Optical-Flow/absolute-rotation-scale.py

# 本作品采用MIT许可证授权。
# 版权所有 (c) 2013-2023 OpenMV LLC。保留所有权利。
# https://github.com/openmv/openmv/blob/master/LICENSE
#
# 绝对光流旋转/缩放
#
# 此示例展示了如何使用您的OpenMV摄像头测量
# rotation/scale by comparing the current and a 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 sensor
import time
import math

sensor.reset()  # 重置并初始化传感器。
sensor.set_pixformat(sensor.RGB565)  # 将像素格式设置为RGB565 (or GRAYSCALE)
sensor.set_framesize(sensor.B64X64)  # Set frame size to 64x64... (or 64x32)...
sensor.skip_frames(time=2000)  # 等待设置生效。
clock = time.clock()  # 创建一个时钟对象来跟踪FPS。

# Take from the main frame buffer's RAM to allocate a second frame buffer.
# There's a lot more RAM in the frame buffer than in the MicroPython heap.
# However, after doing this you have a lot less RAM for some algorithms...
# So, be aware that it's a lot easier to get out of RAM issues now.
extra_fb = sensor.alloc_extra_fb(sensor.width(), sensor.height(), sensor.RGB565)
extra_fb.replace(sensor.snapshot())

while True:
    clock.tick()  # Track elapsed milliseconds between snapshots().
    img = sensor.snapshot()  # 拍照并返回图像。

    # 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
        img.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
        img.rotation_corr(zoom=expected_zoom)

    # For this example we never update the old image to measure absolute change.
    displacement = extra_fb.find_displacement(img, logpolar=True)

    # 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())