# 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.pool(2, 2)" on a 64x64 image. import sensor import time import math sensor.reset() # Reset and initialize the sensor. sensor.set_pixformat(sensor.RGB565) # Set pixel format to RGB565 (or GRAYSCALE) sensor.set_framesize(sensor.B64X64) # Set frame size to 64x64... (or 64x32)... sensor.skip_frames(time=2000) # Wait for settings take effect. clock = time.clock() # Create a clock object to track the 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() # 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.replace(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())