Image Patches Absolute Optical Flow Translation

# 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
#
# Image Patches Absolute Optical Flow Translation
#
# This example shows off using your OpenMV Cam to measure translation
# in the X and Y direction by comparing the current and a previous
# image against each other. Note that only X and Y translation is
# handled - not rotation/scale in this mode.
#
# However, this examples goes beyond doing optical flow on the whole
# image at once. Instead it breaks up the process by working on groups
# of pixels in the image. This gives you a "new" image of results.
#
# NOTE that surfaces need to have some type of "edge" on them for the
# algorithm to work. A featureless surface produces crazy results.
#
# To run this demo effectively please mount your OpenMV Cam on a steady
# base and SLOWLY translate it to the left, right, up, and down and
# watch the numbers change. Note that you can see displacement numbers
# up +- half of the hoizontal and vertical resolution.
#
# 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 B128X128 or B128X64 (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

BLOCK_W = 16  # pow2
BLOCK_H = 16  # pow2

csi0 = csi.CSI()
csi0.reset()  # Reset and initialize the sensor.
csi0.pixformat(csi.GRAYSCALE)  # Set pixel format to GRAYSCALE
csi0.framesize((128, 128))  # Set frame size to 128x128... (or 64x64)...
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.

    for y in range(0, csi0.height(), BLOCK_H):
        for x in range(0, csi0.width(), BLOCK_W):
            # For this example we never update the old image to measure absolute change.
            displacement = extra_fb.find_displacement(
                img, roi=(x, y, BLOCK_W, BLOCK_H), template_roi=(x, y, BLOCK_W, BLOCK_H)
            )

            # Below 0.1 or so (YMMV) and the results are just noise.
            if displacement.response > 0.1:
                pixel_x = x + (BLOCK_W // 2) + int(displacement.x_translation)
                pixel_y = y + (BLOCK_H // 2) + int(displacement.y_translation)
                img.draw_line(
                    (x + BLOCK_W // 2, y + BLOCK_H // 2, pixel_x, pixel_y), color=255
                )
            else:
                img.draw_line(
                    (
                        x + BLOCK_W // 2,
                        y + BLOCK_H // 2,
                        x + BLOCK_W // 2,
                        y + BLOCK_H // 2,
                    ),
                    color=0,
                )

    print(clock.fps())