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74 lines
3.5 KiB
Python
74 lines
3.5 KiB
Python
# Image Patches Differential Optical Flow Rotation/Scale
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#
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# This example shows off using your OpenMV Cam to measure
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# rotation/scale by comparing the current and the previous
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# image against each other. Note that only rotation/scale is
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# handled - not X and Y translation in this mode.
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#
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# However, this examples goes beyond doing optical flow on the whole
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# image at once. Instead it breaks up the process by working on groups
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# of pixels in the image. This gives you a "new" image of results.
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#
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# NOTE that surfaces need to have some type of "edge" on them for the
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# algorithm to work. A featureless surface produces crazy results.
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# NOTE: Unless you have a very nice test rig this example is hard to see usefulness of...
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BLOCK_W = 16 # pow2
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BLOCK_H = 16 # pow2
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# To run this demo effectively please mount your OpenMV Cam on a steady
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# base and SLOWLY rotate the camera around the lens and move the camera
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# forward/backwards to see the numbers change.
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# I.e. Z direction changes only.
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import sensor, image, time, math
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# NOTE!!! You have to use a small power of 2 resolution when using
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# find_displacement(). This is because the algorithm is powered by
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# something called phase correlation which does the image comparison
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# using FFTs. A non-power of 2 resolution requires padding to a power
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# of 2 which reduces the usefulness of the algorithm results. Please
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# use a resolution like B128X128 or B128X64 (2x faster).
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# Your OpenMV Cam supports power of 2 resolutions of 64x32, 64x64,
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# 128x64, and 128x128. If you want a resolution of 32x32 you can create
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# it by doing "img.pool(2, 2)" on a 64x64 image.
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sensor.reset() # Reset and initialize the sensor.
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sensor.set_pixformat(sensor.GRAYSCALE) # Set pixel format to GRAYSCALE (or RGB565)
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sensor.set_framesize(sensor.B128X128) # Set frame size to 128x128... (or 128x64)...
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sensor.skip_frames(time = 2000) # Wait for settings take effect.
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clock = time.clock() # Create a clock object to track the FPS.
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# Take from the main frame buffer's RAM to allocate a second frame buffer.
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# There's a lot more RAM in the frame buffer than in the MicroPython heap.
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# However, after doing this you have a lot less RAM for some algorithms...
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# So, be aware that it's a lot easier to get out of RAM issues now.
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extra_fb = sensor.alloc_extra_fb(sensor.width(), sensor.height(), sensor.GRAYSCALE)
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extra_fb.replace(sensor.snapshot())
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while(True):
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clock.tick() # Track elapsed milliseconds between snapshots().
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img = sensor.snapshot() # Take a picture and return the image.
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for y in range(0, sensor.height(), BLOCK_H):
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for x in range(0, sensor.width(), BLOCK_W):
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displacement = extra_fb.find_displacement(img, logpolar=True, \
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roi = (x, y, BLOCK_W, BLOCK_H), template_roi = (x, y, BLOCK_W, BLOCK_H))
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# Below 0.1 or so (YMMV) and the results are just noise.
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if(displacement.response() > 0.1):
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rotation_change = displacement.rotation()
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zoom_amount = 1.0 + displacement.scale()
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pixel_x = x + (BLOCK_W//2) + int(math.sin(rotation_change) * zoom_amount * (BLOCK_W//4))
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pixel_y = y + (BLOCK_H//2) + int(math.cos(rotation_change) * zoom_amount * (BLOCK_H//4))
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img.draw_line((x + BLOCK_W//2, y + BLOCK_H//2, pixel_x, pixel_y), \
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color = 255)
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else:
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img.draw_line((x + BLOCK_W//2, y + BLOCK_H//2, x + BLOCK_W//2, y + BLOCK_H//2), \
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color = 0)
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extra_fb.replace(img)
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print(clock.fps())
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