mirror of https://bitbucket.org/ausocean/av.git
104 lines
2.7 KiB
Go
104 lines
2.7 KiB
Go
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// +build !nocv
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/*
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DESCRIPTION
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A filter that detects motion and discards frames without motion. The
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algorithm calculates the absolute difference for each pixel between
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two frames, then finds the mean. If the mean is above a given threshold,
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then it is considered motion.
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AUTHORS
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Scott Barnard <scott@ausocean.org>
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LICENSE
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diff.go is Copyright (C) 2020 the Australian Ocean Lab (AusOcean)
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It is free software: you can redistribute it and/or modify them
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under the terms of the GNU General Public License as published by the
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Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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It is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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in gpl.txt. If not, see http://www.gnu.org/licenses.
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*/
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package filter
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import (
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"fmt"
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"io"
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"gocv.io/x/gocv"
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"bitbucket.org/ausocean/av/revid/config"
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)
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const defaultDiffThreshold = 3
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// NewDiff returns a pointer to a new difference motion filter.
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func NewDiff(dst io.WriteCloser, c config.Config) *Motion {
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// Validate parameters.
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if c.MotionThreshold <= 0 {
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c.LogInvalidField("MotionThreshold", defaultDiffThreshold)
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c.MotionThreshold = defaultDiffThreshold
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}
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alg := &Diff{
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thresh: c.MotionThreshold,
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prev: gocv.NewMat(),
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debugging: newWindows("DIFF"),
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}
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return NewMotion(dst, alg, c)
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}
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// Diff is a motion detection algorithm. It calculates the absolute
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// difference for each pixel between two frames, then finds the mean.
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// If the mean is above a given threshold, it is considered motion.
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type Diff struct {
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debugging debugWindows
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thresh float64
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prev gocv.Mat
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}
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// Close frees resources used by gocv. It has to be done manually,
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// due to gocv using c-go.
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func (d *Diff) Close() error {
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d.debugging.close()
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d.prev.Close()
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return nil
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}
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// Detect performs the motion detection on a frame. It returns true
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// if motion is detected.
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func (d *Diff) Detect(img *gocv.Mat) bool {
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if d.prev.Empty() {
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d.prev = img.Clone()
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return false
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}
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imgDelta := gocv.NewMat()
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defer imgDelta.Close()
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// Seperate foreground and background.
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gocv.AbsDiff(*img, d.prev, &imgDelta)
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gocv.CvtColor(imgDelta, &imgDelta, gocv.ColorBGRToGray)
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mean := imgDelta.Mean().Val1
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// Update History.
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d.prev = img.Clone()
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// Draw debug information.
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d.debugging.show(*img, imgDelta, mean > d.thresh, nil, fmt.Sprintf("Mean: %f", mean), fmt.Sprintf("Threshold: %f", d.thresh))
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// Return if there is motion.
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return mean > d.thresh
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}
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