mirror of https://bitbucket.org/ausocean/av.git
110 lines
2.8 KiB
Go
110 lines
2.8 KiB
Go
// +build !circleci
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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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difference.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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"io"
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"gocv.io/x/gocv"
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)
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// Difference is a filter that provides basic motion detection. Difference calculates
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// the absolute difference for each pixel between two frames, then finds the mean. If
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// the mean is above a given threshold, then it is considered motion.
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type Difference struct {
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debugWindows
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dst io.WriteCloser
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thresh float64
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prev gocv.Mat
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}
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// NewDifference returns a pointer to a new Difference struct.
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func NewDifference(dst io.WriteCloser, threshold float64) *Difference {
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d := &Difference{
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dst: dst,
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thresh: threshold,
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prev: gocv.NewMat(),
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}
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d.newWindows("DIFF")
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return d
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}
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// Implements io.Closer.
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// Close frees resources used by gocv, because it has to be done manually, due to
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// it using c-go.
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func (d *Difference) Close() error {
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d.prev.Close()
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d.closeWindows()
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return nil
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}
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// Implements io.Writer.
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// Write applies the motion filter to the video stream. Only frames with motion
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// are written to the destination encoder, frames without are discarded.
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func (d *Difference) Write(f []byte) (int, error) {
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if d.prev.Empty() {
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var err error
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d.prev, err = gocv.IMDecode(f, gocv.IMReadColor)
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if err != nil {
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return 0, err
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}
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return len(f), nil
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}
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img, err := gocv.IMDecode(f, gocv.IMReadColor)
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defer img.Close()
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if err != nil {
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return 0, err
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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.showDebug(img, imgDelta, mean > d.thresh)
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// Don't write to destination if there is no motion.
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if mean < d.thresh {
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return len(f), nil
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}
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// Write to destination.
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return d.dst.Write(f)
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}
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