mirror of https://bitbucket.org/ausocean/av.git
128 lines
3.5 KiB
Go
128 lines
3.5 KiB
Go
/*
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DESCRIPTION
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A filter that detects motion and discards frames without motion. The
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filter uses a K-Nearest Neighbours (KNN) to determine what is
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background and what is foreground.
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AUTHORS
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Ella Pietraroia <ella@ausocean.org>
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LICENSE
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KNN.go is Copyright (C) 2019 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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"image"
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"image/color"
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"io"
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"gocv.io/x/gocv"
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)
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// KNNFilter is a filter that provides basic motion detection. KNN is short for
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// K-Nearest Neighbours method.
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type KNNFilter struct {
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dst io.WriteCloser
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area float64
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bs *gocv.BackgroundSubtractorKNN
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knl gocv.Mat
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debug bool
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windows []*gocv.Window
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}
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// NewKNNFilter returns a pointer to a new KNNFilter.
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func NewKNNFilter(dst io.WriteCloser, area, threshold float64, history, kernelSize int, debug bool) *KNNFilter {
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bs := gocv.NewBackgroundSubtractorKNNWithParams(history, threshold, false)
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k := gocv.GetStructuringElement(gocv.MorphRect, image.Pt(kernelSize, kernelSize))
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var windows []*gocv.Window
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if debug {
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windows = []*gocv.Window{gocv.NewWindow("Debug: Bounding boxes"), gocv.NewWindow("Debug: Motion")}
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}
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return &KNNFilter{dst, area, &bs, k, debug, windows}
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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 (m *KNNFilter) Close() error {
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m.bs.Close()
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m.knl.Close()
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for _, window := range m.windows {
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window.Close()
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}
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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 (m *KNNFilter) Write(f []byte) (int, error) {
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img, _ := gocv.IMDecode(f, gocv.IMReadColor)
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defer img.Close()
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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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m.bs.Apply(img, &imgDelta)
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// Threshold imgDelta.
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gocv.Threshold(imgDelta, &imgDelta, 25, 255, gocv.ThresholdBinary)
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// Remove noise.
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gocv.Erode(imgDelta, &imgDelta, m.knl)
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gocv.Dilate(imgDelta, &imgDelta, m.knl)
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// Fill small holes.
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gocv.Dilate(imgDelta, &imgDelta, m.knl)
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gocv.Erode(imgDelta, &imgDelta, m.knl)
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// Find contours and reject ones with a small area.
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var contours [][]image.Point
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allContours := gocv.FindContours(imgDelta, gocv.RetrievalExternal, gocv.ChainApproxSimple)
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for _, c := range allContours {
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if gocv.ContourArea(c) > m.area {
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contours = append(contours, c)
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}
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}
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// Draw debug information.
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if m.debug {
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for _, c := range contours {
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rect := gocv.BoundingRect(c)
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gocv.Rectangle(&img, rect, color.RGBA{0, 0, 255, 0}, 1)
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}
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if len(contours) > 0 {
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gocv.PutText(&img, "Motion", image.Pt(32, 32), gocv.FontHersheyPlain, 2.0, color.RGBA{255, 0, 0, 0}, 2)
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}
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m.windows[0].IMShow(img)
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m.windows[1].IMShow(imgDelta)
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m.windows[0].WaitKey(1)
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}
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// Don't write to destination if there is no motion.
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if len(contours) == 0 {
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return -1, nil
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}
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// Write to destination.
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return m.dst.Write(f)
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}
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