av/device/raspistill/raspistill.go

/*
DESCRIPTION
  raspistill.go provides an implementation of the AVDevice interface for the
  raspistill raspberry pi camera interfacing utility. This allows for the
  capture of single frames over time, i.e. a timelapse form of capture.

AUTHORS
  Saxon Nelson-Milton <saxon@ausocean.org>

LICENSE
  Copyright (C) 2019 the Australian Ocean Lab (AusOcean)

  It is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  for more details.

  You should have received a copy of the GNU General Public License
  in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

// Package raspistill rovides an implementation of the AVDevice interface for the
// raspistill raspberry pi camera interfacing utility. This allows for the
// capture of single frames over time, i.e. a timelapse form of capture.
package raspistill

import (
	"errors"
	"fmt"
	"time"

	"bitbucket.org/ausocean/av/device"
	"bitbucket.org/ausocean/av/revid/config"
)

// To indicate package when logging.
const pkg = "raspistill: "

// Config field validation bounds.
const (
	minTimelapseDuration = 30 * time.Second    // s
	maxTimelapseDuration = 86400 * time.Second // s = 24 hours
	minTimelapseInterval = 1 * time.Second     // s
	maxTimelapseInterval = 86400 * time.Second // s = 24 hours
)

// Raspistill configuration defaults.
const (
	defaultRotation          = 0                    // degrees
	defaultWidth             = 1280                 // pixels
	defaultHeight            = 720                  // pixels
	defaultJPEGQuality       = 75                   // %
	defaultTimelapseDuration = maxTimelapseDuration // ms
	defaultTimelapseInterval = 3600 * time.Second   // ms
)

// Configuration errors.
var (
	errBadRotation          = fmt.Errorf("Rotation bad or unset, defaulting to: %v", defaultRotation)
	errBadWidth             = fmt.Errorf("Width bad or unset, defaulting to: %v", defaultWidth)
	errBadHeight            = fmt.Errorf("Height bad or unset, defaulting to: %v", defaultHeight)
	errBadJPEGQuality       = fmt.Errorf("JPEGQuality bad or unset, defaulting to: %v", defaultJPEGQuality)
	errBadTimelapseDuration = fmt.Errorf("TimelapseDuration bad or unset, defaulting to: %v", defaultTimelapseDuration)
	errBadTimelapseInterval = fmt.Errorf("TimelapseInterval bad or unset, defaulting to: %v", defaultTimelapseInterval)
)

// Misc errors.
var errNotStarted = errors.New("cannot read, raspistill not started")

// Raspistill is an implementation of AVDevice that provides control over the
// raspistill utility for using the raspberry pi camera for the capture of
// singular images.
type Raspistill struct{ raspistill }

// New returns a new Raspistill.
func New(l config.Logger) *Raspistill { return &Raspistill{raspistill: new(l)} }

// Start will prepare the arguments for the raspistill command using the
// configuration set using the Set method then call the raspistill command,
// piping the image output from which the Read method will read from.
func (r *Raspistill) Start() error { return r.start() }

// Read implements io.Reader. Calling read before Start has been called will
// result in 0 bytes read and an error.
func (r *Raspistill) Read(p []byte) (int, error) { return r.read(p) }

// Stop will terminate the raspistill process and close the output pipe.
func (r *Raspistill) Stop() error { return r.stop() }

// IsRunning is used to determine if the pi's camera is running.
func (r *Raspistill) IsRunning() bool { return r.isRunning }

// Name returns the name of the device.
func (r *Raspistill) Name() string { return "Raspistill" }

// Set will take a Config struct, check the validity of the relevant fields
// and then performs any configuration necessary. If fields are not valid,
// an error is added to the multiError and a default value is used.
func (r *Raspistill) Set(c config.Config) error {
	var errs device.MultiError

	if c.Rotation > 359 || c.Rotation < 0 {
		c.Rotation = defaultRotation
		errs = append(errs, errBadRotation)
	}

	if c.Width == 0 {
		c.Width = defaultWidth
		errs = append(errs, errBadWidth)
	}

	if c.Height == 0 {
		c.Height = defaultHeight
		errs = append(errs, errBadHeight)
	}

	if c.JPEGQuality < 0 || c.JPEGQuality > 100 {
		c.JPEGQuality = defaultJPEGQuality
		errs = append(errs, errBadJPEGQuality)
	}

	if c.TimelapseDuration > maxTimelapseDuration || c.TimelapseDuration < minTimelapseDuration {
		c.TimelapseDuration = defaultTimelapseDuration
		errs = append(errs, errBadTimelapseDuration)
	}

	if c.TimelapseInterval > maxTimelapseInterval || c.TimelapseInterval < minTimelapseInterval {
		c.TimelapseInterval = defaultTimelapseInterval
		errs = append(errs, errBadTimelapseInterval)
	}

	r.cfg = c
	return errs
}