How can I view the sensor_msgs.Image data as an image?

[Maverobot]

I would like to view the image data received by subscriber but don't know where to start. Can someone please help me?

Example code:

package main

import (
	"github.com/aler9/goroslib"
	"github.com/aler9/goroslib/pkg/msgs/sensor_msgs"
)

func main() {
	// create a node and connect to the master
	n, err := goroslib.NewNode(goroslib.NodeConf{
		Name:          "goroslib_sub",
		MasterAddress: "127.0.0.1:11311",
	})
	if err != nil {
		panic(err)
	}
	defer n.Close()

	onMessage := func(msg *sensor_msgs.Image) {
		// TODO: Do something to view the image
	}

	// create a subscriber
	sub, err := goroslib.NewSubscriber(goroslib.SubscriberConf{
		Node:     n,
		Topic:    "goroslib_sub",
		Callback: onMessage,
	})
	if err != nil {
		panic(err)
	}
	defer sub.Close()

	// freeze main loop
	select {}
}

[aler9]

Here's a working example, that works with the rgba encoding (if it's different, you need to convert it)

package main

import (
	"image"
	"bytes"
	"image/jpeg"
	"io/ioutil"
	"time"

	"github.com/aler9/goroslib"
	"github.com/aler9/goroslib/pkg/msgs/sensor_msgs"
)

func main() {
	// create a node and connect to the master
	n, err := goroslib.NewNode(goroslib.NodeConf{
		Name:          "goroslib_sub",
		MasterAddress: "127.0.0.1:11311",
	})
	if err != nil {
		panic(err)
	}
	defer n.Close()

	onMessage := func(msg *sensor_msgs.Image) {
		if msg.Encoding != "rgba" {
			panic("not rgba")
		}

		r := image.Rectangle{image.Point{0, 0}, image.Point{int(msg.Width), int(msg.Height)}}
		i := &image.RGBA{
			Pix:    msg.Data,
			Stride: 4 * r.Dx(),
			Rect:   r,
		}

		var buf bytes.Buffer
		err := jpeg.Encode(&buf, i, &jpeg.Options{
			Quality: 80,
		})
		if err != nil {
			panic(err)
		}

		err = ioutil.WriteFile(time.Now().Format("myimage.jpg"), buf.Bytes(), 0644)
		if err != nil {
			panic(err)
		}
	}

	// create a subscriber
	sub, err := goroslib.NewSubscriber(goroslib.SubscriberConf{
		Node:     n,
		Topic:    "goroslib_sub",
		Callback: onMessage,
	})
	if err != nil {
		panic(err)
	}
	defer sub.Close()

	// freeze main loop
	select {}
}