How to take a picture using command line on webOS on HP touchpad?

问题

on webos, I have openssh running and would like to take a picture using the command line script.

I suspect this is going to include some luna-send command, or alternatively a gst-launch

But I am not having any luck with the docs.

webos doesn't have any of the expected capture tools, but I can access the /dev/video0 device.

Edit: i noticed that the touchpad has the ffmpeg utility installed, but it doesn't recognise the video4linux2 format

So far, I am trying Gopherkhan's suggestions with the following code;

luna-send -n 1 palm://com.palm.mediad.MediaCapture/startImageCapture \
'{"path":"/media/internal/foo1.png","options":[{"quality" \
:100,"flash":2,'reviewDuration':0,'exifData':{}}]}'

but its just hanging there doing nothing, after a while is says this;

{"serviceName":"com.palm.mediad.MediaCapture","returnValue":false,"errorCode":-1 \
  ,"errorText":"com.palm.mediad.MediaCapture is not running."} \
(process:8534): LunaService-CRITICAL **: AppId msg type: 17

回答1:

So to do this with luna-sends is a bit tricky, and technically not supported.

You're probably going to want to hit the MediaCapture library, which can be found on the device here:

/usr/palm/frameworks/enyo/0.10/framework/lib/mediacapture

To include it in your enyo app drop the following in your depends.js:

"$enyo-lib/mediacapture/"

There are three main steps involved.

Initializing the component
Capturing the image
Unloading the device.

Here's a sample:

Declare the component in your scene

{
            kind: "enyo.MediaCapture", name:"mediaCaptureObj", 
            onLoaded:"_setUpLoadedState", onInitialized:"_setUpInitializedState", 
            onImageCaptureStart:"_onImageCaptureStart", onImageCaptureComplete:"_onImageCaptureComplete",
         onAutoFocusComplete:"_onAutoFocusComplete", onError:"_handleError",
            onElapsedTime:"_onElapsedTime", onVuData:"_onVuDataChange", onDuration:"_onDuration"
}

Call the initialize method:

this.$.mediaCaptureObj.initialize(this.$.ViewPort);

In your onInitialized callback

Use the property bag to locate the number of devices that are available. Typically, the descriptions are "Camera/Camcorder", "Front Microphone", and "User facing camera"

var keyString;
for(var i = 0; i < this.pb.deviceKeys.length; i++)
{
    if(this.pb.deviceKeys[i].description.indexOf("Camera/Camcorder") >= 0)
    {
        keyString = this.pb.deviceKeys[i].deviceUri;
        break;
    }
}

if(keyString)
{
    var formatObj = {
                imageCaptureFormat: this.pb[keyString].supportedImageFormats[0]
            };

    this.$.mediaCaptureObj.load(keyString, formatObj);
}

Take a photo.

var obj = {"exifData":"{\"make\": \"Palm\", \"model\": \"Pre3\", \"datetime\": \"2011:05:19 10:39:18\", \"orientation\": 1, \"geotag\": {}}","quality":90,"flash":"FLASH_ON"};

this.$.mediaCaptureObj.startImageCapture("", obj);

Unload the device:

this.$.mediaCaptureObj.unload();

To do this with the old JS frameworks, see: https://developer.palm.com/content/api/reference/javascript-libraries/media-capture.html

Now, you can do something similar with luna-send, but again, I don't think it's technically supported. You might have trouble with starting-up/keeping-alive the media capture service, etc. BUT, if you want to try, you could do something along the lines of:

1. get the media server instance --- this returns a port instance number

luna-send -a your.app.id -i palm://com.palm.mediad/service/captureV3 '{"args":["subscribe":true]}'

This will return a location of the capture service with a port number, a la:

{"returnValue":true, "location":"palm://com.palm.mediad.MediaCaptureV3_7839/"}

Since this is a subscription, don't kill the request. Just open a new terminal.

2. Open a new terminal. Use the "location" returned in step 1 as your new service uri:

luna-send -a your.app.id -i palm://com.palm.mediad.MediaCaptureV3_7839/load '{"args":["video:1", {"videoCaptureFormat":{"bitrate":2000000,"samplerate":44100,"width":640,"height":480,"mimetype":"video/mp4","codecs":"h264,mp4a.40"},"imageCaptureFormat":{"bitrate":0,"samplerate":1700888,"width":640,"height":480,"mimetype":"image/jpeg","codecs":"jpeg"},"deviceUri":"video:1"}]}'

You should see:

{"returnValue":true}

if the call completed correctly. You can safely ctrl+c out of this call.

3. Take your picture. (you can ctrl+c out of the last call, and just supply the args here)

luna-send -a your.app.id -i palm://com.palm.mediad.MediaCaptureV3_7839/startImageCapture '{"args":["", {"exifData":"{\"orientation\": 1, \"make\": \"HP\", \"model\": \"TouchPad\", \"datetime\": \"2011:09:22 15:34:36\", \"geotag\": {}}","quality":90,"flash":"FLASH_DISABLED","orientation":"faceup"}]}'

Again, you should see:

{"returnValue":true}

if the call completed correctly.

You should hear a shutter click, and the image will show up in the Photos app, in your Photo Roll.

回答2:

An alternative, which might some benefit of using cross platform tools, is to the use the gst-launch pipeline. So far I have managed to start the web cam using command line;

gst-launch camsrc .src ! video/x-raw-yuv,width=320,height=240,framerate=30/1 ! palmvideoencoder ! avimux name=mux ! filesink location=test1.avi alsasrc ! palmaudioencoder

but not take a single image;

   gst-launch -v camsrc .src_still take-picture=1 flash-ctrl=2 ! fakesink dump=true

but I can't get it to recognise the .src_still tab. I will update this answer with this alternative method as I proceed.

来源：https://stackoverflow.com/questions/7509675/how-to-take-a-picture-using-command-line-on-webos-on-hp-touchpad

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webos

touchpad