qreator-discuss team mailing list archive

[David Planella <david.planella@xxxxxxxxxx>]

On Mon, Jun 10, 2013 at 5:24 PM, Stefan Schwarzburg <
stefan.schwarzburg@xxxxxxxxx> wrote:

> Hi David,
>
> Thanks for the testing. From the size of the images and the picture, I
>> assume you took those from the desktop.
>>
>>
> True. I do not have any mobile that runs ubuntu :-(
>
>

No worries. I cannot offer a phone, as I only got one myself, but let me
know if you have any snippet or branch you'd like me to test on a device.


> In my case, playing with exposure, white balance or brightness did not
>> make any difference when pictures were taken from the web cam. So we've got
>> two cases here: in my case images are too dark, and in your case images go
>> crazy. I think I share your conclusion that the camera settings *on the
>> desktop* are not very reliable at the moment.
>>
>>
> I'm actually not sure that they are always too dark on your phone as well.
> Maybe 5 out of 500 pictures were bright on my desktop, did you try that
> many on your phone? I have used automatic triggering, you can copy the code
> from my branch. Let it run for 15 minutes or so and then check your images
> for bright ones... :-)
>
>

I still believe there is a difference between desktop and mobile, both at
the hardware level (e.g. my webcam does not support autofocus, whereas the
Nexus' one does) and at the software level (GStreamer-based plugin on the
desktop vs something else -I've not figured out yet what- on the Nexus).

The automatic triggering is a really good idea. But eaven without doing
automatic triggering, for the ~30 or so pictures I've taken manually on the
desktop and on the device, the pictures are invariably always dark on the
desktop, and always ok on the device.

If you've got the automatic triggering code somewhere, I'll give it a shot
on the device, but we should probably decouple it from Qreator and use it
as a separate test app.


>> I'm not sure how we can correct that. In my case, it seemed that the
>> webcam ignored the settings, so it might be that either the hardware does
>> not support them, or that the camera plugin for the desktop is not passing
>> the parameters correctly. Which is weird, as the Qt camera plugin uses
>> GStreamer as a backend afaik, and Cheese, which also uses GStreamer, takes
>> pictures with the right brighthness.
>>
>
> Well, the viewfinder is always totally fine, one the still images are not.
> I also noted, that you do not use camera.searchAndLock() "Start focusing,
> exposure and white balance calculation." Maybe this mixes up exposure for
> viewfinder and still image...
> It would be great to directly get the image from the viewfinder instead of
> taking a picture...
>

Yeah, I'm not sure if it's possible, though. In any case, in the (I must
admit) very limited photography knowledge I have, I always assumed that the
exposure is longer on the video preview, which is why the pictures always
look ok on the preview. Now this might be a totally wrong assumption,
though...

I'll give a shot at searchAndLock(), but I'm a bit disappointed to see that
at least on the desktop the Camera component is not as plug-and-play as the
documentation leads to believe....


>
>
>>
>> In my testing on a device, the white balance/brightness/exposure seem
>> correct, so this issue apparently only affects the desktop version.
>>
>
> Well, if your images are too dark, then exposure is not ok!
>
>

Right, but the point is that images are never dark on the device, only on
the desktop.


>
>> Another issue that I've now got more insight on is the delay in decoding
>> from a device. It takes about 15-20 seconds to decode a QR code, but in the
>> limited testing that I've done it seems to work every time, which is really
>> good.
>>
>
> For me it worked everytime the brightness was ok.
>
>

Yeah, on the desktop, if I point a bright light at the QR code, the
decoding takes about 1s, which is optimal. On the device, it takes these
15-20 seconds, which I assume to be due to the additional time it takes to
process a higher resolution picture.

On the desktop the resolution of my captures is 640x480
On the device I'll have to check when it's finished charging, but I'm
pretty certain it's a very high resolution.

Which resolution do you have on your webcam?


>> I believe what might be happening here is that it takes quite a lot of
>> memory or processing power to scan and decode the images with higher
>> resolution from the device's camera (on my desktop it takes about 1 second
>> to decode the webcam's 640x480 images).
>>
>
> You could try to move a desktop-webcam picture and let it scan on the
> mobile (hardcoded), just to see the time difference. But sure, higher
> resolution should increase the time drastically.
>
>

Yeah, that's a good idea. I've also thought of implementing a very rough
shot of your image-loading feature and get the desktop load a capture from
the device. I think I will try that next.

I really want to nail this one down. We can work the workflow in Balsamiq
in parallell, but I'd really like to get the basics of capturing and
decoding right and solid.


>
>> I'll try to benchmark if the C++ plugin can do this much faster, but in
>> any case, a couple of measures I can think of are:
>>
>> ~ Reduce the resolution of the captured image
>> ~ Crop the captured image to the QR code window before sending it to the
>> decoding library functions
>>
>>
>> In terms of the QR code window, I've started adding some preliminary code
>> to show where the QR code should be positioned in the picture to be
>> scanned, but it's not yet functional (i.e. the window is shown, but it does
>> not do anything).
>>
>>
> The new window looks very nice!
> And I have seen that you added the dialogs, with an even better "dynamc
> text" mechanism :-) Nice!
>
>
Not sure if better, just an alternative :). I've now answered the question
on Ask Ubuntu with the solution. Thanks for your answer! :)

Cheers,
David.


> Cheers,
> Stefan
>
>
>> I've updated the code on the scanner branch: lp:~dpm/qreator/touch-scanner
>>
>> Cheers,
>> David.
>>
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