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Image compression

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14 March, 2012 - 12:16
#1
lacapaca
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Image compression

Hi,

Sorry if this has been addressed before, I tried to search but could not find anything.

I need to upload images to a web application. The image is selected using the image picker. I can get the raw image data with maGetImageSize(), maGetImageData(), encode it with base64 and pass it on, however, the data is huge, especially for a mobile application.

Is there any way I could compress the data in PNG or JPEG? Or, better yet, is there a way I can access the original, compressed file data when using the image picker?

Edit: The app runs on Android and iOS devices.

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14 March, 2012 - 13:01
#2
Sam Pickard
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Hey good question. There isn't an in-built method for compressing images, but the save picture methods call down to the OS to do that. Are you trying to send a picture the user has just taken? If you, so can save the image to their device, and then read the automatically compressed image as binary data!

maCaptureWriteImage(mLatestPictureTakenHandle, "\sdcard\MyPhoto.jpg", 20);

Will save the image to the device, using the (I'm guessing here) the default compression method of that device, which I guess will be JPEG.  You can use the FileSystem API to read back that encoded image, B64 and post.

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14 March, 2012 - 17:27
#3
lacapaca
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Thanks for your reply, Sam. The idea was good, unfortunately it's giving me a MA_CAPTURE_RES_INVALID_HANDLE error.

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14 March, 2012 - 17:33
#4
Sam Pickard
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Have you replaced 'mLatestPictureTakenHandle' with the actual handle to the image you've taken?

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14 March, 2012 - 17:40
#5
lacapaca
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Ummm, yes, otherwise it wouldn't have compiled... :D

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14 March, 2012 - 17:42
#6
lacapaca
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It's not a picture I've just taken, but one returned from maImagePickerOpen().

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15 March, 2012 - 09:43
#7
lacapaca
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I've been digging around a bit and here's what I found:

On iOS, the stock image picker is shown, the maImagePickerOpen() is just a wrapper to handle the event etc. On Android, the picker is implemented from scratch. It's clumsy, doesn't look particularly nice and, worst of all, it force closes every time after some scrolling (most probably due to some bug in the caching code or just simply it runs out of memory).

Why couldn't the Android Gallery be used for this, just like on iOS? Seems like that would have been the "native" way of implementing this.

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15 March, 2012 - 11:48
(Reply to #7) #8
Ovidiu
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From 3.0.1 (end of the month) the Android Gallery will be used (implementation done, waits QA).

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15 March, 2012 - 11:51
#9
lacapaca
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That's awesome, Ovidiu. Thanks for the info! Is it available in the nightlies?

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15 March, 2012 - 12:01
(Reply to #9) #10
Ovidiu
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The implementation has already been integrated in the 3.0.1 branch and it should be in the next nightly build.

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15 March, 2012 - 12:33
#11
lacapaca
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It must be this commit... It was made on the 13th, just like the nightly build. Perhaps it made it into the build. I'll check too. Thanks again.

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15 March, 2012 - 12:44
(Reply to #11) #12
Ovidiu
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Yep, that's it, but I've checked already and it is not there yet :( So you'll have to wait: today or tomorrow there should be another nightly build.

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15 March, 2012 - 13:12
(Reply to #12) #13
lacapaca
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Just checked, it's not in yet. Sigh. And now the app force-closes on start. And I've lost the Eclipse plugins. That'll teach me to install nightlies over stable... :)

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15 March, 2012 - 13:16
(Reply to #13) #14
Ovidiu
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You read my thoughts ;)

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16 March, 2012 - 08:11
#15
lacapaca
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How hard would it be to add an extra parameter to the EVENT_TYPE_IMAGE_PICKER that would be the url of the selected image? This way I could just open the file from the FS and deal with it properly, no need to re-compress.

The (both the old and new) implementation on Android reads the image from the file, but he iOS implementation seems to get an image object and deals with that directly. It is quite possible (not an iOS expert by far...) that the image does not even always come from a file - in that case the point would be of course moot.

The image data associated with a MoSync handle seems to always be in ARGB format (correct me if I'm wrong) - thereby making it impossible to get the original, compressed data back from it. Maybe the best would be after all to add some image compression routines on the platforms that support it (should be all of them)... Thoughts?

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21 March, 2012 - 09:22
#16
lacapaca
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Shameless bump. :)

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27 March, 2012 - 07:20
#17
lacapaca
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Created issue 2069 for this.

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10 April, 2013 - 07:38
#18
carolinenew
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from what i see, image programme an easily convert or compress data.but whether  you can access the original file data,just need to try. i am not so clear.

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26 April, 2013 - 06:40
#19
dannyrough
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you can employ an imaging sdk which can do such kind of compression. there are a lot of such sdks on the internet , just try some and i think you can get what you want.

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