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Decreasing the Stitching time

asked 2012-10-15 04:21:39 -0600

zenberg gravatar image

updated 2012-10-15 10:59:09 -0600

Kirill Kornyakov gravatar image

Hello, I am using the Stitiching module and ROI to stitch two photos (968x1296 each).
On the iPhone 4 it takes more than 30 seconds (about 14 seconds to find features and 18 seconds to compose images + other calculations).

Can you please tell me if there is any way to speed up this process?

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Which features are you using? Did you try Orb or other features?

Kirill Kornyakov gravatar imageKirill Kornyakov ( 2012-10-15 11:00:40 -0600 )edit

Yes, I tried Orb, it works fast, but sometimes it finds it difficult to detect enough features. I came to a conclusion that by changing registrationResol I get much better results with the default feature detector.

zenberg gravatar imagezenberg ( 2012-10-16 11:25:04 -0600 )edit

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answered 2012-10-15 06:31:56 -0600

sammy gravatar image

The first thing to check is whether you compile with full optimizations: set optimization level to -O2/-O3

If that doesn't help you enough, you should play with the stitcher parameters:

double registrationResol()
void setRegistrationResol(double resol_mpx)

double seamEstimationResol()
void setSeamEstimationResol(double resol_mpx)

double compositingResol()
void setCompositingResol(double resol_mpx)

They control the quality and the speed of your stitching process.

Third, you should try it on a Tegra3 device - that's an Android, btw ;)

Finally, if you still do not like the result, why not try to optimize it yourself more? Here is a starting point into image processing optimizations. But beware that you may cut your fingers.

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Hello Sammy. Thank you very much for your answer, it's very useful.

setRegistrationResol helped me to significantly(x2.5) speed up the process of feature detection. I changed the default value to 0.1 and if the search of features is unsuccessful, then I'm automatically changing it to the highest value of 1.0.

zenberg gravatar imagezenberg ( 2012-10-16 11:29:27 -0600 )edit

I have one more issue with "setCompositingResol" though.

I tried to change its value and when the value is "0.1" the stitching process is blazingly fast, but if I try to stitch the stitched photo that I get with this value with a regular photo, then "finding features" shows me an error no matter what's the value of "registrationResol". If I increase "compositingResol", then features can be found, but it requires much more time than it does with the default "compositingResol" value, so unfortunately I failed to decrease the stitching time here.

Maybe you have some ideas why this happens?

zenberg gravatar imagezenberg ( 2012-10-16 11:38:37 -0600 )edit

it's quite clear that when it's very fast it's because it does nothing - so no stitching result. If you want the stitching, you need to set a higher threshold. And do not expect it to work instantly.

sammy gravatar imagesammy ( 2012-10-16 12:24:11 -0600 )edit

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Asked: 2012-10-15 04:21:39 -0600

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Last updated: Oct 15 '12