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Accurate Image Alignment and Registration Using OpenCV

magamig.github.io

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Re: Accurate Image Alignment and Registration Using OpenCV

#11
post #8

The biggest issue in real life use cases is lens distortion - these alignment algorithms usually don't correct barrel, pin-cushion or more complex lens distortions, making the alignment imperfect.

Any of the standard panorama software can solve for a standard simple lens distortion model, it just needs a few more alignment points to do so.

Re: Accurate Image Alignment and Registration Using OpenCV

#12

Image alignment allows for some fun image manipulations like these. I think one of the coolest novel applications of image alignment in recent years must be multi-frame super-resolution. For example, the Pixel phones use it to improve low-light and zoomed in photos[0]. [0] https://sites.google.com/view/handheld-super-res/

Does this mean that objects that are on a trajectory out of the view have less resolution?

Re: Accurate Image Alignment and Registration Using OpenCV

#13
I currently working on an optical respiratory monitor and one of the challenges was image alignment/registration for an optical and a thermal image with wildly different resolutions, fovs.

We ended up doing this by manually calibrating the images in matlab using a custom script and logging out a transformation matrix that we could then multiply the optical image by to get matching pixels in the thermal image.

Really fun project, but definitely a tedious thing to do, especially when its only a small part of the overall project. The project in the link also looks very cool, just not quite right for us as we probably wouldnt consistently have enough landmarks to map.

Re: Accurate Image Alignment and Registration Using OpenCV

#14
post #3

Image alignment allows for some fun image manipulations like these. I think one of the coolest novel applications of image alignment in recent years must be multi-frame super-resolution. For example, the Pixel phones use it to improve low-light and zoomed in photos[0]. [0] https://sites.google.com/view/handheld-super-res/

Cool! I'm planning on using image alignment for enhancing the spatial resolution of hyperspectral (HS) images, through the fusion of RGB and HS images.

You get something similar to a panchromatic image?

Re: Accurate Image Alignment and Registration Using OpenCV

#15
post #10
post #4

Earlier quoted context omitted.

This is called drizzle (with dithering, e.g. the raw photos are taken with offsets) in the astrophotography sphere and is very effective when the images are undersampled. Although, astronomy images have the advantage of being filled with stars that are relatively easy to align very accurately.

'When undersampled' -- time to get a more modern sensor? 3.76um pixels + 800mm focal length is about 1 arcsecond per pixel, so that will end up seeing limited much of the time.

Many undersample on purpose and get better results that way. You can workaround seeing a little with lucky imaging and patience, being very selective.

Also, drizzling was developed originally for the Hubble Deep Field, which isn't limited by seeing :).

Re: Accurate Image Alignment and Registration Using OpenCV

#18
post #14
post #3

Earlier quoted context omitted.

Cool! I'm planning on using image alignment for enhancing the spatial resolution of hyperspectral (HS) images, through the fusion of RGB and HS images.

You get something similar to a panchromatic image?

You can use an high-resolution panchromatic image to increase the spatial resolution of an RGB image. Here the objective is to do the apply the same idea but using an RGB and HS image, increasing the spatial resolution of the latter.

Re: Accurate Image Alignment and Registration Using OpenCV

#19

Image alignment allows for some fun image manipulations like these. I think one of the coolest novel applications of image alignment in recent years must be multi-frame super-resolution. For example, the Pixel phones use it to improve low-light and zoomed in photos[0]. [0] https://sites.google.com/view/handheld-super-res/

I wonder if you could use alignment of multiple samples for better vectorizing of letters of old books. You could create very nice vector only pdfs.

Re: Accurate Image Alignment and Registration Using OpenCV

#20

I currently working on an optical respiratory monitor and one of the challenges was image alignment/registration for an optical and a thermal image with wildly different resolutions, fovs. We ended up doing this by manually calibrating the images in matlab using a custom script and logging out a transformation matrix that we could then multiply the optical image by to get matching pixels in the thermal image. Really…

Direct methods could be useful in your case. https://pages.cs.wisc.edu/~dyer/ai-qual/irani-visalg00.pdf
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