Read an image, correct it for radial lens discortion, and write out the corrected image. More...

Detailed Description

Read an image, correct it for radial lens discortion, and write out the corrected image.

Author: Mitch Richling https://www.mitchr.me

Copyright

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Details

The geomTfrmRevRPoly() method uses a radial polynomial transform. This method may be used to reproduce the behavior of Imagemagick's barrel distortion transformation. In Imagemagick the following terminology and constraints are used:

(X, Y) is the image center for both T & S
A, B, C, & D are constants
A+B+C+D=1 – if you don't provide D it will be computed

This is all put together on the command line something like this:


      -distort Barrel "A B C D X Y"

We can demonstrate the similar behavior between Imagemagick & this example program like this:

Make test images

    make test_images
    ./test_images.exe

Compute the new image with imagemagik

    rm test_images_mcgrid_fimg.tiff
    magick test_images_mcgrid.tiff -background Green -virtual-pixel Background -interpolate Bilinear -filter point -distort barrel "0.0 -0.0160 0.0" test_images_mcgrid_fimg.tiff
    start test_images_mcgrid_fimg.tiff

Compute the new image with MRaster

    make geomTfrm_LensDistortion
    ./geomTfrm_LensDistortion.exe test_images_mcgrid.tiff
    mv geomTfrm_LensDistortion.tiff test_images_mcgrid_fmr.tiff
    start test_images_mcgrid_fmr.tiff

Use compare aginst the two imgages

    magick compare -metric mae test_images_mcgrid_fmr.tiff test_images_mcgrid_fimg.tiff out.tiff
    start out.tiff

Subtract the two images

    magick test_images_mcgrid_fmr.tiff test_images_mcgrid_fimg.tiff -compose Mathematics -define compose:args='0,1,-1,0' -composite out.tiff
    start out.tiff

Note the images are not identical, but they are very close.

Definition in file geomTfrm_LensDistortion.cpp.