Conversion of polar to Cartesian and back (with filtering in between)

[DavidAckerman88]

ImageMagick version

7.1.1.1-31

Operating system, version and so on

MacOS 14.1.2

Description

Total neophyte on ImageMagick searching for a high-fidelity cartesian -> polar warp that I will filter (to create radial blur) and then convert back to cartesian to subtract from the original to create radial high-pass images. (All this for eclipse corona processing). Works for .jpgs but not for 16-bit .tiff files yet. Please recommend a tutorial.

[fmw42]

Read https://imagemagick.org/Usage/distorts/#polar and the sections that follow about depolarization and the full cycle polar and dipolar. All for command line Imagemagick. I know nothing about eclipse corona.

[snibgo]

The IM operations would be "-distort polar" and "-distort depolar". See https://imagemagick.org/script/command-line-options.php#distort

For a tutorial, Polar distortions may be useful.

[DavidAckerman88]

Follow-on question -- is it possible to specify a pair of center coordinates in using polarblur? Or should I simply pad my image so that the desired center of the polar blur ends up in the center of the padded image?

[snibgo]

What is "polarblur"? That isn't an IM operation.

For "-distort polar" and "-distort depolar", yes, they can have specified centres. See https://imagemagick.org/script/command-line-options.php#distort

[DavidAckerman88]

Thank you for your instant response. That will keep me coming back and maybe I'll learn imageMagick. I do like command line programs! All the best, David PS: I do understand that you might not know about the eclipse corona but I do and you have helped me continue to refine my raw photos of it. In the end, if I get what I hope to, I'll send you a copy in case you want to showcase just another thing your IM can do.

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On Tue, Apr 30, 2024 at 3:08 PM snibgo ***@***.***> wrote: The IM operations would be "-distort polar" and "-distort depolar". See https://imagemagick.org/script/command-line-options.php#distort For a tutorial, Polar distortions <http://im.snibgo.com/poldist.htm> may be useful. — Reply to this email directly, view it on GitHub <#7280 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ARCW4XNNOFF47CQ6MER4O2DY77T2ZAVCNFSM6AAAAABHA2AMR2VHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM4TENZYHE4DK> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>

[DavidAckerman88]

Hi again -- and thank you for your quick reply. I am confused between the scripts listed here: http://www.fmwconcepts.com/imagemagick/index.php and the commands that include -distort polar and -distort depolar. I do understand that the scripts on Fred's ImageMagick Scripts page use the lower level commands but how exactly to use them on the command line is something I'm still working out. Moreover, calling them from a high level scripting language, e.g., Matlab, is also something that I'm working on. So, polarblur, which does a rect2polar transform followed by a 1 or 2D Gaussian blur in the polar domain and the transforms back using polar2rect would be very useful to me if I can wrangle it to do what I want,

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On Wed, May 1, 2024 at 2:48 PM snibgo ***@***.***> wrote: What is "polarblur"? That isn't an IM operation. For "-distort polar" and "-distort depolar", yes, they can have specified centres. See https://imagemagick.org/script/command-line-options.php#distort — Reply to this email directly, view it on GitHub <#7280 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ARCW4XOUIXJM4OXDXBT7LKLZAE2GFAVCNFSM6AAAAABHA2AMR2VHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM4TEOBXHE4TM> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>

[fmw42]

You do not need my scripts and they do not do what you are asking.

magick input.suffix \
-distort DePolar -1  \
-blur 0xsigma \
-virtual-pixel HorizontalTile -background black \
-distort  Polar  -1  \
output.suffix

Use whatever value you want for sigma above. That is replace the word sigma with your value. User more depolar/polar distortion arguments as you want: Radius_Max Radius_Min Center_X,Center_Y Start_Angle,End_Angle

See https://imagemagick.org/Usage/distorts/#polar