GNU Astronomy Utilities - Tasks: task #14363, Option for scaling to nearest full...
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task #14363: Option for scaling to nearest full pixel fraction
Submitter: | Lee Kelvin <leeskelvin> | ||
Submitted: | Wed 08 Feb 2017 08:16:03 PM UTC | ||
Should Start On: | Wed 08 Feb 2017 12:00:00 AM UTC | Should be Finished on: | Wed 08 Feb 2017 12:00:00 AM UTC |
Category: | Warp | Priority: | 5 - Normal |
Item Group: | Enhancement | Status: | None |
Privacy: | Public | Percent Complete: | 0% |
Assigned to: | None | Open/Closed: | Open |
Effort: | 0.00 |
( Jump to the original submission )
Mon 13 Feb 2017 11:31:25 PM UTC, comment #8: |
Mohammad Akhlaghi <makhlaghi>![]() |
Fri 10 Feb 2017 03:37:19 PM UTC, comment #7: Sorry, just one note, if you do get the chance to update the book, please use this doc/gnuastro.texi version (on my development branch as part of task #14245). As I am making changes/additions, I am also updating the book when necessary in every commit, the link above will always be up to date with my work, making my job to merge your changes easier later).
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Mohammad Akhlaghi <makhlaghi>![]() |
Fri 10 Feb 2017 03:24:07 PM UTC, comment #6: Thanks, I am really happy that we were able to reach a common understanding. I have modified the title of this task to "Option for scaling to nearest full pixel fraction", if you can think of a better title, please feel free to update it (or if you can't, comment here so I do it).
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Mohammad Akhlaghi <makhlaghi>![]() |
Fri 10 Feb 2017 12:28:22 PM UTC, comment #5: Yes, I see your point, and I accept that scaling in this manner has its uses. As mentioned earlier, I find your recommendation to add a --discretescale or --autoscale to be a good compromise.
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Lee Kelvin <leeskelvin>![]() |
Thu 09 Feb 2017 06:29:36 PM UTC, comment #4: Sorry, this is correction to the previous sentence to make it more clear ("sizes" should have been "numbers":
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Mohammad Akhlaghi <makhlaghi>![]() |
Thu 09 Feb 2017 06:24:33 PM UTC, comment #3: Thanks for the explanation. I am happy that you agree to having a secondary option for he higher-level suggestion you made.
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Mohammad Akhlaghi <makhlaghi>![]() |
Thu 09 Feb 2017 04:49:40 PM UTC, comment #2: Thank you for your detailed reply. As we have discussed, I do not consider this issue to be a misunderstanding, but rather something more fundamental in the way image manipulation with respect to scaling should operate. However, I find your suggestions to add new arguments which do behave in such a manner to be good compromise if I'm the only one who sees an issue with the current operation.
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Lee Kelvin <leeskelvin>![]() |
Thu 09 Feb 2017 02:11:53 AM UTC, comment #1: This is an interesting suggestion, thank you. It would be great if you could mention what part of the ImageWarp documentation created this impression?
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Mohammad Akhlaghi <makhlaghi>![]() |
Wed 08 Feb 2017 08:16:03 PM UTC, original submission:
The current method by which image scaling takes place in ImageWarp may be confusing to many users. The value taken from --scale should be made flexible in order to perform scalings which are non-trivial.
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Lee Kelvin <leeskelvin>![]() |
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Follow 2 latest changes.
Date | Changed by | Updated Field | Previous Value | => | Replaced by |
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2017-02-10 | makhlaghi | Summary | Change the default behaviour of --scale in ImageWarp | ![]() |
Option for scaling to nearest full pixel fraction |
2017-02-08 | leeskelvin | Attached File | - | ![]() |
Added pixmix.png, #39705 |
Warp (the new name for ImageWarp) now comes with the new option `--coveredfrac' (replacing the old `--maxblankfrac' function, see P.S.), which can address the problem you mentioned about a flat image.
What this option does is this: you give it a fraction (between 0 and 1). If the output pixel doesn't cover the input pixels by a fraction larger than the number you gave, the output pixel will be blank.
So, to ensure flat-ness in your example, you can run Warp with `--coveredfrac=1'. In this way, if the output pixel isn't fully covered by the input image pixels, it will have no value, so all your output pixels will also be flat. This comes at the expense of missing the pixels immediately touching the edge, so the total sum of the pixel values will be less than the input image. But you do have access to a continuous warping space.
The great thing with this feature is that it doesn't just apply to `--scale', it applies to any kind of warping.
This isn't a solution to this task, but I am just mentioning it here as one alternative that can be used until this task is implemented.
P.S. the old `--maxblankfrac' just counted the fraction of blank pixels over the output image, so it was useless for edge effects. The new `--coveredfrac' now accounts for both blank pixels and edges of the image.