# Cell phone video three panels

**URL:** <https://boards.straightdope.com/t/cell-phone-video-three-panels/960546>\
**Category:** Factual Questions\
**Created:** [March 6, 2022, 3:05am UTC](https://boards.straightdope.com/t/cell-phone-video-three-panels/960546 "2022-03-06T03:05:36Z")\
**Posts on this page:** 3\
**Page:** 3

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [March 6, 2022, 11:30pm UTC](https://boards.straightdope.com/t/cell-phone-video-three-panels/960546/41 "2022-03-06T23:30:44Z")

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It’s a combination of vertical and horizontal skews. First, you skew the image vertically, so a rectangle is transformed into a parallelogram. Then you skew it horizontally, by twice as much as the first skew. Then you skew it vertically again.

In principle, you could use a larger number of skews, each by a smaller amount, but from what I understand, just the three skews usually produces an acceptable result.

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**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\
**Post date:** [March 6, 2022, 11:41pm UTC](https://boards.straightdope.com/t/cell-phone-video-three-panels/960546/42 "2022-03-06T23:41:31Z")

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Thanks - it looks like [this](https://gautamnagrawal.medium.com/rotating-image-by-any-angle-shear-transformation-using-only-numpy-d28d16eb5076) is what you’re describing, which is interesting, but has some pretty horrible jaggies in the end result. I suspect this could be mitigated a bit by some scaling before and after.

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**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\
**Post date:** [March 6, 2022, 11:48pm UTC](https://boards.straightdope.com/t/cell-phone-video-three-panels/960546/43 "2022-03-06T23:48:54Z")

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You’d never want to use that algorithm in practice. Even a simple bilinear filter would give better results and is absolutely trivial on any modern hardware. Even much more sophisticated filters are trivial with the amount of horsepower available.

Ideally, a rotation filter would take the Bayer arrangement into account. You gain more information if you know where the color subpixels are.

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