Request for Peirce quincuncial projection

[Bicyclops]

Hey!

This is a feature request for a Peirce quincuncial projection:
http://en.wikipedia.org/wiki/Peirce_quincuncial_projection

Equirectangular seems to be the most common type of projection for storing panoramas, yes it is horrible for this purpose. Distortion increases as you move further from the equator, and so the size and distribution of pixels from the original source image (whether fisheye or rectilinear) when forward-mapped into an equirectangular projection varies wildly - this makes it a horrible projection considering how JPEG compression works, considering one may want to denoise the panorama or sharpen it, etc.

The Peirce quincuncial projection has very limited distortion. From Wikipedia, "The part where the exaggeration of scale amounts to double that at the centre is only 9% of the area of the sphere, against 13% for the Mercator projection and 50% for the stereographic projection". When used in cartography, it gives an honest representation of the globe. When used for aesthetic purposes in panoramas, it gives a unique and interesting look.

Please consider adding the Peirce quincuncial projection to Hugin.

[tmodes (tmodes)]

Hugin is using libpano13 for all the remapping. So the projection have to be added to libpano13.

I see at least 2 issue with this projection:
* Blending about the 360 deg border in this projection is not not supported by enblend/smartblend/multiblend. So this projection needs a special treatment for the 360 deg case.
* Even when the projection has less distortion than equirectangular, there are 4 singularities, and all are at the equator (and so in the middle).

[Bicyclops (bugs-8)]

Hello

Thank you for handling this. I'm curious, why is this projection an issue for blending the edges?

[tmodes (tmodes)]

For the normal "equirectanglular" or cylindrical projection the blender blend about the 360 deg border by matching the "left" and "right" border to get a seamless final image.

For the Peirce projection you can't blend about the left/right border - you will get unwanted artefacts. You will have to process each border at its own to don't get jumps in the seams.
This may not be an issue if you don't use this projection in interactive viewers.