Like Silk: RICOH Theta 360

[English/Japanese]
Have fun with spherical images by RICOH THETA.

Theta may record as Equirectangular Panorama Image

The spherical image data taken by the theta is stored as 3584x1792-sized-rectangle JPG files. If you provide any 3584x1792-sized-rectangle JPG images to a theta viewer, RICOH THETA for windows(R)/Mac, you can spherically view the JPG images.

Once we transform the spherical image data to 3584x1792-sized-rectangle JPG format, we can share any spherical image data with the site of the theta360.com. The forward and the inverse mapping from XY-coordinate on the rectangle JPG image to latitude/longitude on the spherical image data are required for this transformation.

I generated border test chart which has 16-pixel-height borders as shown:

You can see this border test chart with the online theta viewer:

From this simple test, the theta may record as the equirectangular panorama image. The relationship between the XY-coordinate and the latitude/longitude might be:
(No guarantee, of course)

$\theta=\frac{360}{3584}X$ , $\phi=(1792/2-Y)\frac{180}{1792}$
$X=\frac{3584}{360}\theta$ , $Y=1792/2-\frac{1792}{180}\phi$
where $\theta$ is longitude [degree], $\phi$ is latitude [degree], $X$ and $Y$ are XY cordinate on the image defined by the bellow.

The latitude at the equator is zero [deg], the north is positive, and the south is negative.

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