New mathematical model could mean better image stitching for panoramas

 

 

Stitching together a series of images into a panorama is a surprisingly tricky business. Some companies, like Sony and Apple, seem to have a really solid grasp on it, and can easily put together a pano from just a sweep of your device. But a new mathematical model could mean that when your photos get combined, you end up getting a much smoother transition of color, shading, and exposure — making for a more natural looking image.

In a paper published in the Society for Industrial and Applied Mathematics Journal on Imaging Sciences, (available free to read as a PDF temporarily), a new method is proposed of stitching images together to better account for differences in lighting.

According to a press release, the new approach helps blend the two images more seamlessly, as it "minimizes seam artifacts by smoothing the transition between the images. The mosaic image here is a weighted combination of the input images. This means the pixel values from the two overlapping images are combined using a weighted average for qualities such as exposure, local contrast, saturation, etc."

Effectively, what that means is that when you stitch two images together, but they have a slightly different exposure (a common problem when shooting on Auto), this algorithm combines them in a way to make a smooth shift between the two, rather than a harsh edge.

The paper itself is fairly dense, but the images below give some sort of idea of what they're talking about:

 

This shows two input images (from left) stitched together using the proposed method (right).

 

(a)–(b), (c)–(d) The input images; (e) and (g) the stitched results by the proposed model; (f) and (h) the corresponding mask functions of (e) and (g), respectively.

 

(a)–(b) The input images; (c) and (g) the stitched results without color correction and its zoomed part; (d) and (h) the stitched results after using [33] for color correction, which is applied to transfer the color from a dark picture to a bright picture and its zoomed part; (e) and (i) the stitched results after using [33] for color correction, which is applied to transfer the color from a bright picture to a dark picture and its zoomed part; (f) and (j) the stitched results after using Retinex for color correction, which is applied to transfer the color from a bright picture to a dark picture and its zoomed part.