Exposure correction

There are some exposure differences between sequences. These makes errors for align images and color fluctuations of stitched image.

Following image is stitched image of test sequence before exposure correction.

Using histograms of overlapped images (two images), I corrected an image. One image is selected (generally brighter image) for standard, and the other image is selected for correction (generally darker). I tried to make histograms of these two images similar using least square method. I used following correcting function.

where, y is output image, x is input image, level is maximum level (parameter) and alpha is also parameter.

Following image shows before and after correction.

After correcting images, images are aligned very well. But, I didn’t apply this scheme to all images. Because the impression of color is not good after images are corrected and some fluctuation of color seems natural for me.