Automated tonal balancing

1. A system for automated generation of large-scale tonally-balanced orthomosaic images, comprising:

a tone-balancing server computer comprising a memory, a processor, and a plurality of programming instructions stored in the memory, wherein the programming instructions, when loaded into the processor, cause the processor to:

receive a group of orthorectified input images associated with a geographic region;

obtain a reference image for the geographic region;

for each orthorectified input image:

subdivide the respective orthorectified input image into a plurality of patches;

compute a pixel-level tonal mapping function for each patch to match a corresponding set of pixels of the reference image;

compute a first global tonal mapping function for the respective orthorectified input image by, for each pair of patches of the respective orthorectified input image, computing a function that smoothly connects the respective pixel-level tonal mapping functions for the pair of patches; and

apply the first global tonal mapping function to each pixel of the respective orthorectified input image to create a respective tonally-balanced orthorectified output image;

compute a second global tonal mapping reference by smoothly matching first global tonal matching functions for each neighboring pair of orthorectified output images; and

apply the second global tonal matching function to each pixel of each tonally-balanced orthorectified output image.

2. A method for automatically generating large-scale tonally-balanced orthomosaic images, the method comprising the steps of:

receiving, at a tone-balancing server computer comprising program code stored in a memory, a group of orthorectified input images associated with a geographic region;

obtaining a reference image for the geographic region;

for each orthorectified input image, performing the steps of:

subdividing the orthorectified input image into a plurality of patches;

computing a pixel-level tonal mapping function for each patch to match a corresponding set of pixels of the reference image;

computing a first global tonal mapping function for the respective orthorectified input image by, for each pair of patches of the respective orthorectified input image, computing a function that smoothly connects the respective pixel-level tonal mapping functions for the pair of patches; and

applying the first global tonal mapping function to each pixel of the respective orthorectified input image to create a plurality of tonally-balanced orthorectified output images;

computing a second global tonal mapping reference by smoothly matching first global tonal matching functions for each neighboring pair of orthorectified output images; and

applying the second global tonal matching function to each pixel of each tonally-balanced orthorectified output image.