Image Tone Adjustment using Local Tone Curve Computation

摘要

Image tone adjustment using local tone curve computation may be utilized to adjust luminance ranges for images. Image tone adjustment using local tone curve computation may reduce the overall contrast of an image, while maintaining local contrast in smaller areas, such as in images capturing brightly lit scenes where the difference in intensity between brightest and darkest areas is large. A desired brightness representation of the image may be generated including target luminance values for corresponding blocks of the image. For each block, one or more tone adjustment values may be computed, that when jointly applied to the respective histograms for the block and neighboring blocks results in the luminance values that match corresponding target values. The tone adjustment values may be determined by solving an under-constrained optimization problem such that optimization constraints are minimized. The image may then be adjusted according to the computed tone adjustment values.

主权项

1. A method, comprising:
performing, by a computing device:
generating target luminance values for each of a plurality of blocks for an image, wherein said generating is based at least in part on a brightness representation of the image;generating luminance histogram information for each of the plurality of blocks;for each of the plurality of blocks of the image:
determining one or more neighboring blocks for the block;determining, for the block, one or more tone adjustment values that when jointly applied to the respective histogram information for the block and each of the one or more neighboring blocks generate new luminance values for the block and each of the one or more neighboring blocks that match the respective target luminance values for the block and each of the one or more neighboring blocks; andperforming one or more tone adjustments on the image according to the one or more tone adjustment values.