Patent ID: 11869455
Assignee: DOLBY LABORATORIES LICENSING CORPORATION
Field: Audio-visual technology (Electrical engineering)
Classification: CPC G | IPC G

Claim 1:
2. A method for modifying an image to compensate for ambient light conditions around a display device, the method comprising:
determining perceptual luminance amplitude quantization (PQ) data of the image;
determining a PQ shift for the PQ data based on a compensation value determined from the ambient light conditions and the image,
wherein the compensation value is calculated from C=M√{square root over (X)}+B, where C is the compensation value, M is a function of surround luminance values S, X is a mid PQ value of the image representing an average luminance of the image, and B is a function of surround luminance values, wherein M=a*S+b and B=c*S2+d*S+e, where a, b c, d and e are constants;
the PQ shift consisting of either: an addition to the compensation value in PQ space followed by a subtraction of the compensation value in linear space calculated by PQout=L2PQ(PQ2L(PQin+C))−PQ2L(C)) for an ambient surround luminance environment being brighter than a reference value, or an addition to the compensation value in linear space followed by a subtraction of the compensation value in PQ space calculated by PQout=L2PQ(PQ2L(PQin)+PQ2L(C))−C for an ambient surround luminance environment being darker than the reference value, wherein PQout is the resulting PQ after the shift, PQin is the original PQ value, L2PQ( ) is a function that converts from linear space to PQ space, and PQ2L( ) is a function that converts from PQ space to linear space;
applying the PQ shift to the image to modify the PQ data of the image.