PRESERVING DYNAMIC RANGE PRECISION IN INTEGER IMAGE FORMATS

摘要

High dynamic range media sensor output is encoded using a hybrid transfer function. The hybrid transfer function conforms to existing industry standards over standard brightness level ranges, such as between black and white reference points, and uses a different function to encode captured signals having intensities below the black point and above the white point. Precision over the expanded dynamic range of captured image data is optimally preserved using a two-byte per pixel representation. The transfer function varies across the full dynamic range without clamping off below the maximum value of the expanded captured intensity range. One hybrid transfer function conforms to BT.1886 up to the white point, and uses a linearly varying encoding gamma above the white point up to 1300% IRE, producing encoded values in a 2.14 fixed point representation. The hybrid transfer function is continuous at the white point, and may also have a continuous gradient there.

主权项

1. A method of encoding digital image data, the method comprising:
receiving signals from an image sensor, wherein a maximum range of possible values of the received signals corresponds to a maximum range of intensity levels capable of being detected by the image sensor, the maximum range of intensity levels capable of being detected by the image sensor including intensity levels above a reference white point level; and encoding the received image signals into a selected image representation using a hybrid transfer function, wherein:
the hybrid transfer function is defined across the maximum range of possible values of the received signals and maps the maximum range of possible values of the received signals to a full range of values that can be represented by the selected image representation; andfor values of the received signals corresponding to a range of intensity levels between a lower intensity level and an upper intensity level over which an industry standard transfer function is defined, the hybrid transfer function conforms to the industry standard transfer function.