Perceptual luminance nonlinearity-based image data exchange across different display capabilities
A handheld imaging device has a data receiver that is configured to receive reference encoded image data. The data includes reference code values, which are encoded by an external coding system. The reference code values represent reference gray levels, which are being selected using a reference grayscale display function that is based on perceptual non-linearity of human vision adapted at different light levels to spatial frequencies. The imaging device also has a data converter that is configured to access a code mapping between the reference code values and device-specific code values of the imaging device. The device-specific code values are configured to produce gray levels that are specific to the imaging device. Based on the code mapping, the data converter is configured to transcode the reference encoded image data into device-specific image data, which is encoded with the device-specific code values.
1. An apparatus processing a bitstream stored on a non-transitory storage media, the bitstream comprising an image and metadata, wherein:
the metadata includes a first luminance value and a second luminance value;
the image is encoded with digital code values D that represent a normalized luminance Y based at least in part on a functional model of
Y
=
(
max
[
(
V
1
/
m
-
c
1
)
,
0
]
c
2
-
c
3
V
1
/
m
)
1
/
n
;
parameters n, m, c 1 , c 2 , and c 3 are predetermined values; and
normalized value V of the digital code values D is 0≤V≤1,
wherein digital code values D exclude reserved code values.
2. The apparatus of claim 1 , wherein a relationship between the normalized value V and the digital code value D is provided by the function:
V
=
D
-
4
·
2
b
-
10
1015
·
2
b
-
10
wherein b is a bit depth corresponding to a number of bits used to represent the digital code value D.
3. The apparatus of claim 2 , wherein the bit depth b is 10 bits.
4. The apparatus of claim 2 , wherein the bit depth b is 12 bits.
5. The apparatus of claim 1 , wherein:
n= 2610/4096×¼≃0.1593017578125;
m= 2523/4096×128≃78.84375;
c 1 =c 3 −c 2 +1=3424/4096≃0.8359375;
c 2 =2413/4096×=≃18.8515625; and
c 3 =2392/4096×32≃18.6875.