Color distance determination
View Patent ↗A method for evaluating color differences of pixels is provided. The method comprises obtaining color information of a first pixel in a color opponent space obtaining color information of a second pixel in the color opponent space, defining a half-line in the color opponent space based on the color information of the first pixel, and determining distance between color information of the second pixel and half-line in the color opponent space.
1. A method comprising:
calculating one or more respective hue distances between a first color associated with a first pixel of an image and one or more other colors associated with one or ore other pixels of the image;
wherein the first color and the one or more other colors are represented within a color opponent space defined by an ab-plane; and
wherein the hue distance between the first color and a given one of the one or more other colors in the color opponent space is calculated as:
if {right arrow over (C)} i ·{right arrow over (C)} j >0, then
a
i
·
b
j
-
b
i
·
a
j
c
j
→
=
Δ
H
,
and
if {right arrow over (C)} i ·{right arrow over (C)} j ≤0, then ∥{right arrow over (C)} j ∥=ΔH, where
ΔH is the hue distance,
{right arrow over (C)} i is a color vector having coordinates a i and b i corresponding to a location of the first color in the ab-plane, and
{right arrow over (C)} j is a color vector having coordinates a j and b j corresponding to a location of the given other color in the ab-plane; and
defining a pixel region around the first pixel based on the one or more hue distances, wherein the pixel region comprises those of the one or more other pixels having other colors corresponding to hue distances less than or equal to a hue distance threshold.
2. The method according to claim 1 , wherein the first color has a larger chrominance than each of the one or more other colors.
3. The method according to claim 1 , wherein the first pixel is an overexposed pixel.
4. The method according to claim 3 , further comprising converting the colors of the pixels of the pixel region such that the first color is non-saturated.
5. A method comprising:
calculating one or more respective hue distances between a first color associated with a first pixel of an image and one or more other colors associated with one or more other pixels of the image;
wherein the first pixel is an overexposed pixel;
wherein the first color and the one or more other colors are represented within a color opponent space defined by an ab-plane; and
wherein the hue distance between the first color and a given one of the one or more other colors in the color opponent space is calculated as:
if {right arrow over (C)} i ·{right arrow over (C)} j >0, then
a
i
·
b
j
-
b
i
·
a
j
c
j
→
=
Δ
H
,
and
if {right arrow over (C)} i ·{right arrow over (C)} j ≤0, then ∥{right arrow over (C)} j ∥=ΔH, where
ΔH is the hue distance,
{right arrow over (C)} i is a color vector having coordinates a i and b i corresponding to a location of the first color in the ab-plane, and
{right arrow over (C)} j is a color vector having coordinates a j and b j corresponding to a location of the given other color in the ab-plane;
defining a pixel region around the first pixel based on the one or more hue distances, wherein the pixel region comprises those of the one or more other pixels having other colors corresponding to hue distances less than or equal to a hue distance threshold; and
converting the colors of the pixels of the pixel region such that the first color is non-saturated.
6. The method according to claim 5 , wherein the first color has a larger chrominance than each of the one or more other colors.
7. An apparatus comprising:
a processor; and
a memory coupled to the processor that stores instructions when executed by the processor configure the processor to:
calculate one or more respective hue distances between a first color associated with a first pixel of an image and one or more other colors associated with one or more other pixels of the image;
wherein the first color and the one or more other colors are represented within a color opponent space defined by an ab-plane; and
wherein the hue distance between the first color and a given one of the one or more other colors in the color opponent space is calculated as:
if {right arrow over (C)} i ·{right arrow over (C)} j >0, then
a
i
·
b
j
-
b
i
·
a
j
c
j
→
=
Δ
H
,
and
if {right arrow over (C)} i ·{right arrow over (C)} j ≤0, then ∥{right arrow over (C)} j ∥=ΔH, where
ΔH is the hue distance,
{right arrow over (C)} i is a color vector having coordinates a i and b i corresponding to a location of the first color in the ab-plane, and
{right arrow over (C)} j is a color vector having coordinates a j and b j corresponding to a location of the given other color in the ab-plane; and
define a pixel region around the first pixel based on the one or more hue distances, wherein the pixel region comprises those of the one or more other pixels having other colors corresponding to hue distances less than or equal to a hue distance threshold.
8. The apparatus according to claim 7 , wherein the first color has a larger chrominance than each of the one or more other colors.
9. The method according to claim 7 , wherein the first pixel is an overexposed pixel.
10. The apparatus according to claim 9 , wherein the memory stores further instructions that when executed by the processor further configure the processor to convert the colors of the pixels of the pixel region such that the first color is non-saturated.