U.S. patent application number 10/309448 was filed with the patent office on 2003-05-01 for brightness adjustment method.
Invention is credited to Mazzapica, Douglas.
Application Number | 20030081141 10/309448 |
Document ID | / |
Family ID | 25495265 |
Filed Date | 2003-05-01 |
United States Patent
Application |
20030081141 |
Kind Code |
A1 |
Mazzapica, Douglas |
May 1, 2003 |
Brightness adjustment method
Abstract
A brightness adjustment method. An image of a scene is provided.
The image is segmented into a plurality of areas, where each area
has a plurality of pixels. One of the areas is selected as a
transition area, and a transition brightness of the transition area
is defined. The brightness of each remaining area of the image is
also defined and compared to the transition brightness. According
to the comparison result, the remaining areas are grouped into a
plurality of regions, and a coefficient is determined for each
region. The rightness of each pixel of the areas in each region is
then adjusted by the corresponding coefficient.
Inventors: |
Mazzapica, Douglas;
(Lakewood, CA) |
Correspondence
Address: |
Kit M. Stetina, Esq.
STETINA BRUNDA GARRED & BRUCKER
Suite 250
75 Enterprise
Aliso Viejo
CA
92656
US
|
Family ID: |
25495265 |
Appl. No.: |
10/309448 |
Filed: |
December 4, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10309448 |
Dec 4, 2002 |
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09954326 |
Sep 17, 2001 |
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Current U.S.
Class: |
348/362 ;
348/E5.028; 348/E5.04; 348/E5.08 |
Current CPC
Class: |
H04N 5/238 20130101;
H04N 5/3572 20130101; H04N 1/40093 20130101; H04N 5/235 20130101;
H04N 1/407 20130101 |
Class at
Publication: |
348/362 |
International
Class: |
H04N 005/235 |
Claims
What is claimed is:
1. A brightness adjustment method, comprising: providing a scene of
which an image is to be captured; segmenting the image into a
plurality of areas, each area comprising a plurality of pixels;
selecting one of the areas as a transition area and defining a
transition brightness of the transition area; defining brightness
of each remaining area of the image; comparing the brightness of
the remaining areas to the transition brightness; grouping the
remaining areas into a plurality of regions in response to the
results of the comparing step; determining a coefficient for each
region; and adjusting brightness of each pixel of the remaining
areas in each region by the corresponding coefficient.
2. The method according to claim 1, further comprises using an
image capture device to capture the image.
3. The method according to claim 1, further comprises using a
charged-coupled device to capture the image.
4. The method according to claim 1, wherein the step of selecting
the transition area further comprises selecting the transition area
from one area of the image mapping a predetermined element of the
scene.
5. The method according to claim 1, wherein the step of selecting
the transition area further comprises selecting the transition area
from one area of the image located in a predetermined position.
6. The method according to claim 1, wherein the step of selecting
the transition area further comprises selecting the transition area
from one area of the image with a brightness closest to a
predetermined brightness value.
7. The method according to claim 1, wherein the step of defining
the transition brightness further comprises computing an average
brightness of the pixels of the transition area.
8. The method according to claim 1, wherein the step of defining
the transition brightness further comprises determining a
percentage of a peak brightness among the pixels of the transition
area.
9. The method according to claim 1, wherein the step of defining
the transition brightness further comprises selecting a medium
brightness among the pixels of the transition area.
10. The method according to claim 1, wherein the step of grouping
the remaining areas further comprises grouping the remaining areas
into a higher region and a lower region, wherein the areas in the
higher region have brightness higher than the transition
brightness, and the areas in the lower region have brightness lower
than the transition brightness.
11. The method according to claim 10, wherein the step of
determining the coefficient further comprising determining a first
coefficient for the lower region and a second coefficient for the
higher region.
12. The method according to claim 11, wherein the brightness of
each pixel of each area in the lower region is adjusted by
multiplying the first coefficient.
13. The method according to claim 11, wherein the brightness of
each pixel of each area in the higher region is adjusted by
multiplying the second coefficient and then adding a constant.
14. A brightness adjustment method, comprising: providing an image
of a scene; segmenting the image into a plurality of areas, each
area comprising a plurality of pixels of three primary colors;
selecting one of the areas as a transition area, and defining a
transition brightness of the transition area; comparing brightness
of each area to the transition brightness to determine an
adjustment coefficient for each area; and adjusting brightness of
the pixels of at least one color in at least one area by the
corresponding adjustment coefficient.
15. The method according to claim 14, wherein the step of selecting
the transition area further comprises selecting the transition area
from one area of the image mapping a predetermined element of the
scene.
16. The method according to claim 14, wherein the step of selecting
the transition area further comprises selecting the transition area
from one area of the image with a brightness closest to a
predetermined brightness value.
17. The method according to claim 14, wherein the step of defining
the transition brightness further comprises computing an average
brightness of the pixels of the transition area.
18. The method according to claim 14, wherein the step of defining
the transition brightness further comprises determining a
percentage of a peak brightness among the pixels of the transition
area.
19. The method according to claim 14, further comprising the step
of filtering brightness of the pixels of the remaining colors in
the area adjusted by the adjustment coefficient.
20. The method according to claim 19, wherein the step of filtering
brightness of the pixels of the remaining colors includes
multiplying the brightness of the pixels of the remaining colors by
another coefficient.
21. The method according to claim 20, wherein the step of filtering
brightness of the pixels of the remaining colors includes
displaying the adjusted pixels only.
22. A brightness adjustment method, comprising: providing an image
of a scene; segmenting the image into a plurality of areas, each
area comprising a plurality of pixels of three primary colors;
selecting one of the areas as a transition area, and defining a
transition brightness of the transition area; comparing brightness
of the remaining areas to the transition brightness to determine
one adjustment coefficient for the pixels of each color in each of
the remaining areas; and adjusting brightness of the pixels of each
color in at least one area by the corresponding adjustment
coefficient.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This invention is a continuation-in-part of the previously
filed application Ser. No. 09/954,326.
STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT
[0002] (Not Applicable)
BACKGROUND OF THE INVENTION
[0003] The present invention relates generally to a brightness
adjustment method, and more particularly, to a method modifying the
relationship between the actual brightness of a scene and the
brightness of the image recorded in a photograph, such that the
scene can be reproduced with enhanced fidelity.
[0004] A digital camera has an image capturing device such as a
charge couple device (CCD) to capture an image and to save it to a
memory. The exposure step allows the image capture device exposed
to the image of the scene to be captured and photographed in a
medium such as a film, a disk or a display screen. The modern image
capturing device is sensitive to a broad range of brightness or
light levels reflected from or emitted from the scene. However,
when the image is recorded in the medium, overexposure and
underexposure frequently occurs to some part of the image due to
excessive and insufficient brightness thereof, respectively. This
is because most of the currently available media for recording the
image accept relatively small range of light levels (brightness)
compared to the image capture device. For many media, a black image
can be rendered as black as it is, but the image with very high
light level such as the sun can hardly be resolved.
[0005] To obtain a properly exposed image recorded by the digital
camera, particularly when the scene from which the image is
captured contains an element much brighter than the others, the
exposure value has to be controlled or adjusted. In many
applications such as digital still cameras, digital video cameras,
film and print scanners and motion picture transfer systems that
convert a light image into a recordable image, overall exposure
adjustment and color shift can be achieved. That is, the exposure
value of the whole scene is adjusted to render the image of the
much brighter or to resolve the remaining darker elements of the
scene. When the exposure value is adjusted (normally reduced) to
adequately reproduce the brighter element, the remaining elements
are very likely to be underexposed. In contrast, by adjusting the
exposure value to resolve the remaining darker elements, the
details of the brighter element is blown out of the acceptable
range, that is, overexposed.
[0006] FIG. 1 shows a graph of how a digital camera translates the
input image brightness into the light intensity rendered in the
picture processed by the digital camera. In FIG. 1, the dash line
shows the exposure adjustment to render the brighter element of the
scene, and the dot line shows the exposure adjustment for
reproducing the remaining objects darker than the brighter element
of the scene. In either case, a part of the scene will be lost in
the picture.
[0007] An alternative to photograph a scene with an element much
brighter than the remaining elements is to manually filter the
brighter element. That is, a neutral density filter is disposed
between the brighter element of the scene and the digital camera or
an illumination source of the brighter element. Therefore, the
brightness of the brighter element can be effectively reduced to an
acceptable range of the digital camera.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention provides a method of brightness
adjustment similar in concept to the manual filtering as mentioned
above. An image capture device is used to capture an image of a
scene. The image capture device includes a charged-coupled device,
for example. The image is segmented into a plurality of areas, and
each area comprises a plurality of pixels. One of the areas is
selected as a transition area, and a transition brightness of the
transition area is defined. The brightness of the remaining area of
the image are then defined and compared to the transition
brightness. According to the comparison result, the remaining areas
are grouped into various regions, and a coefficient is determined
for each of the remaining area. The brightness of the pixels in the
areas of each region is then adjusted by the corresponding
coefficient.
[0009] In the above method, the transition area may be selected
from an area that maps with a particular element of the scene, or
an area of which the brightness is closest to a predetermined
value. The transition area may also be selected from an area
located at a specific position. The transition brightness may be
defined by computing an average brightness of the pixels of the
transition area, or a predetermined percentage of a peak brightness
among the pixels of the transition area. Alternatively, the
transition brightness may also be selected from a medium brightness
among the pixels of the transition area.
[0010] In one embodiment of the present invention, the remaining
areas are grouped into a lower region and a higher region. The
areas grouped into the lower region have brightness lower than the
transition brightness, while the areas grouped into the higher
region have brightness higher than the transition brightness.
Consequently, a first coefficient and a second coefficient are
determined for the areas in lower and higher regions, respectively.
The brightness of the pixels of each area in the lower region is
adjusted by multiplying the first coefficient, and the brightness
of the pixels of each area in the higher region is adjusted by
multiplying the second coefficient plus a constant. Preferably, the
first coefficient is larger than the second coefficient.
[0011] The present invention further provides a brightness method,
in which an image of a scene is captured by an image capture
device. The image is segmented into a plurality of areas, where
each area comprises a plurality of pixels in three primary colors.
One of the areas is selected as a transition area, and a transition
brightness for the transition area is defined. The brightness of
each of the remaining area is compared to the transition area, and
a coefficient is determined for each of the remaining area. The
brightness of the pixels of at least one color in at least one area
is adjusted by the corresponding adjustment coefficient.
[0012] In one embodiment of the present invention, when the
brightness of pixels of one color in at least one area is adjusted
by the determined coefficient, the brightness of the pixels of
other colors may be filtered according to specific requirements.
For example, the brightness of the pixels of other colors may be
filter by a percentage of the adjustment coefficient of the
adjusted color, or only the adjusted color is displayed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] These, as well as other features of the present invention,
will become more apparent upon reference to the drawings
wherein:
[0014] FIG. 1 shows a graph of conventional exposure adjustments
for a digital camera;
[0015] FIG. 2 shows a flow chart of an brightness adjustment method
in one embodiment of the present invention;
[0016] FIG. 3 shows the process flow for selecting a transition
area under an automatic selection mode;
[0017] FIG. 4 shows the process flow for selecting a transition
area under a manual selection mode; and
[0018] FIG. 5 is a graph illustrating the relationship between the
input brightness of the captured image and the output intensity of
the adjusted image.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present invention provides a method for adjusting
brightness of an image similar in concept to the manual filtering
as mentioned above. In essence, in the brightness adjustment method
provided by the present invention, a neutral density filter is
placed over an element of the scene to be photographed when the
brightness of the element is beyond the acceptable range of the
recording medium. A fluid electronic masking grid is applied to the
brightness adjustment method. The detailed description of the fluid
electronic masking grid can be referred to the previously filed
application Ser. No. 09/954,326.
[0020] To adequately reproduce an image of a scene or an object, in
the present invention, the image of the scene is captured by an
image capture device and converted in a digital format. In the
image to be captured, an area is selected as a reference area or
transition area. The brightness of remaining areas of the image are
then compared to the brightness of the reference area. Depending on
specific requirements, the brightness or exposure values of the
other areas of the image to be captured are adjusted (or filtered)
with reference to the brightness of the reference area. Therefore,
the element with brightness beyond the acceptable range can be
adjusted to render the details of the element without underexposing
the remaining elements of the scene.
[0021] FIG. 2 shows a flow chart of an embodiment in which an area
of an image to be captured is selected as a transition area, and
the brightness of the remaining areas of the image is filtered in
response to the brightness of the transition area. In step 200, an
image is made ready to be captured by an image sensor such as a
charge-coupled device or a complementary metal-oxide semiconductor
(CMOS) sensor. The to-be-captured image is then partitioned or
segmented into a plurality areas in step 202, and each of the areas
comprises a plurality of pixels. Among the areas of the
to-be-captured image, a transition area is selected either manually
or automatically in step M204 or A204, respectively.
[0022] When the transition area is selected, the brightness of the
transition area is defined as the transition brightness in step
206. According to specific requirement, the step of defining the
transition brightness can be performed in various ways. For
example, the transition brightness may be defined by computing an
average brightness of the pixels of the transition area. The
transition brightness may also be represented by a percentage of a
peak brightness among the pixels of the transition area. Or
alternatively, a medium brightness among the pixels of the
transition area may be selected as the transition brightness.
[0023] Similarly, the brightness of the remaining areas of the
to-be-captured image is also defined. The way for defining the
brightness of the remaining areas is similar to that of defining
the brightness of the transition brightness. After the brightness
of the remaining areas is defined, the brightness of the remaining
areas is compared to the transition brightness in step 208.
According to the comparison result, the remaining areas are grouped
into a plurality of regions in step 210. In response to the
comparison result and the acceptable brightness range of the
recording medium, a coefficient is determined for each region in
step 212. In step 214, the brightness of each pixel in each of the
remaining areas is then adjusted by the corresponding coefficient,
allowing all elements of the scene from which the image is captured
to be adequately photographed.
[0024] As mentioned above, the transition area can be selected
either manually or automatically. FIG. 3 shows the process flow of
the automatic selection mode and FIG. 4 shows the process flow of
the manual selection mode. As shown in FIG. 3, when the automatic
selection mode is selected, the step A204 further comprises the
sub-steps A300 and A302. In the sub-step A300, the brightness of
each area is defined. Similarly to the method of defining the
transition brightness, the brightness of each area can be defined
by an average brightness, a percentage of a peak brightness, or a
medium brightness of the pixels in the corresponding area. In step
A302, the area having the brightness closest to a predetermined
brightness is selected as the transition area. The predetermined
brightness can be preprogrammed in the digital camera, or input by
the operator or the user according to specific requirement.
[0025] In a manual selection mode, the operator or user may select
the transition area according to various factors as shown in FIG.
4. In step M400, a user interface is provided to display the raw
image captured by the image capture device. In step M402, the
operator may select an element as a reference element for adjusting
images of other elements of the scene. That is, the area of the raw
image mapping the reference element of the scene is selected as the
transition area in step M402. In M404, the operator may simply
observe the raw image and decide which area of the image is
selected as the transition area. Or alternatively, the operator may
selects an area at a particularly position of the image as the
transition area in step M406. Rather than displaying a raw image of
the scene, the brightness of each area may be defined and shown by
the user interface in step M410, such that the operator can select
the transition area based on the brightness of the areas in step
M412. As mentioned above, the brightness of each area is defined
according to the brightness of every pixel of the corresponding
area. For example, an average brightness of the pixels can be
computed and defined as the brightness of the corresponding area. A
predetermined percentage of a peak brightness of the pixels can
also be defined as the brightness of the corresponding area. Or
alternatively, the medium brightness of the pixels can also be
referred as the transition brightness of the corresponding
area.
[0026] FIG. 5 shows a graph of the relationship between the
brightness of the to-be-captured image and the output intensity of
the translated image. In FIG. 5, the remaining areas of the
captured image are grouped into two regions, including one lower
region and one higher region. The areas in the lower region have
brightness lower than the transition brightness, and the areas in
the higher region have brightness higher than the transition
brightness. A first and a second adjustment coefficients C1 and C2
are determined for the areas of the areas in the lower and higher
region, respectively. Again, the first and second adjustment
coefficients are determined based on the brightness difference
between the remaining areas and the transition area, and the
acceptable brightness range, or in other words, the maximum
resolvable brightness of the recording medium. As shown in FIG. 5,
the relationship between the brightness of the captured image Bi
and the output intensity of the translated image Bo for the lower
region is:
Bo=C1*Bi;
[0027] and the relationship for the higher region is:
Bo=C2*Bi+Const,
[0028] where Const is a constant. According to FIG. 5, C1 is larger
than C2, allowing the brightness of the areas in the lower region
adjusted relatively higher, and the brightness of the areas in the
higher region adjusted relatively lower.
[0029] In the above method, the brightness, that is, the light
level or the exposure value, of each pixel adjusted by the
adjustment coefficient can be represented by numbers of f-stops. As
mentioned above, currently, the image sensors accept a wider range
of brightness than the recording media. For example, an image
sensor may have a resolution of about 10 bits to about 16 bits with
each bit equivalent to one f-stop, while most recording media have
resolution of only 8 bits per color. This indicates that about 2 to
8 f-stops of the captured image will be lost in the image recorded
by the media by the conventional image process. By the above method
provided by the present invention, the f-stops of the captured
image beyond the acceptable range of the medium are scaled into the
acceptable range from two ends with reference to a selected number
of f-stops. Therefore, the captured image can be adequately
translated to render every element of the scene.
[0030] Further, in the above brightness adjustment method, the same
adjustment coefficient is introduced to the pixels of three primary
colors in the same area. In one embodiment of the present
invention, to make the image more visible or to obtain a specific
color effect, the neutral density adjustment is no longer neutral.
That is, rather than adjusting the brightness of the pixels of all
three primary colors by the same adjustment coefficient, separate
adjustment coefficients may be applied to the pixels of different
colors. For example, in FIG. 5, the second adjustment coefficient
is only applied to the blue pixels of the corresponding area, while
the red and green pixels of the corresponding area are adjusted by
coefficients different from the second adjustment coefficient. When
the areas in the higher region are required to display in
monochrome blue, the second adjustment coefficient is applied to
the blue pixels only, while the coefficients applied to the red and
green pixels are zero.
[0031] A software is stored in the digital camera for segmenting
the image captured by the image capture device recording area a
plurality of areas. All the areas are active and ready to accept a
brightness adjustment of neutral density or color. The above method
can be applied to digital camera, digital video camera, film
scanners and other digital image processing systems.
[0032] Indeed, each of the features and embodiments described
herein can be used by itself, or in combination with one or more of
other features and embodiment. Thus, the invention is not limited
by the illustrated embodiment but is to be defined by the following
claims when read in the broadest reasonable manner to preserve the
validity of the claims.
* * * * *