Digital Camera Patent Abstract
A device (PR) and a method is proposed for determining image correction
values for printing on printing material an image acquired with
a digital camera. The type (KT1, . . . , KTn) of the digital camera,
which acquired the image to be printed, is identified. The image
correction values for printing the image are determined as a function
of the identified type (KT1, . . . , KTn) of the digital camera.
Digital Camera Patent Claims
What is claimed is:
1. A method for correcting digital images produced by a digital
camera, comprising the steps of: identifying the camera type used
to produce the digital images from image data provided by the camera;
correlating said camera type with correction values specific to
the camera type to correct flaws common to images captured with
said camera type; and adjusting all of the images produced by the
camera according to said correction values.
2. The method according to claim 1, wherein information identifying
the camera type is hidden in the image data provided by the camera
using a steganographic method.
3. A device for determining correction values for digital images
produced by a camera, comprising: identification means responsive
to digital image data produced by the camera for detecting the camera
type that captured the digital image; and control means for determining
camera type specific image correction values as a function of the
identified camera type; and means responsive to said control means
for correcting the digital images produced by the camera, whereby
all of the images produced by the camera are corrected according
to said correction values.
4. The device according to claim 3, wherein information identifying
the camera type is hidden in the image data provided by the camera
using a steganographic method.
Digital Camera Patent Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method for
determining image correction values for printing an image acquired
with a digital camera and device for printing an image on printing
material.
2. Description of the Related Art
A large number of digital cameras of various designs and including
different components are commercially available. More particularly,
the different digital cameras include different image acquisition
sensors which converts light into electrical signals. These image
acquisition sensors have different characteristics, in particular
different spectral sensitivity. For this reason, the color rendition
and density representation of the images acquired by the different
digital cameras is different.
The images acquired by the digital cameras are converted by the
image acquisition sensors to digital image data which are stored
in a memory device. Such a memory device can be, for example, a
chip card. The image acquisition sensors in digital cameras are
mostly in the form of so-called CCD (charge coupled devices) image
sensors.
It is desirable to transfer the image data which are produced by
the digital camera and represent the acquired images to a device
capable of printing the acquired images. Such a printing device
can be, for example, a so-called photo printer, a so-called mini
lab or a printer controlled by a computer. The printing device produces
from the acquired images prints on photographic paper, on printer
paper or another printing material. The term "printing"
is therefore to be understood as a general term for reproducing
the acquired images on any type of printing material.
Due to the different characteristics of the components used in
the various digital cameras, in particular the characteristics of
the image acquisition sensors, unwanted color and density distortions
can occur when the acquired images are printed on photographic paper
or on other printing materials. A specific object captured by different
digital cameras can therefore be reproduced differently on these
prints.
It is therefore an object of the present invention to provide on
printing materials an accurate and true reproduction of the images
acquired with digital cameras.
SUMMARY OF THE INVENTION
According to the invention, the camera type, which is used to acquire
an image to be printed, can be identified. The term "camera
type" refers here to the physical components and the technical
performance of the respective digital camera. The term "camera
type", however, does not refer to the name or label under which
the respective camera is sold commercially. It may be possible that
a manufacturer of a digital camera changes the components or technical
specification of the camera without also changing the commercial
name or label. On the other hand, digital cameras having the same
technical features and physical components may be available commercially
under different labels.
The color and/or density response function of a specific type of
digital camera with respect to the printed images can be taken in
to account by determining the image correction values as a function
of the specific digital camera type. The image correction values
can be, for example, characteristic preset values for a color and/or
density setting, for the gradation and/or image manipulation. For
example, an exposure station used for final prints of the recorded
images on the printing material, may use a color transformation
table, a so-called 3-D lookup table.
Information about the type of the digital camera which acquired
the image to be developed can be easily transmitted to be apparatus
of the invention. This information is acquired by the apparatus
of the invention. The apparatus of the invention can use this information
to directly access a respective print data set. With the identification
means implemented in this manner, the information specifying the
type of the digital camera should be explicitly and clearly specified
and preset.
The identification means can also be adapted to evaluate image
data of at least one image to be printed. This evaluation can be
limited to identifying the resolution or the color saturation of
the acquired image or the type of formatting or compression of the
data set. A complete evaluation of the image data which would be
required to independently generate image correction values, is not
required in this case. The type of the digital camera can thereby
advantageously be identified quickly and unambiguously without knowing
the camera specifications in advance.
According to another particularly advantageous embodiment of the
invention, several print data sets which contain the image correction
values for printing the images, are stored in a memory device. The
print data sets are associated with predetermined types of digital
cameras. The apparatus of the invention is capable of recognizing
from the data transferred to the apparatus the type of the digital
camera that acquired the image. The print data set for a specific
camera can thereby be selected in response to the identified camera
type.
According to yet another advantageous embodiment of the apparatus
of the invention, the information containing the type of the digital
camera is a hidden by a steganographic method in other captured
data. The identification means can also use a steganographic method
to identify the information containing the camera type. In this
way, existing formats used for transmitting, storing and processing
of image data can advantageously be retained.
The apparatus of the invention for determining image correction
values can advantageously be directly integrated in a device which
prints the image on the printing material. Alternatively, the apparatus
can also be implemented separately from the actual printing device
which prints the image on the printing material based on the data
transmitted to the printing device. This may be the case, for example,
when a computer running suitable application programs is used to
determine the image correction values and a printer connected to
this computer prints the image based on the data transmitted by
the computer.
Other objects and features of the present invention will become
apparent from the following detailed description considered in conjunction
with the accompanying drawings. It is to be understood, however,
that the drawings are intended solely for purposes of illustration
and not as a definition of the limits of the invention, for which
reference should be made to the appended claims.
BRIEF DESCRIPTION OF THE DRAWING
The invention and its advantages will be described hereinafter
with reference to a specific embodiment and the drawing.
The only FIGURE shows an embodiment of an apparatus according to
the invention for determining image correction values for printing
an image acquired with a digital camera.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
The FIGURE shows the embodiment of an apparatus for printing images
on printing material which in the present example is a so-called
photo printer PR and includes an apparatus according to the invention
for determining the image correction values for printing an image
acquired with a digital camera. The FIGURE shows a portion of the
printer PR, which includes a control device CR for controlling the
functions which can be executed by the printer PR. A plurality of
data sets DS1 to DSn is stored in a first memory device SP1. The
data sets DS1 to DSn include image data generated by a digital camera
during the image acquisition. Each of the data sets DS1 to DSn includes
image data of a respective one of the acquired images. The printer
includes a receiver EP which is capable of receiving data and/or
signals of any kind. The receiver EP can read a memory device, for
example chip cards.
The printer PR includes a second memory device SP2 which stores
different print data sets GD1 to GDn. These print data sets GD1
to GDn include image correction values for printing the images to
photographic paper. More particularly, the image correction values
contain information about the color and/or density settings to be
used for printing the images on the photographic paper. The print
data sets GD1 to GDn are associated with different camera types
KT1 to KTn. The term "camera type" here refers to the
technical specifications and the physical components of the respective
digital camera. In the exemplary embodiment, the print data set
GD1 is associated, for example, with the camera type KT1, the print
data set GD2 with the camera type KTi and the print data set GDn
with the camera type KTn.
The image correction values contained in the different print data
sets GD1 to GDn are specifically matched to the respective camera
types. The image correction values include the known characteristics
of the different camera types. These characteristics are determined--before
the of the printer PR is operated--by a calibration process wherein
several digital cameras of the same type are measured to determine
the specific physical and electronic properties of this camera type.
The characteristics of the camera type can, for example, produce
color and/or density deviations in the acquired image, so that an
image with a color cast or with saturated colors would be produced
when printed on the particular printing material. The image correction
values required for the respective camera type can be determined
from the measured specific physical and electronic properties for
this camera type and combined in a print data set. The print data
sets GD1 to GDn advantageously have a fixed preset value which does
not change during the operation of the apparatus of the invention.
The receiver EP can receive detailed information about the type
of the digital camera used to acquire the image to be printed. Since
the information about the camera type is unambiguous, it can be
matched directly with the stored print data sets GD1 to GDn. The
data set DS1 to DSn with the image data of the image to be printed
can already include the information about the camera type. The information
about the camera type can be determined by the control device CR,
and the associated print data set stored in the second memory device
SP2 can be selected. The exposure station subsequently uses the
image correction values included in the selected print data set
to produce the prints.
By applying a steganographic method, the information about the
digital camera type is hidden in the other acquired image data which
are included in the data sets DS1 to DSn, and can be identified
by the control device CR also using a steganographic method. Steganographic
methods are described, for example, in the article "Hinters
Licht gefuhrt" by J. Rink in the journal c't, 1997, vol. 6,
pp. 330-336.
If such information about the camera type is not explicitly transmitted
to the printer PR, then alternatively one of the data sets DS1 to
DSn stored in the first memory device SP1 can be evaluated, so that
the camera type used to acquire the respective picture can be identified
from the image data stored in this data set. Each digital camera
has certain characteristics with respect, for example, the resolution
or the color saturation of the recorded images. In addition, each
digital camera formats and compresses the generated image data in
a particular manner. For determining the camera type, it is therefore
sufficient to evaluate, for example, the format of the image data
of the image to be printed. The actual contents of the image to
be printed need not be evaluated. To determine the camera type more
reliably, the format or other characteristic features of several
data sets may be evaluated.
The device PR of the invention has a bus BUS for transmitting data
within the device PR, with the components being connected to the
device PR via bi-directional data transmission lines.
The control device CR subsequently uses the determined image correction
values which are specific for the digital camera and combined in
the selected print data set, to determine image-specific color print
values for printing the respective image on the printing material.
The individual color print values are then transmitted to an exposure
station (not shown) which produces a print of the acquired image
on photographic paper based on the color print values. The determination
of the individual color print values for each image to be printed
is not a part of the invention. The color print values can be determined,
for example, by a method used for determining color print values
for printing photographic masters on photographic paper, as described
in the German patent DE-PS 28 40 287.
Thus, while there have been shown and described and pointed out
fundamental novel features of the invention as applied to a preferred
embodiment thereof, it will be understood that various omissions
and substitutions and changes in the form and details of the devices
illustrated, and in their operation, may be made by those skilled
in the art without departing from the spirit of the invention. For
example, it is expressly intended that all combinations of those
elements and/or method steps which perform substantially the same
function in substantially the same way to achieve the same results
are within the scope of the invention. Substitutions of elements
from one described embodiment to another are also fully intended
and contemplated. It is also to be understood that the drawings
are not necessarily drawn to scale but that they are merely conceptual
in nature. It is the intention, therefore, to be limited only as
indicated by the scope of the claims appended hereto.
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