Image analysis – Color image processing – Color correction
Reexamination Certificate
2000-08-08
2003-09-30
Boudreau, Leo (Department: 2621)
Image analysis
Color image processing
Color correction
C382S305000, C382S165000
Reexamination Certificate
active
06628829
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates broadly to the matching of a target surface color and more particularly to automated analysis of a digital image of the target color to produce a closest match from a known color database.
The matching of a target color is highly important in a wide variety of industries, but particularly in industries requiring the matching of new paint to previously painted surfaces. The perceived color of a previously painted surface is dependent on the nature of the surface, the nature of the old paint and the pigments included therein, the lighting conditions under which the surface is observed and the limitations of the perceiving person or device. As a consequence, results can be highly variable.
Under controlled conditions, highly accurate spectrographic equipment can be used to determine spectral characteristics of a target surface color. These characteristics can be used to select a coating or paint that under similarly controlled conditions will produce a color having substantially the same spectral characteristics. However, in most instances, the use of such equipment and controlled conditions in the field (e.g., to obtain color data on a construction site or in an automotive body shop) is likely to be impracticable or prohibitively expensive. Moreover, there is no guarantee that the color that matches the target color under controlled lighting conditions will match the color under typical ambient lighting conditions.
One alternative method of matching a target surface color in the field is to place each of a series of color sample cards adjacent the surface and select what appears to be the nearest matching color. This method has the virtues of simplicity, portability and relatively low cost. However, it suffers from several sources of error including the perception of the person making the comparisons, the limited number of colors that may be compared, variance between the colors of the sample cards and the actual paint colors and variance between sample cards produced at different times by different methods.
Another method involves the hand matching of the color using actual paints. Though potentially accurate, this is obviously a highly time-consuming and expensive approach. Also, this method still requires a subjective determination of a match and is thus subject to the limitations of the perception of the person implementing the method.
There is accordingly a need for a practical, inexpensive, yet accurate method for matching a target color that does not require highly specialized equipment or controlled lighting conditions.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide an accurate method of matching a target color under typical ambient lighting conditions.
It is another objective of the present invention to provide a method of matching a target color that includes capturing a digital image of the target color and using an automated process to model and adjust for the effects of ambient lighting conditions and distortions introduced by the equipment used to produce the image.
It is still another object of the present invention to provide a system for matching a target color including a data processing system having software for analysis of a digital image of the target surface and a specially configured test card that may be purchased by the user.
It is also an objective of the present invention to provide a method of providing an automated color-matching service wherein a user can purchase one or more uses of the service.
Toward these ends, a method for matching a color of a target surface comprises providing a test card having a pattern of at least one color field printed thereon. Each of the at least one color field is substantially monochromatic and has a true color. The method further comprises positioning the test card adjacent the target surface. A digital record is then produced that includes a digital image of the test card and at least a portion of the target surface exhibiting the target surface color. The target surface color produces a captured target color on the digital image and each of the at least one color field produces a captured pattern color on the digital image. An estimated true target color is determined using the captured pattern color and the true color of each of the at least one color field. The method also comprises providing a database of product color information. A nearest matching product color is determined using the estimated true target color and the database of product color information.
Determining an estimated true target color in a method for matching a color of a target surface according to the present invention may include determining a set of captured pattern color components for the captured pattern color of each of the at least one color field. The step may further include building a correction model having a set of empirical equations derived from the true color and the set of captured pattern color components of each of the at least one color field. A set of captured target color components for the captured target color may be determined and the correction model applied to the captured target color components to obtain the estimated true target color.
The step of determining an estimated true target color of a method for matching a color of a target surface according to the present invention may include determining the location and orientation within the digital record of the digital image of the test card and the at least a portion of the target surface exhibiting the target surface color. The step may further include locating within the digital image the captured pattern color of each of the at least one color field and the captured target color.
A method for matching a color of a target surface according to the present invention may further include the step of loading the digital record into a data processing system. In this embodiment, the step of determining an estimated true target color is accomplished by the data processing system. The data processing system may include a central data processor operatively connected to a data entry processor. In such an embodiment, the step of loading the digital record into the data processing system includes loading the digital record into the data entry processor and transferring the digital record to the central data processor. The central data processor and the data entry processor may be connected through a network. The central data processor and the data entry processor may be connected through the Internet.
The test card provided in a method for matching a color of a target surface according to the present invention may include an identification code printed thereon. The method may further comprise obtaining spectral data for each of the at least one color field of the test card under lighting conditions configured to establish the true color of the at least one color field. A set of true color components of the at least one color field is derived from the spectral data and stored in association with the identification code of the test card. This allows the set of true color components to be selectively retrieved. The step of determining an estimated true target color may then include retrieving the set of true color components of each of the at least one color field for use in constructing the correction model.
The test card used in a method for matching a color of a target surface according to the present invention may be one of a batch of test cards, the test card including an identification code printed thereon. The method may further comprise obtaining from a sample subset of the batch of test cards spectral data for each of the at least one color field of the test card under lighting conditions configured to establish the true color of the at least one color field. A representative set of true color components of each of the at least one color field is derived for the test card from the spectral data of the at least one color field of each of the sample subset of the batc
Boudreau Leo
Hunton & Williams
Sherali Ishrat
LandOfFree
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