Image analysis – Color image processing
Reexamination Certificate
1998-01-27
2001-09-11
Johns, Andrew W. (Department: 2621)
Image analysis
Color image processing
Reexamination Certificate
active
06289119
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for adjusting signal levels of image signals and image read apparatus adopting the method and, more particularly, to a method, in which light reflected from or transmitted through an original image are separated into color components, for automatically adjusting conditions for reading the original image depending upon the type of the original image so that the original image is properly expressed by image signals within a predetermined signal level range and an image read apparatus, such as an image scanner, adopting the method.
When adjusting image data of an original image inputted by a scanner so as to be within a signal level range which can be expressed on hard copies, a method of generating tone histograms of the image data and determining the proper signal level range by analyzing the histograms is generally used (Summary of the Digital Photo Print System “Frontier”, Material for The 4th Camera Technology Seminar in Meeting of Japan Photograph Society, pp. 13-16).
The most fundamental technique of the method is to convert the distribution of the obtained histogram into a balanced distribution as disclosed in the U.S. Pat. No. 4,745,465. Further, in the U.S. Pat. No. 4,639,769, means for expressing an image in good contrast by changing mapping of each pixel data based on a histogram is disclosed.
Further, in a case of separating a color image into primary color components to generate digital data, by performing the aforesaid conversion of distribution on each of the color components, color bias of the original image, e.g., color cast in a color photograph, taken under fluorescent light, other than daylight, is compensated, thereby a final image is expressed in a desired contrast.
However, in the aforesaid conventional method, the signal level range is determined without considering characteristics of an original image. Furthermore, whether an imbalance in tone and color of the separated color components is due to color cast of the color image to be corrected, caused by light source other than daylight, or due to the original colors, of an object of the image, which are not to be corrected is not distinguished for determining the signal level range.
Accordingly, in a case where vivid colors fill most of the original image, a problem in which vividness of the colors is easily lost arises. Further, when the colors of the original image are biased, a phenomenon, called subjective color failure, occurs.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to provide a method capable of determining whether the imbalance in tone and color of an original image is to be corrected or not, and, by determining conditions for scanning the original image, compensating the imbalance in tone and color, when necessary and properly expressing the original image by image signals within a predetermined signal level range, and an image read apparatus adopting the method.
According to the present invention, the foregoing object is attained by providing an image read method comprising: a pre-scanning step of pre-scanning an original image and outputting an image signal; a color separation step of separating the image signal obtained in the pre-scanning step into primary color component signals; a type determination step for determining a type of the original image on the basis of signal levels of the color component signals obtained in the color separation step; and a condition determination step of determining scanning conditions for main scanning operation on the basis of the type of the original image determined in the type determination step.
Further, the foregoing object is also attained by providing An image read system comprising: image read means for scanning an original image and outputting an image signal; color separation means for separating the image signal obtained by the pre-scanning means into color component signals; type determination means for determining a type of the original image on the basis of signal levels of the color component signals obtained by the color separation means; and condition determination means for determining scanning conditions for main scanning operation on the basis of the type of the original image determined by the type determination means.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.
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Azarian Seyed
Canon Kabushiki Kaisha
Henderson & Finnegan, L.L.P.
Johns Andrew W.
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