Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
2000-03-08
2004-08-24
Williams, Kimberly (Department: 2626)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S518000, C382S162000
Reexamination Certificate
active
06781715
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of and a system for carrying out image processing on image data obtained by a color image read-out means such as an image scanner.
2. Description of the Related Art
When a dark picture or a light picture is output from a color image output means such as a printer which is narrow in color reproduction range, jump in brightness occurs in a light part and a chromaticity differentiation loss occurs in a dark part. Conventionally, such jump in brightness and/or chromaticity differentiation loss are prevented by enhancing gradation of an image represented by image data obtained by a color image read-out means such as an image scanner by carrying out contrast enhancement processing on the image data. In the contrast-enhanced image data, color information of the image data is compressed within the color reproduction range of the color image output means so that the color information on the image is held after output of a picture.
As methods of enhancing contrast, there have been known a graylevels mapping method, a histogram equalization method and the like. (See “Handbook of Image Analysis”, Tokyo University Publisher) Further, the color compression has been carried out by employing such processing as illustrated in FIG.
8
or
9
. In the processing shown in
FIG. 8
, a color P
1
inside the color reproduction range of the image output means is output as it is, and a color P
2
outside the color reproduction range is output as a color P
2
′ which is the closest to the color P
2
among colors inside the color reproduction range. In the processing shown in
FIG. 8
, colors of the original which are inside the color reproduction range of the image output means are faithfully reproduced on the output picture. Accordingly, the processing shown in
FIG. 8
is generally referred to as “faithful color reproduction compression processing”. To the contrast, in the processing shown in
FIG. 9
, a color transformation curve is obtained on the basis of the ratio between the color read-out range of the image read-out means and the color reproduction range of the image output means, and colors are transformed according to the color transformation curve irrespective of whether the color is inside or outside the color reproduction range, e.g., a color P
1
inside the color reproduction range is transformed to a color P
1
′ and a color P
2
outside the color reproduction range is transformed to a color P
2
′ inside the color reproduction range. In accordance with the processing shown in
FIG. 9
, colors outside the color reproduction range cannot be saturated and a chromaticity differentiation loss cannot occur. Accordingly, the processing shown in
FIG. 9
is generally referred to as “desaturated color reproduction compression processing”.
However, when the faithful color reproduction compression processing is carried out on image data having a lot of colors outside the color reproduction range of the image output means, an excessive number of colors are concentrated near the outer periphery of the color reproduction range, whereby a chromaticity differentiation loss occurs with colors in the whole picture. Accordingly, when the image represented by the input image data (which will be referred to as “the input image”, hereinbelow) is a light image, jump in brightness occurs in a light part of the output picture, and when the input image is a dark image, a chromaticity differentiation loss occurs in a dark part of the output picture. Further when the input image is bright, color saturation occurs in a bright part of the output picture and the appearance of the output picture becomes very unnatural. On the other hand, when desaturated color reproduction compression processing is carried out on image data having a lot of colors inside the color reproduction range of the image output means, chroma of the output picture greatly deteriorates since the color range of the input image is compressed though the image output means is able to faithfully reproduce almost all the colors of the input image.
In order to overcome such a problem, there has been proposed a method in which picture elements of the input image having colors inside the color reproduction range of the image output means are counted and the faithful color reproduction compression processing or the desaturated color reproduction compression processing is selected on the basis of the number of the picture elements having colors inside the color reproduction range. See, for instance, Japanese Unexamined Patent Publication No. 4(1992)-287569.
In the graylevels mapping method and the histogram equalization method, contrast enhancement processing is uniformly carried out over the entire image, and accordingly, when such a method is applied to an image having a part where gradation locally changes, gradation of the part is flattened. Accordingly, when the graylevels mapping method or the histogram equalization method is applied to image data representing an image such as a picture taken against the light where light parts and dark parts are mingled with each other, jump in brightness and/or chromaticity differentiation loss in the output picture can be enhanced.
When the method disclosed in Japanese Unexamined Patent Publication No. 4(1992)-287569 is applied to an image where though picture elements having colors inside the color reproduction range of the image output means are larger in number than those having colors outside the range, the picture elements having colors outside the range are localized in a small region, the faithful color reproduction compression processing is selected. However, if the faithful color reproduction compression processing is carried out on such an image, a chromaticity differentiation loss occurs in the small region. On the other hand, when the method disclosed in Japanese Unexamined Patent Publication No. 4(1992)-287569 is applied to an image where though picture elements having colors outside the color reproduction range of the image output means are larger in number than those having colors inside the range, the picture elements having colors inside the range are localized in a small region, the desaturated color reproduction compression processing is selected. However if the desaturated color reproduction compression processing is carried out on such an image, gradation of the small region deteriorates.
SUMMARY OF THE INVENTION
In view of the foregoing observations and description, the primary object of the present invention is to provide a method of and a system for image processing which can process image data representing an image like a picture taken against the light where a dark part or a light part is localized in a small part in the image so that a picture which is visually excellent and free from local jump in brightness or local chromaticity differentiation loss can be output from an image output means having a limited color reproduction range.
In accordance with a first aspect of the present invention, there is provided an image processing method for carrying out image processing on a color image signal which is made up of a plurality of signal components representing respective picture elements and is obtained by a color image read-out means having a limited color read-out range and outputting a processed color image signal to a color image output means having a limited color reproduction range, the method comprising the steps of
counting, for each of the picture elements represented by the color image signal, picture elements whose colors are inside the color reproduction range of the color image output means out of the picture elements included in a predetermined region including the picture element,
generating, according to the number of picture elements whose colors are inside the color reproduction range of the color image output means out of the picture elements included in said predetermined region, a transformation curve for compressing the color image signal within the color reproducti
Koichi Hashimoto
Nakajima Masato
Lett, II Thomas
Nixon & Peabody LLP
Riso Kagaku Corporation
Studebaker Donald R.
Williams Kimberly
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