Image analysis – Color image processing
Reexamination Certificate
1998-12-08
2001-02-06
Au, Amelia (Department: 2723)
Image analysis
Color image processing
C382S167000, C358S523000, C345S440000
Reexamination Certificate
active
06185325
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for transforming a color image. This invention particularly relates to an image transforming method and apparatus, wherein transformed values are calculated previously by carrying out operations with respect to a limited number of values (colors), and a transformed value corresponding to an arbitrary picture element value is calculated by carrying out an interpolating operation on the previously calculated transformed values. This invention also relates to a recording medium, on which the information representing a procedure for image transformation has been recorded.
2. Description of the Prior Art
Color transformation has heretofore been carried out as one kind of digital image processing. For example, in the cases of digital processing of color photographs, if a digital image having been processed for the formation of a print is displayed directly on a monitor, the displayed image will not necessarily look in appropriate colors. Therefore, it is desired that color transformation with a predetermined transformation formula is carried out on the digital image, and thereafter the image obtained from the color transformation is displayed on the monitor.
In the color transformation of a color image, the picture element value of each picture element may be transformed literally by carrying out an operation with a transformation formula. However, such a technique has the problems in that, in cases where the relation formula is a complicated one, the time required to carry out the operation cannot be kept short. Therefore, ordinarily, in systems in which the processing should be carried out quickly as in digital processing of photographs, a technique referred to as the direct mapping process is employed.
In the direct mapping process, transformed values are calculated previously by carrying out accurate operations with respect to a limited number of colors, and the information representing the calculated transformed values is stored in a memory. When an actually inputted value is to be transformed, instead of the accurately operation being carried out, an interpolating operation is carried out by using the previously calculated transformed values, and a transformed value corresponding to the actually inputted value is thereby presumed. Specifically, a multi-dimensional color space is divided into a plurality of blocks, and transformed values are calculated previously by carrying out accurate operations with transformation formulas with respect to coordinates of vertexes of each block. Thereafter, a transformed value corresponding to an arbitrary point is interpolated from the transformed values of the coordinates of the vertexes.
When the interpolating operation is to be carried out, eight vertexes surrounding the inputted picture element value are specified, and the information representing the transformed values of the coordinates of the eight vertexes is read from the memory. The eight vertexes are weighted in accordance with the position of the picture element value in the block. Factors, which represent the weights of the respective vertexes, and the corresponding transformed values, which have been read from the memory, are multiplied by each other, and the thus obtained products are added together. In this manner, the interpolated value is obtained. The interpolating operation is constituted of the simple operations, i.e. the multiplications and the additions. Accordingly, with the interpolating operation, the processing can be carried out more quickly than with the technique in which the operation with a transformation formula is carried out.
In the technique described above, eight times of multiplications and seven times of additions (i.e., the adding of eight values) are necessarily carried out for one time of interpolating operation. However, in cases where the inputted picture element value is the one located at a point on a surface or a line of the block, the weight factors of the vertexes other than the vertexes, which constitute the surface or the line of the block, become 0. Therefore, in such cases, actually, it is unnecessary for the multiplications to be carried out with respect to the weight factors of the vertexes other than the vertexes constituting the surface or the line of the block.
Also, in the technique described above, the weight factors are calculated each time a picture element value is inputted. However, actually, in cases where the relative position in a block is the same, the weight factors of the vertexes do not vary. Therefore, the technique described above has the drawbacks in that the weight factors are calculated many times with respect to the same pattern.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide an image transforming method, wherein useless processing in a direct mapping technique is eliminated, and image transformation processing is carried out quickly such that no error may occur.
Another object of the present invention is to provide an apparatus for carrying out the image transforming method.
A further object of the present invention is to provide a recording medium, on which the information representing a procedure for image transformation has been recorded.
The present invention provides an image transforming method, in which a first picture element value of each of picture elements constituting a color image is replaced by a second picture element value that is set to have correspondence to the first picture element value by a predetermined transformation formula, the method comprising:
dividing a multi-dimensional color space into a plurality of blocks in units of a block having a predetermined size,
carrying out an operation with the transformation formula with respect to coordinates of each of vertexes of each block, transformed values of the coordinates of vertexes of each block being thereby calculated previously, and
carrying out an interpolating operation with respect to the first picture element value and in accordance with weight factors of the vertexes, which weight factors are determined in accordance with a position of the first picture element value in a block, and the transformed values of the coordinates of the vertexes of the block, which contains the first picture element value, the second picture element value being thereby calculated,
wherein the improvement comprises the steps of:
i) in cases where a block having a size different from the predetermined size is contained in the plurality of the blocks, replacing the block having the different size by a virtual block, which has a size identical with the predetermined size, transformed values of coordinates of vertexes of the virtual block being then calculated from the transformed values of the coordinates of the vertexes of the block having the different size,
ii) previously storing information, which represents a transformed value table, and information, which represents a factor table, in a memory, the transformed value table recording the transformed values of the coordinates of the vertexes with respect to each of the blocks, including the virtual block, the factor table recording vertexes, which have weight factors other than 0, and the weight factors of the vertexes, which have weight factors other than 0, with respect to each of positions in a block, and
iii) carrying out the interpolating operation by utilizing only the vertexes, which have weight factors other than 0, and in accordance with the transformed values, which have been recorded in the transformed value table, and the vertexes and their weight factors, which have been recorded in the factor table.
In the image transforming method in accordance with the present invention, the picture element value is the one represented by (R, G, B). Also, the multi-dimensional color space is the coordinate space, which have R, G, and B axes and visually represents the picture element value (color) as a coordinate point.
As for the weight factor, for example, in cases wher
Hara Shoji
Sakaida Hideyuki
Au Amelia
Fuji Photo Film Co. , Ltd.
Wu Jingge
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