EP0487304A2
Expired / Lapsed
EP
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Color image processing
Assignee: Canon Inc
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Filing: 1991-11-19
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Granted: —
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Expires: 2011-11-19
Abstract
Abstract Interpolation processing is applied to the output of a look-up table in which a correlation between color-separation signals and density signals ideal for these color-separation signals are stored, with a quantization error produced when quantizing the color-separation signals being adopted as an interpolation coefficient. The quantization and the interpolation processing are executed in a uniform coordinate space.
Inventors
- 👤 Takashi Kawai
- 👤 Akihiro Usami
- 👤 Ken-Ichi Ohta
- 👤 Yoshiko Horie
- 👤 Seita Shono
- 👤 Eiji Ohta
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 20:47
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/60; H04N1/6016; H04N1/6022; H04N1/6025
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
76 words
A color image processing apparatus which comprises: input means for inputting color component signals; quantization means for quantizing said input color component signals and outputting quantized color component signals; a look-up table for storing a correlation between said quantized color component signals and density signals suitable for respective ones of the quantized color component signals; interpolation means for interpolating the density signals output from said look-up table in accordance with the levels of the density signals.
Claim 2
Dependent Claim
50 words
The apparatus according to claim 1, wherein said interpolation means computes a quantization error which arises when input color component signals are quantized by said quantization means, and executes the interpolation processing with regard to an output from said look-up table by using the quantization error as an interpolation coefficient.
Claim 3
Dependent Claim
25 words
The apparatus according to claim 1, wherein a correlation between inputs and outputs of said look-up table independent of an approximation equation may be obtained.
Claim 4
Dependent Claim
22 words
The apparatus according to claim 1, wherein said look-up table is constituted by a read only memory or a random access memory.
Claim 5
Dependent Claim
38 words
The apparatus according to claim 1, wherein said interpolation means performs an interpolation by using a quantization error computed by said quantization means and levels of the density signals with regard to an output from said look-up table.
Claim 6
Dependent Claim
141 words
A color image processing apparatus which comprises: image input means for inputting color-image information; a look-up table for storing a correlation between color-separation signals, which are obtained by separating the color-image information into individual color components, and density signals suitable for respective ones of the color-separation signals; image processing means for converting the color-separation signals into corresponding density signals by referring to said look-up table; and image output means for permanently visibly displaying a color image on a multicolor recording medium in conformity with the density signals from said image processing means; wherein said image processing means quantizes the color-separation signals and inputs the quantized signals to said look-up table, and said image processing means executes interpolation processing with regard to an output from said look-up table in accordance with the levels of the density signals output from said look-up table.
Claim 7
Dependent Claim
46 words
The apparatus according to claim 6, wherein said image processing means computes a quantization error which arises when the color-separation signals are quantized, and executes the interpolation processing with regard to an output from said look-up table by using the quantization error as an interpolation coefficient.
Claim 8
Dependent Claim
23 words
The apparatus according to claim 6, wherein said image processing means executes the quantization of the color-separation signals in a uniform coordinate space.
Claim 9
Dependent Claim
27 words
The apparatus according to claim 8, wherein said uniform coordinate space is a rectangular coordinate system in which mutually orthogonal axes are adopted as the coordinate axes.
Claim 10
Dependent Claim
58 words
The apparatus according to claim 8, wherein said image processing means obtains lattice points by equally dividing, at predetermined tones, a color distribution of the color-separation signals in the uniform coordinate space, and adopting, as the interpolation coefficient, an internal dividing ratio of the quantization error within a cube of a minimum unit formed at said lattice points.
Claim 11
Dependent Claim
40 words
The apparatus according to claim 10, wherein said image processing means executes interpolation processing based upon interpolation data decided by the product of a signal value and the interpolation coefficient for each color corresponding to lattice points of the cube.
Claim 12
Dependent Claim
28 words
The apparatus according to claim 8, wherein said uniform coordinate space is a cylindrical coordinate system in which a cylindrical coordinate axis is adopted as the central axis.
Claim 13
Independent Claim
77 words
A method of converting intensity colour component signals to density colour component signals, characterised by the steps of: quantizing the colour component signals to produce most significant look up values and least significant quantization error values; supplying said look up values to the input of a look up table and reading density colour values from said table; and interpolating said read density values in response to said quantization error values to produce output density colour component values.
References Cited (Backward Citations)
No citation records indexed.
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