US 4,477,833 AGranted

Method of color conversion with improved interpolation

AssigneeR. R. Donnelley & Sons Company

InventorsDavid A. Clark, David C. Strong, Thomas Q. White, II

Life of this patent

Estimating the term…

Abstract

An apparatus for converting a color image from one color space to another color space includes a memory in which is stored a finite number of output signals which represent colors in the output space and which is addressed by signals representing a color in the input space. In order to derive an output color value for an input color located between colors stored in the memory, an interpolation process is utilized. The interpolation process takes into account the four closest color values in the memory above and below the input color and develops an interpolated output color value from vectors derived from the four color values.

Claims15

Dependent claims

In the conversion of a color image from one color space to another color space including the steps of providing a three dimensional input signal representing the color of a pixel of said image in said one space and providing a memory with a finite number of three dimensional addresses representing colors in said one space, said memory having at each address output signals representing the corresponding color in said other space, an improved method of interpolating to determine the output signals for pixel color input signals between two memory addresses, comprising:

determining the base output signals for the base memory address next below said input signals;
determining the high, mid and low valued input signal components representing the difference between the pixel color input signal and the base memory address below the input signal;
determining additional signals for memory addresses next above said input signals in accordance with said high, mid and low valued input difference signal components;
interpolating between output signals for the memory addresses below and above the input signal in accordance with the low valued input difference signal component to establish a first output signal increment from said base output signals;
interpolating between output signals for the memory addresses below and above the input signal in the plane of the mid and high input difference signals in accordance with the excess of the mid valued input difference signal component over the low valued input difference signal component to establish a second output signal increment from said base output signals;
interpolating between output signals representing memory addresses below and above the input signal along the axis of the high valued input difference signal component in accordance with the excess of the high valued input difference signal component over the mid valued input difference signal components to establish a third output signal increment from said base output signals;
and
summing the base output signals with said first, second and third output signal increments to generate output signals representing the color of said pixel in said other color space.

5 more elements

Dependencies are inferred from the claim text.

patentgrep

Loading patent…

Abstract

determining the base output signals for the base memory address next below said input signals;
determining the high, mid and low valued input signal components representing the difference between the pixel color input signal and the base memory address below the input signal;
determining additional signals for memory addresses next above said input signals in accordance with said high, mid and low valued input difference signal components;
interpolating between output signals for the memory addresses below and above the input signal in accordance with the low valued input difference signal component to establish a first output signal increment from said base output signals;
interpolating between output signals for the memory addresses below and above the input signal in the plane of the mid and high input difference signals in accordance with the excess of the mid valued input difference signal component over the low valued input difference signal component to establish a second output signal increment from said base output signals;
interpolating between output signals representing memory addresses below and above the input signal along the axis of the high valued input difference signal component in accordance with the excess of the high valued input difference signal component over the mid valued input difference signal components to establish a third output signal increment from said base output signals;
and
summing the base output signals with said first, second and third output signal increments to generate output signals representing the color of said pixel in said other color space.

5 more elements