Method for conversion of a colour space using separate chromatic and luminance look-up tables

• US 7,847,989 B2
• Filed: 09/17/2007
• Issued: 12/07/2010
• Est. Priority Date: 09/21/2006
• Status: Expired due to Fees

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Thollot, Julien, Stauder, Jurgen, Blonde, Laurent
• Primary Examiner(s): Zimmerman; Mark K
• Assistant Examiner(s): WILLIAMS, MIYA J
• Application Number:
  US11/901,615
• Publication Number:
  US 20080074717A1
• Time in Patent Office: 1,177 Days
• Field of Search: None
• US Class Current: 358/518
• CPC Class Codes: G06T 11/001 Texturing; Colouring; Generation of texture or colour inpainting G06T5/77
• CPC Class Codes: H04N 1/6019 using look-up tables H04N1/6025 takes precedence

Abstract

According to the method,

• • starting from the chromatic components x_S, y_S of the color vector to be converted, the components of an intermediate color vector R_INT-CR, G_INT-CR, Σ_INT-CR are-interpolated, whose chromatic components, expressed in the source color space are: x_INT-CR=x_S, y_INT-CR=y_S;
  • starting from the luminance component S_S of the color vector to be converted and from the luminance component Σ_INT-CR of the intermediate color vector, the luminance component Σ_D of the converted color vector is interpolated;
  • the chromatic components R_D, G_D of the converted color vector are calculated from its luminance component Σ_D and from the components of the intermediate color vector R_INT-CR, G_INT-CR, Σ_INT-CR. The conversion methods of the prior art are substantially improved.

Claims

1. Method for converting the n components (x_S, y_S, S_S) of a colour vector expressed in an n-dimensional source colour space into m components (R_D, G_D, Σ

_D) of this same vector expressed in an m-dimensional destination colour space, the said n components comprising a source luminance component (S_S) and (n-1) source chromatic components (x_S, y_S), the said m components also comprising a destination luminance component (Σ

_D) and (m-1) destination chromatic components (R_D, G_D),

the said method comprising the following steps ;

finding an intermediate colour vector having, in the source color space, approximately the same chromatic components (x_INT-CR=x_S, y_INT-CR=y_S) as those (x_S,y_S) of said colour vector to be converted and a given luminance component (S_INT-CR),

interpolating the components (R_INT-CR, G_INT-CR, Σ

_INT-CR) of this intermediate colour vector in the destination colour space,

interpolating the luminance component (Σ

_D) of this colour vector expressed in the destination colour space by using a normalized luminance look-up table comprising a plurality of pairs (S_S-N, Σ

_D-N) of values, where each pair comprises a normalized luminance component

2. Method according to claim 1, wherein, for the finding of the intermediate coulour vector and the interpolation of its components in the destination color space, a chromatic look-up table is used that comprises a plurality of multiplets (x_S-Ci, Y_S-Ci, S_S-Ci, R_D-Ci, G_D-Ci, Σ

_D-Ci) with (n+m) values comprising the n components (x_S-Ci, y_S-Ci, S_S-Ci) that define a conversion colour vector in the source colour space and the m components (R_D-Ci, G_D-Ci, Σ

_D-Ci) that define this same conversion colour vector in the destination colour space.

3. Method according to claim 1, where the source space is a colorimetric space independent of any device, and where the destination space is a space dependent on a device.

4. Method according to claim 1, where the destination space is a colorimetric space independent of any device, and where the source space is a space dependent on a device.