Method of processing image signal

• US 6,668,079 B2
• Filed: 05/11/2001
• Issued: 12/23/2003
• Est. Priority Date: 11/29/1996
• Status: Expired due to Fees

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Takemoto, Fumito
• Primary Examiner(s): Dastouri, Mehrdad
• Application Number:
  US09/852,633
• Publication Number:
  US 20030053085A1
• Time in Patent Office: 956 Days
• Field of Search: 382/162, 382/167, 358/500, 358/501, 358/518, 358/521, 358/523, 358/527, 358/515, 358/522
• US Class Current: 382/167
• CPC Class Codes: H04N 1/6022 Generating a fourth subtractive colour signal, e.g. under colour removal, black masking
• CPC Class Codes: H04N 1/6033 using test pattern analysis H04N1/6055 takes precedence
• CPC Class Codes: H04N 1/6058 Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut

Abstract

R, G, B signals outputted from a digital camera or a color scanner are converted into calorimetric signals by a colorimetric converter having a colorimetric conversion matrix and a calorimetric conversion table. Colorimetric signals are processed for setup by a calorimetric setup unit. Colorimetric signals processed for setup are converted by a cmyk converter into c, m, y, k signals that are half tone dot % signals for being supplied to an image output unit such as a film producing device, a color printer, or the like.

Claims

1. A method of processing an image signal, comprising:

converting device-dependent image signals produced from an original scene into a plurality of colorimetric signals and converting said colorimetric signals into colorimetric equivalent-neutral-density signals of said original scene;

generating rough data of said colorimetric equivalent-neutral-density signals;

setting up automatically a gradation conversion curve based on said rough data;

converting gradations of said colorimetric equivalent-neutral-density signals based on said gradation conversion curve; and

converting the colorimetric equivalent-neutral-density signals whose gradations have been converted into a plurality of colorimetric signals;

wherein setting up the gradation conversion curve comprises determining a cumulative histogram of density values and assigning a high density point and a low density point based on the histogram values.

2. A method according to claim 1, wherein said step of converting colorimetric signals into colorimetric equivalent-neutral-density signals comprises converting the colorimetric signals into R, G, B signals in a RGB color system, and logarithmically converting ratios of said R, G, B signals to a basic stimulus into the colorimetric equivalent-neutral-density signals, and wherein said step of converting the colorimetric equivalent-neutral-density signals whose gradations have been converted into colorimetric signals comprises inversely logarithmically converting the colorimetric equivalent-neutral-density signals whose gradations have been converted into R, G, B signals, and converting the R, G, B signals into the colorimetric signals.

3. A method according to claim 2, wherein said RGB color system comprises a range including reference color stimuli and containing a color reproduction range of a reversal film.

4. The method of claim 3, wherein the plurality of colorimetric signals comprise a plurality of device-independent colorimetric signals.

5. The method of claim 1, wherein the high density point is associated with a colorimetric END value corresponding to a highlight halftone percentage, and the low density point is associated with a colorimetric END value corresponding to a shadow halftone dot percentage.