Image processor

• US 5,398,124 A
• Filed: 06/26/1992
• Issued: 03/14/1995
• Est. Priority Date: 06/29/1991
• Status: Expired due to Term

• Current Assignee: Minolta Camera Kabushiki Kaisha
• Original Assignee: Minolta Camera Kabushiki Kaisha
• Inventors: Hirota, Yoshihiko
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US07/905,112
• Time in Patent Office: 991 Days
• Field of Search: 358/500, 358/501, 358/518, 358/520, 358/521, 358/523, 358/530, 358/533, 358/537, 358/538, 358/443, 358/447, 358/448, 358/452, 358/458, 358/462, 358/468, 355/218, 355/246, 355/266, 355/326 R, 355/327
• US Class Current: 358/530
• CPC Class Codes: H04N 1/58 Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction H04N1/62 takes precedence
• CPC Class Codes: H04N 1/6022 Generating a fourth subtractive colour signal, e.g. under colour removal, black masking

Abstract

In an image possessor, two kinds of color differences in the orthogonal coordinate axes in the hue plane in the color space are separated from the digital data of three primary colors, and the separate color signals are synthesized to generate the chroma signal. When the digital data of the three primary colors are converted to the data of the reproduction colors with use of the under color remove amount and the black paint amount, an under color remove amount is subtracted from the digital data of the three primary colors, while a black paint amount which is the black data obtained from the digital data is generated to print with black toners. The under color remove amount and the black paint amount are increased with increase in the chroma signal according to the color data of the three primary colors and the chroma signal at the same pixel position. The edge emphasis is performed not on the image data of the three primary colors in the subtractive color system, but on the image data of the black color, in an edge image portion of achromatic color. Further, in the edge emphasis, a first change in the value signal and a second change in the image data for image reproduction are detected, and the two changes are synthesized. Then, the edge emphasis is conducted on the image data for printing or on the image data for color reproduction according to the synthesized change.

Claims

1. An image processor, wherein each image data is processed to obtain image data for printing for each pixel, comprising:

a read means for reading a document image to send an image data of three primary colors of an additive color system;

an edge decision means for deciding an edge image portion according to the image data received from said read means;

an achromatic color decision means for deciding an achromatic color according to the image data received from said read means;

a generation means for generating image data of three primary colors in a subtractive color system and of a black color from the image data received from said read means;

a correction means for conducting edge emphasis processing not on the image data of the three primary colors in the subtractive color system, but on the image data of the black color, in an edge image portion of achromatic color decided by said edge decision means and said achromatic color decision means.

2. An image processor according to claim 1, further comprising a first signal generation means for generating a value signal from the image data obtained by said read means, wherein said edge decision means decides the edge image portion according the value signal.

3. An image processor according to claim 1, further comprising a second signal generation means for generating two kinds of color difference signals from the image data obtained by said read means, wherein said achromatic color decision means decides an achromatic color image portion according to the two kinds of color difference signals.

4. An image processor, wherein each image data is processed to obtain image data for printing for each pixel, comprising:

a read means for reading a document image to send an image data of three primary colors of an additive color system;

a calculation means for calculating the chroma from the image data received from said read means;

a generation means for generating image data of three primary colors in a subtractive color system and of a black color from the image data received from said read means;

a first determination means for determining an under color remove amount which is subtracted from the image data of the three primary color generated by said generation means according to the chroma calculated by said calculation means; and

a second determination means for determining a black paint image data to be used as one of image data for printing according to the chroma calculated by said calculation means.

5. An image processor according to claim 4, wherein said first determination means increases the under color remove amount with increasing chroma.

6. An image processor according to claim 4, wherein said second determination means increases the black paint image data with increasing chroma.

7. An image processor, wherein each image data is processed to obtain image data for printing for each pixel, comprising:

a read means for reading a document image to send an image data;

a first generation means for generating a value signal from the image data obtained by said read means;

a first edge detection means for detecting a change in the value signal generated by said first generation means;

deciding an edge image portion according to the image data received from said read means;

a second generation means for generating image data for printing from the image data obtained by said read means;

a second edge detection means for detecting a change in the image data for printing generated by said second generation means;

a synthesis means for synthesizing the change of the value signal detected by said first edge detection means and the change of the image data detected by said second edge detection means as to the same pixel in the document image; and

a correction means for conducting edge emphasis processing on the image data for printing according to the change synthesized by said synthesis means.

8. An image processor according to claim 7, wherein said image data for a printing is image data for black color.

9. An image processor, wherein each image data is processed to obtain image data for color reproduction for each pixel, comprising:

a read means for reading a document image to send an image data of three primary colors of an additive color system;

a first generation means for generating a value signal from the image data obtained by said read means;

a first edge detection means for detecting a change in the value signal generated by said first generation means;

deciding an edge image portion according to the image data received from said read means;

a second generation means for generating image data for color reproduction from the image data obtained by said read means;

a second edge detection means for detecting a change in the image data for color reproduction generated by said second generation means;

a synthesis means for synthesizing the change of the value signal detected by said first edge detection means and the change of the image data detected by said second edge detection means as to the same pixel in the document image; and

a correction means for conducting edge emphasis processing on the image data for color reproduction according to the change synthesized by said synthesis means.

10. An image processor according to claim 9, wherein said synthesis means comprises means for obtaining a product of the change of the value signal obtained by said first edge detection means with the change of the image data for color reproduction obtained by said second edge detection means.

11. An image processor according to claim 9, wherein said correction means conducts the edge emphasis processing on a plurality of the image data for color reproduction successively.

12. An image processor according to claim 11, wherein said plurality of image data includes image data of three primary colors in a subtractive color system.