Method of predicting and processing image fine structures

Details Method of predicting and processing image fine structures Method of predicting and processing image fine structures

1999-08-12

2001-11-20

Mancuso, Joseph (Department: 2624)

Facsimile and static presentation processing

Static presentation processing

Attribute control

C358S534000

Reexamination Certificate

active

06320676

ABSTRACT:

BACKGROUND ART
This invention relates to a method of predicting and processing image fine structures. More particularly, the invention relates to a method of predicting and processing image fine structures which, when applied to a system for preparing color proofs with an image output device such as a color printer or a CRT display before a printed color document carrying halftone dot images (or simply “halftone images”) is actually produced with a color printing machine using rotary presses or the like that have press plates mounted thereon, can ensure that image fine structures such as moiré and a rosette image which would occur in the actually produced printed document are represented in advance either as an image on the display such as CRT (the image is generally referred to as “soft proof”) or as an image on a hard copy output from the color printer (which is generally referred to as “hard proof”).
The process of producing printed documents carrying halftone images with a color printing machine using rotary presses or the like is not only time-consuming but also costly and, hence, it is common practice to produce proofs with a device other than the color printing machine which is commonly referred to as a proofer before the printed document is output as the actual product. The production of proofs with a proofer has two purposes, one for predicting the colors to be reproduced on the printed document (this may be called “simulation of color reproductions”) and the other is for predicting the image fine structures to be produced on the printed document (which may be called “simulation of image fine structures”).
Two types of proofers have heretofore been proposed for use in the production of proofs for printed documents, one being a proofer which involves dot formation and the other being a non-dot forming proofer. Proofing technology, or the techniques for predicting and processing image fine structures using proofers, is conventionally implemented by the following three methods. In the first method, a high-resolution digital printer is used as a dot-forming proofer and halftone images are actually produced. This technique has the advantage of correctly simulating the image fine structures which will appear on the printed document.
A dot-forming proofer is also used in the second method and halftone images (pictures) formed on printing lith films for four plates of C (cyan), M (magenta), Y (yellow) and K (black) are individually transferred to special chemical materials by exposure and the resulting four sheets of chemical materials for the C, M, Y and K plates which are commonly referred to as “transfer films” are placed one on another. An example of such proofers is one that employs the transfer films marketed by the Applicant. In this method, transfer films for the four plates of C (cyan), M (magenta), Y (yellow) and K (black) are prepared by dot formation using the actual screen ruling and transferred onto a print sheet at the actual screen angles to thereby produce a hard proof. This approach also has the advantage of correctly simulating the image fine structures which will appear on the printed document.
The third method uses a non-dot forming proofer which is exemplified by a system employing a continuous-tone color printer such as one which uses sublimable dye pigmented inks and which operates on a density modulation process to achieve a resolution of 300 dpi. This type of color printer represents the original image as a continuous-tone image without forming dots and, hence, has the advantage of producing proofs by simple procedures.
Of the two methods that use a dot forming proofer, the first approach which actually produces halftone dots with a high-resolution digital printer allows for halftone representation and is capable of correctly simulating the image fine structures which will appear on the printed documents. On the other hand, the high-resolution digital printer is an expensive device and requires high running cost; hence, the first method is not a convenient way to be performed in practice.
The second approach which superposes four transfer films for the plates of CMYK which are made of special chemical materials also allows for halftone representation and is capable of correctly simulating the image fine structures which will appear on the printed document. However, the apparatus used in the method is also costly. In addition, the cost of the print sheet is relatively high and the transfer films made of special chemical materials are also expensive. What is more, the process up to the stage of proof production is cumbersome (i.e., requires much labor due to manual operations) and, hence, a comparatively long time is taken to produce the desired proof; in other words, the second method is not necessarily an easy way to operate. In addition, it has been theoretically difficult to achieve color matching with the ultimate printed document.
In the third method which uses a non-dot forming proofer, the original image is represented as a continuous-tone image by means of a continuous-tone printer without producing dots. Therefore, this method is inexpensive, is convenient and can produce a proof within a short time. On the other hand, the method gives no consideration to representation by dots and is not capable of representing halftones; hence, the proof produced by the method can be used in simulating color reproduction but not in simulating image fine structures.
Under the circumstances, there has been a strong need for a technology that retains the advantage of low cost and convenience of the third method using a non-dot forming proofer and which yet is capable of representing dot-generated image fine structures as in the first and second methods which employ a dot-forming proofer.
Further referring to the third approach which uses a non-dot forming proofer, it has heretofore been customary to produce color proofs for examining and correcting colors and so forth before a printed color document carrying halftone images is ultimately produced by a color printing machine. The proofs are produced using a color printer that forms an image for each pixel by a density gradation process (also called “continuous gradation process”) and this is primarily because the color printer is of a comparatively simple Composition and inexpensive. In addition, by means of the color printer, a hard copy having an image formed on a sheet can easily be produced a plurality of times within a short period of time since, as is well known in the art, the preparation of process-plate films and press plates which are required by color printing machines are not needed by the color printer.
FIG. 23
shows the flow of a conventional process for producing color proofs using a color printer. First, the image on an image document
52
is read two-dimensionally with an image reader such as a color scanner having a CCD linear image sensor or the like and gradation (continuous-tone) image data Ia for each of the colors R (red), G (green) and B (blue) are generated (step S
51
: image reading step).
Then, in step S
52
, the RGB gradation image data Ia are rendered by a color conversion process using conversion lookup tables or the like into dot area percentage data (also referred to as “dot percentage data” or “original image pixel dot percentage data”) aj for the four plates of respective colors C (cyan), M (magenta), Y (yellow) and K (black), where j=0, 1, 2, 3 (0 represents the color C, 1 the color M, 2 the color Y, and 3 the color K). The color conversion process allows for various versions in relation to the color printing machine to be described later on and it is usually the proprietary know-how of individual printing companies who employ different color printing machines.
Halftone images are produced by the color printing machine and, hence, in order to produce a printed color document in the actual practice, the dot area percentage data aj produced by the color conversion process are rendered into bit map data, on the basis of which a process-plate film or the like is generated

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