JPH1196347A - Image processing method and image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently apply anti-aliasing processing to rasterized image data for one page. SOLUTION: In image data Ik1 rasterized for one page containing characters, drawings and images, only the image data corresponding to a prescribed part set by an anti-aliasing condition setting means 30 are specified by an anti- aliasing range specifying means 26 and only to that specified prescribed part [such as only the image data of K (Indian ink) version], anti-aliasing processing is selectively loaded by an anti-aliasing processing means 28. Since anti-aliasing processing is not loaded over all the image data, the image required for anti- aliasing processing can drastically be reduced. Further, since anti-aliasing processing is not loaded to the part unnecessitating anti-aliasing processing, the degradation of image quality such as image blurring does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to image data supplied to an image output device such as a color printer, a DDCP device, an image setter and the like, and is used for characters on an image output from the image output device. , Line drawing, and / or anti-aliasing (anti) that suppresses high-frequency components generated near the respective edges of the image.
The present invention relates to an image processing method and apparatus for performing an aliasing process.

[0002]

2. Description of the Related Art In the field of desktop publishing, for example, characters or line drawings obtained as code data or vector data and images obtained as image data decomposed into pixel data by photoelectrically scanning a photograph or the like. (Pictures) are comprehensively integrated and edited at the workstation, and then one page of data is RI
P (raster image processor, raster image processing device) converts the image data into rasterized (converted into a group of points) image data.

[0003] The rasterized image data of one page is converted into a color printer which expresses an image by pixels, DD, or the like.
When supplied to an image output device such as a CP (direct digital color proofing) device, an image setter or a color monitor, a character,
You can see line drawings and images (pictures).

[0004]

By the way, vector data expressing characters and line drawings is rasterized to 300-400.
When the image data is converted into image data having a resolution of about 400 dpi (dots / inch), there is a problem that a so-called jagged line appears on an oblique line and image quality deteriorates.

Further, the rasterized image data is
For example, in the case where the resolution is converted from 350 dpi to a close resolution such as 400 dpi, if a periodic pattern such as a textile material, a sweater, or a protective cover portion of a speaker is present in the image, moire fringes are generated, or oblique lines are formed in the image. If it exists, there is a problem that a beat is generated and the image quality is degraded.

Therefore, conventionally, in order to solve these problems, anti-aliasing processing is applied to all rasterized image data of one page by software on a computer. Since the anti-aliasing processing is a calculation of convolution, there is a problem that the calculation requires a very long time.

The anti-aliasing processing may be performed by using a hardware product such as a product-sum operation unit and a memory. However, in this case, a problem occurs in that the scale of the hardware resource becomes large. .

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and provides an image processing method capable of efficiently performing anti-aliasing processing and greatly reducing the time required for anti-aliasing processing. It is intended to provide the device.

[0009]

According to the present invention, an anti-aliasing process is selectively applied only to image data corresponding to a predetermined portion of image data.

Since anti-aliasing processing is not performed on the entire image data, the time required for anti-aliasing processing can be greatly reduced. Moreover,
Since the anti-aliasing process is not applied to the unnecessary portion of the anti-aliasing process, the image quality such as image blur does not deteriorate.

As a predetermined portion, the image data is C,
When it is composed of four color plates of M, Y, K, etc., a portion having a specific color plate can be selected from them.

If the image data is multi-valued image data of, for example, 0, 1,..., 255 levels, a portion having a specific pixel value can be selected.

Further, as the predetermined portion, a portion defined by a specific range in the image represented by the image data can be selected.

When applying anti-aliasing processing,
Of the image data for one page rasterized at a resolution higher than the output resolution (resolution N), only image data corresponding to a predetermined portion is subjected to anti-aliasing processing in which the resolution becomes 1 / N. Alternatively, the image data corresponding to the other portions may not be subjected to the anti-aliasing process, but may be simply subjected to the process of reducing the resolution to 1 / N. By performing such processing, a higher quality image can be obtained empirically.

[0015]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a basic configuration of an image processing / reproducing system 10 to which an embodiment of the present invention is applied.

The image processing and reproducing system 10 basically includes a workstation 12 and a RIP (raster image processor) 14 as a raster image processing device.
And an image data processing device 16 including a computer;
And an image output device 18.

In the workstation 12, code data such as characters and line drawings and vector data (for example, data approximated by broken lines and recorded as a series of coordinate points), and pixel resolution including a picture read from a photographic original by a scanner or the like. For example, as a page description language including color information (color information) that is comprehensively integrated with edited image data and edited,
Output as postscript data PS.

Postscript data PS for one page
Is one page of image data I rasterized (converted to a pixel grid, which is a group of dots) by the RIP 14.
kl. When a raster image is formed by the RIP 14, the resolution after the RIP process is specified by the user through the resolution specifying means 20 such as a keyboard. In this embodiment, the specified resolution is
The same resolution as the resolution of the image output device 18, or the second,
The resolution is about three times. As a specific numerical value, when the resolution of the image output device 18 is 400 dpi, the resolution specified by the resolution specifying unit 20 is 400 dpi of the same resolution or 800 of a resolution approximately twice or three times the same.
dpi, 1200 dpi, or the like. Of course, the resolution may be converted to another resolution.

Here, it should be noted that code data and vector data such as character and line drawings generally have a pixel value of 2 pixels.
55 (colorization, for example, blackening) and pixel value 0 (non-colorization, for example, non-blackening, and the ground color white on the finally output photographic paper) are converted into binary data. As shown in FIG. 2, in the case of a line 44 obliquely crossing a pixel grid 41 composed of pixels 40 arranged vertically and horizontally, a jaw 46 may be visible after rasterization.

Another point to be noted is that the resolution of pixel-decomposed image data including a picture read from a photographic original by a scanner or the like is, for example, 350 dpi, and this is converted by the RIP 14 into a 400-d
When converted to pi resolution, as shown in FIG.
The point is that the jagged edges 42 that periodically become, for example, two pixels may occur on the line 44a that crosses obliquely due to the beat.

In FIG. 1, one page of image data Ikl rasterized by the RIP 14 is temporarily stored in an image data memory 22. Note that in this embodiment, the image data Ikl is data separated into C (cyan), M (magenta), Y (yellow), and K (black) plates, and constitutes each separated data. Each pixel data to be
It is assumed that the data is any one of pixel values of 0, 1, 2,..., 255. In this case, the pixel value of the pixel data corresponding to the character or the line drawing is converted into data having a value of 0 or 255 by raster image processing.

From the image data memory 22, address data AD and image data Ikl, which are coordinate data, are supplied to a monitor (image display device) 24, an anti-aliasing range specifying means 26 and an anti-aliasing processing means 28.

In this case, the anti-aliasing range specifying means 26 and the monitor 24 are connected to an anti-aliasing condition setting means 30 such as a keyboard.
The anti-aliasing condition setting means 30 outputs the image data Ikl supplied to the anti-aliasing processing means 28.
Among them, for setting (inputting) conditions for specifying image data corresponding to a predetermined portion to be subjected to anti-aliasing processing by the anti-aliasing processing means 28.

In this embodiment, the conditions for specifying image data corresponding to a predetermined portion to be subjected to anti-aliasing processing include, first, a specific color plate, for example,
Second, only the K plane image data is specified. Second, a specific pixel value, for example, a value 0 or a value 255 in the image data is specified.
(In other words, specify only the portion having the minimum value and the maximum value of each plate in the data separated into each plate of C, M, Y, and K). Third, a preview is displayed on the monitor 24, and a portion specified in a specific range designated for trimming, for example, a textile material in which the occurrence of moiré fringes is predicted during the screen display. , A sweater, or a protection cover portion of a speaker can be selected.

The predetermined portion to be subjected to the anti-aliasing processing is not limited to these, and may be applied only to the unsharp masking signal when performing the sharpness enhancement processing.

When anti-aliasing processing is performed on the image data Ikl by the anti-aliasing processing means 28, filter setting / resolution conversion presence / absence setting means 32
Thus, a desired anti-aliasing filter is set, and whether resolution conversion processing is performed simultaneously with anti-aliasing processing is specified. Since this designation is a designation for matching the resolution of the image data after the anti-aliasing processing to the output resolution of the image output device 18, the resolution designated by the resolution designation means 20 is 400 dpi which is the same as the output resolution. In this case, the resolution conversion becomes unnecessary, and the resolution specified by the resolution specifying means 20 is 800 dpi or 1200 dpi.
In the case of pi, it is necessary to set the resolution to あ る い は or そ れ ぞ れ, respectively.

FIGS. 4A to 4C show examples of the configuration of an anti-aliasing filter Aij (x-axis coordinate values are represented by i and y-axis coordinate values are represented by j) which can be set in this embodiment. I have. Each is a 2 × 2, 3 × 3 linear filter, and each coefficient (weight) is standardized so as to be 1 in total. As shown in FIG. 4C, good results are often obtained when a filter is applied in which the weight decreases from the center to the periphery.

The image data after the anti-aliasing processing by the anti-aliasing processing means 28 is supplied to the color conversion processing means 34, and the image data after the anti-aliasing processing, specifically, C, The image data is converted into C, M, Y, and K color printer image data for realizing the same color as the printed matter corresponding to the M, Y, and K halftone dot area ratio data.
Supplied above.

In the image output device 18 such as a color printer or a DDCP device, a so-called proof of a printed matter is created based on the C, M, Y, and K color printer image data.

Next, the operation relating to the anti-aliasing processing in the example of FIG. 1 will be described with reference to the flowchart shown in FIG.

In this case, first, the user operates the anti-aliasing condition setting means 30 to set the conditions of the anti-aliasing process (step S1).
That is, it is applied only to the image data of a specific color plane, only to a specific pixel value (0, 255), or to a specific image area in a display image on the monitor 24 and applied only to the specified area. And other conditions are set.

Next, the user operates the filter setting / resolution conversion presence / absence setting means 32 to set a desired anti-aliasing filter Aij and to determine whether resolution conversion is necessary (step S2). Here, as an anti-aliasing filter Aij, FIG.
Is selected, and the resolution designating means 20 for the image data output from the RIP 14 is used by the image output device 1
8, an output resolution of 400 dpi is specified, and the anti-aliasing processing means 28 supplies the resolution 400
It is assumed that “no resolution conversion” is set, which does not require resolution conversion, as the image data Ikl of dpi is supplied.

Next, based on the settings in steps S1 and S2, only the pixel data corresponding to the specified processing portion of the image data Ikl is fetched by the anti-aliasing range specifying means 26 (step S3).

FIG. 6 shows a part of the image data Ikl before the anti-aliasing processing. The x coordinate value is represented by k, and the y coordinate value is represented by 1. At this time, first, FIG.
Pixel data “I11, I12, I21, I22” of four pixels at the upper left corresponding to the size (2 × 2) of the anti-aliasing filter Aij shown in A = “70, 30,
20, 40 ".

Then, it is determined by the anti-aliasing range specifying means 26 whether or not the captured pixel data of four pixels meets the condition specified in step S1 (step S4). That is, it is determined whether the image data is a specific color plane image data, a specific pixel value (0, 255), or a specific image area designated using the monitor 24. In this case, whether the image data is a specific color plane image data or a specified specific image area can be determined based on the address data AD.
It can be determined by comparing the value of the pixel value specified by the address data AD with the value 0 or the value 255. Here, it is assumed that the image area is determined to be the specific image area specified in step S1, and the determination in step S4 is affirmed.

At this time, an anti-aliasing process, which is a well-known convolution operation (convolution calculation) according to the following equation (1), is performed on the pixel data captured in step S3 (step S5).

[0038]

(Equation 1)

That is, input image data Ikl for the upper left four pixels = “I11, I12, I21, I22” = “7
0, 30, 20, 40 "for the output image data I '
kl = I′11 = (１ ／) × (70 + 30 + 20 + 4
0) is performed, and the value of the image data Ikl = I11 = 70 before the anti-aliasing processing is converted into the value of the image data I′kl = I′11 = 40 after the anti-aliasing processing, and is shown in FIG. Thus, in the image data I'kl after the anti-aliasing processing, the coordinate value (k, l) =
The pixel data is (1, 1).

Next, returning to step S3, the next pixel data is fetched. Here, the image data Ikl of FIG.
Image data Ikl shifted by one pixel to the middle and right = “I1
2, I13, I22, I23 "=“ 30, 50, 40,
The pixel data of "40" is captured. Assuming that this pixel data also satisfies the condition determination in step S4, by the processing in step S5, I′kl = I′12 =
The calculation of (１ ／) × (30 + 50 + 40 + 40) is performed, and the image data Ikl before the anti-aliasing processing is performed.
= I12 = 30 is converted to anti-aliasing processed image data I'kl = I'12 = 40, and as shown in FIG. 7, the coordinate values in the anti-aliased image data I'kl (K, l) = (1, 2) pixel data.

Hereinafter, similarly, steps S3 to S
5 is repeated, I'kl = I'13 = 54, etc. are determined, and the anti-aliasing processing ends when the processing is completed up to the last pixel data of the input image data Ikl.

Next, the rasterized image data Ikl that has been processed by the RIP 14 is equal to 8 times the output resolution of 8 times.
Considering the case of 00 dpi, step S
2 is set to “Yes = １ ／”. Here, for simplicity, the image data Ikl shown in FIG.
Is 800 dpi image data, and the case where the determination in step S4 is positive is considered.

At this time, the image data I 'after the resolution conversion
kl = I′11 means that image data Ikl = “I11, I12, I21, I22” for four pixels at the upper left of FIG.
[0, 30, 20, 40] becomes one pixel of image data I'11 = 40 obtained by performing anti-aliasing processing (see FIG. 8).

The next image data I 'after the resolution conversion is performed.
kl = I′12 is equivalent to image data Ikl = 4 pixels each shifted two pixels to the right from the upper left pixel data in FIG.
“I13, I14, I23, I24” = “50, 60,
40, 65 "to I'kl = I'12 = (1/4) .times.
The operation of (50 + 60 + 40 + 65) is performed, and the image data Ikl for these four pixels = “I13, I14, I2
3, I24 "is converted into the value of the image data I'kl = I'12 = 54 after the anti-aliasing processing, and as shown in FIG. k, l) = (1, 2) pixel data.

As described above, in general, after the rasterization is performed by the RIP 14 at a resolution about twice or three times the resolution (output resolution) of the image output device 18, an average of 2 × 2 pixels or 3 × 3 pixels is obtained. Reverting to a resolution of / 2 or 1/3 often gives good results (high image quality) as anti-aliasing processing.

Next, it is assumed that the anti-aliasing processing is applied only to a specific pixel value (0, 255) by the condition setting processing in step S1.

In this case, in the image data Ikl, the pixel value 0
Alternatively, only the image data Ikl having the pixel value 255 is selected by the processing in step S4, and only the selected image data Ikl is subjected to the anti-aliasing processing.
Although not described in detail here because it becomes complicated, the image data Ikl for which the processing in step S4 is positive is shown in FIG.
9 is shown in FIG. It is easily understood that the image data I′kl without resolution conversion is as shown in FIG. 10, and the image data I′kl with resolution conversion is as shown in FIG.

As described above, according to the above-described embodiment, R
When performing anti-aliasing processing on image data Ikl for one page including characters, line drawings, and / or images rasterized by the IP 14, anti-aliasing processing is performed only on image data corresponding to a predetermined portion. . For this reason, the processing time can be drastically reduced in a normal case as compared with the conventional technique in which the anti-aliasing processing is applied to all the image data of one page.

Here, the normal case means that the image data for one page includes the image data of each of the CMYK planes, and the image data of each of the planes includes all the characters, line drawings, and images. , Or the image data of one page includes the image data of each of the CMYK plates,
This refers to the case where either a line drawing or an image is included. In this case, the anti-aliasing condition setting means 3
According to the present invention, the process designation by 0 can be, for example, partial designation of a K-version character, a C-version character, a line drawing and an image, or a CMYK-version within a certain range (a certain address area). Therefore, it is understood that the processing time is much shorter than in the conventional technique in which anti-aliasing processing is performed on all image data of one page.

In addition, since only the portion to be blurred can be blurred, only the portion having the jagged portions 46 and the jagged portions 42 indicated with reference to FIGS.
By specifying an area such as a color plate, a pixel value, an area, or a sweater, it is possible to blur only that part (area). As a result, jaggies 46 and jagged 4
2 and moire fringes can be prevented.

It should be noted that the present invention is not limited to the above-described embodiment, but can adopt various configurations without departing from the gist of the present invention.

[0052]

As described above, according to the present invention, the anti-aliasing process is selectively applied only to the data of a predetermined portion considered to be necessary among the image data. Since the anti-aliasing processing is not performed on the entire image data, the anti-aliasing processing is made more efficient, and the effect that the time required for the anti-aliasing processing can be significantly reduced can be achieved.

Moreover, since the anti-aliasing process is not applied to the portion where the anti-aliasing process is unnecessary, the effect that the image quality such as image blur does not occur in the portion is simultaneously achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image processing / reproduction system to which an embodiment of the present invention has been applied.

FIG. 2 is a diagram used to explain the occurrence of so-called jaggies.

FIG. 3 is a diagram used to explain what is called jaggedness.

4 is a diagram showing a configuration example of an anti-aliasing filter, FIG. 4A is a 2 × 2 filter, FIG. 4B is a 3 × 3 filter, and FIG. 4C is an example of a 3 × 3 weighting filter; ing.

FIG. 5 is a flowchart provided to explain an operation relating to an anti-aliasing process according to the embodiment;

FIG. 6 is a diagram illustrating an example of image data before anti-aliasing processing;

FIG. 7 is a diagram showing image data after anti-aliasing processing.

FIG. 8 is a diagram showing image data after resolution conversion anti-aliasing processing.

FIG. 9 is a diagram showing an example of image data before anti-aliasing processing.

FIG. 10 is a diagram showing image data after anti-aliasing processing.

FIG. 11 is a diagram showing image data after resolution conversion anti-aliasing processing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Image processing / reproduction system 12 ... Work station 14 ... Raster image processing device (RIP) 16 ... Image data processing device 18 ... Image output device 20 ... Resolution designation means 22 ... Image data memory 24 ... Monitor (image display device) 26 ... Anti-aliasing range specifying means 28 Anti-aliasing processing means 30 Anti-aliasing condition setting means 32 Filter setting / resolution conversion presence / absence setting means 34 Color conversion processing means AD Address data Ikl Image data before anti-aliasing processing I'kl … Image data after anti-aliasing processing

Claims (6)

[Claims] An image wherein an anti-aliasing process is applied only to image data corresponding to a predetermined portion of one page of rasterized image data including a character, a line drawing, and / or an image. Processing method. 2. A rasterizing process for converting one page of image data including a character, a line drawing, and / or an image into rasterized image data; An anti-aliasing process of applying an anti-aliasing process only to the image data corresponding to the portion; and an image output process of outputting an image based on one page of image data including the anti-aliasing portion. Converting the image data into rasterized image data having a higher resolution than the output resolution in the image output step; and in the anti-aliasing processing step, converting the high-resolution rasterized image data back to the output resolution. Anti-aliasing processing including Performing an image processing. 3. The image processing method according to claim 1, wherein the predetermined portion is a portion having a specific color plate. 4. The image processing method according to claim 1, wherein said predetermined portion is a portion having a specific pixel value. 5. The image processing method according to claim 1, wherein the predetermined portion is a portion defined in a specific range. 6. An anti-aliasing processing means for applying anti-aliasing processing only to image data corresponding to a predetermined portion of one page of rasterized image data including characters, line drawings, and / or images. An image processing apparatus characterized by the above-mentioned.