JPS6319082A - Printing quality estimating method - Google Patents

Abstract

PURPOSE:To estimate objectively printing quality in matching with the real sense of visual observation by displaying the extent of the blur of the outline of a printing image with the width of an edge. CONSTITUTION:The image of an original 1 is read through a microscope 2 by a television camera 3 and converted to an electric signal. The electric signal is stored through an A/D converter 4 to an image memory 5. A computer 6 obtains the average value of the width of the edge of a normal direction in respective points from the reflection factor of paper and an image to respective areas of the image stored in the image memory 5. The average value of the width of the edge is displayed at a CRT 8 as the estimating criterion of a printing quality and printed out by a printer 9.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for evaluating the quality of images printed by a printer or the like.

<Prior Art> In recent years, printers, especially printers as terminal devices, have become widespread and are used in all fields of industry. There are various types of printers, from high-end laser printers to simple thermal transfer printers.

In recent years, with the spread of such printers, interest in their image quality has also increased.

(Problems to be Solved by the Invention) Conventional methods for evaluating the printing quality of printers include, for example, in the case of thermal transfer printers, edge characteristics,
Criteria for judgment include the crushing of the printed pattern and the handling of the transfer, but the reality is that the actual evaluation relies entirely on visual sensation. Although research has been conducted on the evaluation of print quality or image quality of printers, it is still at the stage of theoretical research and cannot be said to be of practical use.

The present invention has been made in view of these points, and
The purpose is to realize a print quality evaluation method that can objectively evaluate print quality in accordance with visual perception.

(Means for Solving the Problems) The present invention, which solves the problems described above, calculates the average value of the edge width in the normal direction at each point from the reflectance of the paper and the image for each region of the sample image. is determined, and the average value of this edge width is used as an evaluation standard for print quality.

(Function) The present invention uses a method based on the average value of edge widths to evaluate print quality.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a flowchart showing one embodiment of the method of the present invention. The following will be explained along this flowchart.

Step 2: Find the edge width in the normal direction at each point from the reflectance of the paper and image for each of the top, bottom, left, and right sides of the sample image.

As a measure for evaluating the printing quality of a sample image, there may be considered measures such as ① a measure related to edge unevenness (edge smoothness), ① a measure related to edge blur (edge sharpness), and ① other measures.

The method used in the present invention falls within the scope of (2) measures regarding edge blur.

Figure 2 is a sample image. It is displayed within a frame of 4503 pixels each in the vertical and horizontal directions. The sample image shown in the figure is a binary image obtained by reading an actual printed image with an image reading device and converting it into 211. The following equation was used for the binarization threshold 7h at this time.

Th = 0.6 <t≧0.6) t (t <0.6> ... (1) where t = (dw+db) / 2dvB paper reflection density db; reflection density of image area shown in Figure 2 Consider expressing a sample image in terms of reflectance (luminance).In the present invention, the edge width is defined as shown below.The edge width is defined as the reflectance R of each pixel.
is Rλ≦R≦Rh (2)
The width in the normal direction of the part that satisfies the following conditions. here,
Rh and RJ are each expressed as in the following equations.

Rh = (25Rw +75Rb)/100...
(3) RJ = <75Rw +25Rb)
, /100... (4) RW: Reflectance Rb of paper; Reflectance of image area When the width that satisfies formula (2) is determined and displayed for the entire surface of the sample image shown in Figure 2, it is shown in Figure 3. You will get an image like this. The width indicated by diagonal lines in the figure indicates the width of the portion with a reflectance that satisfies the condition shown in equation (2), and generally an image with a lot of blur becomes wider.

Therefore, it can be said that areas where the width of the contour line is narrow are areas where the print quality is good. When calculating this width, the difference in reflectance (R
h - RJ ) and the length of 450X450 shown in Figure 3.
After establishing the correspondence with the pixel plane, the width in the normal direction of each point on each side can be sequentially determined in units of length by ratio calculation. Here, the interval between each point may be set, for example, for each pixel, or one interval may be set for every several pixels. Incidentally, FIG. 4 is a diagram showing an edge locus with a reflectance of 50%.

Step ■ Find the average value of the edge width at each point for each side.

When calculating the average value of the edge width for each side, the average value W is given by the following equation.

W-Σwi/n...(5
) Here, Wl is the jth line width, and n is the number of sample points.

To actually find the average value of the edge widths for the top, bottom, left, and right sides of a quadrilateral image, do as follows.

For example, when calculating the average value for the upper side, assume a region where 10% of the top, bottom, left and right sides of each side are cut (shaded region in FIG. 5), and apply the present invention to this hatched region. Also, to find the width of the edge, find the area of the shaded area from the image shown in Figure 3, then find the length of the corresponding area from the image shown in Figure 4, and calculate the area by the area. ) may be used to find the width of the contour line on each side and use it as an average value. Specifically, the area is obtained by counting the number of pixels in FIG. 3, and the length is obtained by counting the number of pixels in FIG. This method is convenient when the calculation is performed by a computer.

Step ■ Use the obtained average value of the edge width for each side as the evaluation standard for printing quality.

As mentioned above, the reflectance was determined for each side as a reference (
The average value of the edge width for each side shown in equation 5) can be used as a measure of blurring of the edge portion of the image. That is, if the average value W is large, the print quality will be poor, and if the average value W is small, the print quality will be good.

Next, experimental results of print quality evaluation using the present invention will be explained.

For each of the top, bottom, left, and right sides of the binary image shown in Figure 2, 10% of both ends were cut, and the present invention was applied to the remaining 80% of the sides to find the average edge width. However, the top side, bottom side, left side, and right side are 0.064 <mm> and 0.0.
055 <mm>, 0.052 <mm), 0.
It became 060 (mm). As is clear from Figure 2, the left side is higher than the right side.

Although the print quality is poor on the lower side, the experimental results also agree well with this.

If the images shown in Figures 3 and 4 have a simple shape with little curvature, each section (top, bottom, left, right, or the entire surface) is further subdivided into small sections, and each small section is divided into straight lines or quadratic curves. The length may be determined by applying a trend line such as In this case as well, the area is determined from FIG. 3, the length is determined from FIG. 4, and the width of the edge is calculated by (area)/(length).

FIG. 5 is a diagram showing an example of the configuration of a hardware system for implementing the method of the present invention. The image recorded on the original 1 is optically magnified by a microscope 2 and then viewed by a television camera 3.
is read and converted into an electrical signal. The image signal converted into an electrical signal is converted into digital data by an A/D converter 4. Here, the number of bits of the A/D converter 4 may be as long as it has a resolution of about 256 gradations to discriminate between gray levels. That is, an A/D converter of about 8 bits may be used.

The output of the A/D converter 4 is sequentially stored in the image memory 5 pixel by pixel. Here, the memory capacity of the image memory 5 is a capacity large enough to store all the images recorded on the original 1, for example, 512 x 640.
Vixel level is appropriate. If necessary, the computer 6 sequentially reads out the image data stored in the image memory 5, performs binarization processing, and stores the binary data for each pixel on the floppy disk 7. Here, the image of the binary image stored on the floppy disk 7 is as shown in FIG.

Next, the computer 6 reads the reflectance data of the edge portions of the top edge, bottom edge, left edge, right edge, or other areas over the entire surface of the sample from among the data stored in the image memory 5, and calculates the edge portion of the portion forming the outline. The reflectance of a predetermined width is determined, and the width of the edge in the normal direction is calculated from the area and length of the image. The edge width determined for each side is displayed on the CRT 8 or printed out by the printer 9. The keyboard 10 gives various commands to the computer 6.

In addition to the edge width calculation method according to the present invention, as a measure of edge blur, acutance (Δcutanc
e) Able to think of methods. The number of pixels is n for each side of the printed image as shown in Figure 2, the difference between the maximum density and the minimum density is calculated, and the density change ΔDi of adjacent pixels in the X direction and the X direction is Then, acutance A is defined by the following formula.

A-Σ((ΔDi/Δxi) 2+(ΔDi/Δyi)
1+11 2)/n-D (6) Here, Δxi is the distance between pixels in the X direction (for example, 10μ)
, Δy1 is the distance between pixels in the X direction. When the acutance was calculated for the image shown in Figure 2, the top, bottom, left, and right sides were each 252°7 (dn/ll1m
2), 306.5 (dn/mm2), 378
, 6 (dn/w+m2) , 217.5 (dn
/mn+2). The larger the value, the better the print quality. Here, dn is the concentration.

In the above explanation, the range of reflectance from 25% to 75% was used as a reference for determining the width of the edge, but this is not necessarily the case. etc. can be used. or,
In the above-mentioned embodiment, the case where the average value of the edge width is calculated for each of the top, bottom, left, and right sides of the sample was taken as an example, but the present invention is not limited to this, and the present invention can be applied to any area over the entire surface of the sample. Can be applied. The printed image used in the present invention may be printed by any type of printer such as thermal transfer, inkjet, wire dot, etc. The present invention is equally applicable to all of these printed images.

<Effects of the Invention> As explained in detail above, according to the present invention, by expressing the degree of blurring of the outline of a printed image by the width of the edge,
It is possible to realize a print quality evaluation method that can objectively evaluate print quality in accordance with visual perception.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an example of the process of the present invention;
FIG. 2 shows an example of a binary image for explaining the present invention;
FIG. 3 is a diagram showing an example of an image with an edge width, FIG. 4 is a diagram showing an example of an edge image with a reflectance of 50%, FIG. 5 is an explanatory diagram of edge width calculation, and FIG. 6 is a diagram for implementing the present invention. FIG. 2 is a diagram showing an example of the configuration of a hardware system. 1... Manuscript 2... Microscope 3...
TV camera 4...A/D converter 5...Image memory 6...Computer 7...Floppy disk 8...CRT9...Printer
10...Keyboard patent applicant Roku Konishi Photo Industry Co., Ltd. Representative Patent attorney Ii
Shimafuji Jigai 1 person Figure 2 (045C

Claims (1)

[Claims] For each area of the sample image, the average value of the edge width in the normal direction at each point is determined from the reflectance of the paper and the image, and this average value of the edge width is used as the evaluation standard for print quality. A printing quality evaluation method featuring: