DE4105263A1 - Image processor for characters and symbols - introduces correction to eliminate stepped profile of lines due to aliasing - Google Patents

Abstract

The boundary of a character or graphical symbol printed by a matrix unit can create a stepped profile due to the 'aliasing effect' and a system is proposed to generate a smooth profile. A memory (1) stores data in x and y coordinate form and these are evaluated by a detector (2) that determines the inclination of boundary lines. A point counting module (3) determines the vertical point count changes for specified horizontal moves. The data are used by the correction module (4) to provide additional points to eliminate the stepped effect in the reproduced boundary line. ADVANTAGE - Relatively simple processing eliminates stepped symbol boundary lines.

Description

The invention relates to an image processing device according to the preamble of claim 1 and relates in particular an image processing device which has a contour of a smoothes the image to be processed and the image data with a smooth contour to an output device, such as a printer and outputs a display to points on the output device to create.

When image data including graphics and character information are processed and image data supplied to an output device is usually composed of a matrix of dots which are arranged horizontally and vertically in a regular manner. In Fig. 6A in an enlarged view an example of the output image data is shown containing horizontal and vertical rows. An outline or contour portion of a dispensed image that is inclined in a horizontal or vertical direction often shows a stair-shaped irregularity that the human eye would notice if the image were reduced back to its original size. Such a stair-shaped irregularity is hereinafter referred to as "aliasing". Usually, one conceivable method of eliminating such a stair-shaped irregularity from the outline or contour part of the image (which method is referred to below as "antialiasing") is to match gradation or gradation points or tone points to each related one Add point of the outline part of the image, as shown in Fig. 6B, so that the output image would show a visually smooth outline or a corresponding contour without irregularities. Such a conventional image processing device is disclosed, for example, in Japanese Patent Application Laid-Open No. 57-24268.

One difficulty, however, is that the conventional one Image processing device in which gradation or Halftone dots that are appropriate to the given Image to be added using a complicated Control unit requires to include such image data to process the gradation or gradation points, by complicated calculations for an outline or contour smoothing process be performed. In addition, must the conventional device with an image data storage have a relatively large capacity to additional Save gradation data as well as the image data, and a delivery device, which the image data from the conventional Image processing device must be supplied have complicated output control and function to the halftone data in addition to the image data including a stepped irregularity or "alienation".

According to the invention, an image processing device is therefore intended be created in which the above Difficulties have been eliminated, and which or contour part of image data and accordingly a visually smoothed contour of the image data with a non-complicated Control unit can deliver. According to the invention this is an image processing device according to the preamble of claim 1 by the features in the characterizing Part reached. Advantageous further developments are Subject of the claim 1 directly or indirectly  back-related subclaims. According to the invention, a staircase irregularity or "alienation" from one Outline or contour part of an image can be eliminated so that creates a visually smoothed outline in the outline portion of the image becomes. The number of points divided by a count length L has been displayed, which is the inclination of an outline or corresponds to a contour is determined; then one Correction dot pattern based on the number found Points are created, and the outline with a stepped irregularity is corrected in that the correction dot pattern is added to the outline to thereby create a to produce a visually smoothed outline of the image.

The invention is illustrated below by means of preferred embodiments with reference to the accompanying drawings explained in detail. It shows

Fig. 1 is a block diagram of an embodiment of an image processing device according to the invention;

Figs. 2A and 2B are flowcharts based on which an image processing is explained, which is performed by means of the shown in Figure 1 image processing means.

Fig. 3 is a flowchart to be used to explain a "counter-alienation process" of the image processing as shown in Figs. 2A and 2B;

. 4A, is shown in which an outline or contour part of image data with a step-like irregularity shows a diagram before is carried out "counter-alienation process";

. 4B, in which the contour portion represented shows a diagram after the "alienation process" is carried out;

Fig. 5 is a diagram based on which of the invention is explained in "counter-alienation process" according to, and

, Which has been performed by a conventional image processing device Fig. 6A and 6B are diagrams representing the result of a "counter-alienation process."

First, an image processing device according to the invention will be described with reference to FIG. 1, which can process binary image data by smoothing an outline or contour part of an image and which outputs the binary image data with a visually smoothed outline to a binary data output device which, for example, a display or a Printer or printer can be. The image processing device according to the invention generally has a coordinate recording part 1 , an inclination determining part 2 , a point counting part 3 and a correction part 4 . The coordinate recording part 1 receives two sets of x and y coordinates of a start and an end point with respect to a line which is contained in an outline or a contour of an image to be processed, from image data stored in a memory. The inclination detecting part 2 determines an inclination of the line with the start and end points after the point data indicating the line has been processed as binary image data and has been supplied to a memory (not shown) for storing binary information by the to deliver binary information. The point data is processed and output on the basis of the values of the x and y coordinates which have been recorded by the coordinate recording part 1 . The point counting part 3 selectively calculates the number of points aligned in a predetermined horizontal direction with respect to a change in the y coordinate of the line or the number of points aligned in a predetermined vertical direction with respect to a change in an x -Coordinate of the line on the basis of the determined inclination of the line which has been supplied by the inclination determining part 2 . The correction part 4 generates a number of sets of correction points to be added to the line having "alienation" on the basis of the calculated number of points supplied by the point counting part 3 . The correction part 4 supplies a number of sets of correction data in order to eliminate a step-like irregularity or "alienation" from the outline or the contour of the image, so as to produce a visually smoothed outline of the image to be output.

Next, the image processing procedure performed by the above-described image processing device will be described. In Fig. 2A and 2B, a flow chart is shown to a coordinate capture procedure, which is performed by means of the coordinate-receiving part 1, a tilt detection procedure by means of the inclination detecting forming part 2 and a point counting procedure by means of the point counting part 3 to explain. FIG. 3 shows a flowchart which is used to explain a "counter-alienation procedure" which is carried out by means of the correction part 4 . In Fig. 2A, 2B and 3 are vector data with respect to a contour or a contour which is included in an image to be processed, from sets or groups of x- and y-coordinates with respect to a starting and end point of the outline or contour of the and this image can include graphics and drawing information. The starting point of the outline or the contour is expressed by real number coordinates (xs, ys), and its end point is expressed by real number coordinates (xe, ye). According to the invention, these real number coordinates of the starting and ending points are transformed into device coordinates, and these device coordinates are expressed in whole numbers. The image data is represented by the device coordinates in integers to produce sets or groups of points in a binary data dispenser, and this transformation is performed to form the sets or groups of points that have a resolution that corresponds to a resolution of the Binary data delivery device corresponds. This resolution of an output device is defined below as the number of distinguishable picture elements or dots per distance unit on a display or a delivery device. In general, a transformation from real number coordinates (x, y) to integer coordinates (X, Y) as described above is referred to as a device coordinate transformation, and this transformation is shown in the following description as follows:

X ≡ x, Y ≡ y.

In this formula, x and y (lowercase) are values of real numbers before the transformation and X and Y (capital letters) are values of integer coordinates after the Transformation.

As shown in Fig. 2a and 2B, a device coordinate transformation is performed at step S 1, to transform the x and y coordinates (real numbers), the vector data in the X and Y device coordinates (integers) which correspond to a resolution of a binary data delivery device. The real number coordinates (xs, ys) of a starting point of the outline or the contour are transformed into integer device coordinates (Xs, Ys), and the real number coordinates (xe, ye) of their end points are transformed into integer device coordinates (Xe, Ye). In a step S 2 , a difference Δx (= xe-xs) in an x coordinate, which is expressed in a real number between the starting point and the end point, and a difference Δy (= ye-ys) in a y- Coordinate calculated, which is expressed in a real number. Steps S 1 and S 2 are carried out by the coordinate receiving part 1 described above. In a step S 3 , an absolute value of the difference Δx is compared with an absolute value of the difference Δy in order to determine whether a stair-shaped irregularity of the contour or the contour in the horizontal direction (in the x-axis direction) or in the vertical direction (in the y -Axis direction) is given.

A case will now be described in which a stair-shaped irregularity is removed from an outline part shown in Fig. 4A to smooth the outline part. In this case, the slope of the outline is between 0 ° and 45 ° with respect to the horizontal direction (the x-axis direction), the absolute value of the difference Δx is greater than that of the difference Δy, and the step-shaped "alienation" lies in the vertical direction ( in the x-axis direction). Therefore, a determination is made in step S 3 so as to carry out steps S 4 to S 17 , which are shown in FIG. 2A. In step S 4 , an inclination of the outline is calculated by using a formula: Δ = Δy / Δx in the present case. Steps S 3 and S 4 are carried out by means of the part 2 determining the inclination, as described above.

Next, in a step S 5, the facility coordinates Xs of the starting point are compared with the coordinate Xe of the ending point. If Xe is greater than Xs, ie the slope of the outline is between 0 ° and + 45 ° with respect to the horizontal direction, then an increment "a" of a variable X is set to 1 in step S 6 . If Xe is less than Xs, ie the inclination of the outline is between 0 ° and -45 ° with respect to the horizontal direction, then in step S 7 the increment "a" at variable X is set as -1. After this increment "a" is thus determined at the variable X, in step S 8, a length count L of the above-described point count part 3 is set to zero "0" as the initial value, and the variable X is set to "Xs as the initial value "the set-up coordinate of the starting point. The length count L of the point counting part 3 is provided in this case to count points in the horizontal direction. The steps S 9 to S 15 in FIG. 2a described below are carried out by means of the point counting part 3 described above and shown in FIG. 1.

Next, it is determined at a step S9 whether or not the variable X is equal to the coordinate "Xe" is the endpoint. If the variable X is not equal to the value "Xe", the subsequent steps S 10 to S 17 are carried out repeatedly. In step S 10 , the value of the coordinate Y 1 with respect to the variable X and the value of Y 2 with respect to the variable (X + a) are calculated. In this case, the values of Y 1 and Y 2 are determined as follows:

Y 1 ≡ Δ (X- xs) + ys
Y 2 ≡ Δ (X + a-xs) + ys (1)

At step S 11 , it is determined whether Y 2 for (X + a) is Y 1 for X. When Y 2 is Y 1 , it means that the outline in a range between X and (X + a) is parallel to the horizontal direction (the y-axis direction), and the device coordinate Y 2 remains with (X + a) seen from the coordinates Y 1 , unchanged with respect to X. Thus, in step S 12, the length count L is incremented by 1 to (L + 1), and the variable X is incremented by "a" to (X + a). Steps S 9 to S 11 are repeated until it is decided in step S 11 that Y 2 is not equal to Y 1 ; the number of consecutive horizontal dots are counted as the length count L when the device coordinate Y 2 is first changed from Y 1 . On the other hand, if it is decided at step S 11 that Y 2 is not equal to Y 1 , that is, the value of the facility coordinate Y 2 with respect to the variable (X + a) is different from the value with the coordinate Y 1 with respect to the variable X, then at Step S 13 generates such successive points in a binary data output device by a length which is equivalent to the length count L supplied from the point count part 3 when Y 2 is changed from Y 1 by the variable X which is in a corresponding value has been changed.

In step S 14 , it is determined whether the length count L is greater than a predetermined length Lref, which may be 4, for example. If the length count L is not greater than the predetermined length Lref, then at a step S 15 No, that is carried out "counter-alienation process", for the reason since the inclination of the outline in this case, is large enough to conclude the outline is already visually smoothed, and a "counter-alienation process" (step S 16 ) need not be carried out in order to eliminate a stair-like irregularity. At step 15 , the facility coordinate Xs of the starting point is incremented to (X + a) as the initial value, and the value of the variable X is changed to Xs. The steps S 9 to S 14 described above are then repeated with respect to a next area of the outline, starting from the reset position (X + a) of the variable X.

On the other hand, if it is found at step S 14 that the length count L when the device coordinate is changed first is larger than a predetermined length Lref (for example, equal to 4), the "counter-alienation process" (step S 16 ) is performed. In this case, the slope of the outline in this area is small enough, and it is decided that there is a stair-shaped irregularity in the area of the vertical direction (the y-axis direction), and the "counter-alienation process" has to be performed to make a visual to produce smoothed outlines. After the "counter-alienation process" (step S 16 ), the same procedure as above in step S 15 is carried out in step S 17 ; then steps S 9 to S 16 are repeated.

FIG. 5 shows an example of a correction dot pattern to explain the "counter-alienation process" which is carried out in a step S 16 of the procedure shown in FIG. 2A. This correction dot pattern is added to the outline of the image, as shown in Fig. 4A, to produce a visually smoothed outline. The correction dot pattern with a number of sets or groups of dots CP 1 to CP 6 , as indicated by shading in Fig. 5, is generated by the "counter-alienation process" shown in Fig. 3. These groups of points contain, for example, a first group of three points (CP 1 , CP 2 , CP 3 ) with a starting point CP 1 at a position which is indicated by coordinates (Xs + L-2 × 3, Y 2 ), and with end point CP 3 at a point indicated by coordinates (Xs + L-2 × 3 + 2, Y 2 ), a second group of two points CP 4 , CP 5 with a starting point CP 4 , which at (Xs + L-2 × 3-2 × 2, Y 2 ) is arranged, and with an end point CP 5 , which at (Xs + L × 2 × 3-2 × 2 + 1, Y 2 ) and with an end point CP 6 , which is located at (Xs + L-2 × 3-2 × 2-2 × 1, Y 2 ) as shown in FIG. 5. These groups of points in the correction points are determined in a prescribed manner depending on the count length L described above. That is, the starting point CP 1 of the first group (CP 1 , CP 2 , CP 3 ) is apart from the end position (Xs + L) of the outline by "-2n" (in this case n = 3) along a horizontal line at a Y device coordinate which is equal to Y 2 . The starting point CP 4 of the second group (CP 4 , CP 5 ) is arranged apart from the end position (Xs + L) by "-2n-2 (n-1)" along the horizontal line at Y 2 . The end point CP 6 of the correction points is arranged apart from the end position (Xx + 1) by "-2n-2 (n-1) -2 (n-2)" along the horizontal line at Y 2 . Thus, as shown in Fig. 4B, the number of sets or groups of correction points are arranged on the outline so that the first group of points, the second group of points and the final point are set at predetermined intervals, and Both the number of points contained in the respective groups of correction points and the values of the predetermined intervals between different groups of correction points are changed in an increasing sequence from the central point of the outline to its end point. These numbers and values are both previously set to 1, 2,. . . (n-1), n from the central position (Xs + L / 2, Y 2 ) of the outline to the end position (Xs + L, Y 2 ) previously set.

The integer "n" described above is represented by the Length value L shown as follows:

L / 2 (n + 1) n (2)

In this Eq. (2) n is the maximum integer which is given by Eq. (2) is shown. For example, if the length count L is 24, as in the case of FIG. 5, n is equal to or greater than 3.

In particular, in a step T 1 of the "counter-alienation process" shown in FIG. 3, the above integer "n" is replaced by the following Eq. (3) determines which is easily derived from Eq. (2) can be obtained.

According to Eq. (3) the integer "n" can be determined based on the value of the length count L, ie by subtracting 2 from the value of a square root of (4 + 8L) and dividing the value of the resulting difference by 4 and by rounding the value of the resulting quotient to an integer such as the integer "n" described above. In the case of FIG. 5, the length count L is 24 and the integer "n" is 3.

In a step T 2 , an absolute value of the x coordinate difference Δx is compared with an absolute value of the y coordinate difference Δy. Since the absolute value of the coordinate difference Δx in the present case is greater than that of the coordinate difference Δy, as shown in FIG. 4A, steps T 3 to T 9 are carried out next. If this is not the case, then another procedure is selected in accordance with steps T 11 to T 17 .

In a step T 3 , the value of an X coordinate of a starting point for a first group of points is determined, which have been generated in the correction point pattern as follows:

X = Xs + a (L - 2n) (4)

In a case shown in Fig. 5, the value of an X coordinate is equal to (Xs + L-2 × 3). In step T 4 , the value of a first counter i is set to 1 as the initial value, so that the points of the first group (CP 1 , CP 2 , CP 3 ) are obtained in succession. At step T 5 it is determined whether the value of the first counter i is greater than the value of n. If the value of the first counter i is not greater than the value of n, then the value of a second counter j is set to 1 as the initial value in a step T 6 . In a step T 7 , it is checked whether the value of the second counter j is greater than the value of the first counter j. If the value of the second counter j is not greater than the value of the first counter i, then a point CP 1 at a position (X, Y 2 ) is assumed in a step T 8 , the value of the variable X is increased to (X + a) reset and the value of the second counter j is incremented by 1. Step T 7 is repeated until the value j is greater than the value i. If in step T 7 described above the value j is greater than the value i, then in step T 9 the value of the variable X is reset to (X + ai) and the value i is incremented by 1. Steps T 5 to T 9 are repeated until the value i is greater than the value n.

For example, in the case shown in Fig. 5, the value of the X coordinate is equal to (Xs + L-2 × 3-1), and a next point CP 2 is made at (X, Y 2 ) on the outline, which one is closest to point CP 1 , steps T 5 to T 8 being carried out first. A next point CP 3 (X, Y 2 ) is then made on the contour line which is closest to point CP 2 , steps T 5 to T 8 being carried out again. After the first group of correction data (CP 1 , CP 2 , CP 3 ) is generated in the case shown in FIG. 5, the value i is increased to 4. Then in step T 5, the value i is greater than the value n, and the procedure with regard to the first group of correction points (CP 1 , CP 2 , CP 3 ) is ended.

Next, the same procedure as described above is repeated so that the second group of correction data (CP 4 , CP 5 ) and the final group of correction points CP 6 are made on the outline. As a result, the outline of the image shown in Fig. 4A can be corrected with a stair-shaped irregularity or "alienation" in the outline shown in Fig. 4B, which is visually smoothed.

If the slope of an outline is either between 45 ° and 90 ° or between -45 ° and - 90 ° with respect to a horizontal direction (the x-axis direction) and a stepped irregularity or "alienation" in the horizontal direction (in the x-axis direction) is present, steps S 21 to S 34 shown in FIG. 2B are carried out instead of steps S 4 to S 17 described above with reference to FIG. 2A. The "counter-alienation process" is carried out with the steps T 11 to T 17 shown in FIG. 3 instead of the steps T 3 to T 9 described above. A procedure similar to the procedure described above is carried out, so that this need not be described again.

As described above, a multi-level sound, which has been used in conventional technology of the present invention is not for smoothing an outline or an outline of an image. It also becomes a complicated one Control technology, which was previously used for conventional Facility has been required at the image processing facility no longer needed according to the invention. According to the invention, a step-like irregularity can or "alienation" of a contour part of an image be eliminated so that a visual smoothed contour in the contour part of the image is generated. The number of points which has been indicated by the count length L, which according to the inclination of a contour or an outline is counted, it is determined, then a correction dot pattern based on the number of points found, and the outline or contour of a staircase Irregularity is corrected using the correction dot pattern is added to the outline or correction, whereby then a visually smoothed contour or a corresponding one Outline of the image is generated.

Claims (7)

1. Image processing device, which has a detection device ( 2 ) for determining an inclination of an outline or a contour of image data stored in a memory, the contour or the outline being inclined with respect to a predetermined direction, and for the determined inclination of the contour or of the outline, and has a point counter ( 3 ) for selectively calculating the number of consecutive points aligned along a horizontal line and ending with a change in a vertical direction or the number of consecutive points passing along are aligned with a vertical line and end with a change of a point in the horizontal direction in accordance with the determined inclination, which have been supplied by the detection device ( 2 ), and in order to supply the calculated number and the number of successive points to an output memory, characterized in that the image processing device comprises a correction device ( 4 ) for generating, on the basis of the calculated number of successive points supplied by the point counting device ( 3 ), a number of correction points which extend along a new horizontal line which extends in the vertical direction a point has been changed from the horizontal line, or is arranged along a new vertical line which has been changed in the horizontal direction by one point from the vertical line, and to supply the number of correction points to the output memory so as to have a visually smoothed one Generate contour or outline of the image data in the output memory. 2. Device according to claim 1, characterized in that the correction device ( 4 ) generates the number of correction points, which have a number of groups of points, which are each arranged either along the changed horizontal line or along the changed vertical line, both the number Points contained in each of these groups of points and the values of intervals between different groups of points are changed in increasing order from a central point of the successive points to their end point, the number of points as well as the value of the intervals starts from 1. 3. Device according to claim 1, characterized in that the multitude of correction points which have been fed to the output memory, the same resolution like the consecutive points that have the output memory have been supplied. 4. Device according to claim 1, characterized in that the correction device ( 4 ) generates the plurality of correction points after checking that the calculated number of successive points is greater than a predetermined integer. 5. Device according to claim 1, characterized by an output device for outputting the successive points which have been stored in the output memory after the calculated number has been fed from the point counting device ( 3 ), and for outputting the plurality of correction points which are stored in the output memory. 6. Device according to claim 1, characterized by a coordinate recording device ( 1 ) to record two sets or groups of x and y coordinates of a starting point and an end point, which are contained in the outline or contour line, from the image data, which are stored in the memory, and in order to feed the detection device ( 2 ) to two groups or sets of coordinates of the starting point and of the end point in which the two groups or sets of x and y coordinates are transformed. 7. Device according to claim 6, characterized in that the coordinate recording device ( 1 ) transforms the two groups or sets of x and y coordinates obtained into two groups or sets of coordinates of the output device, the coordinates of the output device in a whole Number can be expressed and have a resolution which is appropriate to that of the output memory.