JP3633689B2 - Image processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing method, and more particularly, to an image processing method in which the density can be set to an optimum value when a space generated between each original pixel is interpolated with an enlarged pixel in accordance with an enlargement magnification. .
[0002]
[Prior art]
In the enlargement processing in the conventional image processing apparatus, a simple enlargement method that repeatedly uses the same pixel the number of times corresponding to the enlargement magnification when interpolating the space created between each original pixel according to the enlargement magnification with the enlargement pixel is adopted. It had been. However, in such a simple enlargement method, there is a problem that not only the resolution is deteriorated but also the image quality is greatly deteriorated due to jaggy in the shaded portion. Therefore, for example, in Japanese Patent Application Laid-Open No. 62-145482, the internal division ratio relating to the position of each newly generated enlarged pixel in the quadrangular region having the four original pixels arranged in a matrix as the apexes is calculated. A four-point interpolation process has been proposed in which a pixel position is obtained as a reference and the density of each enlarged pixel is determined based on the internal ratio and the density of each of the four vertex pixels.
[0003]
[Problems to be solved by the invention]
FIG. 21 is a diagram for clarifying the problems of the four-point interpolation process. Now, paying attention to the four original pixels A1, A2, A3, A4 shown on the left side of the figure,About length3x magnification(Hereinafter the same)Then, as shown in the right side of the figure, 12 pixels (enlarged pixels) indicated by “Δ” are newly generated. Here, in the above-described conventional four-point interpolation processing, each enlarged pixel “Δ” is affected by all the original pixels A1 to A4, so each of the enlarged pixels “1”, A2 and A3 in the region 21a close to the high density original pixels A1, A2 and A3. The density of the enlarged pixel is set to a relatively high density, but each enlarged pixel in the region 21b close to the low density original pixel A4 is strongly affected by the original pixel A4, and is therefore set to a relatively low density. That is, as indicated by the broken line arrow in the figure, the density of the enlarged pixel “Δ” gradually decreases from the original pixel A1 toward A4.
[0004]
Therefore, when the original pixels A2 and A3 constitute the shaded portion of the character outline, the outline is blurred because the pixel density of the region 21a is low in the enlarged image. Similarly, when the original pixels A1, A2, and A3 constitute a right-angle portion of the character outline, the right-angle portion becomes dull.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image processing method that solves the above-described problems of the prior art and prevents blurring in a hatched portion of a character outline and blunting in a right angle portion in an enlarged image. .
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, in an image processing method for enlarging a processing target image at an arbitrary magnification, and interpolating a space generated between each original pixel with an enlarged pixel according to the enlargement magnification, The target image has a size corresponding to 2 original pixels × 2 original pixels.WindowsAt each scanning position.WindowsIf the density distribution of the four original pixels is detected and only the density of the three original pixels is equal to or higher than the predetermined value, the density of the enlarged pixel generated in the triangle having the three original pixels as vertices is determined as the predetermined density. It is characterized in that it is set to be higher than the value.
[0007]
According to the above-described configuration, the density of all the enlarged pixels that are generated on the line connecting two pixels facing each other and are the outline of the enlarged image among the three original pixels having the density equal to or higher than the predetermined value are all the predetermined values. Since the above density is set, blurring of the character outline is prevented.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. 1 and 2 are diagrams schematically showing the operation of one embodiment of the present invention. In the present embodiment, as shown in FIG. 2, at least the main part of the input enlargement target image 1 (22 pixels × 22 pixels) has a size corresponding to 2 original pixels × 2 original pixels.Windows20 to scan from the upper left corner to the lower right corner.WindowsThe density distribution of the original pixel in 20 is detected. And for exampleWindowsIs at the scanning position indicated by reference numeral 20a, and as shown in FIG.WindowsIf the density of any three of the four original pixels A, B, C, and D in 20a (in this embodiment, the original pixels A, B, and C) is greater than or equal to a predetermined value, the three original pixels Only the density of each enlarged pixel “Δ” generated in the triangle ABC having the vertices of the pixels A, B, and C is all set to the predetermined value or more.
[0009]
According to the present embodiment, since the density of all the enlarged pixels generated on the character outline connecting the original pixels B and C is set to a density equal to or higher than the predetermined value, blurring of the character outline is prevented.
[0010]
FIG. 3 is a flowchart showing the operation of another embodiment of the present invention. In step S1, as shown by the solid line frame in FIG. 4A, a second image having a size corresponding to 4 pixels × 4 pixels at the upper left corner of the input enlargement target image 1 (22 pixels × 22 pixels).WindowsSet. In step S2, as shown in FIG.WindowsCodes A11 to A44 are assigned to the 16 pixels that fall within 10 according to their positions, and the density data a11 to a44 of the original pixels A11 to A44 are read out. In the present embodiment, it is assumed that the density data aij of each original pixel Aij is represented by 256 gradations (8-bit digital data) from 0 (white) to 255 (black).
[0011]
In step S3, as will be described in detail later, based on the respective density data a11 to a44, the secondWindowsFirst of 2 pixels × 2 pixels secured in the center of 10WindowsWhether any three of the four original pixels A22, A23, A32, and A33 in 20 form a right-angle portion of the character outline in the enlargement target image 1 is determined as follows.
[0012]
FIG. 5 shows the firstWindows20 is a diagram schematically representing four conditions in which any three of the four original pixels A22, A23, A32, and A33 in 20 are determined to constitute a right-angle portion of the character outline. It is as follows.
(1) First condition
As shown in FIG. 5A, the density of the original pixel A12 matches the density of the original pixels A22, A32, A33 and A34, and the density of the original pixel A23 and the density of the original pixel A32 match. Otherwise, it is determined that the original pixels A22, A32, A33 constitute a right-angle portion of the character outline. The “density match” referred to in this embodiment is not only when the 8-bit digital data is completely matched, but also when the upper several bits (for example, the upper 4 bits) are matched. Shall be included.
(2) Second condition
As shown in FIG. 5B, the density of the original pixel A13 matches the density of the original pixels A23, A33, A32, and A31, and the density of the original pixel A22 matches the density of the original pixel A33. Otherwise, it is determined that the original pixels A23, A33, A32 constitute a right-angle portion of the character outline.
(3) Third condition
As shown in FIG. 5C, the density of the original pixel A21 matches the density of the original pixels A22, A23, A33, and A43, and the density of the original pixel A23 and the density of the original pixel A32 match. Otherwise, it is determined that the original pixels A22, A23, A33 constitute a right-angle portion of the character outline.
(4) Fourth condition
As shown in FIG. 5D, the density of the original pixel A42 and the densities of the original pixels A32, A22, A23 and A24 match, and the density of the original pixel A22 and the density of the original pixel A33 match. Otherwise, it is determined that the original pixels A23, A22, A32 constitute a right-angle portion of the character outline.
[0013]
For example, the secondWindowsIs at the scanning position indicated by reference numeral 10 in FIG.WindowsThe density distribution of each original pixel within 10 is as shown in FIG. For this reason, the density other than the original pixels A33, A34, A43 and A44 is equal to or higher than a predetermined reference value and satisfies the condition shown in FIG.WindowsIt is determined that the three original pixels A22, A23, A32 in 20 form a right-angle portion of the character outline. The secondWindowsAre at the scanning positions indicated by reference numerals 10a, 10b, and 10c, the first condition shown in FIG. 5 (a), the second condition shown in FIG. 5 (b), and the conditions shown in FIG. 5 (c), respectively. Since the third condition is satisfied, it is determined that a right-angle portion of the character outline is formed as described above.
[0014]
If any of the above four conditions is satisfied, the process proceeds from step S3 to step S12. If any of the conditions is not satisfied, the process proceeds to step S4. FIG. 7 shows the case where any one of the four conditions is satisfied, that is, the firstWindows20 is a diagram schematically representing an interpolation method by nearest neighbor interpolation executed in step S12 when it is determined that three original pixels in 20 form a right-angle portion of a character outline. , FirstWindowsAn example will be described in which it is determined that the three original pixels A22, A23, and A32 in 20 form a right-angle portion.
[0015]
In this embodiment, the secondWindowsIn order to set the density of each enlarged pixel generated in 10 to the density of the nearest neighbor original pixel, the area after enlargement is divided into two parts in each of the main scanning direction and the sub-scanning direction, so that four areas E1 to E1. E4 is characterized in that the newly generated pixel in each area is set to the density of the original pixel included in the area.
[0016]
That is, the three enlarged pixels generated in the first area E1 including the original pixel A22 are all set to the density of the nearest original pixel A22. Similarly, all the enlarged pixels in the second area E2 including the original pixel A23 are set to the density of the original pixel A23, and all the enlarged pixels in the third area E3 including the original pixel A32 are set to the density of the original pixel A32. All the enlarged pixels in the third region E4 including the original pixel A33 are set to the density of the original pixel A33.
[0017]
If the above-mentioned interpolation method by nearest neighbor interpolation is adopted, the pixels in the areas E1, E2, and E3 all have high density, and all the pixels in the area E4 have low density. The enlarged area becomes a right angle even after enlargement, and “blunting” in that part is prevented.
[0018]
On the other hand, if the determination in step S3 is negative, in step S4, the first timeWindowsAmong the four original pixels A22, A23, A32 and A33 in 20, the opposing pixels (original pixels A22 and A33 or original pixels A23 and A32) constitute the shaded portion of the character outline in the enlargement target image 1 It is determined whether or not there is.
[0019]
FIG. 8 is a diagram showing four conditions in which it is determined that any of the opposing pixels constitutes the shaded portion of the character outline. Each condition is as follows.
(1) First condition
As shown in FIG. 8A, when the density of the original pixel A22 is equal to or higher than the predetermined value, the densities of the original pixels A22, A32, and A33 are equal, and the densities of the original pixels A23 and A32 are not equal, It is determined that the pixels A22 and A33 constitute the shaded portion of the character outline.
(2) Second condition
As shown in FIG. 8B, when the density of the original pixel A23 is equal to or higher than the predetermined value, the densities of the original pixels A23, A32, and A33 are equal and the densities of the original pixels A22 and A33 are not equal, It is determined that the pixels A23 and A32 constitute the shaded portion of the character outline.
(3) Third condition
As shown in FIG. 8C, when the density of the original pixel A22 is not less than the predetermined value, the densities of the original pixels A22, A23, and A33 are equal, and the densities of the original pixels A32 and A23 are not equal, It is determined that the pixels A22 and A33 constitute the shaded portion of the character outline.
(4) Fourth condition
As shown in FIG. 8D, when the density of the original pixel A23 is not less than the predetermined value, the densities of the original pixels A23, A22, and A32 are equal, and the densities of the original pixels A33 and A22 are not equal, It is determined that the pixels A23 and A32 constitute the shaded portion of the character outline.
[0020]
For example, the secondWindowsIf 10 is at the scanning position shown in FIG.WindowsThe density distribution of each original pixel in FIG. 10 is as shown in FIG. 5B, and the density of the original pixel A23 is equal to or higher than the predetermined value and the density of the original pixels A23, A32, and A33 is equal. A23 and A32 are determined to constitute the shaded portion of the character outline. If any of the above four conditions is satisfied, the process proceeds to step S11. If any of the conditions is not satisfied, the process proceeds to step S5.
[0021]
FIG. 10 is a diagram schematically illustrating the interpolation method dedicated to the oblique line executed in step S11. Here, it is determined that the three original pixels A22, A23, and A32 constitute the shaded part of the character outline. This will be described as an example.
[0022]
In the present embodiment, among the 12 newly generated enlarged pixels, the density of all the pixels included in the triangle obtained by connecting the three original pixels A22, A23, A32 whose density is equal to or higher than the predetermined value is calculated as described above. The density is set higher than the planned value. As a result, as shown on the right side of FIG. 10, the density of the enlarged pixels generated on the line connecting the original pixels A32 and A23 is also set to a density equal to or higher than a predetermined value, so that blurring of the character outline is prevented. It becomes like this.
[0023]
On the other hand, if the determination in step S4 is also negative, in step S5, the first is again based on the density data a11 to a44.WindowsIt is determined whether or not the four original pixels A22, A23, A32, and A33 in 20 form a character outline other than a right angle or diagonal line in the enlargement target image.
[0024]
FIGS. 11 and 12 are diagrams showing eight conditions for determining that each original pixel constitutes a character outline other than a right angle or diagonal line. In particular, FIGS. 11A to 11D show the original pixel. There are four conditions for determining that any one of the original pixels A22, A23, A32, and A33 constitutes a character outline (the determination in the subsequent step S9 is affirmative), and FIGS. Are four conditions in which it is determined that two original pixels adjacent to each other in the scanning direction among the original pixels A22, A23, A32, and A33 form a character outline (determination in step S9 is negative).
(1) First condition
As shown in FIG. 11A, the densities of the original pixels A22, A32, and A33 are all less than the predetermined value, and the density of the original pixel A23 is equal to or higher than the predetermined value, and the value is adjacent to the main scanning direction. When it is equal to one of the matching original pixel A24 and the adjacent original pixel A13 in the sub-scanning direction, it is determined that the original pixel A23 forms a character outline.
(2) Second condition
As shown in FIG. 11B, the densities of the original pixels A23, A33 and A32 are all less than the predetermined value, and the density of the original pixel A22 is equal to or higher than the predetermined value, and the values are adjacent in the main scanning direction. If the matching original pixel A21 is equal to either the adjacent original pixel A12 or the adjacent original pixel A12 in the sub-scanning direction, it is determined that the original pixel A22 forms a character outline.
(3) Third condition
As shown in FIG. 11C, the densities of the original pixels A22, A23, and A33 are all less than the predetermined value, and the density of the original pixel A32 is equal to or higher than the predetermined value, and the value is adjacent to the main scanning direction. If the matching original pixel A31 is equal to one of the adjacent original pixel A42 in the sub-scanning direction, it is determined that the original pixel A32 forms a character outline.
(4) Fourth condition
As shown in FIG. 11D, the densities of the original pixels A23, A22, and A32 are all less than the predetermined value, and the density of the original pixel A33 is equal to or higher than the predetermined value, and the value is adjacent to the main scanning direction. When it is equal to one of the matching original pixel A34 and the adjacent original pixel A43 in the sub-scanning direction, it is determined that the original pixel A33 forms a character outline.
(5) Fifth condition
As shown in FIG. 12A, the density of the original pixel A22 is equal to or higher than a predetermined value, the density of the original pixel A22 and the density of the original pixel A32 match, and the density of the original pixel A23 and the original pixel A33. If the density of both is less than the predetermined value, it is determined that the original pixels A22 and A32 constitute a character outline.
(6) Sixth condition
As shown in FIG. 12B, the density of the original pixel A22 is equal to or higher than a predetermined value, the density of the original pixel A22 and the density of the original pixel A23 match, and the density of the original pixel A32 and the original pixel A33 If both the density and the density are less than the predetermined value, it is determined that the original pixels A22 and A23 constitute a character outline.
(7) Seventh condition
As shown in FIG. 12C, the density of the original pixel A23 is equal to or higher than a predetermined value, the density of the original pixel A23 and the density of the original pixel A33 match, and the density of the original pixel A22 and the original pixel A32 When both the density and the density are less than the predetermined value, it is determined that the original pixels A23 and A33 constitute a character outline.
(8) Eighth condition
As shown in FIG. 12D, the density of the original pixel A32 is equal to or higher than a predetermined value, the density of the original pixel A32 and the density of the original pixel A33 match, and the density of the original pixel A22 and the original pixel A23. If the density of both is less than the predetermined value, it is determined that the original pixels A32 and A33 constitute a character outline.
[0025]
For example, the secondWindowsIf 10 is at the scanning position shown in FIG.WindowsThe density distribution of each original pixel in FIG. 10 is as shown in FIG. 7B. At this position, the densities of the original pixels A22, A23 and A33 are all less than the predetermined value, and the density of the original pixel A32 Is equal to or greater than a predetermined value, and the value is equal to the adjacent original pixel A42 in the sub-scanning direction. Accordingly, since the original pixel A32 satisfies the condition described with reference to FIG. 11C, it is determined that the original pixel A32 constitutes a character outline, and the process proceeds to step S10.
[0026]
FIG. 14 is a diagram schematically illustrating the interpolation method executed in step S10. Here, a case where only the original pixel A32 forms a character outline will be described as an example.
[0027]
The interpolation method of this embodiment is a modification of the nearest neighbor interpolation method described with reference to FIG. 7 and divides the enlarged region into four regions E1 to E4 as described above. The original pixels generated in the first, second, and fourth regions including the three original pixels A22, A23, A33 determined not to constitute the character outline are the original pixels A22, A23, A33, respectively. Although the density is set, the original pixels generated in the third area E3 including the original pixel A32 determined to constitute the character outline use the other original pixels A22, A23, and A33 except the original pixel A32. Then, the concentration is set by nearest neighbor interpolation. As a result, in the third region E3, the density of the other three enlarged pixels excluding the original pixel A32 is less than the planned density.
[0028]
On the other hand, the secondWindowsIs at the scanning position indicated by reference numeral 10 in FIG.WindowsThe density distribution of each original pixel within 10 is as shown in FIG. 10B, and the density distribution at this position satisfies the conditions described with reference to FIG. Therefore, the firstWindowsIt is determined that the two original pixels A22 and A32 adjacent in 20 form a character outline other than a right angle and a diagonal line, and the process proceeds to step S12. The secondWindowsIs set at the positions indicated by reference numerals 10a, 10b, and 10c in FIG.WindowsIt is determined that an original pixel having a density equal to or higher than a predetermined value within 20 forms a character outline other than a right angle and a diagonal line.
[0029]
FIG. 15 is a diagram schematically representing the interpolation method executed in step S12 when it is determined in step S9 that there is not one original pixel constituting the character outline.
[0030]
Also in this embodiment, among the 12 newly generated enlarged pixels, the regions E3 and E4 including the two original pixels A32 and A33 whose density is equal to or higher than the predetermined value are set to the densities of the original pixels A32 and A33, respectively. The regions E1 and E2 including the two original pixels A22 and A23 whose density is less than the predetermined value are set to the densities of the original pixels A22 and A23, respectively. The firstWindowsIf the determination of step S5 is negative as in the case where the density of all the original pixels in 20 is equal to or higher than the predetermined value or less than the predetermined value, the interpolation process by the conventional linear expansion between four points is executed in step S6. .
[0031]
When any of the interpolation processes is completed as described above, in step S7, the current secondWindows10 is determined whether it is located in the lower right corner. If it is located in the lower right corner as shown in FIG. 17, the process is terminated. If it is located in any other position, the position is determined in step S8. Depending on the secondWindowsMove 10 position. For example, as shown by the broken line frame in FIG.WindowsIf 10 is not located at the right end, it is moved by one pixel in the main scanning direction. Further, when it is located at the right end as shown by the solid line frame in FIG. 18, it is shifted by one pixel in the vertical direction and moved to the left end in the horizontal direction. In the same manner, the secondWindowsEach of the above determinations is repeated while sequentially scanning in the main scanning direction and the sub-scanning direction.
[0032]
By the way, in the above-described embodiment, the original pixel represented by “●” or “◯” in FIG.In lengthWhen the enlargement process of 4 times is executed, for example, the first surrounded by the original pixels A22, A23, A32, A33WindowsSince the condition shown in FIG. 12D is satisfied at 20, the nearest neighbor interpolation method is applied at step S12. For this reason, all the enlarged pixels in the region 19 are set to a density equal to or higher than a predetermined value. However, it is desirable that all the enlarged pixels in the area 19 are set to be less than or equal to the predetermined value. Therefore, in such a case, the nearest neighbor interpolation may be applied based only on the remaining pixels (original pixels A22, A23) excluding the original pixels A32, A33. In this way, as shown in FIG. 20, all the enlarged pixels in the region 19 are set to a density less than the predetermined value.
[0033]
In each of the embodiments described above, an example in which interpolation processing is performed by regarding a pixel having a density equal to or higher than a predetermined value as a character pixel is described. The same can be applied to the interpolation processing in the case of viewing.
[0034]
【The invention's effect】
As described above, according to the present invention, the following effects are achieved.
(1) According to claim 1, 2 original pixels × 2 original pixelsWindowsAmong the three original pixels whose density is equal to or higher than the predetermined value, the density of the enlarged pixels newly generated on the character outline connecting the two original pixels facing each other is set to be higher than the predetermined value. Blur is prevented and an enlarged image faithful to the original image can be obtained.
(2) According to claim 2, 2 original pixels × 2 original pixelsWindows3 original pixels whose density is more than the expected valueSince the density of each enlarged pixel is set to the density of the nearest neighbor pixel, the dullness at the right angle part of the character outline is prevented, and an enlarged image that is faithful to the original picture is created. It will be obtained.
(3) According to claim 3, 2 original pixels × 2 original pixelsWindows3 original pixels whose density is more than the expected valueAmong the two original pixels that face each other, the shaded area of the character outline Since the density of each enlarged pixel generated in the triangle with the three original pixels as vertices is set to a predetermined value or more when the minutes are configured, the blur of the character outline is prevented and the enlargement is faithful to the original image. An image can be obtained.
(4) According to claim 4, 2 original pixels × 2 original pixelsWindowsAt the innerIn the scanning directionIf two adjacent original pixels constitute a character outline, the density of each enlarged pixel is set to the density of the nearest original pixel, so that the outline of the character outline is prevented and an enlarged image faithful to the original image is obtained. Be able to.
(5) According to claim 5, 2 original pixels × 2 original pixelsWindowsIf only one original pixel constitutes the character outline, the density of each enlarged pixel is set to the density of the nearest original pixel, so that the outline of the character outline is prevented and an enlarged image faithful to the original picture is displayed. It will be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an operation of an embodiment of the present invention.
FIG. 2 is a diagram for explaining the operation of an embodiment of the present invention.
FIG. 3 is a flowchart showing the operation of another embodiment of the present invention.
[Fig. 4]WindowsIt is a figure for demonstrating the structure of these.
FIG. 5 is a diagram schematically showing conditions for determining that the original pixel constitutes a right-angle portion of the character outline.
FIG. 6 is a diagram illustrating a case where it is determined that an original pixel constitutes a right-angle portion of a character outline.
FIG. 7 is a diagram schematically showing an interpolation processing method executed when it is determined that the original pixel constitutes a right-angle portion of the character outline.
FIG. 8 is a diagram schematically showing a condition for determining that an original pixel constitutes a hatched portion of a character outline.
FIG. 9 is a diagram illustrating a case where it is determined that an original pixel constitutes a shaded portion of a character outline.
FIG. 10 is a diagram schematically illustrating an interpolation processing method that is executed when it is determined that three original pixels constitute a shaded portion of a character outline.
FIG. 11 is a diagram schematically illustrating a condition for determining that one original pixel constitutes a character outline.
FIG. 12 is a diagram schematically showing a condition for determining that two original pixels constitute a character outline.
FIG. 13 is a diagram showing a case where it is determined that one original pixel constitutes a shaded portion of a character outline.
FIG. 14 is a diagram schematically illustrating an interpolation processing method executed when it is determined that one original pixel constitutes a character outline.
FIG. 15 is a diagram schematically illustrating an interpolation processing method executed when it is determined that two original pixels form a character outline.
FIG. 16 is a diagram illustrating a case where it is determined that two original pixels constitute a character outline.
FIG. 17WindowsIt is the figure which showed this scanning method.
FIG. 18WindowsIt is the figure which showed this scanning method.
FIG. 19 is a diagram illustrating an interpolation result according to another embodiment.
FIG. 20 is a diagram illustrating an interpolation result according to another embodiment.
FIG. 21 is a diagram showing a conventional four-point interpolation method.
[Explanation of symbols]
1 ... enlargement target image, 10 ... firstWindows20 ... 1stWindows

Claims (1)

In an image processing method for enlarging a processing target image at an arbitrary magnification, and interpolating a space generated between each original pixel according to the enlargement magnification with an enlarged pixel,
Scan the image to be enlarged in a window corresponding to 2 original pixels × 2 original pixels,
Detecting the density distribution of the four original pixels in the window at each scanning position;
If only the density of the three original pixels is equal to or higher than the predetermined value, the density of the enlarged pixel generated on each line including the outline connecting the three original pixels in the triangle having the three original pixels as vertices An image processing method, wherein the image processing method is set to be equal to or greater than a value.

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