JPH06261206A - Image processor - Google Patents

Abstract

PURPOSE:To enable the limit elimination of the set range of magnification by executing a sub-scanning variable power preceding to a main-scanning variable power. CONSTITUTION:Preceding to a main scanning variable power, an interpolation operation is performed in a sub-scanning variable power part 1 by using a line buffer 3 and an N times sub-scanning variable power is performed in a sub-scanning variable power part 1. An L times main-scanning variable power is performed for this image information for which the variable power is performed in a main scanning variable power part connected with a latch circuit 4 in the same way. Thus, because the number of main scanning picture element is not increased even if the sub-scanning variable power is performed, as compared with the case where the main scanning variable power is preceding, the capacity of the line buffer can be reduced by the number of picture element of LXN-L=L (N-1) and the limit of the set limit of magnification due to mechanical factors can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus for performing main scanning scaling and sub scanning scaling by image processing.

[0002]

2. Description of the Related Art Image data scaling processing (also referred to as resolution conversion) is usually divided into two systems, a scaling processing in the main scanning direction and a scaling processing in the sub-scanning direction. . And, conventionally, in the digital copying machine,
The main scanning scaling is performed by the image processing circuit, while the scaling processing in the sub-scanning direction is performed by switching the speed of the scanner according to the magnification.

[0003]

To perform the variable magnification processing in the sub-scanning direction by switching the scan speed of the scanner, the scan speed is set to 1 / N times the magnification N (magnification 0.25). In that case, the scan speed must be four times higher), and the motor power must be increased. Also, when the set value of the magnification is a value that is significantly different from the unity magnification of 1, for example, the magnification is 0.0
At 5 times reduction, the scan speed becomes 20 times,
This not only increases the motor power remarkably, but also causes the mechanical mechanism to reciprocate within a limited space, resulting in large impulses and shocks, which is usually not possible. When the magnification is 20 times, the scan speed is 0.05.
It is not possible to control the mechanical mechanism of the scanner smoothly at such an ultra-low speed with respect to the speed at the same magnification, without special consideration such as using a stepping motor.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an image processing apparatus for performing main scanning scaling and sub-scanning scaling by image processing. It is characterized in that the sub-scanning variable magnification processing is performed prior to the double processing.

[0005]

By performing the scaling process in the digital copying machine by performing only the main scanning scaling and the sub-scanning scaling only with the image processing, the limit of the range of the scaling factor caused by mechanical factors is solved. To do.

[0006]

Various methods of scaling have been proposed, but in the embodiments of the present invention described below, the pixel density at a required pixel position is obtained by linear approximation from the data of two adjacent pixels. And

FIG. 2 is a diagram for explaining the operating principle of the present invention. In FIG. 2, the vertical axis represents the density value, the horizontal axis represents the pixel position, and pixel positions a ₁ , b _{1 in the} main scanning direction and Interpolation position Y
Image density interpolation position Y ₁ to be predicted than ₁ (Y) is calculated from the following equation. Density (Y) = density (a) + {density (b) -density (a)}
Xx Here, x indicates the distance from the pixel position a ₁ to the pixel position Y ₁ , and is a quantized decimal number of 1 or less. Further, the distance from the pixel a ₁ to the pixel b ₁ is 1.

When the magnification N is determined, the pitch of the interpolation position is calculated as follows. Pitch = 1 / N The interpolation position can always be expressed as Yn = Y _n-1 + pitch = Y _n-1 + 1 / N. When the interpolation position Yn is determined, pixel data is similarly obtained from the data of two adjacent pixels sandwiching Yn. Density (Y) = density (a) + {density (b) -density (a)}
A general formula of xx is calculated.

FIG. 1 is a block diagram of a scaling unit based on the above-described algorithm. In the figure, 1 is a sub-scanning scaling unit, and 2 is a main-scanning scaling unit. First, sub-scanning scaling is performed. Here, in the sub-scanning scaling, one line buffer 3 is used to calculate interpolation data at the interpolation position Yn from two adjacent pixel data A and B in the sub-scanning direction, and the result is changed to the main scanning scaling. Double latch 4
Output to. In the main scanning magnification changing unit 2, interpolation data Y in the main scanning direction is calculated from the inputs a and b before and after the latch, that is, the density data of two adjacent pixels a and b in the main scanning direction, and the result is calculated. Output.

Although an example in which the interpolation data is calculated from the data of two adjacent pixels has been described above, the number of adjacent pixels can generally be expanded to N pixels, and the larger N is, the more complicated interpolation is performed. The accuracy of the interpolation value is improved.

Next, the reason why the sub-scan calculation is executed before the main-scan calculation processing will be described. 3A and 3B show respective sizes of input and output of an image. FIG. 3A is an input image for scaling and FIG. 3B is an output image. In consideration of independent scaling, the scaling value is set to N for the main scanning scaling value and M for the sub-scanning scaling value. Therefore, if the number of pixels before scaling is L and the number of lines is K, the number of pixels after scaling is L × N and the number of lines is K × M.

In FIG. 4, an input image (a) is first subjected to main scanning scaling (b) and then subjected to sub scanning scaling (c).
The following shows the case. In this case, the number of pixels in the main scanning first increases to L × N due to the main scanning scaling (N is of course N.
> 1 magnification). Therefore, the following line buffer for sub-scanning scaling corresponds to the line buffer 3 in FIG. 1, but it is necessary to secure a value determined by the number of pixels L × N as the memory capacity of this line buffer, and the magnification The number of pixels determined by the maximum value of N must be considered as the maximum number of pixels.

FIG. 5 is a diagram showing the method of the present invention in which the sub-scanning scaling (c) is first performed on the input image (a) and then the main-scanning scaling (b) is performed. The capacity of the line buffer in this method is determined by the number of pixels L in the main scanning direction of the input because the number of pixels in the main scanning does not increase even if the sub scanning scaling (c) is performed. The capacity of the line buffer 3 can be reduced by the number of pixels L × N−L = L (N−1), as compared with the case where the scaling (b) is performed first. Although the embodiment in which the scaling is performed based on the density data of the two adjacent pixels has been described above, the same idea is applied to the case of the adjacent N pixels, and in the scaling, first, the sub-scanning scaling is performed. It can be seen that the load on the hardware can be reduced by performing the main scanning scaling after that.

In addition to the above, the digital copying machine, the DTP
The present invention is not limited to the above example, and the description is based on the magnification conversion in the system. FAX (300 dpi)
It can be easily understood that the present invention can be applied to the resolution conversion that occurs when the data of (1) is printed by a printer (400 dpi).

[0015]

As described above, during the enlargement / reduction, the main scanning magnification is performed after the sub-scanning magnification, so that the memory used can be reduced. Also, in the scaling process in a digital copying machine,
Since both the main-scanning scaling and the sub-scanning scaling are executed only by the image processing, it is possible to eliminate the limit of the setting range of the magnification caused by a mechanical factor. As for the mechanical operation of the scanner, variable magnification processing can be performed only by the standard operation of 100% normal size, and at the same time, the motor power can be set by the power only at the normal size, which enables downsizing of the motor. Further, the motor speed switching circuit is not required, and the mechanism control and the structure can be simplified.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of a block diagram suitable for executing image processing according to the present invention.

FIG. 2 is a diagram for explaining the operation principle of the present invention.

FIG. 3 is a diagram for explaining an example of image processing (image input and output sizes).

FIG. 4 is a diagram for explaining an example of image processing (main scanning scaling → sub scanning scaling).

FIG. 5 is a diagram for explaining an example of image processing according to the present invention (sub-scanning magnification-> main scanning magnification).

[Explanation of symbols]

1 ... Sub-scanning scaling unit, 2 ... Main scanning scaling unit, 3 ... Line buffer, 4 ... Latch circuit.

Claims (1)

[Claims] 1. An image processing apparatus for performing main-scanning scaling and sub-scanning scaling by image processing, wherein during enlargement scaling, the sub-scanning scaling is performed prior to the main-scanning scaling. Image processing device.