JP2858661B2 - Image processing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus having an image enlargement function and used for a facsimile, a printer, an image scanner, and the like. The present invention relates to an image processing method for enlarging image data in a predetermined scanning line direction while reading.

[Prior art] Conventionally, in a facsimile or an image scanner, image data read by an image sensor may be enlarged to a predetermined size and transmitted to the other receiver. In some cases, image data expanded in a memory is enlarged to a predetermined size and output to the print engine side. As a method of enlarging such image data to a predetermined size, for example, image data in a predetermined scanning line direction is converted to a predetermined image clock. In an apparatus that performs image processing while alternately writing and reading data to and from a plurality of line buffers based on a frequency, it is possible to repeatedly read out image data at an interval corresponding to a predetermined magnification during the reading. To substantially increase the number of images, There are methods for expanding. In an apparatus for performing image processing while alternately writing and reading image data in a predetermined scanning line direction to and from a plurality of line buffers based on a predetermined image clock frequency, There is also a method of enlarging image data by making the clock frequency at the time (n) different from the clock frequency at the time of reading (m) and setting the frequency ratio (m / n) corresponding to the image enlargement ratio. (JP
(Problems to be solved by the invention) However, in the former method of iterative processing of image data, when the iterative processing is performed for every pixel like A5A3 (200%), B5A3 (163%)
In the case of B5B4 (141%), image distortion does not appear remarkably because the repetitive pixels are distributed at a substantially equal rate.
(122%) Furthermore, as B5A4 (115%), the smaller the magnification ratio, the smaller the repetition rate, the smaller the repetition rate. There is a problem in image reproducibility.

In the latter technique, a plurality of clock generators having different division ratios with respect to the original oscillation clock are used to generate the write and read clocks. The speed of the original oscillation clock for generating the write and read clocks must be increased, resulting in an increase in the cost of the device.

In view of the drawbacks of the prior art, the present invention provides an image processing method capable of obtaining a preferable enlarged image in terms of image reproducibility and readability without noticeable image distortion even when the enlargement ratio is set to a small value. The purpose is to provide.

Another object of the present invention is to provide an image processing method capable of accurately obtaining an enlarged image corresponding to a variable size without increasing the speed of an original oscillation clock for generating a pixel clock.

[Means for Solving the Problems] In the present invention, it is necessary to perform image enlargement only by making the clock frequency different at the time of writing (n) and at the time of reading (m) without performing image enlargement only by iterative processing. Instead, a combination of the two is used to write the data into the storage means 4 with the input clock of the original image data by the frequency divider 72 and read out the data into the shift register 61 using the clock from the frequency divider 71 having a higher frequency than the input clock. By combining the repetition processing operations by the repetition control circuit 62 of the original image data, as a result, the disadvantages of the two operations can be canceled out by performing the two-stage scaling processing operation, thereby performing the preferable image enlargement processing. Things.

That is, the present invention writes, for example, data corresponding to an original image into a storage unit using a write clock synchronized with an input clock of data of the original image, and then uses a read clock having a higher frequency than the write clock to write the image. By performing an iterative processing operation at a repetition rate larger than the target enlargement rate while performing an apparent image reduction operation by reading data from the storage means, an enlarged image having a desired magnification is obtained. is there.

[Operation] According to the technical means, the repetition processing operation is performed at a repetition rate larger than the target image enlargement rate because the repetition processing operation is performed while substantially reducing the image by the first operation. This makes it possible to distribute the repetition rate of each pixel almost evenly even when the enlargement ratio is small as in B5A4 (115%), and as a result, the image reproducibility without noticeable image distortion It is possible to obtain a magnified image which is preferable in terms of readability and legibility.

For example, when the clock cycle ratio is set to 75%, the repetition rate can be set to 153% even when the image enlargement rate is 115%, and the repetition rate is set to 1 when the image enlargement rate is 122%.
An equalization of the repetition rate between 63% and each pixel can be achieved, and the above effect is further achieved.

On the other hand, the read clock is not set to a frequency different from that of the write clock to set the image enlargement ratio, but is merely set to increase the repetition rate of the repetition processing operation. It is not necessary to make the clock cycle variable, and a fixed clock cycle is sufficient.

That is, it is not necessary to change the read clock cycle in accordance with the enlargement ratio. As a result, there is no need to speed up the original oscillation clock for generating the write and read clocks, and to generate each of the clocks. With only two frequency dividers, the complexity of the device configuration can be avoided.

When the read clock cycle ratio is set to 75%, the read operation is performed without performing the repetitive processing operation.
An image reduced to 75% is obtained.

Therefore, when it is desired to obtain a reduction ratio of 86% (A4B5) or 81% (B4A4), it is sufficient to perform an apparent enlargement process by repeating the same pixel while reading from the storage means side using the read clock, As a result, although some image distortion is generated, a reduced image with high legibility can be obtained because essential pixels are not lost unlike the conventional thinning processing. Note that the above-described reduction processing by the clock can be performed during the write operation.

Hereinafter, preferred embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. It's just

FIG. 1 is an overall block diagram showing an image processing apparatus having an enlargement or reduction function according to an embodiment of the present invention.

Reference numeral 1 denotes a video memory which stores, for example, image data for one page in the form of dots and stores the image data. The video memory 1 is thinned out or repeatedly controlled in the sub-scanning direction in advance in correspondence with a predetermined scaling size when storing the image data. It is stored in the state where it was set. (The scaling process in the sub-scanning direction is not an essential part of the present invention, so the description thereof is omitted.) Reference numeral 2 denotes a control unit which shifts the image data stored in the video memory 1 by one main scanning line or by n bits. After reading data into the register 21 in parallel, the pixel data in the shift register 21 can be serially output to the temporary storage unit 4 while being sequentially shifted based on the write clock generated by the clock generation circuit 7.

The temporary storage means 4 includes two sets of line buffers 41 and 42 for performing a toggle operation and a selector 43, and switches the selector 43 alternately for each scanning line based on a main scanning synchronization signal.
The line buffer based on the write clock and the read clock generated by the clock generation circuit 7
The writing and reading to and from 41 and 42 are performed in parallel.

Reference numeral 6 denotes a read control circuit for reading out the image data after the repetitive processing from the line buffers 41 and 42 via the selector 43 as it is or while performing the repetitive processing as necessary. As shown in FIG. Shift register 61
A repetition designating circuit 60 for transmitting a repetition designation signal corresponding to a desired image enlargement ratio, and reading of corresponding image data output from an N-bit register 61 based on the repetition designation signal transmitted from the designation circuit 60 Is performed repeatedly.

Reference numeral 7 denotes a clock generation circuit including a pair of frequency dividers 71 and 72 for generating write and read clocks.
By dividing the original oscillation clock by 4 by 2, a write clock synchronized with the image input clock is generated. On the other hand, dividing the original oscillation clock by 3 by the divider 71 has a clock cycle of 75% of the write clock. A read clock will be generated.

According to this embodiment, the operation of the present invention described above can be smoothly achieved.

That is, in the present embodiment, the original image data stored in the shift register in the control unit (video memory) is directly stored in the temporary storage unit using the write clock synchronized with the image input clock, and then the 75% cycle of the write clock is used. Since the repetition processing is performed in the read control circuit while reading based on the read clock set in the above, the number of repetitions performed in the repetition control circuit 62 is set to be larger than the actual enlargement ratio by the clock cycle ratio. I can do it.

For example, as described above, the repetition rate can be set to 153% even when the image enlargement rate is 115%, and to 163% when the image enlargement rate is 122%.

Note that, as described above, even when it is desired to obtain a reduction ratio of 86% or 81% which is larger than the clock cycle ratio of 75%, the apparent enlargement processing may be performed by the iterative control circuit as described above.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain a magnified image that is preferable in terms of image reproducibility and legibility without noticeable image distortion even when the magnification is set to a small value. In addition, even when a read clock having a higher frequency than the write clock is used, it is not necessary to increase the speed of the original oscillation clock for generating the pixel clock, and as a result, the device configuration is simplified.

And so on.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing an image processing apparatus for enlarging an image according to an embodiment of the present invention. FIG. 2 is a block diagram showing a read control circuit used in the processing device.

Claims (1)

(57) [Claims] 1. An image processing system for enlarging image data in a predetermined scanning line direction while writing and reading data to and from a storage means at a predetermined clock, wherein the write clock to the storage means is an input clock of original image data. The read clock is a clock having a higher frequency than the write clock, and the image data written to the storage unit is read out using the read clock, and a predetermined repetitive process is performed. An image processing method characterized by obtaining an enlarged image of a desired magnification by performing an iterative processing operation at a repetition rate larger than an enlargement rate while performing image reduction.