JPH106560A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a printer good in the reading of a character image even in a saving mode by providing the saving mode recording the black pixel of binary image data in the intermediate level of the total black level and the total white level. SOLUTION: When binary image data being printing data is inputted, this data is accumulated in the data buffer of a control part. Binary image data corresponding to one pixel to be recorded is inputted from the data buffer (processing 101) and it is investigated whether the binary image data is a black pixel (judge 102). When the judge result is YES, the value corresponding to an intermediate level is set as the recording data of the recording pixel (processing 103) and the recording data is transmitted to a plotter (processing 104) and an image of a recording pixel of an intermediate density level is recorded and outputted. When the judge result is NO, the value corresponding to the total while level is set as the recording data of the recording pixel (processing 105) and the recording data is transmitted to the plotter (processing 105) and an image of a recording pixel of the total white level is recorded and outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer having a multi-value image recording function.

[0002]

2. Description of the Related Art Conventionally, printers having a multi-level image recording function capable of setting a recording density in multiple steps have been put to practical use. This printer device includes, for example, a laser beam printer device that generates recording image light by a laser beam and transfers an image using an electrophotographic process.

[0003] In such a printer device, if the data to be recorded is binary image data such as a character document, the entire recording density can be adjusted, and if it is photographic image data, the gradation of the original image can be adjusted. Can be reproduced,
Very high quality recorded matter can be obtained.

Some of such printers are capable of selecting a so-called saving mode recording mode in which the toner consumed in the transfer process can be saved. In this saving mode, a method is applied in which the recorded image data is evenly thinned out according to the ratio of the toner to be saved, and the pixels recorded as black pixels are converted into white pixels according to the thinning rate.

[0005]

However, in such a saving mode of the conventional apparatus, the following inconvenience occurs.

That is, since the pixels recorded as black pixels are converted into white pixels in accordance with the thinning rate, the number of black pixels constituting the character image is reduced, and therefore, the character image on the recorded matter is blurred, making it difficult to read. That situation occurs.

The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a printer capable of reading a character image even in a saving mode.

[0008]

According to the present invention, there is provided a printer apparatus having a multi-level image recording function, which includes a saving mode for recording black pixels of binary image data at an intermediate level between an all black level and an all white level. It is a thing.

In a printer having a multi-valued image recording function, edge detection means for detecting edge pixels of binary image data is provided, and among the black pixels of the binary image data, the edge pixels are detected by the edge detection means. And a saving mode in which black pixels detected as are recorded at an all-black level, and black pixels not detected as edge pixels by the edge detecting means are recorded at an intermediate level between the all-black level and the all-white level. .

In a printer having a multi-level image recording function, a thinning-out pixel determining means for determining a thinning-out pixel of a black pixel of binary image data is provided. Those determined as thinned-out pixels by the thinned-out pixel determining means are recorded at the all-white level, while those of the black pixels which are not determined as thinned-out pixels by the thinned-out pixel determining means are set to the full black level. It has a saving mode for recording at an intermediate level of the all white level.

Further, in a printer having a multi-valued image recording function, an edge detecting means for detecting an edge pixel of the binary image data and a thinned-out pixel determining means for determining a thinned-out pixel of a black pixel of the binary image data. And among the black pixels of the binary image data, the black pixels detected as edge pixels by the edge detection means are recorded at all black levels, and the black pixels not detected as edge pixels by the edge detection means are recorded. For the pixel determined as the thinned-out pixel by the thinned-out pixel determining unit, the image is recorded at the all white level, while among the black pixels, the one not determined as the thinned-out pixel by the thinned-out pixel determining unit is: This is provided with a saving mode for recording at an intermediate level between the all black level and the all white level.

In a printer having a multi-valued image recording function, recording density setting means for setting the recording density of black pixels of binary image data to a multi-step intermediate level is provided.
The black pixels of the binary image data are provided with a saving mode for recording at the intermediate level set by the recording density setting means.

Further, in a printer apparatus for setting the density of a recording pixel by PWM control and recording a multi-valued image,
The recording timing of two consecutive pixels in the main scanning direction is made continuous.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described in detail.

FIG. 1 shows a printer according to an embodiment of the present invention.

In FIG. 1, a control unit 1 controls the operation of the printer device.
Is for recording an image on a recording sheet with a predetermined resolution in multiple gradations, and is composed of a so-called laser beam printer engine. For example, the plotter 2 can record an image in multiple gradations with 16 gradations, and when the value of the recording data is “0”, the recording density becomes all white, and the recording data value is “15”. ", The recording density is all black, and when the value of the recording data is" 1 "to" 14 ", the recording density is in accordance with the value. The recording density can be set appropriately for each pixel serving as a recording unit.

The level converter 3 converts black and white pixels of the binary image data into level signals for recording by the plotter 2, and the external interface circuit 4 uses the printer as a recording device. It is for connecting an external device (for example, a personal computer device) to be used and exchanging various data such as print data with the external device.

The control unit 1, the plotter 2, the level conversion unit 3, and the external interface circuit 4 are connected to a system bus 5, and exchange of data between these elements is performed mainly through the system bus 5. Has been made through.

The printer apparatus appropriately selects two modes of print quality: a normal quality mode in which the amount of toner used is not reduced, and a saving mode in which the amount of toner used is reduced to about 40%. be able to. The setting of the print quality mode can be performed by transmitting a predetermined command from an external device to the printer device, and can also be performed by, for example, operating an operation display unit (not shown) attached to the control unit 1. .

FIG. 2 shows an example of the processing of the printer when the saving mode is set.

When binary image data, which is print data, is input from an external device, the binary image data is stored in a data buffer of the control unit 1. Then, binary image data for one pixel to be recorded is input from the data buffer (process 101), and it is checked whether the binary image data is a black pixel (decision 102).

If the result of determination 102 is YES, a value corresponding to the intermediate level, for example, “8” is set as the recording data of the recording pixel (intermediate level conversion processing; processing 103), and the recording data Is transferred to the plotter 2 (process 104), and the image of the recording pixels of the intermediate density level is recorded and output. Here, the value corresponding to the intermediate level is
It can be set appropriately. The setting can be performed from an external device each time printing is performed, or can be performed by operating an operation display unit (not shown) attached to the control unit 1.

If the result of the determination 102 is NO, "0" which is a value corresponding to the all white level is set as the recording data of the recording pixel (all white level conversion processing; processing 105). The process shifts to step 104, where the print data is transferred to the plotter 2, and an image of print pixels of all white levels is printed.

When the normal quality mode is set, when the recording pixel is a black pixel, "15" which is a value corresponding to all black levels is set as recording data, and the recording pixel is set to white. In the case of a pixel, “0” which is a value corresponding to an all white level as print data is used as in the case described above.
Set.

As described above, in the present embodiment, when the saving mode is set, the black pixels of the recorded image are converted to the intermediate level, so that the recorded image of the black pixel portion only becomes thin. , Can be read well. At the same time, the amount of toner consumed when recording the black pixel portion can be reduced, so that the cost in the saving mode can be reduced.

In the embodiment described above, the recording density of the black pixel portion of the recording image is set to the intermediate density,
Although the amount of toner consumption is reduced, if the pixels to be recorded as the intermediate density are thinned out in the recorded image of the black pixel portion,
The effect of saving toner is greater.

For example, when the total amount of toner saved is set to 60%, 30% is saved by thinning and 30% by intermediate density, rather than 60% of toner is saved by thinning alone.
%, The print quality is good and toner can be saved effectively.

In this case, for example, the recording pixels in the black pixel portion are thinned out according to the matrix MM shown in FIG. That is, in this case, for the odd-numbered recording lines, the odd-numbered black pixels are recorded and the even-numbered black pixels are thinned out, and for the even-numbered recording lines, the odd-numbered black pixels are thinned out and the even-numbered black pixels are thinned out. Are recorded.

FIG. 4 shows an example of the processing of the printer when the saving mode is set in this case.

When binary image data, which is print data, is input from an external device, the binary image data is stored in a data buffer of the control unit 1. Then, binary image data for one pixel to be recorded is input from the data buffer (process 201), and it is checked whether or not the binary image data is a black pixel (decision 202).

If the result of the judgment 202 is YES, it is checked according to the matrix MM whether or not the recording pixel is a thinned-out pixel (decision 203). When the result of the determination 203 is NO, since the recording pixel is a pixel to be recorded as a black pixel, a value corresponding to the intermediate level as recording data of the recording pixel, for example,
"8" is set (intermediate level conversion processing; processing 204),
The recording data is transferred to the plotter 2 (processing 20).
5) Recording and outputting the image of the recording pixel of the intermediate density level. Here, the value corresponding to the intermediate level can be set as appropriate. The setting can be performed from an external device each time printing is performed, or can be performed by operating an operation display unit (not shown) attached to the control unit 1.

Also, judgment 20 is made when the recording pixel is a white pixel.
If the result of No. 2 is NO, or if the result of the judgment 203 is YES when the recording pixel corresponds to the thinned pixel, “0” which is the value corresponding to the all white level is recorded as the recording data of the recording pixel. Setting (all white level conversion processing;
The process proceeds to step 206) and step 205, where the print data is transferred to the plotter 2, and an image of print pixels of all white levels is printed out.

When the normal quality mode is set, when the recording pixel is a black pixel, "15" which is a value corresponding to an all black level is set as recording data, and the recording pixel is set to white. In the case of a pixel, “0” which is a value corresponding to an all white level as print data is used as in the case described above.
Set.

In the above-described embodiment, the recording densities of the black pixels are all set to the same intermediate density. However, depending on the set value of the intermediate density, there is a possibility that toner transfer failure may occur.

This toner transfer failure occurs when the recording density is set to a small value, because the amount of toner transferred to the recording paper by the image recording process becomes too small and becomes visually very thin.

In order to prevent such transfer failure of the toner and to make the recording density of the black pixel portion an intermediate density,
It is conceivable to set the intermediate density to a relatively large value, but in that case, the toner saving effect may be reduced.

Therefore, as the recording density of the black pixel portion, an intermediate density having a large density level at which toner transfer failure does not occur, and an intermediate density having a small density level at which toner transfer failure may occur but toner saving effect is large. When the density is set and image recording is performed in such a manner that these two types of intermediate densities are alternately arranged, the amount of toner on the intermediate density part of the lower density level is the same as the amount of toner on the intermediate density part of the higher density level. Therefore, toner transfer failure can be prevented. Further, in this case, the effect of saving the toner is greater than when all the black pixel portions are recorded at an intermediate density of a large density level.

In addition, the matrix MM shown in FIG. 3 can be used to select whether to record the recording pixels at the intermediate density level of a large density or at the intermediate density level of a small density. That is, in this case, for the odd-numbered recording lines, the odd-numbered black pixels are recorded at the intermediate density level with a large density, and the even-numbered black pixels are recorded at the intermediate density level with a small density. With regard to (2), odd-numbered black pixels are recorded at a low-density intermediate density level, and even-numbered black pixels are recorded at a high-density intermediate density level.

FIG. 5 shows an example of the processing of the printer when the saving mode is set in this case.

When binary image data, which is print data, is input from an external device, the binary image data is stored in the data buffer of the control unit 1. Then, binary image data for one pixel to be recorded is input from the data buffer (process 301), and it is checked whether the binary image data is a black pixel (decision 302).

If the result of the determination 302 is YES, it is checked according to the matrix MM whether or not the print density of the print pixel is high (determination 30).
3). When the result of the determination 303 is YES, a value corresponding to the intermediate density level of a large density, for example, “8” is set as the recording data of the recording pixel (large density intermediate level conversion processing; processing 304). The print data is transferred to the plotter 2 (process 305), and an image of a print pixel having a large density and an intermediate density level is printed out.

If the result of determination 303 is NO, a value corresponding to the intermediate density level of a small density, for example, "3" is set as the recording data of the recording pixel (small density intermediate level conversion processing; Step 306), Step 30
In step 5, the print data is transferred to the plotter 2, and an image of a print pixel having a low density and an intermediate density level is printed out.

Here, the value corresponding to the high-density intermediate density level and the value corresponding to the low-density intermediate density level can be appropriately set. The settings are
It can be specified by an external device each time printing is performed, or can be performed by operating an operation display unit (not shown) attached to the control unit 1.

Further, judgment 30 is made when the recording pixel is a white pixel.
If the result of No. 2 is NO, "0" which is a value corresponding to the all white level is set as the recording data of the recording pixel (all white level conversion processing; processing 307), and the processing shifts to processing 305, where the recording is performed. The data is transferred to the plotter 2, and the image of the recording pixels of all white levels is recorded and output.

When the normal quality mode is set, when the recording pixel is a black pixel, "15" which is a value corresponding to the all black level is set as recording data, and the recording pixel is set to white. In the case of a pixel, “0” which is a value corresponding to an all white level as print data is used as in the case described above.
Set.

In each of the embodiments described above, since the image of the black pixel portion is recorded at an intermediate density, the recording portion is thinned as a whole. For this reason, although the characters and the like of the recorded contents can be read, there is a possibility that a situation may occur in which the recorded contents are difficult to see.

In order to eliminate such a situation, when the edge portion of the image of the black pixel portion is recorded at the full black level and the other black pixel portions are recorded at the intermediate density, for example, the outline of the character is clearly recorded. Therefore, the image quality becomes very good, and the reading becomes easy.

At the same time, since the black pixel portion other than the edge portion is recorded at the intermediate density, it is possible to effectively save toner as a whole.

FIG. 6 shows a printer according to another embodiment of the present invention. In the figure, the same parts as those in FIG. 1 and corresponding parts are denoted by the same reference numerals.

In FIG. 1, a control unit 1 is for controlling the operation of the printer device.
Is for recording an image on a recording sheet with a predetermined resolution in multiple gradations, and is composed of a so-called laser beam printer engine. For example, the plotter 2 can record an image in multiple gradations with 16 gradations, and when the value of the recording data is “0”, the recording density becomes all white, and the recording data value is “15”. ", The recording density is all black, and when the value of the recording data is" 1 "to" 14 ", the recording density is in accordance with the value. The recording density can be set appropriately for each pixel serving as a recording unit.

The level converter 3 converts black and white pixels of the binary image data into level signals for recording by the plotter 2, respectively. The external interface circuit 4 uses the printer as a recording device. It is for connecting an external device (for example, a personal computer device) to be used and exchanging various data such as print data with the external device.

The edge detecting section 6 performs an edge detecting process for detecting a contour portion of a black pixel portion. This edge detection processing is performed by, for example, using the matrix MN shown in FIG.
If B, C, and D are selected, and the target pixel X is a black pixel and one or more of the adjacent pixels A, B, C, and D are white pixels, the target pixel X is an edge pixel. The processing for determining that there is a data can be applied.

The control unit 1, the plotter 2, the level conversion unit 3, the external interface circuit 4, and the edge detection unit 6 are connected to the system bus 5, and exchange of data between these elements is mainly performed. This is done via this system bus 5.

The printing apparatus appropriately selects two modes of print quality: a normal quality mode in which the amount of toner used is not reduced, and a saving mode in which the amount of toner used is reduced to about 40%. be able to. The setting of the print quality mode can be performed by transmitting a predetermined command from an external device to the printer device, and can also be performed by, for example, operating an operation display unit (not shown) attached to the control unit 1. .

FIG. 8 shows an example of the processing of the printer device when the saving mode is set.

When binary image data, which is print data, is input from an external device, the binary image data is stored in the data buffer of the control unit 1. Then, one pixel of binary image data to be recorded is input from the data buffer (processing 401), and it is checked whether the binary image data is a black pixel (decision 402).

If the result of the judgment 402 is YES, it is checked whether or not the pixel to be processed at that time is judged as an edge pixel by the edge detecting section 6 (decision 403). When the result of the determination 403 is YES, “15” which is a value corresponding to the all black level is set as the recording data of the recording pixel (all black level conversion processing; processing 404), and the recording data is plotted into the plotter 2. (Process 405), and prints out the image of the recording pixel at the edge portion of the all black level.

If the result of determination 403 is NO, a value corresponding to a predetermined intermediate density level, for example, “5” is set as the recording data of the recording pixel (intermediate level conversion processing; processing 406). , The print data is transferred to the plotter 2, and the image of the print pixels of the intermediate density level is printed out. Here, the value corresponding to the intermediate density level can be set as appropriate. The setting can be performed from an external device each time printing is performed, or can be performed by operating an operation display unit (not shown) attached to the control unit 1.

Also, judgment 40 is made when the recording pixel is a white pixel.
If the result of Step 2 is NO, "0" which is a value corresponding to the all white level is set as the recording data of the recording pixel (all white level conversion processing; processing 407), and the processing shifts to processing 405, where the recording is performed. The data is transferred to the plotter 2, and the image of the recording pixels of all white levels is recorded and output.

When the normal quality mode is set, when the recording pixel is a black pixel, "15" which is a value corresponding to the all black level is set as the recording data, and the recording pixel is set to white. In the case of a pixel, “0” which is a value corresponding to an all white level as print data is used as in the case described above.
Set.

FIG. 9 shows another example of the processing of the printer when the saving mode is set in the apparatus of FIG.

When binary image data, which is print data, is input from an external device, the binary image data is stored in the data buffer of the control unit 1. Then, binary image data for one pixel to be recorded is input from the data buffer (process 501), and it is checked whether the binary image data is a black pixel (decision 502).

When the result of the judgment 502 is YES, it is checked whether or not the pixel to be processed at that time is judged as an edge pixel by the edge detecting section 6 (decision 503). If the result of the determination 503 is YES, “15”, which is a value corresponding to the all black level, is set as the recording data of the recording pixel (all black level conversion processing; processing 504), and the recording data is plotted into the plotter 2. (Process 505), and the image of the recording pixel at the edge portion of the all black level is recorded and output.

When the result of the judgment 503 is NO, it is checked according to the matrix MM whether or not the recording pixel is a thinned-out pixel (decision 506).
When the result of determination 506 is YES, “0” which is a value corresponding to the all white level as print data of a print pixel.
(All white level conversion processing; processing 507), and processing 5
In step 05, the print data is transferred to the plotter 2, and an image of print pixels of all white levels is printed.

If the result of determination 506 is NO, a value corresponding to the intermediate level, for example, “8” is set as the recording data of the recording pixel (intermediate level conversion processing; processing 508), and the processing is performed. The flow shifts to 505, where the print data is transferred to the plotter 2, and the image of the print pixels at the intermediate density level is printed and output. Here, the value corresponding to the intermediate level can be set as appropriate. The setting can be performed from an external device each time printing is performed, or can be performed by operating an operation display unit (not shown) attached to the control unit 1.

The judgment is made in the case where the recording pixel is a white pixel.
If the result of step 2 is NO, the value "0" corresponding to the all white level is set as the recording data of the recording pixel (all white level conversion processing; processing 509), and the processing shifts to processing 505, where the recording is performed. The data is transferred to the plotter 2, and the image of the recording pixels of all white levels is recorded and output.

As described above, in this case, since the black pixels other than the edge pixels are recorded at the intermediate density in a thinned state as in the above-described embodiment, the toner saving effect is greatly enhanced.

FIG. 10 shows still another example of the process of the printer device when the saving mode is set in the device of FIG.

When binary image data, which is print data, is input from an external device, the binary image data is stored in the data buffer of the control unit 1. Then, one pixel of binary image data to be recorded is input from the data buffer (process 601), and it is checked whether or not the binary image data is a black pixel (determination 602).

If the result of the judgment 602 is YES, it is checked whether or not the pixel to be processed at that time is judged as an edge pixel by the edge detector 6 (decision 603). If the result of determination 603 is YES, “15” which is a value corresponding to the all black level is set as the recording data of the recording pixel (all black level conversion processing; processing 604), and the recording data is plotted into the plotter 2. (Process 605), and the image of the recording pixel at the edge portion of the all black level is recorded and output.

If the result of decision 603 is NO, it is checked according to the matrix MM whether or not the recording density of the recording pixel is high (decision 60).
6). When the result of the determination 606 is YES, a value corresponding to the intermediate density level of the large density, for example, “8” is set as the recording data of the recording pixel (large density intermediate level conversion processing; processing 607), and the processing is performed. The flow shifts to 605, where the print data is transferred to the plotter 2, and an image of a print pixel of a medium density level having a large density is printed out.

If the result of determination 606 is NO, a value corresponding to the intermediate density level of a small density, for example, "3" is set as the recording data of the recording pixel (small density intermediate level conversion processing; Process 608), Process 60
In step 5, the print data is transferred to the plotter 2, and an image of a print pixel having a low density and an intermediate density level is printed out.

Here, the value corresponding to the high-density intermediate density level and the value corresponding to the low-density intermediate density level can be set as appropriate. The settings are
It can be specified by an external device each time printing is performed, or can be performed by operating an operation display unit (not shown) attached to the control unit 1.

Further, the judgment is made when the recording pixel is a white pixel.
If the result of Step 2 is NO, "0" which is a value corresponding to the all white level is set as the recording data of the recording pixel (all white level conversion processing; processing 609), and the processing shifts to processing 605, where the recording is performed. The data is transferred to the plotter 2, and the image of the recording pixels of all white levels is recorded and output.

As described above, in this case, as the recording density of the black pixel portion, the intermediate density having a large density level at which the toner transfer failure does not occur, and the toner saving although the transfer failure of the toner may occur. Since the image recording is performed by setting a small intermediate density of a density level having a large effect and alternately arranging the two types of intermediate densities, the amount of toner on the intermediate density portion of the small density level is large. This increases in relation to the amount of toner on the intermediate density portion of the level. As a result, it is possible to prevent toner transfer failure in the image portion recorded at the intermediate density. Further, in this case, the effect of saving the toner is greater than when all the black pixel portions are recorded at an intermediate density of a large density level.

Further, since the edge pixels are recorded at the all black level, a visually excellent recorded image can be obtained.

The plotter 2 can set the density of the recording pixels in multiple steps, for example, by controlling the power of the laser beam according to the recording density level, or by setting the laser beam power during the recording timing of one pixel. There are two methods of controlling the period during which is irradiated according to the recording density level. The latter method is called a so-called PWM (pulse width modulation) method.

In the case of recording an image at 1/4 density in the PWM method, as shown in FIGS.
During a period corresponding to 1/4 of one pixel of the pixel clock, PW
An M signal is formed, and an electrostatic latent image by a laser beam is formed on the photosensitive member while the PWM signal is being output.

As a result, in the recorded image, the toner is applied only to a quarter of the area of one pixel, so that an intermediate density can be expressed.

However, in this case, the size of one pixel is
When the recording resolution is 400 dpi (dot / 25.4 mm), one side is approximately 0.0635 (mm), which is very fine, and the amount of toner on the electrostatic latent image formed on the photoreceptor is small. Transfer failure may occur.

In order to solve this situation, FIG.
As shown in (a) to (c), the generation timing of the PWM signal may be set to a timing that is continuous in two pixels that are continuous in the main scanning direction.

In such a case, of the area of one pixel,
Since the toner is applied to a half of the area of one pixel, there is no possibility that transfer failure occurs. Even in this case,
When viewed from an image, since the toner is on a quarter of the area of two consecutive pixels, the same density can be expressed.

In the above description, the case where the density can be set in five steps by the PWM method has been described. However, the present invention is similarly applied to a case where the intermediate density can be set in more steps than that. be able to.

In the above-described embodiment, the recording density is set to 1
The case where a plotter capable of expressing in six gradations is used has been described. However, the case where a plotter capable of expressing an intermediate density with a higher or lower number of gradations is also used.
The present invention can be similarly applied.

In the above-described embodiment, the case where the laser beam printer is used as the plotter has been described. However, the present invention can be similarly applied to the case where another printer is used.

In addition, a method other than the method described in the above embodiment can be applied to the method of selecting a thinned pixel and the method of selecting an intermediate density to be applied from a plurality of densities in the present invention.

[0087]

As described above, according to the present invention,
When the saving mode is set, the black pixels of the recorded image are converted to the intermediate level, so that the recorded image in the black pixel portion only becomes thin, and an effect is obtained that the image can be sufficiently read. Further, since the amount of toner consumed at the time of recording the black pixel portion can be reduced, the effect that the cost in the saving mode can be reduced can be obtained.

When the saving mode is set,
Since the black pixels of the recorded image are converted to the intermediate level and the pixels recorded as the intermediate density are thinned out, the effect of greatly reducing the toner consumption is obtained.

The recording density of the black pixel portion is an intermediate density having a large density level at which toner transfer failure does not occur, and an intermediate density having a small density level at which toner transfer failure may occur but a toner saving effect is large. Since the image is recorded by setting the density and alternately arranging the two types of intermediate densities, the amount of toner on the intermediate density part of the lower density level is less than the amount of toner on the intermediate density part of the higher density level. As a result, the effect of preventing poor transfer of toner can be obtained. Further, in this case, the toner can be more effectively saved as compared with a case where all the black pixel portions are recorded at a medium density of a large density level.

Further, since the edge portion of the image of the black pixel portion is recorded at the full black level and the other black pixel portions are recorded at the intermediate density, for example, the outline of the character is recorded clearly, so that the image quality is reduced. This has the effect of being very good and easy to read. Further, since the black pixel portion other than the edge portion is recorded at the intermediate density, the effect that the toner can be effectively saved as a whole can be obtained.

Further, since the edge portion of the image of the black pixel portion is recorded at the full black level, the other black pixel portions are recorded at the intermediate density, and the recording pixels of the intermediate density are thinned out.
The effect of greatly increasing the toner saving effect is obtained.

The recording density of the black pixel portion is an intermediate density having a large density level at which toner transfer failure does not occur, and an intermediate density having a small density level at which toner transfer failure is likely to occur but toner saving effect is large. Since the image is recorded by setting the density and alternately arranging the two types of intermediate densities, the amount of toner that rides on the intermediate density part with the small density level is on the intermediate density part with the large density level. This increases in relation to the amount of toner, and as a result, an effect of preventing poor transfer of toner in an image portion recorded at an intermediate density can be obtained. Also, in this case, an effect is obtained that the toner saving effect is increased as compared with the case where all the black pixel portions are recorded at a medium density of a large density level. Furthermore, since the edge pixels are recorded at the all black level, an effect that a visually better recorded image can be obtained is also obtained.

Further, since the toner is applied by the same ratio in two consecutive pixels, the area on which the toner is applied is substantially doubled. As a result, there is also obtained an effect that there is no possibility that transfer failure occurs.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a printer device according to one embodiment of the present invention.

FIG. 2 is a flowchart illustrating an example of a process performed by the printer of FIG. 1 when a saving mode is set.

FIG. 3 is a schematic diagram showing an example of a matrix for specifying thinned pixels and density switching pixels.

FIG. 4 is a flowchart showing another example of the processing of the printer of FIG. 1 when the saving mode is set.

FIG. 5 is a flowchart showing still another example of the processing of the printer of FIG. 1 when the saving mode is set.

FIG. 6 is a block diagram showing a printer device according to another embodiment of the present invention.

FIG. 7 is a schematic diagram showing an example of a matrix applied when detecting edge pixels.

FIG. 8 is a flowchart showing an example of processing of the printer of FIG. 6 when the saving mode is set.

FIG. 9 is a flowchart showing another example of the processing of the printer of FIG. 6 when the saving mode is set.

FIG. 10 is a flowchart showing still another example of the processing of the printer of FIG. 6 when the saving mode is set.

FIG. 11 is a timing chart for explaining an outline of a method of setting a density to multiple gradations by a PWM method.

FIG. 12 is a diagram illustrating a PWM according to still another embodiment of the present invention.
4 is a timing chart for explaining an outline of a method of setting a density to multiple gradations by a method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control part 2 Plotter 3 Level conversion part 4 External interface circuit 5 Edge detection part

Claims (7)

[Claims] 1. A printer device having a multi-valued image recording function, comprising a saving mode for recording black pixels of binary image data at an intermediate level between an all black level and an all white level. . 2. A printer device having a multi-value image recording function, comprising: edge detection means for detecting edge pixels of binary image data; and, among black pixels of binary image data, edge pixels by the edge detection means. The present invention is characterized in that there is provided a saving mode in which black pixels detected as are recorded at all black levels, and black pixels not detected as edge pixels by the edge detecting means are recorded at an intermediate level between all black levels and all white levels. Printer device. 3. A printer device having a multi-valued image recording function, comprising: a thinning-out pixel determining means for determining a thinning-out pixel of a black pixel of binary image data; Those determined as thinned-out pixels by the thinned-out pixel determining means are recorded at the all-white level, while those of the black pixels which are not determined as thinned-out pixels by the thinned-out pixel determining means are set to the full black level. A printer device comprising a saving mode for recording at an intermediate level of an all white level. 4. A printer device having a multi-level image recording function, comprising: edge detecting means for detecting edge pixels of binary image data; and thinning pixel determining means for determining thinning pixels of black pixels of binary image data. Among the black pixels of the binary image data, black pixels detected as edge pixels by the edge detection means are recorded at all black levels, and black pixels not detected as edge pixels by the edge detection means are recorded. For the pixel determined as the thinned pixel by the thinned pixel determining means, the pixel is recorded at an all white level, and among the black pixels,
A printer device comprising a saving mode in which a pixel not determined as a thinned pixel by the thinned pixel determining means is recorded at an intermediate level between an all black level and an all white level. 5. A printer device having a multi-valued image recording function, comprising: recording density setting means for setting the recording density of black pixels of binary image data to an intermediate level of multiple levels, wherein And a saving mode for printing at the intermediate level set by the printing density setting means. 6. A printer device having a multi-level image recording function, comprising: edge detecting means for detecting edge pixels of binary image data; and setting the recording density of black pixels of the binary image data to an intermediate level of multiple levels. Recording density setting means for recording, among the black pixels of the binary image data, the black pixels detected as edge pixels by the edge detection means are recorded at an all black level, and are detected as edge pixels by the edge detection means. A printer device comprising a saving mode in which black pixels that have not been recorded are recorded at an intermediate level set by the recording density setting means. 7. A printer apparatus for setting the density of a recording pixel by PWM control and recording a multi-valued image, wherein the recording timing of two consecutive pixels in the main scanning direction is continuous.