JPH09244475A - Image output apparatus and control method thereof - Google Patents

Abstract

(57) [Summary] (Correction) [PROBLEMS] To obtain an output image with high image quality in a saving mode for saving image forming materials such as toner and ink. SOLUTION: When gradation conversion is performed on an input image by a gradation conversion unit, conversion is performed using a conversion table 601 for normal mode in normal mode, and conversion table 602 for save mode is converted in save mode. Convert using. The conversion rule based on the conversion table 602 is such that the maximum density level after conversion is lower than the maximum density level that can be represented by the image output unit (printer engine), and the density levels of the input image and the output image have a proportional relationship. . Therefore, the gradation difference of the input image is maintained even in the save mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image output apparatus and a control method thereof, and more particularly to an image output apparatus having a saving mode for saving an image forming material forming an image and a control method thereof.

[0002]

2. Description of the Related Art A conventional printer has a function of saving toner by taking a logical product of an image signal and a halftone dot pattern and supplying the logical product to a printer engine to reduce pseudo density of an output image (toner save). Function) was realized.

FIG. 1 is a block diagram showing the structure of a conventional printer. The image information (raster data) sent from the host computer 150 is input to the image input unit 101. When the input image information is multi-valued image information, it is converted by the multi-valued binary conversion unit 103 and drawn in the raster data storage unit 106. The screen stored in the screen storage unit 102 is used for the multi-value binary conversion. If the input image information is a binary image, it is drawn as it is in the raster data storage unit.

In the toner save mode, the image drawn in the raster data storage unit 106 is logically ANDed with the halftone dot pattern created by the halftone dot pattern creating unit 104 to reduce the density of black pixels. The image is output to the image output unit (printer engine) 107. On the other hand, if it is not in the toner save mode (hereinafter referred to as the normal mode)
The image drawn in the raster data storage unit 106 is
It is sequentially output to the image output unit 107 as it is.

FIG. 2 is a diagram schematically showing the principle of binarizing an input multi-valued image. (A) is the image input unit 1
It is a multi-valued image (8 bits / pixel) input to 01, and the value of all pixels is set to 200 for convenience of explanation.
(B) is a binarized screen stored in the screen storage unit 102. The multi-value binary conversion unit 103 compares each pixel value of the multi-valued image shown in (A) with the corresponding element value of the binarization screen shown in (B), and determines the pixel value as “pixel value” according to the magnitude relationship. A binary image having 1 ”or“ 0 ”is generated and drawn in the raster data storage unit 106. (C)
Indicates a binary image generated by the multi-value binary conversion unit 103. In addition, in (C) to (E), the black circle is "1".
Is shown. In the normal mode, the binary image shown in (C) is output to the image output unit 107.

In the toner save mode, the halftone dot pattern creating section 104 creates a halftone dot pattern using the binarizing screen shown in FIG. (D) is a halftone dot pattern in which the predetermined threshold value (128) is compared with the size relationship between each element of the binarized screen, and the element having an element value of 128 or less is "1". In the toner save mode,
By supplying the image output unit 107 with the result of the logical product of the binary image shown in (C) and the halftone dot pattern shown in (D), the density of black pixels is supplied. To save toner.

[0007]

FIG. 3 is a diagram schematically showing the output characteristic in the above conventional example. (A) shows the relationship between the input density and the output density in the normal mode,
(B) shows the relationship between the input density and the output density in the toner save mode. Here, the input density is a pixel value included in the multi-valued image input to the image input unit 101, and the output density is a pseudo density of the output image.

As shown in FIG. 3, in the toner save mode, the density of the output image is lowered only for the image exceeding the predetermined density, and the density of the output image is maintained as it is for the image less than the predetermined density. Next to
The relationship of the density difference is lost.

A specific example in which the density of a low density input image is maintained in the toner save mode will be described below. FIG. 4 is a diagram showing how a low-density input image is processed. (A) is a multi-valued image (8 bits / pixel) input to the image input unit 101, and the pixel values of all pixels are 100 (low density) for convenience of description. (B)
Is a binarization screen stored in the screen storage unit 102. The multi-value binary conversion unit 103 compares each pixel value of the multi-valued image shown in (A) with the corresponding element value of the binarization screen shown in (B), and determines the pixel value as “pixel value” according to the magnitude relationship. Generate a binary image with 1 "or" 0 ",
Drawing is performed in the raster data storage unit 106. (C) shows a binary image generated by the multi-value binary conversion unit 103. In the normal mode, the binary image shown in (C) is output to the image output unit 107.

In the toner save mode, the halftone dot pattern creating section 104 creates a halftone dot pattern using the binarizing screen shown in FIG. (D) is a halftone dot pattern in which the element having an element value of 128 or less is set to "1" by comparing the magnitude relationship between the predetermined threshold value (128) and each element of the binarized screen. In the toner save mode,
The logical product of the binary image shown in (C) and the halftone dot pattern shown in (D), that is, the image shown in (E) is supplied to the image output unit 107.

As shown in (C) and (E) of the same figure, for the input image of the low density area, the output images of the normal mode and the toner save mode are the same, and the output image is also output in the toner save mode. The image density is maintained.

As a method for solving this problem, instead of using a halftone dot pattern and a binarizing screen,
It is conceivable to create the halftone dot pattern independently of the binarized screen, but in this case, the output image is an image containing noise, and the image quality is not preferable as in the above case.

The above-mentioned problem relates to an electrophotographic printer, but this problem also applies to, for example, an ink discharge printer that discharges ink onto a recording medium to form an image.

The present invention has been made to solve the above problems, and an object thereof is to obtain an output image with high image quality in a saving mode for saving an image forming material such as toner or ink.

[0015]

An image output apparatus of the present invention is an image output apparatus having a saving mode for saving an image forming material forming an image, and whether the operation mode is the saving mode or not. Determination means for determining, selection means for selecting any one of at least two conversion rules for converting the input image according to the operation mode, conversion means for converting the input image according to the selected conversion rule, and a conversion result. An image forming means for forming an output image based on
The conversion rule selected in the saving mode does not exceed a certain density level lower than the maximum density level that can be expressed by the image forming unit, and the density level of the output image monotonically increases as the density level of the input image increases. It is characterized by such a rule.

Another image output apparatus of the present invention is an image output apparatus having a saving mode for saving an image forming material forming an image, and determines whether or not the operation mode is the saving mode. Determination means, selection means for selecting any one of at least two conversion rules for converting the input image according to the operation mode, conversion means for converting the input image according to the selected conversion rule, and based on the conversion result. An image forming unit that forms an output image, wherein the conversion rule selected in the saving mode does not exceed a certain density level lower than the maximum density level that can be expressed by the image forming unit, and does not exceed the density level of the input image. It is characterized by a rule that the density levels of the output image have a substantially proportional relationship.

The image output apparatus of the present invention preferably further has the following features. That is, in the image output device of the present invention, it is preferable that the at least two conversion rules are rules for converting the gradation of the input image.

In the image output device of the present invention, it is preferable that the at least two conversion rules are rules for converting the color space of the input image.

In the image output device of the present invention, it is preferable that the at least two conversion rules are rules for performing γ conversion on the input image.

Further, in the image output apparatus of the present invention, it is preferable that the image forming means forms an output image by converting the converted result into pseudo halftone data.

In the image output device of the present invention, it is preferable that the image forming means forms an output image by an electrophotographic method.

Further, in the image output apparatus of the present invention, it is preferable that the image forming means forms an output image by an ink ejection method.

The control method of the image output apparatus of the present invention is a control method of the image output apparatus having a saving mode for saving the image forming material forming the image, and whether the operation mode is the saving mode or not. A determination step of determining, a selection step of selecting any one of at least two conversion rules for converting the input image according to the operation mode, a conversion step of converting the input image according to the selected conversion rule, and a conversion result. An image forming step of forming an output image based on the conversion rule selected in the saving mode, the conversion rule not exceeding a certain density level lower than the maximum density level expressible in the image forming step, The rule is that the density level of the output image monotonically increases as the level increases.

The control method of the image output apparatus of the present invention is a control method of the image output apparatus having a saving mode for saving the image forming material forming the image, and whether the operation mode is the saving mode or not. A determination step of determining, a selection step of selecting any one of at least two conversion rules for converting the input image according to the operation mode, a conversion step of converting the input image according to the selected conversion rule, and a conversion result. An image forming step of forming an output image based on the conversion rule selected in the saving mode, the conversion rule not exceeding a certain density level lower than the maximum density level expressible in the image forming step, The rule is that the level and the density level of the output image have a substantially proportional relationship.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 5 is a block diagram showing an example of the arrangement of a printer according to the present embodiment.
An image input unit 501 takes in image information sent from the host computer 550 (otherwise, it may be a scanner or the like). The form of the input image information may be raster data, a page description language, or another form. Further, the gradation of the input image information is not particularly limited, but in the following description, it is assumed that the image information has a gradation of 2 bits / pixel.

The input image captured by the image input unit 501 is transferred to the raster data storage unit 5 by the image drawing unit 502.
It is sequentially drawn in 04. The image (2 bits / pixel) drawn in the raster data storage unit 504 is the gradation conversion unit 5
At 06, according to the conversion table selected by the table selection unit 505, the image is converted into an image having a gradation of 8 bits / pixel. The details of the gradation conversion table will be described later.

The operation mode setting unit 503 sets the operation mode to the normal mode or the toner save mode based on, for example, an instruction from the host computer 550 or an instruction from an operation unit (not shown) (for example, an operation panel, operation buttons, etc.). To do.

The gradation conversion unit 506 has a gradation conversion table for the normal mode and a gradation conversion table for the toner save mode, and the table selection unit 505 has a gradation conversion table corresponding to the operation mode. specify.

FIG. 6 is a diagram schematically showing a configuration example of the gradation converting unit 506. Reference numeral 601 is a conversion table selected in the normal mode, and 602 is a conversion table selected in the toner save mode.

In the normal mode, the 2-bit / pixel input image 0x0, 0x1, 0x2, 0x3 supplied from the raster data storage unit 504 is converted into 0x00, 0x5.
5, 0xAA, 0xFF (0x means hexadecimal display). On the other hand, in the toner save mode, a 2-bit / pixel input image 0x0, 0x1, 0x2, 0x3 supplied from the raster data storage unit 504.
To 0x00, 0x2A, 0x55, 0x7F. That is, the pixel value of the output image in the toner save mode after gradation conversion is 1 / the value in the normal mode
2, the density of the input image and the density of the output image of the gradation converting unit 506 have a proportional relationship.

It is preferable that the gradation conversion table has a conversion rule capable of obtaining an output image in which the gradation difference of the input image is maintained, as in the above case. Therefore, the gradation conversion table may have a conversion rule such that the density of the output image monotonically increases as the density of the input image increases.

FIG. 12 is a diagram schematically showing the conversion rules of the gradation conversion table. (A) of the figure shows the conversion rules in the gradation conversion tables 601 (normal mode) and 602 (toner save mode). FIGS. 9B and 9C show conversion rules in which the density of the output image monotonically increases as the density of the input image increases in the toner save mode.

The image (converted image) converted by the gradation conversion unit 506 is converted by the pseudo-halftone data generation unit 508 into a binary image of pseudo-halftone display and supplied to the image output unit 507. The image output unit 507 outputs an image by an image forming method such as an electrophotographic method or an ink ejection method. However, the expression "toner save mode" is not appropriate in the case of the ink ejection type, but such expression is used for convenience of description.

When the image output unit 507 is a device capable of outputting a multivalued image, the pseudo halftone data generation unit 5
08 is unnecessary.

FIG. 7 is a flow chart showing the flow of the operation of the printer 500. A control unit (not shown) of the printer 500 controls each internal block in a procedure corresponding to this flowchart. When the processing in the printer 500 is realized by software, a memory medium holding a program corresponding to the memory medium and a program module corresponding to each step of the flowchart may be provided and supplied to the CPU.

In step S701, the image input unit 5
01 captures an image from the host computer 550.
Next, in step S702, the image drawing unit 502.
Draws raster data corresponding to the input image information in the raster data storage unit 504.

In step S703, the table selection unit 5
05 confirms the operation mode (normal mode or toner save mode) set by the operation mode setting unit 503, and in step S704, the table selection unit 50
5 selects the corresponding conversion table (601 or 602).

In step S705, the gradation conversion unit 506
Performs gradation conversion of the image stored in the raster data storage unit 504 according to the selected conversion table, and step S70
6, the image output unit 507 outputs the gradation-converted image.

In the above description, it is assumed that the input image acquired by the image input unit 501 has a gradation of 2 bits / pixel and the image output unit 507 can express the gradation of 8 bits / pixel. As described above, when the input image has another gradation (including the case where the input image and the output image have the same gradation), the conversion table 60 is correspondingly changed.
1 and 602 may be changed. For example, when both the input image and the output image (converted image) have 8 bits / pixel, the image conversion unit 506 can perform conversion such that the pixel value of the input image is halved.

As described above, in the toner save mode, by reducing the pseudo density of the corresponding output image over the entire range of the gradation of the input image, the tone difference of the input image is maintained, and good gradation is maintained. An output image can be obtained.

<Second Embodiment> In the present embodiment, R
When converting GB data into YMCK data, a conversion table used for the conversion is selected according to the operation mode.

FIG. 8 is a block diagram showing a configuration example of the printer according to the present embodiment. An image input unit 801 takes in the RGB data sent from the host computer 550. The input image captured by the image input unit 801 is sequentially rendered as RGB data by the image rendering unit 802 in the raster data storage unit 804.

The image (RGB data) drawn in the raster data storage unit 804 is processed by the color space conversion unit 806.
The YMCK data is converted according to the color space conversion table selected by the table selection unit 805.

The operation mode setting unit 803 sets the operation mode to the normal mode or toner save mode based on, for example, an instruction from the host computer 550 or an instruction from an operation unit (not shown).

The color space conversion unit 806 has a gradation conversion table for the normal mode and a gradation conversion table for the toner save mode, and the table selection unit 805 has a gradation conversion table corresponding to the operation mode. specify.

FIG. 9 is a diagram schematically showing a configuration example of the color space conversion unit 806. Reference numeral 901 is a color space conversion table selected in the normal mode, and 902 is a color space conversion table selected in the toner save mode.

The color space conversion table 902 is, for example, as in the case of the first embodiment (see FIG. 12),
A table may be set so that the pseudo density of the corresponding output image is reduced over the entire gradation range of the RGB data.

The image (converted image) converted by the color space conversion unit 806 is converted into a binary image of pseudo-halftone display by the pseudo-halftone data generation unit 808 and supplied to the image output unit 807. The image output unit 507, for example,
An image is output by an image forming method such as an electrophotographic method or an ink discharge method. However, the expression "toner save mode" is not appropriate in the case of the ink ejection type, but such expression is used for convenience of description.

As described above, by selecting the color space conversion table used when converting the color space according to the operation mode, the image signal for the toner save mode is generated while performing the color space conversion. be able to.

Further, the contents of the color space conversion table for the toner save mode are set so that the pseudo density of the corresponding output image becomes small over the entire range of the gradation of the RGB data. The same effect as that of the embodiment can be obtained.

[Modification] In this modification, the color space conversion unit 80 is used.
6, the color space conversion is performed by the linear conversion using the expressions (1) to (4).

Y = M00 × R + M01 × G + M02 × B equation (1) M = M10 × R + M11 × G + M12 × B equation (2) C = M20 × R + M21 × G + M22 × B equation (3) ) K = M30 * R + M31 * G + M32 * B ... Formula (4) This modification is M00-M02, M10-M12, M30.
Two sets of conversion matrices (for normal mode and toner save mode) having the elements of M32 to M32 are provided, and these are selected and used by means corresponding to the table selection unit 805 according to the operation mode.

<Third Embodiment> In this embodiment, the γ conversion rule is selected according to the operation mode.
FIG. 10 is a block diagram showing a configuration example of the printer according to the present embodiment. An image input unit 1001 takes in image information sent from the host computer 550.

The input image captured by the image input unit 1001 is subjected to γ conversion in the γ conversion unit 1006 according to the γ conversion table selected by the table selection unit 1005.
The converted data is sequentially drawn by the image drawing unit 1002 in the raster data storage unit 1004.

FIG. 11 is a diagram schematically showing a configuration example of the color space conversion unit 1006. Reference numeral 1101 is a γ conversion table selected in the normal mode, and 1102 is a γ conversion table selected in the toner save mode.

The γ conversion table 1102 is, for example, the first
As in the case of the embodiment (see FIG. 12), the table may be set to reduce the pseudo density of the corresponding output image over the entire gradation range of the input image.

The image drawn in the raster data storage unit 1004 is converted into a binary image of pseudo-halftone display in the pseudo-halftone data generation unit 1008, and the image output unit 100
7 is supplied. The image output unit 1007 outputs an image by an image forming method such as an electrophotographic method or an ink ejection method. However, the expression "toner save mode" is not appropriate in the case of the ink ejection type, but such expression is used for convenience of description.

The image output unit 1007 may be a display device. If the image output unit 1007 is a device capable of outputting a multi-valued image, the pseudo halftone data generation unit 1008 is unnecessary.

As described above, by selecting the γ conversion table used for γ conversion according to the operation mode,
An image signal for the toner save mode can be generated while performing γ conversion.

Further, the contents of the γ conversion table for the toner save mode are set so that the pseudo density of the corresponding output image becomes small over the entire gradation range of the input image. It is possible to obtain the same effect as that of the above embodiment.

Even when the present invention is applied to a system composed of a plurality of devices (for example, host computer, interface device, reader, printer, etc.), a device composed of one device (for example, copying machine, facsimile device) Etc.)

Another object of the present invention is to supply a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or apparatus, and to supply a computer (or CPU) of the system or apparatus.
And MPU) read and execute the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

Further, by executing the program code read by the computer, not only the functions of the above-described embodiment are realized, but also the OS (operating system) running on the computer based on the instruction of the program code. It is needless to say that this also includes a case where the above) performs a part or all of the actual processing and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instructions of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0068]

As described above, according to the present invention,
In the mode of saving the image forming material such as toner and ink, it is possible to obtain an output image with high image quality.

[0069]

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a conventional printer.

FIG. 2 is a diagram schematically showing the principle of binarizing an input multi-valued image.

FIG. 3 is a diagram schematically showing output characteristics in a conventional example.

FIG. 4 is a diagram showing how a low-density input image is processed.

FIG. 5 is a block diagram illustrating a configuration example of a printer according to the first embodiment.

FIG. 6 is a diagram schematically showing a configuration example of a gradation conversion unit 506.

FIG. 7 is a flowchart showing a flow of operations of the printer 500.

FIG. 8 is a block diagram illustrating a configuration example of a printer according to a second embodiment.

FIG. 9 is a diagram schematically showing a configuration example of a color space conversion unit 806.

FIG. 10 is a block diagram illustrating a configuration example of a printer according to a third embodiment.

FIG. 11 is a diagram schematically showing a configuration example of a γ conversion unit 1006.

FIG. 12 is a diagram schematically showing conversion rules included in a gradation conversion table.

Claims (16)

[Claims] 1. An image output device having a saving mode for saving an image forming material for forming an image, the determining means determining whether or not an operation mode is the saving mode, and converting at least an input image. A selection means for selecting one of the two conversion rules according to the operation mode; a conversion means for converting the input image according to the selected conversion rule; and an image forming means for forming an output image based on the conversion result. And the conversion rule selected in the saving mode is
The rule is such that the density level of the output image monotonically increases as the density level of the input image does not exceed a certain density level lower than the maximum density level that can be expressed by the image forming unit. Image output device. 2. An image output device having a saving mode for saving an image forming material for forming an image, the determining means determining whether or not the operation mode is the saving mode, and converting at least an input image. A selection means for selecting one of the two conversion rules according to the operation mode; a conversion means for converting the input image according to the selected conversion rule; and an image forming means for forming an output image based on the conversion result. And the conversion rule selected in the saving mode is
An image characterized by a rule that the density level of the input image and the density level of the output image have a substantially proportional relationship without exceeding a certain density level lower than the maximum density level that can be expressed by the image forming unit. Output device. 3. The image output device according to claim 1, wherein the at least two conversion rules are rules for converting the gradation of the input image, respectively. 4. The image output device according to claim 1, wherein the at least two conversion rules are rules for converting a color space of an input image, respectively. 5. The image output device according to claim 1, wherein the at least two conversion rules are rules for performing γ conversion on each input image. 6. The image according to claim 1, wherein the image forming unit forms the output image by converting the converted result into pseudo halftone data. Output device. 7. The image output device according to claim 6, wherein the image forming unit forms an output image by an electrophotographic method. 8. The image output device according to claim 6, wherein the image forming unit forms an output image by an ink ejection method. 9. A method of controlling an image output apparatus having a saving mode for saving an image forming material for forming an image, comprising: a determining step of determining whether an operation mode is the saving mode; A selection step of selecting one of at least two conversion rules to be converted according to the operation mode; a conversion step of converting an input image according to the selected conversion rule; and an image formation for forming an output image based on the conversion result. And the conversion rule selected in the saving mode is
It is characterized in that the density level of the output image monotonically increases as the density level of the input image does not exceed a certain density level lower than the maximum density level that can be expressed in the image forming step. A method for controlling an image output device. 10. A method of controlling an image output apparatus having a saving mode for saving an image forming material for forming an image, comprising: a determining step of determining whether an operation mode is the saving mode; A selection step of selecting one of at least two conversion rules to be converted according to the operation mode; a conversion step of converting an input image according to the selected conversion rule; and an image formation for forming an output image based on the conversion result. And the conversion rule selected in the saving mode is as follows.
An image characterized by a rule that the density level of the input image and the density level of the output image have a substantially proportional relationship without exceeding a certain density level lower than the maximum density level that can be expressed in the image forming step. Output device control method. 11. The method of controlling an image output device according to claim 9, wherein the at least two conversion rules are rules for converting the gradation of the input image, respectively. 12. The method of controlling an image output device according to claim 9, wherein the at least two conversion rules are rules for converting a color space of an input image, respectively. 13. The method of controlling an image output device according to claim 9, wherein the at least two conversion rules are rules for performing γ conversion on each input image. 14. The image according to claim 9, wherein the image forming step forms the output image by converting the converted result into pseudo halftone data. Output device control method. 15. The method of controlling an image output apparatus according to claim 14, wherein the image forming step forms an output image by an electrophotographic method. 16. The image forming step forms an output image by an ink ejection method.
Of controlling the image output device described in 1.