JPH09200526A - Lightness correction device, image scanner and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the lightness correction device without deteriorating gradation, production of distortion and deterioration is accuracy by providing a selection means that selects and outputs a high-order n-bit image data or low-order n-bit image data among (n+k)-bit image data. SOLUTION: A shading correction section 230 inputs 8-bit image data and generates 9-bits b8 -b0 , which are fed to a selector 231. The selector 231 inputs lightness selection information stored in a control register 211. The lightness selection information has a level '1' when the lightness of an original being read is bright entirely and the lightness selection information has a level '0' when the lightness of an original being read is dark. When the lightness selection information is at '1', the selector 231 selects the bits b8 -b0 inputted by one terminal group and inputs the selected bits to a gamma RAM 232. Moreover, when the lightness selection information is at '0', the selector 231 selects the bits b7 -b0 inputted by other terminal group and inputs the selected bits to a gamma RAM 232.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brightness correction device for brightness correction or contrast conversion, an image scanner device, and a control method of the image scanner device, and more particularly to a floor of image data having low brightness. Preventing deterioration of tonality.

[0002]

2. Description of the Related Art Conventionally, in an image scanner device, for example, γ conversion is performed in an image scanner device or a host computer in order to correct the contrast of read image data.

[0003]

However, when the contrast correction is performed on the image data of the original image whose overall lightness is low, if the correction is a correction in the direction of increasing the lightness, the data before and after the correction is also used. Since the accuracy of does not change, there is a problem that gradation tends to be rough. That is,
For example, when the gradation is read with 8-bit (b _{8 to} b ₁ ) gradation, the most significant bit of the image data is, for example, b ₅
In this case, even if the lightness is increased and the lightness information for one pixel is carried, the information of the least significant bit (b ₀ ) does not exist. Becomes rough.

Therefore, it is conceivable to correct the brightness at the stage of analog image data before digitization.
If the threshold voltage is lowered and the analog image data is digitized in order to perform the brightening correction by the A / D converter, a quantization error occurs and distortion occurs. Therefore, the present invention provides a lightness correction device that does not deteriorate the gradation even for a lightness or dark original image, and does not cause distortion or decrease in accuracy.
Another object of the present invention is to propose an image scanner device and a control method thereof.

[0005]

In order to achieve this object, for example, a lightness correction device for correcting digital image data from a low-lightness original image in the direction of high lightness according to the present invention is an input image data of n + k bits. Of the n + k-bit image data, the first n-bit image data continuous from the highest order to the low-order direction, and the second n-bit image data continuous from the lowest order to the high-order direction. And a selecting means for selecting and outputting.

When the original image is dark, the lower k-bit image data is utilized. According to a preferred aspect of the present invention, the selection means determines the brightness of the input image data, and according to the determination result, the first n-bit image data and the second n-bit image data. Select one of According to a preferred aspect of the present invention, the selecting means selects the second n-bit image data when the most significant bit image data of the input image data is invalid.

In order to achieve the above object, the image scanner device of the present invention for digitally performing predetermined preprocessing on digitally read image data and outputting n-bit image data is the preprocessing. Go to n +
a preprocessing unit for generating k-bit image data, and n +
Of the k-bit image data, either the first n-bit image data continuous from the highest order to the lower direction or the second n-bit image data continuous from the lowest order to the upper direction is selected and output. It is characterized by comprising a selecting section and a post-processing section for inputting the selected n-bit image data as an address signal and performing a predetermined post-processing.

According to a preferred aspect of the present invention, the selection section inputs a selection signal from the outside to select either the first n-bit image data or the second n-bit image data. To do. According to a preferred aspect of the present invention, the selection unit is a selector that inputs n + k bits and outputs n bits.

According to a preferred aspect of the present invention, the pre-processing unit performs a shading correction process, and the post-processing unit performs a γ correction. Similarly, the control method of the image scanner apparatus for reading the original image and outputting the n-bit image data to the host side according to the present invention for achieving the above object is as follows.
The host sends a pre-scan command to the image scanner device to read the image data, sends the image data to the host, judges the lightness of the original image based on the read image data, and sends the judgment result and the main scan command to the host. From the image data to the image scanner, and in the case of the determination result that the image is a dark original image, the image scanner device generates image data of n + k bits, and outputs the lower n bits of image data from the host. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an embodiment according to the present invention will be described in detail below with reference to the accompanying drawings. <Description of Configuration> FIG. 1 shows a block configuration of an image scanner according to the embodiment, and FIG. 2 shows a block configuration of a host computer which is a host device of the scanner. The host computer is, for example, a personal computer, and is connected to the image scanner of the embodiment by a general-purpose parallel interface provided in the host computer (however, an interface capable of bidirectional communication).

First, the host computer (reference numeral 100) will be described with reference to FIG. Reference numeral 101 is a CPU that controls the entire host computer 100, 102 is a ROM that stores a boot program, and 103 is an OS.
(MS-WINDOWS of Microsoft Corporation in the United States, hereinafter simply referred to as MS-WINDOWS) and applications, RAM for developing the scanner driver program in this embodiment and used as a work area of the CPU 101, 104 is a keyboard, mouse, etc. Is an input device configured with a pointing device of.
A display control unit 105 draws an image to be displayed and generates a display signal, and has a VRAM inside. Reference numeral 106 denotes a display device that displays a visible image based on a video signal from the display control unit 105, 107 denotes an OS and each application,
Further, the hard disk drive stores a scanner driver program and the like. The data (for example, image data) generated by the application is stored in this hard disk drive 107. 108
Is an interface connected to the image scanner of the embodiment, and is a parallel interface capable of bidirectional communication as described above.

In the above configuration, the host computer 1
00 is turned on, the CPU 101 causes the ROM 10
2 according to the boot program in the hard disk 107
Then, the OS is loaded into the RAM 103 and the OS is activated.
After that, for example, when the operator gives an instruction to start an application for image editing, the corresponding application program is loaded from the hard disk drive 107 onto the RAM 103 and editing processing is performed.
For example, when an image reading instruction is given from the image scanner on this application, the image scanner driver program of the embodiment is similarly activated, controls communication with the image scanner via the interface 108, and transmits image data to the apparatus. It will be read into the RAM 103. The details of the operation of the image scanner driver program will be described later.

Next, the configuration of the image scanner (reference numeral 200 shown) of the embodiment will be described with reference to FIG. The image scanner 200 has the following configuration including a control unit 201 that performs data communication with the host computer 100 and generates control signals for various components of the entire apparatus.

Reference numeral 202 denotes a pulse motor for conveying a document image, 203 denotes an LED array for illuminating the document surface, 2
Reference numeral 04 is a CCD for reading the original image line by line, 20
5 is an A / D converter for converting the read analog signal into a digital signal, and 206 ′ and 206 ″ are each 1
This is a buffer for storing the read image for the lines (hereinafter, the buffer 206 'is referred to as the buffer A and the buffer 20).
6 "is referred to as a buffer B), and 207 is a sensor for detecting the presence or absence of a document to be read.

The control unit 201, which is constituted by an ASIC in the embodiment, has reference numerals 210 to 215 as internal functions. Reference numeral 210 is an interface block for performing data communication with the host computer 100, and reference numeral 211 is a control register for storing information corresponding to a command from the host computer 100. For example, by writing a predetermined instruction command (data) in this control register, the CCD 204 is driven or the pulse motor 20
It is possible to drive the document for two lines by driving two lines. A status register 212 stores information to be notified or transferred to the host computer 100. For example, when the sensor 207 detects the absence of the original, the corresponding bit of the status register 212 is set, so that the host computer 100 can detect the absence of the original by reading the content. Also, when one line of data is stored in any of the buffers A and B, or when data transfer to the host computer 100 is not completed within the main scanning line period when the CCD 204 is not read. The corresponding bit (flag) is set.

Reference numeral 213 is an interface register control block for rewriting the contents of the status register according to an instruction from the host computer 100. Reference numeral 214 denotes the LED array 203 and the CCD 204 according to the information stored in the control register 211.
Is an image sensor control block for driving (details will be described later).

Reference numeral 215 denotes shading correction of digital data (each pixel has 8 bits) obtained from the A / D converter 205, and pseudo halftone processing (for example, simple binarization, error diffusion, dither processing, or The multi-valued data is left as it is) and stored in either one of the buffers A and B, or read from one and transferred to the host computer 100 via the status register 212. The control register 211 is used to determine each processing in the image processing block 205 (selection of pseudo halftone processing, whether to write in any of the buffers A and B, and from which to read and output to the host computer). It complies with the stored information.

<Description of Operation> Next, an outline of the operation of the apparatus of the above embodiment will be described below. A of this image scanner
The / D converter 205 has a resolution of 8 bits. The CCD sensor 204 has a length of 1760 pixels. Therefore, the sensor 204 reads and the converter 20
As shown in FIG. 3, the image data converted into digital data by 5 has the amount of 8 bits × 1760. This image data is buffer 206 '(or buffer 206'')
Stored in. In this embodiment, the buffer 206 '
(Or 206 ″), when writing the read data, the transfer control of the image data is performed such that the host data is sent from the buffer 206 ″ (or 206 ′). Hereinafter, for convenience of explanation, the buffer is designated by 206.

In this embodiment, the read image data is transferred to the host by 8 bits at a time.
As described above, the shading correction is performed by the image processing block 215. However, since the shading-corrected data is transferred to the host in 8-bit units, the block 215 performs shading correction in 1-pixel units (further, γ correction). Is sufficient.

Preparation is required for shading correction. In the preparation process, in the system of the present embodiment, the host computer causes the image scanner device to read a reference original document (white original document and black original document) in advance to obtain reference image data, and the host computer transmits the reference image data. Analyze and determine shading correction data.
At the time of actual reading, the image scanner receives the shading correction data from the host and stores it in the control register 211 every time one original is read, and stores it in the register 211 for the image data read by the CCD. The shading correction is performed using the correction data that has been set.

The shading correction involves a lightness conversion process, and when the image data is digital image data, a multiplication or division of 2 ^m (m is an integer). FIG.
The principle of shading correction in this embodiment will be described.
Image data, when generally have the gradation of n bits, the image data is represented by b _n ~b _1. A feature of the shading of the present embodiment is that an operation for shading correction is performed with an accuracy of n + k bits (in FIG. 4, k = 1, that is, an operation with an accuracy of n + 1 bits is shown for convenience). In addition, if the read original is an original with normal brightness, the upper bit position (b _{n in} the example of FIG. 4) may include valid (“1” value) data. Is high, the n-bit data of b _{n to} b ₁ is treated as shading-corrected image data.

Further, if the read original is an original of low brightness
, The lower bits b_nk~ B_1-k(FIG. 4
In this example, k = 1 and b_n-1~ B₀) Shadin
It is treated as image data that has undergone image correction. This is
If the original is a low brightness original for
Of 1-pixel image data of_n(In some cases b_n-1…
Also) is 0. Therefore, the correction to increase the brightness (example of Fig. 4
Then 2^mMultiplication operation of m,
Information contained in the data by bit shift operation)
Is never lost. On the contrary, this shift operation
Bit position b ₀The following bits are currently valid bits.
Therefore, the gradation of the image after shading correction is maintained
Is done. The carried bit information is the shading
The normal bit information generated by the correction
Therefore, the image data is not distorted.

The above is a description of the principle of shading correction in this embodiment. That is, the shading correction of the present embodiment discloses a lightness correction device that generates image data that maintains gradation and is free of distortion. Next, how the brightness correction device (shading correction) specifically operates in the image scanner device of FIG. 1 will be described in detail.

FIG. 5 shows the configuration of the image processing block 215 shown in FIG. That is, the image processing block 215 includes the shading correction unit 230, the selector 231, and the γ conversion RA.
And M232. The shading correction unit 230
8-bit image data is input, 9 bits (b _{8 to} b ₀ ) are generated and sent to the selector 231. The selector 231 inputs the brightness selection information stored in the control register. The brightness selection information will be described later.

The structure of the selector 231 is shown in FIG. The selector 231 is an 8-bit selector and has b ₈ to
Input b ₁ and input b _{7 to} b ₀ to the B terminal group. The brightness selection information is information sent from the host computer and has a value of "1" when the host computer determines that the brightness of the document being read is generally bright, and "0" when it is dark. Has a value of ". Therefore, the selector 231, when the brightness of the document being read overall bright, select b ₈ ~b ₁ which is input to the A terminals to input to the address input terminals of GanmaRAM232, lightness of the document being read There when dark overall, also select the b ₇ ~b ₀ being input to the B terminal group RAM232
Enter in the address input of.

When the γ conversion RAM 232 receives the above address input, it outputs the γ converted image data. FIG. 7 illustrates sequence control in the image sensor control block 214. The driver software of the host computer calculates shading correction data in advance and sends it to the image scanner. In step S2, the image scanner receives the shading correction data and stores it in the register 211. The correction data includes the brightness selection information described above. In step S4, an original reading command sent from the driver software is received. In step S6, the selector 231 is set based on the brightness selection information. In step S8, the image data of one line sentence is read and stored in the buffer 206. In step S10, data (8 bits) for one pixel is read from the buffer 206, and shading correction is performed by the shading correction unit 230. As described with reference to FIGS. 5 and 6,
The image data from the shading correction unit 230 is output from b ₈ to b ₈ by the selector 231 according to the brightness selection information.
Either b ₁ or b _{7 to} b ₀ is selected, and the γ conversion R
It is sent to AM232. In step S14, the image data for one pixel which has been subjected to the shading correction and the γ correction is sent to the host side.

The operations of steps S10 to S14 are repeated for each pixel read by the buffer 206.
The operations of steps S8 to S14 are repeated for each line. As described above, the present embodiment clarifies a lightness conversion device, an image scanner device, and a control method of the image scanner, which obtain image data without distortion and with gradation maintained.

In the above-described embodiment, the image scanner is controlled by the sequencer, reads line by line under the control of the host, and sends each pixel to the host under the control of the host. Is not limited to such an image scanner, but can be applied to a normal flatbed type image scanner. In addition, a document is read one by one and DM
It is also applicable to an image scanner that sends image data to a host by A transfer.

Further, the image scanner device itself may make the judgment without obtaining the brightness selection information from the host.
In this case, the image scanner performs a prescan to determine whether the entire image is a dark image.

[0030]

As described above, according to the lightness conversion device, the image scanner device and the control method of the present invention, it is possible to obtain image data free from distortion and preserving gradation.

[Brief description of drawings]

FIG. 1 is a block diagram of an image scanner according to an embodiment.

FIG. 2 is a block configuration diagram of a host computer in the embodiment.

FIG. 3 is a diagram showing a configuration of image data read by a CCD sensor of the present embodiment.

FIG. 4 is a diagram illustrating the principle of shading correction according to the embodiment.

FIG. 5 is a diagram showing a configuration of an image processing block.

FIG. 6 is a diagram showing a configuration of a selector.

FIG. 7 is a flowchart illustrating a control procedure in the image scanner of the embodiment.

[Explanation of symbols]

 202 pulse motor 203 LED array 204 CCD 205 A / D converter 206 'and 206 "buffer 207 sensor 210 interface block 211 control register 212 status register 213 interface register control block 214 image sensor control block 215 image processing block

Claims (8)

[Claims] 1. A lightness correction device for correcting digital image data from a low-lightness original image in the direction of higher lightness, comprising means for generating input image data of n + k bits, and of the n + k bit image data. A selection means for selecting and outputting either the first n-bit image data continuous from the highest order to the lower direction or the second n-bit image data continuous from the lowest order to the higher direction. A brightness correction device characterized by. 2. The selecting means judges the lightness of the input image data, and selects either the first n-bit image data or the second n-bit image data according to the judgment result. The lightness correction device according to claim 1, wherein 3. The selection means selects the second n-bit image data when the most significant bit image data of the input image data is invalid. The brightness correction device described. 4. An image scanner device for digitally performing predetermined pre-processing on digitally read image data to output n-bit image data, wherein the pre-processing is performed to obtain n + k-bit image data. A pre-processing unit for generating, a first n-bit image data continuous from the highest order to the lower direction of the n + k-bit image data, and a second n-bit image data continuous from the lowest order to the upper direction. An image scanner device comprising: a selection unit that selects and outputs any one of them, and a post-processing unit that inputs the selected n-bit image data as an address signal and performs a predetermined post-processing. 5. The selection unit inputs a selection signal from the outside to select one of the first n-bit image data and the second n-bit image data. The image scanner device according to item 4. 6. The image scanner device according to claim 4, wherein the selection unit is a selector that inputs n + k bits and outputs n bits. 7. The image scanner device according to claim 4, wherein the pre-processing unit performs shading correction processing, and the post-processing unit performs γ correction. 8. A method of controlling an image scanner device for reading an original image and outputting n-bit image data to a host side, wherein the host sends a prescan command to the image scanner device to read the image data. Then, the brightness of the original image is judged based on the read image data, and the result of this judgment and the main scan command are sent from the host to the image scanner. A method for controlling an image scanner device, wherein in the scanner device, image data of n + k bits is generated and the image data of lower n bits is output from the host.