Patent Description:
In the related art, an image forming apparatus, such as a multifunction peripheral (MFP,) includes an image reading apparatus that scans documents. Some image reading apparatuses have a multi-crop scanning function. With a multi-crop scanning function multiple smaller-sized documents arranged on a document table of the image reading apparatus can automatically be read as independent images. The smaller-sized documents are, for example, L-sized photographs (equivalent to 3R size in U. designation), business cards, or magazine clippings. The multi-crop scanning function detects the different documents arranged on the document table, separately corrects a placement angle (document tilt) for each detected document, and then isolates the individual images from each other for saving as separate files if desired.

Furthermore, in the related art, some image reading apparatuses also have an automatic color selection (ACS) function. The ACS function is a function for automatically determining whether the document that has been read is a color document or a monochrome document. This process may be referred to as performing a "color determination. " In general, the ACS function measures the image feature values related to color for the pixels that forms the image as read from the document. A feature value related to color (hereinafter, referred to as "color information") is, for example, a value such as saturation. The ACS function makes a color determination based on the measurement results of color information from the image.

There are cases where color documents and monochrome documents are mixed on the document table. In such a case, with the multi-crop scanning function of the related art, when the ACS function is used, it will be uniformly determined that all of the scanned documents are color documents or all of the scanned documents are monochrome documents. Accordingly, a color document may be incorrectly encoded as a monochrome image, or a monochrome document may be incorrectly encoded as a color image. In this manner, the multi-crop scanning function of the related art has a problem in that there are cases where it is not possible to most appropriately encode each image read from the plurality of documents placed on the document table.

<CIT> describes a system for handling multiple documents while scanning. <CIT> describes an image processing device capable of performing encoding processing according to a compression method respectively for compressing multilevel image data and compressing binary image data. <CIT> describes an image processing apparatus capable of executing a multi-cropping process for cutting out an image of each original document from the scanned images.

An image reading apparatus of an embodiment includes a reading unit and a controller. The reading unit is configured to read a plurality of documents on a document table and generates an overall scan image as color image data including images of all the documents in the plurality of documents. The controller is configured to isolate an image of each document from the overall scan image, perform a color determination on each of the isolated images to determine if the document corresponding to the isolated image is a color document or a non-color document, and encode each of the isolated images with an image encoding method selected based on the color determination for the isolated image.

Preferably, the controller is further configured to store each encoded image in a storage unit.

The controller is further configured to detect edges of image regions for each of the documents in the overall scan image, and correct a tilt of each of the image regions.

If the document corresponding to the isolated image is determined to be a non-color document, the controller is configured to encode the isolated image with one of a binary image encoding or a multi-value image encoding.

The controller is further configured to select the one of the binary image encoding or the multi-value encoding based on pixel values of the isolated image.

The controller is further configured to convert the isolated image to gray-scale image data when the document corresponding to the isolated image is determined to be a non-color document.

There is also provided an image forming apparatus, comprising the image reading apparatus as described above and a printer unit configured to form images on a recording medium.

Preferably, the printer unit is configured to form images on the recording medium based on encoded images.

Preferably, the controller is further configured to send each encoded image to the printer unit.

There is also provided an image reading method, comprising: reading a plurality of documents on a document table and generating an overall scan image as color image data including images of all the documents in the plurality of documents; isolating an image of each document from the overall scan image; performing a color determination on each of the isolated images to determine if the document corresponding to the isolated image is a color document or a non-color document; and encoding each of the isolated images with an image encoding method selected based on the color determination for the isolated image.

Preferably, the image reading method further comprises storing each encoded image in a storage unit.

The image reading method further comprises detecting edges of image regions for each of the documents in the overall scan image, and correcting a tilt of each of the image regions.

The image reading method further comprises encoding the isolated image with one of a binary image encoding or a multi-value image encoding, if the document corresponding to the isolated image is determined to be a non-color document.

The image reading method further comprises selecting the one of the binary image encoding or the multi-value encoding based on pixel values of the isolated image.

The image reading method further comprises converting the isolated image to gray-scale image data when the document corresponding to the isolated image is determined to be a non-color document.

In an image reading apparatus, an image forming apparatus, an image reading method, and an image reading method of an embodiment, it becomes possible to appropriately encode each of images read using a "multi-crop scanning function," which is a function of automatically reading a plurality of smaller-sized documents on a document table to be images independent from each other.

An image forming apparatus <NUM> according to the present embodiment has a multi-crop scanning function. The image forming apparatus <NUM> reads the entire scannable region of the document table as a color image in a single pass and generates image data corresponding to the entire scannable region. The generated image data for the entire scannable region is referred to as "entire image data.

The image forming apparatus <NUM> then cuts out (isolates) an image region for each of the separately placed smaller-sized documents from the generated entire image data. Accordingly, image data for each separate document (which is also referred to as "individual image data" or "individual document image data") can be generated.

The image forming apparatus <NUM> also determines whether or not each read document is a color document based on the corresponding the individual document image data. If it is determined that the read document is not a color document, the image forming apparatus <NUM> next determines whether the document is a monochrome binary document or a grayscale document. The image forming apparatus <NUM> performs appropriate processing, such as encoding and file creation, depending on the determination result, and then stores the individual image data that has been subjected to the processing.

The image forming apparatus <NUM> can print or form an image according to the encoded individual image data.

First, the overall configuration of the image forming apparatus <NUM> according to an embodiment will be described with reference to <FIG>.

<FIG> is an external view illustrating the overall configuration example of the image forming apparatus <NUM>. The image forming apparatus <NUM> is, for example, a multifunction peripheral (MFP). The image forming apparatus <NUM> includes a display <NUM>, a control panel <NUM>, a printer unit <NUM>, a sheet accommodation unit <NUM>, and an image reading unit <NUM>. The image forming apparatus <NUM> is one example of an image reading apparatus, and, in other examples, may be a copying machine, a scanner, or the like.

The display <NUM> is an image display device, such as a liquid crystal display (LCD) or an organic electro luminescence display (OLED). The display <NUM> displays various pieces of information related to the image forming apparatus <NUM>. The display <NUM> and the control panel <NUM> may be configured as an integrated touch panel (also referred to as an input and output unit).

The control panel <NUM> has a plurality of buttons. The control panel <NUM> receives an input operation of the user. The control panel <NUM> outputs an operation signal that corresponds to the user's input operation to a control unit <NUM> of the image forming apparatus <NUM>.

The printer unit <NUM> forms an image on a sheet based on the image data generated by the image reading unit <NUM>. The printer unit <NUM> may be of a type that fixes a visible image such as a toner image on a sheet or may be an ink jet type device. The sheet is, for example, paper or label paper. In general, the sheet may be any material type as long as the image forming apparatus <NUM> can form an image on the surface thereof. The sheet may be accommodated in the sheet accommodation unit <NUM> or may be a sheet manually fed to the image forming apparatus <NUM>.

The sheet accommodation unit <NUM> accommodates a sheet used for image formation in the printer unit <NUM>.

The image reading unit <NUM> reads an image formed on a document (referred to as a "sheet S" below) placed on the document table based on the brightness and darkness of reflected light, and generates image data (entire image data) which is digital data. The image reading unit <NUM> records the generated image data in an auxiliary storage device <NUM> (see <FIG>). The image reading unit <NUM> may output the generated image data to the control unit <NUM> or the printer unit <NUM>. The image reading unit <NUM> may also output the generated image data to another information processing apparatus or the like via a network.

Next, a configuration of the image reading unit <NUM> of the image forming apparatus <NUM> according to the embodiment will be described with reference to <FIG> is a schematic view illustrating a part of a configuration example of the image reading unit <NUM>.

The image reading unit <NUM> includes a document table <NUM> (also referred to as a platen or document platen), a first carriage <NUM>, a second carriage <NUM>, an imaging unit <NUM>, and an image reading control unit <NUM>. The direction in which the first carriage <NUM> moves is the sub-scanning direction y. On the document table <NUM>, the direction orthogonal to the sub-scanning direction y is the main scanning direction x. The direction orthogonal to both the main scanning direction x and the sub-scanning direction y is a height direction z.

The document table <NUM> includes a document table glass <NUM>, a shading plate <NUM>, a document scale <NUM>, and a through-read glass <NUM>.

The document table glass <NUM> has a placement surface 201a on which the sheet S is placed. The shading plate <NUM> is composed of a white member. The shading plate <NUM> has white color that serves as a reference when shading correction is performed on an image read from the sheet S. The shading plate <NUM> is long shaped in the main scanning direction x.

When the multi-crop scanning function is not used and only one sheet S is being read, the document scale <NUM> indicates the appropriate or expected position of the sheet S on the document table glass <NUM>. A distal end reference portion 203a is provided at the end portion of the document scale <NUM>. The distal end reference portion 203a forms a projection portion for pressing against the end portion of the sheet S by forming a step between the distal end reference portion 203a and the placement surface 201a of the document table glass <NUM>. The position of the sheet S is set by being pressed against the distal end reference portion 203a on the document table glass <NUM>. The position for placing the corner of the distal end of the sheet S is predetermined on the placement surface 201a. By placing the corner of the distal end of the sheet S at the predetermined position, positioning in the main scanning direction x and the sub-scanning direction y is performed.

The first carriage <NUM> includes a light source <NUM>, a reflector <NUM>, and a first mirror <NUM>. The light source <NUM> emits light. The reflector <NUM> reflects the light emitted from the light source <NUM>. The light reflected by the reflector <NUM> is uniformly applied to the shading plate <NUM> and the sheet S. The light distribution characteristics in the main scanning direction x at the reading position of the sheet S is adjusted based on the reflected light. The first mirror <NUM> reflects the light that has been reflected by the shading plate <NUM> and the sheet S toward a second mirror <NUM> of the second carriage <NUM>.

The second carriage <NUM> includes the second mirror <NUM> and a third mirror <NUM>. The second mirror <NUM> reflects the light reflected by the first mirror <NUM> to the third mirror <NUM>. The third mirror <NUM> reflects the light reflected by the second mirror <NUM> to a condenser lens <NUM> of the imaging unit <NUM>.

The imaging unit <NUM> includes the condenser lens <NUM>, a CCD sensor <NUM>, and a CCD substrate <NUM>. The condenser lens <NUM> focuses the light reflected by the third mirror <NUM>. The condenser lens <NUM> focuses the condensed light on an image formation surface (reading surface) of the CCD sensor <NUM>. The CCD sensor <NUM> is installed on the CCD substrate <NUM>. For example, the CCD sensor <NUM> is a hybrid <NUM>-line (<NUM>-channel) sensor. The hybrid <NUM>-line sensor includes a <NUM>-line sensor for reading a color image and a <NUM>-line sensor for reading a monochrome image. The <NUM>-line sensor reads R (red), G (green) and B (blue) light. The CCD sensor <NUM> converts the light focused by the condenser lens <NUM> into electric charges. By this conversion, the CCD sensor <NUM> converts the image formed by the condenser lens <NUM> into an electric signal. The CCD substrate <NUM> generates image data based on the electric signal generated by the photoelectric conversion of the CCD sensor <NUM>. When generating the image data, the CCD substrate <NUM> generates the image data by using the correction information obtained in advance by the shading correction processing. The CCD substrate <NUM> outputs the generated image data to the image reading control unit <NUM>. The processing performed by the CCD substrate <NUM> is executed by an analog front end (AFE) installed on the CCD substrate <NUM>.

The image reading control unit <NUM> controls the first carriage <NUM>, the second carriage <NUM>, and the imaging unit <NUM>. For example, the image reading control unit <NUM> controls the movement of the first carriage <NUM>, and the turning on and off of the light source <NUM> of the first carriage <NUM>. For example, the image reading control unit <NUM> controls the operation of the imaging unit <NUM>.

The first carriage <NUM> moves in the sub-scanning direction y according to the control of the image reading control unit <NUM>. The second carriage <NUM> moves in the same direction as the first carriage <NUM> at a speed of <NUM>/<NUM> the movement speed of the first carriage <NUM>. By such an operation, even when the first carriage <NUM> moves, the optical path length of the light reaching the image formation surface of the CCD sensor <NUM> does not change. In other words, the optical path length of the light in the optical system formed by the first mirror <NUM>, the second mirror <NUM>, the third mirror <NUM>, and the condenser lens <NUM> is constant. In other words, the optical path length from the placement surface 201a to the image formation surface of the CCD sensor <NUM> is constant.

In the example of <FIG>, the first carriage <NUM> moves from left to right along the sub-scanning direction y. As the first carriage <NUM> moves in the sub-scanning direction y, a reading position P for the sheet S also moves. Therefore, the reading position P moves from left to right along the sub-scanning direction y. The reading position P is a position for one line in the main scanning direction x. As the reading position P moves in the sub-scanning direction y, the images of the reading position P of the sheet S are sequentially formed on the image formation surface of the CCD sensor <NUM>. The CCD sensor <NUM> outputs a signal corresponding to the formed image of the reading position P as a signal for one line in the main scanning direction x. The CCD substrate <NUM> generates image data over the entire region of the document table glass <NUM> based on signals of a plurality of lines.

Next, the functional configuration of the image forming apparatus <NUM> according to the embodiment will be described with reference to <FIG> is a block diagram illustrating a hardware configuration of the image forming apparatus <NUM>.

The image forming apparatus <NUM> includes the control unit <NUM>, a network interface <NUM>, the auxiliary storage device <NUM>, a memory <NUM>, the display <NUM>, the control panel <NUM>, the printer unit <NUM>, the sheet accommodation unit <NUM>, and the image reading unit <NUM>. Each functional unit included in the image forming apparatus <NUM> is connected to each other via an internal bus and can input and output data to and from each other. Each functional unit already described with reference to <FIG> is given the same reference numerals as used with the description of <FIG>, and additional description thereof will be omitted.

The control unit <NUM> controls the operations of each functional unit of the image forming apparatus <NUM>. The control unit <NUM> causes each functional unit to execute various processing by executing a program. The program is stored in advance in the memory <NUM>, for example.

The network interface <NUM> transmits and receives data to and from an external device. The network interface <NUM> operates as an input interface and receives data transmitted from an external device. The network interface <NUM> operates as an output interface and transmits data to an external device.

The auxiliary storage device <NUM> is a storage medium such as a hard disk drive (HDD) or a solid-state drive (SSD). The auxiliary storage device <NUM> stores various pieces of data. The various pieces of data are, for example, image data and the like. The image data is digital data generated by the image reading unit <NUM>, for example.

The memory <NUM> is a storage medium, such as a random access memory (RAM). The memory <NUM> temporarily stores data and programs used by each functional unit included in the image forming apparatus <NUM>. The digital image data generated by the image reading unit <NUM> may be recorded in the memory <NUM> instead of the auxiliary storage device <NUM>.

Next, the configuration of the control unit <NUM> of the image forming apparatus <NUM> according to the embodiment will be described with reference to <FIG>. <FIG> is a schematic view illustrating a configuration example of the control unit <NUM>.

The control unit <NUM> includes a document region detection unit <NUM>, a tilt correction unit <NUM>, an image cutting-out unit <NUM>, a color determination unit <NUM>, a color image encoding unit <NUM>, a non-color image encoding unit <NUM>, and a filing unit <NUM>.

The document region detection unit <NUM> acquires the entire image data as a color image generated by the image reading unit <NUM> from, for example, the auxiliary storage device <NUM>. In other examples, the document region detection unit <NUM> may acquire the entire image data when the entire image data is stored in the auxiliary storage device <NUM> or when the operation signal indicating the instruction information input by the user from the control panel <NUM> is acquired.

An example of entire image data will be described with reference to <FIG> is a view illustrating a plurality of sheets S placed on the document table glass <NUM> when the multi-crop scanning function is used. <FIG> is a view when the document table glass <NUM> is viewed from directly above. In the example illustrated in <FIG>, four rectangular sheets S (sheets Sa, Sb, Sc, and Sd) are placed on the document table glass <NUM>. For example, the sheet Sa is a sheet on which an image illustrating a color photograph is formed. For example, the sheet Sb is a sheet on which an image illustrating a monochrome binary line drawing is formed. For example, the sheet Sc is a sheet on which an image illustrating a monochrome binary character string (text) is formed. For example, the sheet Sd is a sheet on which a grayscale image is formed.

As illustrated in <FIG>, the orientations of the edges of the four sheets S do not match either of the main scanning direction x or the sub-scanning direction y. In other words, the four sheets S are at various angles with respect to the scanning directions. For example, the long side of the sheet Sa and the long side of the sheet Sb are inclined slightly to the left with respect to the sub-scanning direction y. Further, for example, the long side of the sheet Sc and the long side of the sheet Sd are inclined slightly to the right with respect to the sub-scanning direction y. A sheet S placed on the document table glass <NUM> is generally arranged manually by the user, and thus the document tilt or misalignment often occurs.

<FIG> is a view schematically illustrating an example of the entire image data A as generated by reading the entire imaging region of the document table glass <NUM> illustrated in <FIG>. When the multi-crop scanning function is used, the entire region on the document table glass <NUM> is read by the <NUM>-line sensor, and the entire image data A is generated as RGB data (also referred to as color image data).

When the multi-crop scanning function is to be used, it is desirable to read the entire region on the document table glass <NUM> with the cover of the document table <NUM> open. This is because, when reading is performed in a state where the cover of the document table <NUM> is open, the region where a sheet S is not placed becomes darker in the generated entire image data A. Accordingly, the difference in brightness between the region where a sheet S is present and the region where a sheet S is not present becomes large. Therefore, the outline (edge) of the individual image data is more easily detected, and the individual image data is easily isolated.

As illustrated in <FIG>, the entire image data A includes four image regions Ba, Bb, Bc, and Bd (sub-image regions) corresponding to the four sheets Sa, Sb, Sc, and Sd illustrated in <FIG>, respectively. Further, in the entire image data A, the region other than those occupied by the four image regions Ba, Bb, Bc, and Bd is relatively darker in color than the four image regions Ba, Bb, Bc, and Bd.

The document region detection unit <NUM> detects edges of the image regions corresponding to each sheet S placed on the document table glass <NUM> in the acquired entire image data A. The document region detection unit <NUM> detects an edge based on the difference in brightness of pixels that form the entire image data A. For example, the document region detection unit <NUM> detects every edge of the four image regions Ba, Bb, Bc, and Bd. The document region detection unit <NUM> outputs "edge information" indicating the detected edges to the tilt correction unit <NUM>.

The tilt correction unit <NUM> acquires the edge information output from the document region detection unit <NUM>. The tilt correction unit <NUM> identifies the tilt of each image region based on the direction of the edge(s) indicated in the acquired edge information. For example, the tilt correction unit <NUM> identifies the tilt of each of the four image regions Ba, Bb, Bc, and Bd individually. The tilt correction unit <NUM> corrects the tilt of the four image regions Ba, Bb, Bc, and Bd. For example, the tilt correction unit <NUM> rotates each image region such that either the long side direction or the short side direction of each image region matches to one of the main scanning direction x or the sub-scanning direction y. Accordingly, the tilt of each image region is corrected. For example, the tilt correction unit <NUM> selects the one of the main scanning direction x and the sub-scanning direction y requires a smaller rotation angle of the image region to match and rotates each image region accordingly.

An example of the correction of the tilt of the image regions will be described with reference to <FIG> and <FIG> depicts image data C for which a tilted image region Ba included in the entire image data A of <FIG> has been corrected by the tilt correction unit <NUM>. <FIG> illustrates image region Da corresponding to the tilted image region Ba corrected by making the long side direction match the main scanning direction x or the sub-scanning direction y. The image region Da has been subjected to the correction of the tilt such that the long side of the image region Ba now matches the sub-scanning direction y. In addition, the remaining three image regions (image regions Bb, Bc, and Bd) included in the entire image data A are also corrected in tilt in a manner similar to the above.

The tilt correction unit <NUM> outputs image data C for which the tilt of each image region has been corrected to the image cutting-out unit <NUM>.

The image cutting-out unit <NUM> acquires the image data output from the tilt correction unit <NUM>. The image cutting-out unit <NUM> isolates ("cuts-out") the image region included in the image data and generates individual image data corresponding to the isolated image region. The image cutting-out unit <NUM> outputs the generated individual image data to the color determination unit <NUM>.

<FIG> depicts the isolated image regions from the image cutting-out unit <NUM>. As illustrated in <FIG>, the image cutting-out unit <NUM> separates each image region from each other image region and generates the individual image data Ea, Eb, Ec, and Ed respectively corresponding to the image regions Ba, Bb, Bc, and Bd that were illustrated in <FIG>.

The color determination unit <NUM> acquires the individual image data output from the image cutting-out unit <NUM>. The color determination unit <NUM> makes a "color determination" to determine whether or not each read document is a color document. The color determination unit <NUM> makes the color determination based on feature values related to the color of the pixels that forms the individual image data. Various methods can be used for the color determination.

For example, the color determination unit <NUM> converts the individual image data, which is received as RGB data, into saturation data. The color determination unit <NUM> RGB data may be subjected to filter processing in order to enhance conversion accuracy from the RGB data to the saturation data. The color determination unit <NUM> compares the saturation of pixels that form the individual image data with a predetermined saturation threshold value (hereinafter, referred to as "saturation threshold value") for each pixel.

The color determination unit <NUM> counts the number of pixels for which the saturation is greater than the saturation threshold value among the pixels included in the individual image data. The color determination unit <NUM> compares the number of pixels for which the saturation is greater than the saturation threshold value to a predetermined threshold number of pixels (hereinafter, referred to as "auto color select (ACS) threshold value"). The color determination unit <NUM> determines that the individual image data is color image data when the number of pixels for which the saturation is greater than the saturation threshold value is greater than the ACS threshold value. The color determination unit <NUM> may determine that the individual image data is not a color document when the number of pixels for which the saturation is greater than the saturation threshold value is equal to or less than the ACS threshold value. In other words, the color determination unit <NUM> may determine that the individual image data is a monochrome binary document or a grayscale document rather than a color document.

In this manner, the ACS threshold value is a parameter that determines how readily individual image data will be deemed a color document by the color determination of the color determination unit <NUM>. The ACS threshold value may be varied. For example, the ACS threshold value may be changeable based on instructions input by the user from the control panel <NUM>.

<FIG> illustrate an example of a setting screen to be displayed on a touch panel (that is, display <NUM> integrated with the control panel <NUM>). <FIG> each illustrate a setting screen for the user to adjust of the level of the ACS threshold value used in determining whether individual image data corresponds to a color document. Hereinafter, adjustment of the level for determining whether a document is a color document will be referred to as "ACS adjustment". The setting screen for the user to perform the ACS adjustment illustrated in <FIG> can be referred to as an "ACS setting screen".

As illustrated in <FIG>, the ACS setting screen includes a setting state display region <NUM>, a setting button image <NUM>, and a setting button image <NUM>. In the present embodiment, it is assumed that the ACS adjustment can be adjusted by seven (<NUM>) different increments. The setting state display region <NUM> includes seven rectangular images arranged in a horizontal row. Each of the rectangular images represents one increment out of seven increments for the ACS adjustment.

In these depicted seven rectangular images, the color of one rectangular image is different from the colors of the other six rectangular images. Accordingly, the user can easily visually recognize at which increment, out of the <NUM> increment, the ACS adjustment value has been set. The setting is such that, as rectangular images closer to the right of setting state display region <NUM> are selected, individual image data is more readily determined to be a color document. Selection of a rectangular image closer to the left of setting state display region <NUM> are selected, individual image data is less readily determined to be a color document.

Furthermore, among the depicted seven rectangular images of this example, the rectangular image positioned at the center in the left-right direction is longer than the others in the vertical direction. The setting of the ACS adjustment value to correspond to the center rectangular image (also referred to as the middle or fourth rectangular image) of the seven rectangular images is referred to as the "standard setting". Accordingly, the user can easily visually recognize whether or not the current setting for the ACS adjustment is the standard setting state. In addition, the user can easily visually recognize whether the current setting of the ACS adjustment is results in color documents being more readily or less readily determined a color document compared to the standard setting.

The user can perform the ACS adjustment by tapping the region where the setting button image <NUM> is displayed or the region where the setting button image <NUM> is displayed, on the touch panel. Each time the setting button image <NUM> is tapped, the ACS adjustment shifts one increment to the left. Each time the setting button image <NUM> is tapped, the ACS adjustment shifts one increment to the right. <FIG> illustrates a state where the ACS adjustment is at the standard setting. <FIG> illustrates a state where the ACS adjustment has been shifted by two increments to the right (that is, more likely to identify a document as a color document as compared to the standard setting).

In the embodiment, a configuration in which the ACS setting screen is displayed on a touch panel is described, but the present disclosure is not limited thereto. For example, a configuration in which the control panel <NUM> is provided with seven light emitting units, corresponding to the seven rectangular images described above, and two physical buttons, corresponding to the setting button image <NUM> and the setting button image <NUM>, may be provided.

For example, a different ACS threshold value can be assigned to each of seven separate increments (ACS adjustment levels), but the present disclosure is not limited to seven increments and, in general, any number of increments can be adopted. As described above, the ACS threshold value relates to the number of pixels having a saturation greater than a set saturation threshold value from among the total number of pixels included in individual image data. In the setting state display region <NUM>, as the selected ACS adjustment increment corresponding to the rectangular image moves to the right, the ACS threshold value becomes smaller (fewer saturated pixels are required). Accordingly, it is more readily deemed that the individual image data corresponds to a color document. As the selected rectangular image moves to the left, the ACS threshold value becomes greater (more saturated pixels are required). Accordingly, individual image data is more readily deemed to not to be a color document.

In the embodiment, the color determination unit <NUM> is configured to make a color determination based on the number of pixels having a saturation greater than the saturation threshold value from among all the pixels that form the individual image data. It is possible to make the adjustment such that, by performing the color determination based on the number of pixels, if, for example, a size of the color image region is about the size of just one document stamp or the collective size of a few document stamps, the document can still be treated as not a color document. Accordingly, even when a color region is included in a document, the image encoding for the grayscale image or the binary image can still be performed on such a document, and thus the encoding amount can be reduced.

However, the color determination is not limited to the above-described configuration. For example, the color determination unit <NUM> may make the color determination based on the ratio of the number of pixels having the saturation greater than the saturation threshold value to the total number of pixels of the individual image data. In this case, a value indicating a ratio (e.g., a percentage of total pixels that are saturated pixels) can be set as the ACS threshold value rather than a number of pixels.

Further, for example, the color determination unit <NUM> may make the color determination using the RGB values instead of saturation values.

The color image encoding unit <NUM> performs the image encoding on individual image data that has been determined to be a color document by the color determination unit <NUM>. The color image encoding unit <NUM> performs predetermined image encoding for color image data. In general, any method can be used as the image encoding method performed by the color image encoding unit <NUM>. For example, the color image encoding unit <NUM> may perform image encoding of a Joint Photographic Experts Group (JPEG) type, which is an international standard for still image encoding.

The non-color image encoding unit <NUM> performs image conversion from RGB data to grayscale image data for the individual image data that has been determined not to correspond to a color document by the color determination unit <NUM>. In general, any method can be used as the image conversion method performed by the non-color image encoding unit <NUM>. For example, the non-color image encoding unit <NUM> may convert the RGB data into grayscale image data by calculating the average value of each color signal of the RGB data. Otherwise, for example, the non-color image encoding unit <NUM> may convert the RGB data into grayscale image data by adding the signals after weighting to each signal of the RGB data.

As illustrated in <FIG>, the non-color image encoding unit <NUM> includes both a binary image encoding unit <NUM> and a multi-value image encoding unit <NUM>.

The binary image encoding unit <NUM> performs binary image encoding on individual image data that has been converted into the grayscale image data. In general, any method can be used as the binary image encoding method performed by the binary image encoding unit <NUM>. For example, the binary image encoding unit <NUM> binarizes individual image data (which has already been converted to grayscale image data, for example), based on a predetermined binarization threshold value. The binary image encoding unit <NUM> may perform binary image encoding on binarized individual image data using, for example, a run-length method that is a reversible compression method.

The multi-value image encoding unit <NUM> performs multi-value image encoding on individual image data that has already been converted into grayscale image data. In general, any method can be used as the multi-value image encoding method performed by the multi-value image encoding unit <NUM>. For example, the multi-value image encoding unit <NUM> may perform JPEG type image encoding on grayscale-converted individual image data, in a manner similar to the color image encoding unit <NUM>.

The non-color image encoding unit <NUM> determines whether to perform binary image encoding or multi-value image encoding on individual image data determined not to correspond to a color document according to preset conditions. For example, the image encoding method can be designated in advance by the user.

<FIG> is a view illustrating an example of a setting screen displayed on a touch panel in which the display <NUM> and the control panel <NUM> are integrated. The setting screen illustrated in <FIG> is referred to as "encoding method setting screen" and can be used for selecting an encoding method to be performed on the individual image data that has been determined not to correspond to a color document.

As illustrated in <FIG>, the encoding method setting screen includes a setting image region <NUM>. The setting image region <NUM> includes a setting button image <NUM> and a setting button image <NUM>. In the setting button image <NUM>, text "Store As Binary Image" is displayed. In addition, in the setting button image <NUM>, text "Save As Grayscale Image" is displayed.

When the user taps the setting button image <NUM>, the control panel <NUM> generates an operation signal indicating that binary image encoding is to be performed on individual image data determined not to correspond to a color document. The control panel <NUM> outputs the generated operation signal to the non-color image encoding unit <NUM> of the control unit <NUM>. When the user taps the setting button image <NUM>, the control panel <NUM> generates an operation signal indicating that multi-value image encoding is to be performed on individual image data determined not to correspond to a color document. The control panel <NUM> outputs the generated operation signal to the non-color image encoding unit <NUM> of the control unit <NUM>.

In addition to, or instead of, user selections, the non-color image encoding unit <NUM> automatically determines whether to perform binary image encoding or multi-value image encoding on individual image data determined not to correspond to a color document. For example, the non-color image encoding unit <NUM> can generate a histogram of pixel values for pixels that form individual image data that has been converted into grayscale image data. The non-color image encoding unit <NUM> then automatically determines whether to perform binary image encoding or multi-value image encoding based on the shape of the generated histogram.

For example, in a case of a histogram having a shape in which the number of pixels is relatively low in the area near the center of the histogram, the read document is likely to be a monochrome binary document corresponding to a black and white line drawing or a text document. Therefore, in such a case, the non-color image encoding unit <NUM> performs binary image encoding on individual image data. If the histogram has a shape in which the number of pixels in the area near the center of the histogram is not low, then the read document is likely to be a grayscale document such as a black and white photograph. Therefore, in such a case, the non-color image encoding unit <NUM> performs multi-value image encoding on individual image data.

If the non-color image encoding unit <NUM> is configured to automatically select between binary image encoding or multi-value image encoding, the user can adjust the selection decision criteria similarly to the above-described ACS adjustment process.

<FIG> is a view illustrating an example of a setting screen displayed on the touch panel in which the display <NUM> and the control panel <NUM> are integrated. <FIG> illustrates an example of a setting screen for a user to adjust the values associated with identifications of monochrome binary documents and grayscale documents. As illustrated in <FIG>, the setting screen includes a setting state display region <NUM>, a setting button image <NUM>, and a setting button image <NUM>. The configurations of the setting state display region <NUM>, the setting button image <NUM>, and the setting button image <NUM> are similar to the configurations of the setting state display region <NUM>, the setting button image <NUM>, and the setting button image <NUM> illustrated in <FIG>. The user can tap the region where the setting button image <NUM> is displayed and the region where the setting button image <NUM> is displayed to change whether a document is more likely to be treated as monochrome binary image or a grayscale image.

The filing unit <NUM> creates at least one file for individual image data from the entire image data. For example, the filing unit <NUM> individually creates files for each individual image data encoded by the color image encoding unit <NUM>, the binary image encoding unit <NUM>, and the multi-value image encoding unit <NUM>. The filing unit <NUM> may alternatively create a collective file (one file) for all of the individual image data encoded by the color image encoding unit <NUM> and a collective file (one file) for all of the individual image data encoded by the binary image encoding unit <NUM> and the multi-value image encoding unit. Alternatively, the filing unit <NUM> creates one file for all of the individual image data encoded by the color image encoding unit <NUM>, one file for all of the individual image data encoded by the binary image encoding unit <NUM>, and one file for all of the individual image data encoded by the multi-value image encoding unit <NUM>. Alternatively, the filing unit <NUM> creates a single file including all of the individual image data encoded by the color image encoding unit <NUM>, the binary image encoding unit <NUM>, and the multi-value image encoding unit <NUM>.

The method of filing the individual image data can be designated in advance by the user, for example.

<FIG> is a view illustrating an example of a setting screen displayed on the touch panel in which the display <NUM> and the control panel <NUM> are integrated. The setting screen illustrated in <FIG> is a filing method setting screen for selecting a method of filing the individual image data.

As illustrated in <FIG>, the filing method setting screen includes a setting image region <NUM>. The setting image region <NUM> includes a setting button image <NUM>, a setting button image <NUM>, a setting button image <NUM>, and a setting button image <NUM>. In the setting button image <NUM>, text "make each image as one file" is displayed. Further, in the setting button image <NUM>, text "make each color image and non-color image as one file" is displayed. Further, in the setting button image <NUM>, text "make each color image, grayscale image, and binary image as one file" is displayed. Further, in the setting button image <NUM>, text "make all images as one file" is displayed.

When the setting button image <NUM> is tapped by the user, an operation signal indicating individual files for each of the isolated individual image data are to be generated. The control panel <NUM> outputs the generated operation signal to the filing unit <NUM> of the control unit <NUM>. When the user taps the setting button image <NUM>, the control panel <NUM> generates an operation signal indicating a collective file for all of the color image data is to be created and a collective file for all of the non-color image data is to be created. The control panel <NUM> outputs the generated operation signal to the filing unit <NUM> of the control unit <NUM>. When the user taps the setting button image <NUM>, the control panel <NUM> generates an operation signal indicating three collective files, one for each of the color image data, the binary encoded non-color image data, and the multi-value encoded non-color image data, are to be created. The control panel <NUM> outputs the generated operation signal to the filing unit <NUM> of the control unit <NUM>. When the setting button image <NUM> is tapped by the user, the control panel <NUM> generates an operation signal indicating all of the individual image data is to be saved together as one. The control panel <NUM> outputs the generated operation signal to the filing unit <NUM> of the control unit <NUM>.

In addition, the filing unit <NUM> may individually file each isolated individual image data, and then allocate each of the files to a plurality of folders. For example, the filing unit <NUM> may collectively allocate files for individual image data encoded by the color image encoding unit <NUM> to one folder, and collectively allocate files for the individual image data encoded by the binary image encoding unit <NUM> and the multi-value image encoding unit <NUM> to another folder. Likewise, the created files may be allocated to various folders, either by data or image type, or any other criteria.

The filing unit <NUM> stores files in a storage medium, such as the auxiliary storage device <NUM>. The filing unit <NUM> may output files to, for example, an external storage medium. In addition, the filing unit <NUM> may output files to the printer unit <NUM> instead of electronically recording in the storage medium. In this case, the printer unit <NUM> forms an image on a sheet based on the data acquired from the filing unit <NUM>.

Next, the operation of the control unit <NUM> of the image forming apparatus <NUM> according to the embodiment will be described with reference to <FIG> is a flowchart illustrating an example of the operation of the control unit <NUM>.

The document region detection unit <NUM> of the control unit <NUM> acquires the entire image data generated by the image reading unit <NUM> from the auxiliary storage device <NUM> (ACT <NUM>). The document region detection unit <NUM> performs detection of edges (ACT <NUM>) for each image region (hereinafter, referred to as "document region") included in the acquired entire image data. Each document region corresponds to a document that was placed on the document table glass <NUM>. When the document region detection unit <NUM> determines there is no document region (ACT <NUM>, No), the operation of the control unit <NUM> illustrated in the flowchart in <FIG> ends.

When the document region detection unit <NUM> determines that there is a document region (ACT <NUM>, Yes), the edge information indicating the detected document region is output to the tilt correction unit <NUM> of the control unit <NUM>. The tilt correction unit <NUM> identifies a tilt or angle to the image regions based on the direction of an edge indicated by the acquired edge information. The tilt correction unit <NUM> corrects the identified tilt/angle (ACT <NUM>). The tilt correction unit <NUM> outputs the image data for each document region, including those for which the tilt of the image region has been corrected, to the image cutting-out unit <NUM> of the control unit <NUM>.

The image cutting-out unit <NUM> isolates the image regions included in the entire image data acquired from the tilt correction unit <NUM> (ACT005). The image cutting-out unit <NUM> generates individual image data corresponding to an isolated image region. The image cutting-out unit <NUM> outputs the generated individual image data to the color determination unit <NUM> of the control unit <NUM>.

The color determination unit <NUM> makes a color determination on the individual image data acquired from the image cutting-out unit <NUM> (ACT <NUM>). When it is determined by the color determination unit <NUM> that the document corresponding to the individual image data is a color document (ACT <NUM>, Yes), the color image encoding unit <NUM> of the control unit <NUM> performs color image encoding on individual image data and stores the encoded data (ACT <NUM>).

To store the encoded data, the color image encoding unit <NUM> outputs the encoded individual image data to the filing unit <NUM> of the control unit <NUM>. The filing unit <NUM> stores the individual image data acquired from the color image encoding unit <NUM> in the auxiliary storage device <NUM> or the like.

When it is determined by the color determination unit <NUM> that the document corresponding to the individual image data is not a color document (ACT <NUM>, No), the non-color image encoding unit <NUM> of the control unit <NUM> performs conversion of the individual image data from RGB data to grayscale image data (ACT <NUM>).

When the binary image encoding is selected for the individual image data (ACT <NUM>, Yes), the binary image encoding unit <NUM> of the control unit <NUM> binarizes the grayscale individual image data based on a predetermined binarization threshold value (ACT <NUM>). The binary image encoding unit <NUM> performs binary image encoding on the binarized individual image data and stores the encoded data (ACT <NUM>). To store the binarized individual image data, the binary image encoding unit <NUM> outputs the encoded individual image data to the filing unit <NUM>. The filing unit <NUM> stores the individual image data acquired from the binary image encoding unit <NUM> in the auxiliary storage device <NUM> or the like.

When the multi-value image encoding is selected for the individual image data (ACT <NUM>, No), the multi-value image encoding unit <NUM> of the control unit <NUM> performs multi-value image encoding on the grayscale individual image data and stores the encoded data (ACT <NUM>). To store the encoded data, the multi-value image encoding unit <NUM> outputs the encoded individual image data to the filing unit <NUM>. The filing unit <NUM> stores the individual image data acquired from the multi-value image encoding unit <NUM> in the auxiliary storage device <NUM> or the like.

If there is a document region on which image encoding is not yet been performed (ACT <NUM>, Yes), the control unit <NUM> repeats the operations from ACT <NUM> onward. Once the image encoding has been performed on all the detected document regions (ACT <NUM>, No), the operation of the control unit <NUM> illustrated in the flowchart of <FIG> ends.

As described above, the image reading apparatus includes the reading unit and the control unit. The image forming apparatus <NUM> is an example of an image reading apparatus. The image reading unit <NUM> is an example of a reading unit. The control unit <NUM> is an example of a controller. The reading unit reads a plurality of documents placed on the document table at once as a color image. The document table glass <NUM> is an example of a document table. The sheet S is an example of a document. The control unit isolates images for each document from the entire image data acquired by reading the plurality of document with the reading unit. The control unit then determines, for each of the isolated images, whether or not the corresponding document is a color document. The control unit encodes each image by an image encoding method which may differ, image to image, depending on the determination result. The control unit records the encoded images in the storage unit. The auxiliary storage device <NUM> is an example of a storage unit.

With such a configuration, the image reading apparatus is capable of appropriately and independently encoding each image corresponding to one of the plurality of small-sized documents arranged on the document table. The image reading apparatus can perform color image encoding on an image determined to be a color document. Further, the image reading apparatus can perform image encoding by appropriately selecting binary image encoding or multi-value image encoding for an image determined not to be a color document. For example, the image reading apparatus can perform binary image encoding on a monochrome binary document, such as a line drawing or a text document, and further reduce the encoding amount. The image reading apparatus can perform multi-value image encoding on grayscale documents such as black and white photographs.

Claim 1:
An image reading apparatus (<NUM>), comprising:
a reading unit (<NUM>) configured to read a plurality of documents on a document table (<NUM>) and generate an overall scan image as color image data including images of all the documents in the plurality of documents; and
a controller (<NUM>) configured to:
detect edges of image regions for each of the documents in the overall scan image, and
correct a tilt of each of the image regions and separate each of the image regions from each other to isolate an individual image of each document from the overall scan image,
characterized in that the controller is configured to:
perform a color determination on each of the isolated images to determine if a document corresponding to each of the isolated images is a color document or a non-color document,
convert an isolated image to gray-scale image data when a document corresponding to the isolated image is determined to be a non-color document,
generate a histogram of pixel values for pixels that form the isolated image which has been converted into the grayscale image data, and
encode each of the isolated images with an image encoding method selected based on the color determination for each of the isolated images, wherein the isolated image which has been converted into the grayscale image data is encoded with a binary image encoding or a multi-value image encoding selected based on a shape of the generated histogram.