JP2008206073A - Image processing apparatus, control method, program, and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for appropriately determining a portion corresponding to the foreground of an image. <P>SOLUTION: There are provided: an input means for inputting an image; an edge detecting means for detecting an edge of the image; an output means for judging continuity of the same kind of images for each of lines of the image to output packet data indicating a starting point, an ending point and a color of the same kind of images; and a determination means for determining packet data, both the starting point and the ending point of which correspond to the edge, as data corresponding to the foreground. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for compressing and encoding an image.

  In recent years, there has been a digital multi-function peripheral in which a copier and a printer are integrated. This is equipped with a function for scanning and copying a paper document and a function for printing out data received from a personal computer.

  In such devices, there are cases where scanned image data and PDL (page description language) data are mixed and printed. In this case, it is necessary to handle scanned image data and PDL data in a unified manner.

  For example, consider a case where all these data are once expanded into bitmap data and compressed using JPEG compression. In this case, distortion due to JPEG compression will occur in the character portion and graphics portion of the document.

As a method for expressing such a character image with high image quality, an expression method using vector data is known.
JP-A-2006-334069

  An object of the present invention is to provide a technique for appropriately determining a portion corresponding to a foreground of an image in order to efficiently encode, for example, an image in which characters and other types of partial images are mixed.

  In order to achieve the above object, an image processing apparatus of the present invention comprises: That is, an input means for inputting an image, an edge detection means for detecting an edge of the image, and by determining the continuity of the same type of image for each line of the image, the start and end points of the same type of image can be obtained. Output means for outputting packet data indicating a color; and determining means for determining that both the start point and the end point are packet data corresponding to the edge as data corresponding to the foreground.

  According to the present invention, a portion corresponding to the foreground of an image can be determined appropriately.

  Embodiments according to the present invention will be described below in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram of an encoding unit of the present invention. Reference numeral 10 denotes an image (scanned image) read by the scanner, and reference numeral 11 denotes an image (PDL drawing image) in which PDL data is drawn. This PDL data is converted into a display list.

  13 is an area dividing unit, 14 is a foreground compression unit, 15 is a background compression unit, and 12 is a memory.

  The scanned image and the PDL data are separated into a foreground and a background in 13 area division units.

  The foreground is subjected to compression processing using foreground vectorization (foreground portion compression processing) in the foreground compression unit 14.

  For the background, the background compression unit 15 compresses the bitmap data (background portion compression processing).

  These compressed data are recorded in the memory 12, respectively. Detailed description will be given below.

  The scan image 10 is subjected to noise removal by the noise removal unit 101 and then supplied to the run packet generation unit 102 and the edge extraction unit 103.

  The run packet generation unit 102 determines how many pixels of the same color are continuous for each row. As a result of the determination, packet data composed of a combination of the start point, end point, and color is generated. This packet data is called a run packet. Instead of the end point, the length of the continuous number (run) may be recorded.

  The edge extraction unit 104 obtains the edge portion of the image using various filter operations.

  The start point / end point determination unit 103 extracts run packet candidates to be vectorized. Specifically, it is determined whether both the start point and end point of the run packet generated by the run packet generation unit 102 match the edge pixels of the image extracted by the edge extraction unit 104. If they match, it is determined to be the foreground part. As a result, it is possible to separate a portion where a run packet is simply formed by arranging pixels of the same color in a portion considered to be the background and a portion of the run packet considered to be the foreground.

  In the foreground / background separation unit 105, a part other than the foreground part is used as a background. Here, the foreground portion is extracted from the original image, and this portion is filled with the average color of surrounding pixels by the background hole filling portion 109.

  The labeling unit 106 is a processing unit that performs labeling of the foreground part. Here, the region connected to the pixel is determined as one region by observing the continuity of the packet data that has entered the line unit with the previous line. Then, “labeling processing” is performed in which an independent number is given to each block.

  Reference numeral 107 denotes an outline extraction unit for each label area, and reference numeral 108 denotes a part that approximates the extracted outline data using a Bezier curve or the like. It is assumed that the Bezier curve and the internal color are connected to form vector data of the image.

  The background hole filling unit 109 extracts the foreground part from the original image and generates a background image in which this part is filled with the average color of surrounding pixels.

  Reference numeral 110 denotes a bitmap encoding unit that compresses a background image as bitmap data. This processing unit can use known JPEG, JPEG2000, or the like. The compression encoded data obtained here is recorded in the memory 12.

  The PDL drawing image 11 is obtained by expanding PDL data into bitmap data (bitmap image) by a drawing method suitable for each. The PDL drawing image is handled in the same manner as the scan image 10 after the processing of the run packet generation unit 102 and the edge extraction unit 104.

  FIG. 2 is a diagram illustrating a decoding unit in the present embodiment.

  Reference numeral 12 denotes a memory similar to that shown in FIG. Here, vector data (vectorized data) and bitmap data (data obtained by compression-coding bitmap data) are recorded.

  The foreground decoding unit 16 reads the vector data from the memory 12 and performs decoding (foreground part decoding process). On the other hand, the background decoding unit 17 reads the bitmap data compressed and encoded from the memory 12 and performs decoding (background decoding process). These decoded image data are combined in the combining unit 18 and displayed on the display 19. Hereinafter, the processing of each unit will be described in detail.

  The contour drawing unit 201 converts the vector data into contour data representing the contour of bitmap data (bitmap image). At this time, the vector coordinate value is converted in accordance with a predetermined display magnification.

  The intermediate coating unit 202 fills the inside of the contour with the instructed color. This result is held in the foreground drawing unit 203.

  On the other hand, the bitmap decoding processing unit 204 decodes the compression-coded bitmap data. This result is held in the background drawing unit 205.

  The image drawn based on the vector data is subjected to a process (smoothing) for blurring edges in the smoothing unit 206.

  On the other hand, the resolution of the bitmap data is converted by the resolution conversion unit 207 in accordance with the display magnification size.

  A combining unit 208 combines the images obtained by the smoothing unit 206 and the resolution conversion unit 207. The display unit 19 displays the synthesized image.

FIG. 3 shows an example in which a region (character tile) including characters is separated into a foreground and a background.
Reference numeral 31 denotes an input image, which is an image including the letter “H” on the background.
Reference numeral 32 denotes an image representing only the character portion (only the portion H), which is referred to as the foreground.
Reference numeral 33 denotes a state in which the outline (outline) of the foreground part is converted into vector data (vectorized). Here, a raster scan is performed, the first significant pixel is detected, and the boundary is traced from that portion. Then, the process is completed when the boundary of the area is traced back to the start point.

  In FIG. 3, the contour of the original image can be reproduced by recording the coordinates of the corner points and connecting them with straight lines. If the internal color of the original image is extracted and painted with this color, the original image ("H" color character) can be reproduced. In FIG. 3, all are composed only of straight lines, but when a curve is included, it can be expressed by approximation using a known Bezier function. This is called an outline vector.

  On the other hand, 34 is an image in which the foreground is extracted from the input image. In this state, there is a strong edge component at the boundary between the original background portion (region other than “H”) and the extracted image portion (region “H”), so that it is not suitable for compression such as JPEG. Therefore, the processing described later is performed.

  Reference numeral 35 denotes a state in which the extracted image portion (“H” region) is filled with the average color of surrounding pixels. The image 35 obtained here is compressed as bitmap data (JPEG compression) at a later stage. Here, the surrounding pixels for obtaining the average color may be determined in advance. For example, the average color may be obtained based only on the surrounding pixels circumscribing the “H” region.

  FIG. 4 is a diagram showing a process of generating a run packet for each line.

  Here, the input image is processed in units of lines. Reference numeral 41 denotes a processing line to be processed. Reference numeral 42 denotes a line one line before (upper) the processing line. Reference numeral 43 denotes a processed line (a line further before the pre-processing line). Reference numeral 44 denotes a processing waiting line scheduled to be processed after the processing line.

  First, the start point and end point (start point 45a, end point 45a) (start point 45b, end point 46b) of the run are detected for the processing line.

  Next, it is determined whether or not there is one label area by looking at the connection relationship with the detection results (start point 45c, end point 46c) (start point 45d, end point 46d) in the previous line.

FIG. 5 is a diagram illustrating processing of the edge extraction unit.
Reference numeral 51 denotes a one-dimensional filter for removing horizontal edges, and the processing unit 53 converts the output value of this filter into an absolute value.
A one-dimensional filter 52 removes vertical edges, and the processing unit 54 converts the output value of this filter into an absolute value.
The two absolute values are added by the processing unit 56. Next, the comparator 55 compares the added value with the threshold value 57. The result of this comparison is the edge strength (edge extraction result) of the target pixel.

  FIG. 6 shows the edge extraction result. In this example, strong edge strength (edge extraction result) appears only in the contour pixels around the character. Using the edge extraction result (edge pixel), the foreground and background of the run packet are separated.

  FIG. 7 shows an example of determination when dividing an area.

  If both the start and end points of the same color pixel match, it is determined that the run packet data (foreground data) is the target of labeling. If both the start and end points are not edge pixels, the background data It is determined that

  FIG. 8 is a diagram illustrating a method of performing labeling for each line.

  Based on the relationship between the processing line 81 of the packet data to be labeled and the coordinate value of the start point and end point of the previous line 82, it can be expressed by a plurality of connection relationships. 83 is the case where the start point is connected, and 84 is the case where the end point is connected. These can be processed with the same label number. Reference numerals 85 and 86 denote overlapping cases, and these can also be processed with the same label number.

  87 is an example of a complicated pattern. In the previous line, three independent packets are all connected, but all three can be processed with the same label number. These can be easily processed by providing a connection relation management table for managing the connection relation.

  As shown in FIG. 9, since the conversion from the edge list to the labeling target pixel may be determined to be the edge pixel at both the start point and the end point, the labeling target pixel can be easily generated.

  FIG. 10 shows an example of a contour tracking method.

  The next boundary point is searched counterclockwise from the previous boundary point with the focused boundary point as the center.

  That is, an operation of searching for a pixel that changes from 0 to 1 among 8 pixels near (around) the target pixel is performed. This process is continued until returning to the point where the process is started. Thereby, an outline can be extracted as a loop.

  Further, vectorization is performed by approximating with a straight line or a curve using the end points of the contour and holding approximate vector data.

  In the present embodiment, the run packet generation condition is described as the arrangement of pixels of the same color. However, the present invention is not limited to this. For example, applying a method that allows variation in a certain range to be regarded as pixels of the same color, or a method that uses a sequence of pixels determined as pixels of the same class as a result of image processing such as clustering as a run packet. Gives the same result.

  In this embodiment, in an image processing apparatus that separates a foreground and a background of an image and separately compresses and encodes the foreground and the background, an input means (step) for inputting an image and edge detection for detecting an edge of the image Means (step), output means (step) for outputting packet data indicating the start point, end point and color of the same type of image by determining the continuity of the same type of image for each line of the image, and the above It is characterized by comprising determination means (step) for determining that both the start point and the end point are packet data corresponding to the edge as packet data corresponding to the foreground. This foreground corresponds to a character portion or a graphic portion.

  Note that a control method for controlling the image processing apparatus, a program for executing the control (recorded in a state readable by a computer), a storage medium storing the program, and the like are also included in the scope of the present invention. .

Diagram explaining encoding process Diagram explaining decryption process Diagram showing how the foreground and background are separated The figure explaining the method of producing | generating the run packet for every line Diagram explaining edge extraction Diagram showing edge extraction results The figure explaining the judgment which divides an area Diagram explaining labeling in line units Figure showing how to change from edge list to bitmap The figure which shows an example of the tracking method of an outline

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Scan image 11 PDL drawing image 13 Area division part 14 Foreground compression process part 15 Background compression process part

Claims (4)

An input means for inputting an image;
Edge detecting means for detecting an edge of the image;
For each line of the image, output means for outputting packet data indicating the start point, end point, and color of the same type of image by determining the continuity of the same type of image,
An image processing apparatus comprising: a determination unit that determines that both the start point and the end point are packet data corresponding to the edge as data corresponding to the foreground. An input process for inputting an image;
An edge detection step of detecting an edge of the image;
For each line of the image, an output step of outputting packet data indicating the start point, end point, and color of the same type of image by determining the continuity of the same type of image,
And a determination step of determining that both the start point and the end point are packet data corresponding to the edge as data corresponding to the foreground. A program for causing an image processing apparatus to execute the following:
An input process for inputting an image;
An edge detection step of detecting an edge of the image;
For each line of the image, an output step of outputting packet data indicating the start point, end point, and color of the same type of image by determining the continuity of the same type of image,
Determining the packet data in which both the start point and the end point correspond to the edge as data corresponding to the foreground,
A program readable from the computer.   A storage medium storing the program according to claim 3 in a state readable from a computer.

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