Image analysis – Image compression or coding – Interframe coding
Reexamination Certificate
1998-10-06
2001-10-09
Grant, II, Jerome (Department: 2624)
Image analysis
Image compression or coding
Interframe coding
C348S416100
Reexamination Certificate
active
06301391
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coding apparatus which codes data to be transmitted.
2. Description of the Related Art
Recently, almost all documents used in offices are produced by personal computers or word processors. There are relatively few documents produced through handwriting.
Most documents produced by personal computers or word processors include letters and ruled lines, but typically do not include photographs.
In images of these documents, a certain degree of regularity is present in sizes, shapes, intervals, arrangements and so forth of letters. In contract to this, in images of photographs or handwritten documents, such characteristics are not present.
In an apparatus which treats an image as electronic information such as a facsimile machine or a digital copier, an input image is optically scanned through a scanner or the like so that the input image is converted into electronic information.
An amount of electronic information obtained through this conversion depends on the resolution and the size of the image. This amount becomes larger as the resolution or the size of the image increases. Ordinarily, the electronic information obtained through such conversion is stored in a storage area temporarily. Therefore, as the amount of information increases, the necessary capacity of the storage area increases.
Especially, recently, there is a trend that the resolution increases. Thereby, the necessary capacity of a memory or a disk for storing electronic information of images increases, and the costs therefor increase.
In order to solve this problem, there is a method for efficiently coding an input image. Typical examples of image coding are MH, MR and MMR methods which are used in facsimile machines and so forth. In each of these methods, images are coded for each raster without regard to the types of the images. Therefore, these methods can be used for most types of images.
Such an image coding method will now be described in detail. Image coding methods can be classified into those for bi-level images and those for multilevel images. The MH, MR, MMR coding methods are those for bi-level images, and are standard coding methods for facsimile machines. Further, recently, a coding method using arithmetic code has been watched, and a coding method called QM-coder is used in a JBIG method which is studied as a standard method in ITU-T (International Telecommunication Union—Telecommunication Standardization Sector) and ISO (International Organization for Standardization).
On the other hand, as the coding methods for multilevel images, there is an ADCT (Adaptive Discrete Cosine Transform) method (called a JPEG method) using DCT (Discrete Cosine Transform) which is studied as a standard method in ITU-T and ISO. In this method, after image information is converted into frequency information, the information is coded.
Accordingly, in an image processing apparatus provided with a coding apparatus in the related art, by using such coding in the related art, an amount of information is compressed, and it is possible to reduce a memory capacity.
In the coding apparatus in the related art, it is possible to efficiently code letter images. However, for images of photographs, images of handwritten letters or the like, it is not possible to sufficiently efficiently code the images.
Further, in a case where letter images are coded, information such as characteristics of the letters are not used, and the letter images are simply treated as images. Therefore, it is not possible to code the images with a very high coding efficiency.
SUMMARY OF THE INVENTION
The present invention is directed to eliminating the above-mentioned problems, and an object of the present invention is to provide a coding apparatus which can perform coding at a high speed, accurately, with a very high coding efficiency.
In many cases, in a letter image produced by a personal computer or a word processor, there is regularity in shapes, sizes and so forth of letters. Therefore, by using such regularity, it is possible to perform coding of such a letter image with a high efficiency.
A coding apparatus, according to the present invention, comprises:
an image-area dividing portion dividing input image information into block areas of image information for respective letters and/or figures;
an area-image-information storing portion storing the block areas of image information provided by the image-area dividing portion;
a similar-image selecting portion comparing a currently processed block area of image information with the block areas of image information already coded and stored in the area-image-information storing portion, and selecting and extracting a block area of image information, from the block areas of image information stored in the area-image-information storing portion, which block area is similar to the currently processed block area of image information;
a similar-image determining portion determining the similar block area of image information selected and extracted by the similar-image selecting portion to be an identical block area of image information when determining that the similar block area of image information is identical to the currently processed block area of image information, determining the similar block area of image information to be a useful similar block area of image information when determining that the similar block area of image information is so similar to the currently processed block area of image information that the similar block area of image information is useful in coding the currently processed block area of image information, and determining the similar block area of image information to be a non-useful similar block area of image information when determining that the similar block area of image information is not sufficiently similar to the currently processed block area of image information such that the similar block area of image information is not useful in coding the currently processed block area of image information;
an identical-image coding portion obtaining a code for the currently processed block area of image information as a result of coding an index indicating the identical block area of image information, when the similar-image determining portion determines that the similar block area of image information is the identical block area of image information;
a first predictive coding portion obtaining a code for the currently processed block area of image information as a result of performing predictive coding using the useful similar block area of image information, when the similar-image determining portion determines that the similar block area of image information is the useful similar block area of image information;
a second predictive coding portion obtaining a code for the currently processed block area of image information as a result of performing predictive coding, when the similar-image determining portion determines that the similar block area of image information is the non-useful similar block area of image information; and
a code-information producing portion producing code information based on the codes obtained by the identical-image coding portion, the first predictive coding portion and the second predictive coding portion.
Thereby, it is possible to perform the coding operation with a high efficiency.
The area-image-information storing portion may store information of a size and a position of the block area for each block area of image information, instead of storing the block area of image information itself.
When the block areas of image information themselves are stored, a large storage capacity is needed. As a result of storing the information of the size and the position of the block area for each block area of image information, it is possible to reduce a necessary storage capacity, and the block area of image information can be referred to as a result of the size and the position of the block area being specified. Further, as a result of additionally storing an index for
Grant II Jerome
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
Worku Neggisie
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