Image analysis – Image compression or coding
Reexamination Certificate
1999-05-03
2003-04-15
Mehta, Bhavesh (Department: 2621)
Image analysis
Image compression or coding
C382S284000, C382S305000
Reexamination Certificate
active
06549663
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique for image processing, and more particularly to an apparatus and methods for overwriting image data at low cost and high speed.
2. Discussion of the Related Art
Overwriting of images is the process of overwriting an image with another image of a predetermined unit. It includes, for example, overwriting with non-transparent ink by PS(Post Script,“PostScript Reference Manual, Second Edition” Adobe Systems, Ascii), a type of PDL(Page Description Language). A“predetermined unit” may be a single raster or a plotting object.
Although usual image processing, such as enlargement, reduction and spatial filtering(“lmage Analysis Handbook” Tokyo University Press), can be performed in one direction from the left upper side of an image to the right bottom side, overwriting cannot be performed in one direction with respect to the space coordinates of an image.
In an overwriting process, the overwriting image may be input randomly with respect to the space coordinates of the output image. Therefore, if the process is performed in the input order, it cannot be performed in the order of the space coordinates on the output image side. FIGS.
13
(
a
) and
13
(
b
) show an example of overwriting, wherein
210
and
211
are plotting objects. FIG.
13
(
b
) is the output result of overwriting
210
with
211
. It can be understood from the drawings that a random scan needs to be performed on the output image, and that a page memory is necessary in an overwriting process.
Overwriting is performed by manipulating a data under process. When expressed as a data flow, it can be seen that a feedback loop appears during the process. Feedback loops cause overheads in the processing time that leads to controlling complications, and therefore are generally preferred to be shorter.
Smaller page memories are also preferred. With the high resolution of image data in recent high image quality printing apparatuses, reducing of memories remains a crucial problem despite the decrease in the unit price of memories. The following are examples of methods suggested hereto to reduce page memories.
The first method is disclosed by Japanese Laid-Open Patent Application No.5-31974. This method aims to reduce the required memory volume by applying image compression coding when storing overwritten image data to a page memory.
FIG. 14
is a block diagram illustrating this method. The block diagram is modified to best illustrate this method in relation to the present invention, within limits not prejudiciary to the disclosure.
As shown in
FIG. 14
, an input image data
110
is input to an image input unit
10
. An overwriting unit
20
overwrites the input image data
110
over a stored image data
140
with predetermined small areas as processing units, and outputs the result to a small area buffer
30
as a processed image data
120
. The small area buffer
30
outputs the processed image data
120
to an output switching unit
40
as a processed image data
130
. The output switching unit
40
outputs the processed image data
130
to the coder
50
as an output image data
150
if the overwriting is complete, and if not, to the overwriting unit
20
as the stored image data
140
. The coder
50
performs a predetermined compression coding upon the output image data
150
and outputs the result to a compressed page memory
60
as a code data
160
. The compressed page memory
60
stores the code data
160
until code data correspondent to all of the small areas are complete, and then outputs them to a decoder
70
as a code data
170
. The decoder
70
transforms such decoding that is the reverse transform of the coding performed by the coder, and outputs the result as a decoded image data
180
to an image output unit
80
. The image output unit
80
outputs the decoded image data
180
to an external device.
FIG. 15
is a flow chart showing the operations of this method. In this method, image data are divided into partial image data. Each partial image data is referred to as a small area. The image data currently under processing is called a target image data and the small area currently under processing is similarly called a target small area.
As shown in
FIG. 15
, the input image data
110
is input in the image data input unit
10
in step
10
. In step
20
, the input image data
110
is handled in small area units and the process proceeds to step
30
if the area currently being input is correspondent to the target small area, or to step
50
if it is not. In step
30
, the target small area stored in the target small area
30
is read out as the stored image data
140
through the output switching unit. In step
40
, the overwriting unit
20
overwrites the input image data
110
over the stored image data
140
. In step
50
, the small area is skipped because the input image data
110
does not correspond to the target small area. In step
60
, it is determined if processing is complete for all of the small areas of the target image data. The process proceeds to step
70
if all are complete, and returns to step
20
otherwise.
In step
70
, it is determined if processing is complete for all of the input image data. If all are complete, the process proceeds to step
80
, and to step
90
if not. In step
80
, the coder
50
codes the output image data
150
the overwriting of which is complete, and stores the coded data in the compressed page memory
60
. In step
90
, the next image data becomes the target image data. In step
100
, it is determined if overwriting is complete for all of the small areas. The process proceeds to step
110
if it is, and to step
120
if not. In step
110
, the decoder
70
decodes the coded data
170
and outputs the result to the image output unit
80
. In step
120
, the next is small area becomes the target small area, and the first image data of the input image data
110
becomes the target image data.
The coder
50
and the decoder
70
performs such image data compression coding that renders the resulting data quantity of the code data
160
smaller than that of the processed image data
150
. In the disclosure of this method, compression using DCT(Discrete Cosine Transform) is discussed as an example.
According to this method, the overwritten image data is complete is stored in a coded state. Therefore, reduction of required memory is possible since storage capacity enough to store the code quantity of a page worth of image data is only needed. The memory aimed to store a page worth of image data in a compressed state is referred to as a compressed page memory hereinafter.
This method performs the coding process in the pixel order of the output image. Therefore, it is necessary to repeatedly input the input image in accordance with the output image. The resulting increase in the processing time is a problem with this method.
The second method explained hereafter has been suggested in order to solve this problem and is disclosed by Japanese Laid-Open Patent No. 5-37789. According to this method, image compression coding is performed to image data under an overwriting process and the result is stored in a page memory. This way, the necessary memory capacity is reduced and image data needs to be input only once as well.
FIG. 16
is a block diagram illustrating this method. The parts similar to those of the first method have the same numberings and perform the same functions as in
FIG. 4
, and therefore are not repeatedly discussed in detail.
141
is a stored image data and
181
is a decoded image data.
FIG. 17
is a flow chart showing the operations of this method. Here again, the operations similar to those of the first method have the same numberings and perform the same functions, and therefore are not repeatedly discussed in detail.
As shown in
FIG. 17
, a decoder
70
decodes a code data
170
of a target small area stored in a compressed page memory
60
in step
31
, and the resulting data is stored in an overwriting unit
20
as a stored image data
141
through an
So Ikken
Yokose Taro
Fuji 'Xerox Co., Ltd.
Mehta Bhavesh
Oliff & Berridg,e PLC
Patel Kanji
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