Facsimile and static presentation processing – Static presentation processing – Communication
Reexamination Certificate
1998-01-22
2002-02-19
Popovici, Dov (Department: 2622)
Facsimile and static presentation processing
Static presentation processing
Communication
C358S001170
Reexamination Certificate
active
06348969
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image output control method and printing apparatus for receiving print data from a source for supply of data such as a host computer and printing out the data on a medium such as paper.
2. Description of the Related Art
A system for processing and printing documents such as a document creating and printing system generally is constructed as shown in FIG.
2
. The system is constituted by a host computer
101
serving as a processor for subjecting an output document to processing such as typesetting, and a printer
102
connected to the host computer
101
for fixing output document data, which is the result of processing by the host computer, on a medium such as paper by performing printing on the medium. More specifically, the user employs the host computer
101
to edit an image that is to be output. When editing ends, the host computer
101
converts the edited document data to an output image, i.e. print data, that will be accepted by the printer
102
, and sends this data to the printer
102
. In accordance with the data input thereto, the printer
102
performs the actual printing on the paper.
The printer
102
includes a printer controller
1021
and a printer engine
1022
. The processing executed by the printer controller
1021
will be described in detail with reference to the block diagram of FIG.
3
and flowchart of
FIG. 4
, which exemplify examples of the prior art.
FIG. 3
is a block diagram showing the internal components of the printer controller
1021
. Specifically, an interface
201
receives print data from a source for supply of data such as the host computer and performs an exchange of status with the host computer. A control unit
202
controls the overall printer apparatus and executes data processing. A memory controller
203
controls a DRAM
204
, which is a main memory provided within the printer controller. A DMAC
205
is provided so that the printer controller may send image data to a printer engine
207
at the time of printing. An engine interface
206
sends the printer engine
207
image data output via the DMAC
205
. The printer engine
207
fixes the image data, which has been output by the engine interface
206
, on a medium such as paper, thereby realizing printing.
FIG. 4
is a flowchart showing an example of the operation of the printer controller illustrated in the block diagram of FIG.
3
.
Print data is received from a source for supply of data such as the a computer (step S
301
). The print data may be characteristic code data usable by the printer or a print instruction, referred to as page description language (PDL), to the printer. The received data is stored in the DRAM (step S
302
). In order to compensate for a difference in speed between the communication speed of the interface and the speed of data processing, the received data generally is buffered temporarily in a memory area, referred to as a reception buffer, of the DRAM
204
. The processing of step S
302
corresponds to this operation.
Next, the stored data is analyzed and preparation for printing the image is performed (step S
303
). In this example, band processing is executed. According to banding processing, the memory capacity of a full bitmap area is not used. Rather, use is made of two band memory areas (referred to as band buffers) of a size obtained by partitioning the paper size into prescribed widths in the main-scan direction. Image data is developed in these band buffers. With band processing, image data that has been stored in one band memory area is printed, during which time image data is generated in the other band memory area. Band processing is achieved through use of this double-buffer format employing two band buffers. To accomplish this, conversion of data to intermediate codes capable of undergoing banding processing is carried out at step S
303
. In regard to one page of data, an area obtained by partitioning the data according to the size of the band member is referred to as a band or print band.
Next, the image of the initial print band is developed in one of the band areas (S
304
). In actuality, since the format used here is the double-buffer format, only the images of the initial two bands, for which printing has not yet begun, are generated in the two band memory areas. Processing for generating image data based upon object data such as character codes and visualizing the generated image data shall be referred to as “rendering” below.
When rendering is completed, the DMAC
205
and engine interface
206
are set in a print-enabled state and the printer engine
207
is started (step S
305
). Printing is performed using the bit image already generated at step S
304
(S
306
).
When image data is sent to the printer engine
207
via the DMAC
205
and engine interface
206
and the band memory is left empty, the control unit
202
renders the image data corresponding to the next print band in this band memory via the memory controller
203
(step S
307
).
When the printing of image data in one band memory is completed, page end is judged at step S
308
. If the printing of one page is not finished, the input to the DMAC
205
and engine interface
206
is changed over to the band memory from which printing is be performed next, thereby to prepare for the printing of the next band (S
309
). More specifically, resetting of the DMA transfer address and changing of the band memory address rasterized by the control unit
202
are performed taking advantage of an interrupt which gives notification of the end of transfer of the band image data from the DMAC
205
.
If band changeover has been performed, the DMAC
205
and engine interface
206
transfer the image data of the next band to the printer engine
207
and the next band is printed by the engine. In addition, the control unit
202
rasterizes the image of the next band in the band memory whose image data has already been sent. One page of printing is achieved by repeating this operation.
It has been presumed here that two band memories serve as the areas for developing band images. Before the printer engine
207
is started up, rendering in these two band memories is completed at step S
304
. As a consequence, in the initial band printing, parallel operation in which the image data is rasterized while it is being transmitted does not occur. Further, since data to be printed vanishes also in regard to the operating sequence prior to the end of one page, parallel operation does not occur.
Further, arbitration for access to each DRAM due to a data request from the DMAC
205
at the time of parallel operation and data write by rasterization from the controller
202
is carried out by the memory controller
203
.
In a device which performs one page of printing by executing such band processing without possessing one page of bitmap memory, rasterization processing during parallel operation cannot keep up with the sending of print data when the image to be rendered is complicated or when the printing speed of the printer is high. This phenomenon is known as overrun. The same problem arises also in an apparatus which handles grayscale image data by allocated a plurality of bits to each pixel to realize grayscale representation.
There is available a processing system which, in order to prevent overrun, avoids parallel operation by using a memory area which stores one page of image data. This memory is a so-called bitmap memory (or a byte map memory in case of a multilevel image of eight bits per pixel). This is a processing system equipped with a so-called full-page memory. Further, apparatus have appeared which, in order to improve memory efficiency and hold down cost, come equipped with one page of compression memory that utilizes data compression technology.
In any case, with a processing system of this kind, user interface specifications with which a printer apparatus is equipped, namely printer language (PDL) and commands, are converted to more primitive intermediate codes and image data is generated from these
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Popovici Dov
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