Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1999-04-26
2003-01-28
Evans, Arthur G. (Department: 2622)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S001100
Reexamination Certificate
active
06512595
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a data processing apparatus and data processing method for converting color data into monochrome data to be outputted, and more particularly, to a controlling method of controlling a printer by utilizing a monochrome image printer driver for processing a printer control command transmitted from a host computer to a printer.
When a printer is connected to a host computer to output a print image, the host computer must have an interface corresponding to the printer. Recently computers generally include an OS (Operating System). In order to eliminate limitations of connectable types of printer, a printer driver is installed for each type of printers to maintain compatibility between the printer and OS.
Description will be provided, with reference to
FIG. 10
, on a printer driver for a conventional monochrome image printer which is connected to a host computer.
FIG. 10
is a diagram explaining process of a general image driver.
The host computer includes an OS (Operating System) for controlling interface (I/F) between a device and an application program. The application program
201
and a printer driver exchange data through the API
202
.
In a case where the application program
201
performs image rendering process for drawing a figure by combining an image, drawing, characters or the like, source image data, coordinates for strokes of the drawing, color information, character font information and so forth are transmitted to the printer driver through the API
202
.
In the printer driver, an image processing module
203
performs image processing appropriate for the target printer device in accordance with the type of image and characters. The processed data is transferred to a renderer
204
of the printer driver for performing rendering process on a rendering plane
205
which serves as a memory space.
The rendering plane
205
may be provided for one page, or may be provided as a band memory where one page is divided into plural bands, in accordance with the memory size of the system and the number of tones in a bitmap image. After rendering is performed on the rendering plane
205
, a rasterizer
206
converts the rendering data, rendered on the rendering plane
206
, into monochrome image data in the form which can be transferred to an image printer
207
. Then, the image is printed by the image printer
207
.
The printer driver can set a bit per pixel (BPP) value for the rendering plane
205
.
If an application program is started in the host computer and color image data is generated, data transmitted from the application program to the printer driver is color data. In the conventional technique, in order to accurately superimpose each color of an image, it is ideal to process the data in unit of 24 BPP (24 BPP: 1 pixel is expressed by R, G, B values each having 8 bits) as shown in the box indicated by reference numeral
208
.
However in a monochrome 1 BPP printer, it is inefficient to use memory space for 24 BPP. Therefore, there are ways to set a rendering plane to 8 BPP (
209
), or 1 BPP (
210
).
Note that 8 BPP (bit per pixel) and 1 BPP (bit per pixel) indicate that the number of bits allocated to one pixel is 8 bits and 1 bit respectively. In the case of 8 BPP, values from 0 to 255 can be expressed. Normally, color component data each color having 8 bits is allocated to a palette code expressed by 8 BPP palette.
The conventional process of converting color image data into monochrome image data, using 24 BPP rendering plane, is now described in detail with reference to FIG.
11
.
An object image rendered by the application program is transferred to a driver I/F
301
in unit of the object type (graphics
304
, image
308
). If the rendered object is graphics, the object data transferred to the driver I/F
301
includes coordinate data for a stroke representing a contour of the graphics, and R, G and B data indicative of a color of the contour or a color inside the graphics. If the rendered object is image data, color values of a source image are transferred to the printer driver
305
without being processed.
The printer driver
305
transfers the received data to the system I/F
302
without further processing. The system I/F
302
transfers the data to the rendering system
306
which performs rendering process in the 24 BPP band memory.
Upon completion of rendering all the objects in the 24 BPP band memory, the rendering system
306
transfers the head address of the band memory to the printer driver (rasterizer
307
) through the driver I/F
303
. The rasterizer
307
derives color values, pixel by pixel, from the head address of the band memory, and performs color conversion, monochrome conversion, binarization, and generate data to be transmitted to a printer.
Next, a conventional process using 8 BPP rendering plane is described in detail with reference to
FIGS. 12 and 13
. Only few monochrome printer drivers employ this method. However, this technique is generally used for displaying on a color display unit.
Reference numeral
406
in
FIG. 12
denotes a color palette for outputting color data using 8 BPP rendering plane, based on color values transferred from the application program in the host computer.
Each of the palette numbers
401
is set by the three primary colors: red, green, and blue, each having respectively values (each color having 8 bits) to express various colors. Conventionally, each color changes at a constant rate as shown in
FIG. 12
so that the colors are evenly distributed in the color space.
FIG. 13
shows a process of a monochrome printer driver using a conventional color palette as shown in
FIG. 12
where each color is evenly distributed in the color space.
In the initial setting of the system, a color palette
501
(
FIG. 13
) is registered. An object rendered in the application program side is transferred to a driver I/F
502
in unit of the object type (graphics
506
, image
511
, character
512
).
If the rendered object is graphics, the object data transferred to the driver I/F
502
includes coordinate data for a stroke representing a contour of the graphics, and R, G and B data indicative of a color of the contour or a color inside the graphics. If the rendered object is image data, color values of a source image are transferred to the printer driver
513
without being processed. Note that there is an operating system (OS) (e.g., Microsoft Windows NT 4.0) which designates the color of a character by using a color palette number registered in the system.
The printer driver
513
transfers the received data to the system I/F
503
without further processing. The system I/F
503
transfers the data to the rendering system
508
which performs rendering process in the 8 BPP band memory. The system searches for a palette number, and if the system finds an appropriate color in the color palette
501
, rendering process is performed using the value in the color palette. If the system does not find an appropriate color in the palette
501
, a color mixture pattern is generated with neighboring colors (dither process) and rendering process is performed.
Upon completion of rendering all the objects in the 8 BPP band memory, the rendering system
508
transfers the head address of the band memory to the printer driver (rasterizer
510
) through the driver I/F
504
. The rasterizer
510
derives color values, pixel by pixel, from the head address of the band memory, and performs color conversion, monochrome conversion, binarization, and generate data to be transmitted to a printer.
In monochrome image data generation, high image quality can be achieved if a 24 BPP rendering plane is used. However, using 24 BPP rendering plane requires a large memory capacity for the rendering area, and decreases speed because color conversion processing has to be performed on all pixels after rendering operation.
On the other hand, if a 1 BPP rendering plane or 8 BPP rendering plane is used, the process speed increases compared to the 24 BPP rendering plane, but the image quality is deterior
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