Character pattern generator

Abstract: A character pattern generator which is detachably connected to an output device for outputting a pattern as a set of dots, includes a memory for storing a character or figure pattern in a format other than a dot image format, a CPU for converting the character or figure pattern stored in the memory into a dot image in accordance with a pattern request from the output device, and an interface for sending the dot image of the character or figure converted by the CPU to the output device.

Description: BACKGROUND OF THE INVENTION: Field of the Invention The present invention relates to a character pattern generator which can be attached to an output device. The character pattern generator stores patterns of, e.g., characters, figures, and the like in a format other than a dot image. The stored character or figure pattern are to be converted into a dot image. The dot images are to be sent to the output device. Related Background Art In a detachable character pattern generator for storing patterns of characters, figures, and the like in a format other than a dot image which can be displayed or printed without processing, the output of this generator is its stored content itself, and processing for converting the output into a displayable or printable dot image must be performed by a device (to be referred to as an "output device" hereinafter) to which the detachable character pattern generator is attached. However, since the conventional processing for converting the output from the generator into a displayable or printable dot image is performed in the output device, the following drawbacks are posed. (1) The processing load of the output device is increased, and the entire processing speed is decreased. (2) The generator must store the character pattern in a format corresponding to a processing algorithm so that the stored pattern can be converted into a printable dot image by the output device. The present invention has been made in consideration of the above situation. French Patent Specification No. FR-A-2,588,212 discloses image processing apparatus to which a character generator can be mounted. The conversion of the non-dot data of the character pattern generator is effected in the output device. Patent Abstract of Japan, vol.9, no.40 (P-336) [1763], 20 th Febr. 1985 (JP-A-59 180 678) provides for the conversion of the non-dot data in a subprocessor within a printer. In accordance with the invention there is provided the combination of an image output device and a memory device as set out in claim 1. An embodiment of the present invention provides a character pattern generator which stores a pattern in a format other than a dot image, can convert it into a dot image in parallel with processing in the output device, and can store the dot image in a cache memory. Another embodiment of the present invention provides a character pattern generator which can start and execute development to a dot pattern described above in a cartridge in parallel with processing in the output device when a power switch of the output device is turned on. A still further embodiment of the present invention provides a character pattern generator which, when the output device requests a certain character in a certain character set, can develop a character group of the character set (e.g., fonts, attributes, and the like) into a dot image in parallel with processing in an output device in a cartridge. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a character pattern generator of the present invention; Fig. 2 shows an example of a character which is stored in a format other than a dot image which can be displayed or printed without processing; Fig. 3 shows a character pattern represented by the data shown in Fig. 2; Fig. 4 shows a displayable or printable dot image obtained by converting the data shown in Fig. 2; Figs. 5 to 9 are operation flow charts of an embodiment of the present invention; and Fig. 10 is a sectional view showing a structure of an output device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a block diagram of a character pattern generator which can be attached to an output device. The generator includes a CPU 1 for controlling the overall generator, a bus 2 including address, data, and control lines of the CPU 1, a RAM 3 used as a work area, and the like of the CPU 1, a program ROM 4 for storing processing programs (to be described later) of the CPU 1, a character pattern ROM 5 for storing patterns of characters, figures, and the like in a format other than a dot image format. For example, the ROM 5 stores a pattern as data representing outlines of a character by a coordinate point string (normally called a vector font, outline font, or the like). An output device interface 6 exchanges commands, dot image data, and the like with an output device to which the generator is attached, and normally comprises a sharing RAM, a 2-port RAM, an FIFO memory, or the like. Although not shown, the generator is powered by the output device (printer), as a matter of course. The program ROM 4 and the character pattern ROM 5 may comprise a single ROM. Fig. 2 shows an example of a character or figure pattern stored in a format other than a dot image format which can be displayed or printed without processing. In this case, the outlines of a character "A" are expressed by lines. Fig. 3 shows a pattern of the character "A" represented by the data shown in Fig. 2. A method of storing a character or figure pattern in a format other than a dot image pattern which can be displayed or printed without processing is not limited to that described above. For example, a method of representing outlines of a pattern by lines, various curves or their combinations, a run length font, and the like may be employed as long as a pattern is stored in a format other than a dot image format. Fig. 4 shows a displayable or printable dot image obtained by converting the character "A" expressed by the data shown in Fig. 2. In the above arrangement, an operation of this embodiment will be described below with reference to the flow chart shown in Fig. 5. The program of this flow chart is stored in the ROM 4. When a dot image is requested by, e.g., a command from the output device through the output device interface 6 (S1), the CPU 1 converts a character or figure pattern stored in the character pattern ROM 5 in a format other than a dot image format, into a displayable or printable dot image which can be displayed or printed without processing, (Fig. 4) according to a conversion processing program in the program ROM 4 (S2). The CPU 1 informs completion of conversion to the output device by interruption or the like, and outputs the dot image to the output device through the output device interface 6 (S3). Note that an object to be converted may be, e.g., data of one page to be output or offset character data (according to a frequency, fonts, and the like). Thus, a necessary character need only be transferred to the output device. The output device need not convert the character or figure pattern into a displayable or printable dot image, thus reducing the processing load of the output device and increasing the processing speed. Since the output device does not convert the pattern into a displayable or printable dot image, a character pattern corresponding to a unique conversion method can be stored. In the embodiment shown in Fig. 1, a temporary storage area (normally called a font cache) for temporarily storing a displayable or printable dot image, and for, when the stored dot image of a character or figure is requested from the output device, outputting the temporarily stored dot image to the output device may be allocated in the RAM 3. The CPU 1 need not always be a versatile microprocessor but may be a special-purpose processor such as an outline font processor for converting a pattern into a displayable or printable dot image or a combination of a CPU and a special-purpose ALU. As described above, the character pattern generator comprises a means for storing a character or figure pattern in a format other than a dot image format, converts the stored character or figure pattern into a dot image, and outputs the dot image to an output device. Note that the character pattern generator may be a cartridge or a card which is loaded in a slot of the output device and has a program for conversion to fonts, data, and dots. Conversion to a printable dot image in a cartridge can be executed in parallel with processing in the output device. For example, when the output device comprises a dot printer, the dot printer can parallelly execute processing of data input, data analysis, layout, image drawing, and the like while the character pattern generator converts a character or figure pattern into a printable dot image. The printer may be an ink-jet printer, a thermal printer, a liquid crystal shutter printer, or the like as long as it is a dot printer. The same applies to a case wherein the output device comprises a display device such as a CRT, a liquid crystal display, or the like for displaying a dot pattern. Embodiments shown in Figs. 6 to 9 will be described below. The flow charts of Figs. 6 to 9 are stored in the program ROM 4 or a ROM in an output device (not shown). In these embodiments, an area in the RAM 3 shown in Fig. 1 is used as a cache memory. In step S1 in Fig. 6, it is checked if a dot image request command is received from the output device (host). If YES in step S1, a pattern which is stored in the character pattern ROM in Fig. 1 in a format other than a dot image format is converted to a dot image in step S2. Completion of conversion is informed to a host side by interruption or the like. In step S3, the dot image is stored in a cache memory (3 in Fig. 1). In step S4, the dot image data is sequentially transferred to the output device. In this case, the dot image data is, e.g., data of one page to be output. Fig. 7 shows flow charts for explaining processing operations in the output device (host) and a cartridge. When the power switch of the output device is turned on, the output device is initialized in step S1. In step SS1, offset character data is converted to dot data in the cartridge. In the output device, it is checked in step S2 if an output request command from a host 1100 (Fig. 10) is received. If YES in step S2, the flow advances to step S3. In step S3, layout processing (e.g., determination of output positions, and the like) necessary for output is executed, and a character request command is transferred to the cartridge. In the cartridge, it is checked in step SS2 if the character request command is received from the output device. If YES in step SS2, the flow advances to step SS3. In step SS3, it is checked if a necessary character has already been converted to dot data in step SS1. If YES in step SS3, the flow advances to step SS5; otherwise, the flow advances to step SS4. In step SS4, data corresponding to a necessary character and stored in the ROM 5 (Fig. 1) in a format other than the dot image format is converted to dot image data. It is checked in step SS5 if data of one page necessary for output is converted to dot data. If YES in step SS5, completion of conversion is informed to the output device by interruption. Thereafter, dot data is transferred to the output device through the interface 6 (Fig. 1). The output device performs printing on a printing medium based on the transferred dot data in step S4. Fig. 8 is a flow chart showing still another processing in the cartridge. In step S1, it is checked if a dot image request command is received from the output device. If YES in step S1, the flow advances to step S2 to check the sort of the requested image (e.g., font, character type, size, and the like). In step S3, all images of the sort determined in step S2 are converted to a dot pattern (e.g., if a Gothic type is determined, all the Gothic type characters are converted to dot patterns). In step S4, the dot pattern is stored in a cache memory. Thereafter, the requested image is sent to the output device. Fig. 9 shows processing in the output device. It is checked in step S1 if a cartridge is loaded in a slot. If YES in step S1, execution of the processing operations shown in Figs. 5 to 8 is enabled. If NO in step S1, a dot pattern meeting the request from the host is obtained based on a font (dot font, nondot font) of the printer in step S2. Fig. 10 is a sectional view showing an internal structure of a laser beam printer (to be abbreviated to as an LBP hereinafter) as the output device. The LBP can register character patterns from a data source (not shown) or a standard format (form data). In Fig. 10, a LBP main body 1000 (Fig. 10) receives and stores character data (character code), form data, or a macro command supplied from an external host computer (1100 in Fig. 10), and generates a corresponding character or form pattern according to these data to form an image on a sheet as a medium. The LBP 1000 includes an operation panel 1012 on which operation switches, LEDs and the like are arranged, and a printer control unit 1001 for controlling the entire LBP 1000 and analyzing character data and the like supplied from the host computer. The printer control unit 1001 mainly converts character data into a video signal of a corresponding character pattern, and outputs the signal to a laser driver 1002. The laser driver 1002 is a circuit for driving a semiconductor laser 1003, and ON/OFF-controls a laser beam 1004 emitted from the semiconductor laser 1003 in accordance with the input video signal. The laser beam 1004 is deflected by a rotary polygonal mirror 1005 to scan the surface of an electrostatic drum 1006. Thus, an electrostatic latent image of a character pattern is formed on the electrostatic drum 1006. The latent image is developed by a developing unit 1007 around the electrostatic drum 1006, and is then transferred onto a paper sheet. As the paper sheets, cut sheets are used. The cut paper sheets are stored in a paper cassette 1008, and each sheet is picked up by a paper feed roller 1009 and convey rollers 1010 and 1011 to be fed to the electrostatic drum 1006.

Claims: A combination of an image output device, i.e. a printer, and a character pattern generator, the character pattern generator being detachably connected to the output device and being adapted to store a character or figure pattern in a format other than a dot image format; the combination also comprising means to convert in accordance with a pattern request from the output device the non-dot data of the character pattern generator into a dot image format, characterised in that said converting means is incorporated in the detachable character pattern generator and not in the output device so that conversion into the dot image format can take place in the character pattern generator in parallel with the processing being carried out in the output device thus reducing the load on the output device, the character pattern generator further comprising sending means for sending the dot images converted by the converting means to the output device. A combination according to claim 1 wherein said character pattern generator includes memory means (4) for storing processing programs; a central processing unit (CPU 1) for utilizing the processing programs; and a character pattern memory (5) for storing patterns of characters, figures and the like in a format other than a dot image format. A combination according to claim 2 wherein said character pattern generator includes a volatile memory (3) for storing generated character pattern data to be transmitted to said output device. A combination according to any preceding claim wherein the character pattern generator is in the form of a cartridge detachably mounted on said output device.

Inventors: SHIMURA AKIHIRO, SHIMURA, AKIHIRO
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1990
Main classification: G06K15
IPC codes: B41J2, G06K15, G06F3, G09G5