Printer for printing bold characters

Abstract: A printer that includes a means (13) for storing print data of a character; a first converter (11) for converting print data to be read into a single dot pattern by performing the function of logical OR of a total of four dot patterns, assuming that a print head moving direction is a horizontal direction. The four dot patterns are: the print data, data next to such print data, data four pieces of data ahead, and data five pieces of data ahead. The printer also includes an inverter (13) for inverting the single dot pattern generated by the first converter; a second converter (14) for converting two dot patterns into a single dot pattern by performing the function of logical AND of two dot patterns. These two dot patterns are: a dot pattern newly generated by the first converter and the dot pattern inverted by the inverter, so that the number of horizontally extending data of a bold character is changed and compressed to thereby create a reduced bold character and print such reduced bold character.

Description: The invention relates to printers which are capable of printing bold characters. With respect to characters to be printed by terminal printers, those not bolded, reduced, enlarged, etc. are considered normal characters. As shown in Figures 4(a) through 4(d), a conventional method of printing a reduced bold character involves the steps of creating a normal-width bold character shown in Figure 4(b) from a normal character shown in Figure 4(a), and of printing the created character at the same print timing T as the normal character while reducing the head moving speed V by half to V/2, to produce a reduced bold character shown in Figure 4(d) in a manner similar to a reduced character shown in Figure 4(c), where V is the speed of moving a print head for printing normal-width bold characters and T is the print timing. As another conventional printing method, as shown in Figure 5, the printer has previously stored character data designed as reduced bold character and prints such character data as print data at a head moving speed V that is the same as that of the normal-width bold character and at the same print timing T to produce a reduced bold character. However, the former conventional art requires that a unit for halving the head moving speed be provided. Also, the latter conventional art requires that character data designed as a reduced bold character for a normal character be stored in an internal memory, thus addressing the problem of reserving a memory capacity large enough to accommodate such data. Prior art document EP-A-0 207 789 discloses an apparatus for displaying dot matrix characters in enlarged form. This apparatus uses logic means comprising means for performing an OR function, inverting means and means for performing an AND function in order to increase the density of a character in a horizontal direction or direction of print head movement. It is an object of the present invention to provide a printer which allows a reduced bold character of a normal character to be printed without requiring a unit for halving the moving speed in a print head moving means and without storing reduced bold character data of a normal character in an internal memory. This object is solved by the printer according to independent claim 1. Further advantageous features and details of the invention are evident from the dependent claim, the description and the drawings. The invention creates such reduced bold character data of the normal character based on character data of the normal character. The printer especially includes character print data storage means for storing a plurality of horizontal print data of a character which are associated to respective rows of dots of the character to be printed, said rows being arranged in the direction of the print head movement, OR function performing means for performing an OR function of a group of data of said horizontal print data to obtain a single dot pattern data, said group of data including the present print data, the print data next thereto in the direction of the print head movement, the print data four pieces of print data downstream the print head movement and the print data five pieces of print data upstream the print head movement, inverting means for inverting said single dot pattern data generated by said OR function performing means to obtain an inverted single dot pattern data, and AND function performing means for performing an AND function of said single dot pattern data and said inverted single dot pattern data to obtain a print pattern dot data which is stored in print data creating means. The number of horizontally extending data of a bold character is thus changed and compressed to thereby create a reduced bold character and to print such reduced bold character. According to the printer of the invention, e.g., a 14-dot wide reduced bold character can be created from a 24-dot wide character in the following manner. The function of OR of two adjacent pieces of data and two adjacent pieces of data which are two pieces of data ahead of the reference data is performed. Then, the thus generated print data and a horizontally continuous pattern are masked to generate a single piece of print data. Accordingly, the horizontal print data can be compressed without damaging the vertical print data, thereby allowing a reduced bold character to be printed without changing the head moving speed. Figure 1 is a diagram showing a process configuration of the invention; Figure 2 is a block diagram showing an embodiment of the invention; Figures 3(a) and 3(b) are diagrams showing the basic concept for generating a reduced bold character; Figures 4(a) through 4(d) are diagrams showing an exemplary conventional art for printing a reduced bold character; and Figure 5 is a diagram showing an exemplary conventional art for printing a reduced bold character. An embodiment of the invention will now be described with reference to the accompanying drawings. Figure 2 is a block diagram showing a printer according to an embodiment of the invention. A control section 2, a head drive section 3, a carriage section 4, a sheet forward drive section 5, a character print data storage section 7, a character data conversion section 6, and an external interface section 8 are connected to a system bus 1. The control section 2 includes circuits for controlling the entire system. The head drive section 3 includes a head for printing characters and a drive circuit thereof. The carriage section 4 includes a carriage carrying the head and travelling in a sheet forward direction as well as in the vertical direction, and a drive circuit thereof. The sheet forward drive section 5 includes a motor for forwarding print sheets and a drive circuit thereof. The character print data storage section 7 stores the dot patterns of characters to be printed. The character data conversion section 6 converts the character data of a character to be printed by referencing the character data. The external interface section 8 intercommunicates data with a host computer. A conversion method employed by the character data conversion section 6 will then be described. Figure 1 is a diagram showing a conversion processing flow. Figures 3(a) and 3(b) are diagram showing the basic concept for compressing a 24-dot wide character into a 14-dot wide reduced character. Figure 3(a) shows character data expressed in 240 dots per 2.54 cm (240 dpi (dot per inch)). Each circle indicates a single dot to be printed. It is assumed that 24-dot wide character data are designated from left to right as 1, 2, 3, 4, 5, 6, ... 21, 22, 23, and 24. Numerals 1 to 24 designate the actual character data. Numerals -3 to 0 and 25 to 28 are NULL data appended before and after the actual character data for conversion purposes. Figure 3(b) shows character data of a 14-dot wide reduced bold character expressed in 240 dots per 2.54 cm (240 dpi). As in Figure 3(a) each circle indicates a single dot to be printed. It is also assumed that the 14-dot wide character data are designated from left to right as 1', 2', 3', 4', 5', 6', ... 10', 11', 12', 13', and 14'. The method of converting the data from Figure 3(a) to Figure 3(b) is as follows. The function of OR of NULL data -3, -2 and print data 1, 2 of the horizontal print data, which are stored in a character print data storage means 13 in Figure 1, is performed by an OR function performing means 11, and the function of AND of the above result and the NULL data inverted by an inverting means 12 is then performed by an AND function performing means 14. The data obtained therefrom is stored in data 1' in Figure 3(b) by a print data creating means 15. Similarly, the function of OR of NULL data -1, 0 and print data 3, 4 is performed, and the function of AND of the above result and data inverting the print data generated at data 1' in Figure 3(b) is then performed. The data obtained therefrom is stored in data 2' in Figure 3(b). Then, the function of OR of print data 1, 2, 5 and 6 is performed, and the function of AND of the above result and data inverting the print data generated at data 2' in Figure 3(b) is then performed. The data obtained therefrom is stored at data 3' in Figure 3(b). Further, the function of OR of print data 3, 4, 7 and 8 is performed, and the function of AND of the above result and data inverting the print data generated at data 3' in Figure 3(b) is then performed. The data obtained therefrom is stored at data 4' in Figure 3(b). Then, the function of OR of print data 5, 6, 9 and 10 is performed, and the function of AND of the above result and data inverting the print data generated at data 4' in Figure 3(b) is then performed. The data obtained therefrom is stored at data 5' in Figure 3(b). These operations are similarly performed repetitively to the stage in which the function of OR of print data 21, 22 and NULL data 25, 26 in Figure 3(a) is performed, and the function of AND of the above result and data inverting the print data generated at data 12' in Figure 3(b) is then performed. The data obtained therefrom is stored at data 13' in Figure 3(b). Further, the function of OR of print data 23, 24 and NULL data 27, 28 in Figure 3(a) is performed, and the function of AND of the above result and data inverting the print data generated at data 13' in Figure 3(b) is performed. The data obtained therefrom is stored at data 14' in Figure 3(b). Accordingly, the 14-dot wide reduced bold character is generated from the 24-dot wide character without losing the print data in the vertical direction. In addition, the print data to which emphasis is added is expressed in 240 dots per 2.54 cm (240 dpi) by masking the adjacent contiguous dots. As a result, the 240 dots per 2.54 cm (240 dpi), reduced bold character can be created, and thus created print data is in a density of 240 dots per 2.54 cm (240 dpi). That is, character data having print data whose density is X for a character can produce character data having print data whose density is X for the same character in the form of a reduced size. Since the density of the print data remains unchanged, it is no longer necessary to vary the print density by varying the print head moving speed, thus allowing a print head moving speed varying unit to be dispensed with. Further, since reduced characters are created in a bolded form, it is no longer necessary to internally store the character data thereof, thus allowing the internal memory to be saved. As described above, the invention allows character data for print data whose density is X to be created in a bolded and reduced form from character data for print data whose print data density is X. Therefore, it is not necessary to provide a print head moving speed varying unit to change the print density, nor is it required to internally store character data for reducing print character whose density is X.

Claims: A printer capable of printing a reduced bold character, comprising: character print data storage means (13) for storing a plurality of horizontal print data of a character which are associated to respective rows of dots of the character to be printed, said rows being arranged in the direction of the print head movement, OR function performing means (11) for performing an OR function on a present one of a plurality of sequential groups of said horizontal print data to obtain a present single dot pattern datum, and AND function performing means (14) for performing an AND function to obtain a present print pattern dot datum which is stored in a print data creating means (15), characterized by inverting means (12) for inverting a print pattern dot datum stored in a location relating to a sequential group preceding the present sequential group in said print data creating means (15) to obtain an inverted single dot pattern datum, said AND function performing means (14) performs an AND function on said present single dot pattern datum generated by said OR function performing means (11) and said inverted single dot pattern datum, and said present group of horizontal print data includes a present print datum, the print datum next thereto in the direction of the print head movement, a print datum four pieces of print data downstream the print head movement and a print datum five pieces of print data downstream the print head movement, the present print datum of the next sequential group being two pieces of print data downstream the present print datum of the present group. A printer as claimed in Claim 1, wherein said storage means (13) stores a 24-dot width character data and said AND function performing means (14) creates a 14-dot width character data.

Inventors: MOMOSE HIROAKI, MOMOSE, HIROAKI
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1992
Main classification: G06K15
IPC codes: G06K15, B41J2