GB2327790A - Printing in outline form - Google Patents

Abstract

When outline characters are printed, a modified bit map is produced, wherein each bit of an original bit map and the four bits surrounding it are used to generate a corresponding bit of the printed outline character, and wherein the latter bit is only set when the original bit was on and simultaneously at least one of the four surrounding bits was off. This is simple and effective.

Description

A Printer Capable of and a Method for Outline Printing The present invention relates to printing apparatus and, in particular, is concerned with printing apparatus capable of outline printing.

Known tape printing apparatus of the type with which the present invention is generally concerned are disclosed in EP-A-322 918 and EP-A-322 919 (Brother KK) and EP-A-267 890 (Varitronic, Inc.). The printers each include a cassette receiving bay for receiving a cassette or tape holding case. In EP-A-322 918, the tape holding case houses an ink ribbon, a transparent image receiving tape and a double-sided adhesive tape which is secured at one of its adhesive coated sides to the image tape after printing and which has a backing paper peelable from its other adhesive side. In EP-A-267 890, the cassette houses an image receiving tape and an image transfer medium. With both these apparatus, the image transfer medium (ink ribbon) and an image receiving tape (substrate) are in the same cassette.

Many printers and display devices make use of outline characters, also called blanked characters, from which the inner portions are removed. Since such outline characters are infrequently used, the preparation of special outline fonts for outline characters is disadvantageous from an economical viewpoint. Accordingly, when necessary, outline characters are formed by processing the fonts of ordinary characters memorized in a character generator. In the prior art, different methods for converting normal dot pattern data into outline data are known: DE-C-28 12 433 teaches to transmit data corresponding to an original to a recording apparatus, and to reproduce only the outline when large black areas are to be printed. The decision whether a dot is printed or not depends on the status of the original dot, and the left and right neighbours viewed in the printing direction. When both neighbours are black, the actual dot is not activated, even when it is black. This simple algorithm does apparently not reproduce horizontal lines which constitute a boundary correctly.

EP-A-323 240 proposes to shift a character pattern vertically or horizontally in order to produce an outline of a character pattern. The outline is obtained by an exclusive or operation.

The obtained so-called blank character pattern is enlargened (magnified). Finally, the enlargenend blank character pattern, and a thickened magnified source pattern are used for obtaining a magnified blanked character pattern with a thick contour. The latter operation is performed by shifting the magnified blank character to the same side or sides to which dots are added to the magnified thick character, and removing a portion of dots from the magnified thick character. The enlargened pattern can be displayed or printed.

EP-A-375 219 refers to forming outline characters, as well.

Original character data expressed by a dot pattern are read from a storage means, then the original character data are shortened by removing the upper or lower end of a the data (only when the original character data exist at an upper or lower end of a display space), then the shortened original character pattern is peripherally expanded, and finally the shortened character is removed (exclusive or) from the expanded character.

These methods are however complicated (like those taught in EP A-323 420 or EP-A-375 219), such that it would be expensive to implement them in a tape printer with few available memory space, or too simple, like the method described in DE-C-28 12 433, such that they do not reproduce the outline correctly.

The object of the present invention is to provide a simple printer capable of outline printing, and a method for converting dot pattern data into outline data, which is simple and effective.

According to a first aspect of the invention, there is provided a printer for printing on an image receiving medium, the printer comprising: input means for receiving input data defining an image comprising at least one character and/or symbol to be printed on the image receiving medium; first storage means for holding font data defining characters and/or symbols printable on said image receiving medium, each character or symbol being defined as a bit map in said first storage means or being convertable into a bit map; second storage means for holding a outline conversion algorithm, said printing apparatus being operable to print characters and/or symbols selectively in a first form as characters defined by the bit map, and in a second form as an outline character; processing means connected to receive said input data, said font data and outline selection data and operable to generate therefrom print information comprising a plurality of pixels, wherein each bit of said bit map and the four bits surrounding each bit are used to generate a bit in the printed outline character, and wherein said bit is only set when it is on and simultaneously at least one of the four surrounding bits is off; and printing means for selectively printing the image on the image receiving medium in accordance with the print information.

The original bit map of a character and/or symbol is used for producing the bit map of an outline character, whereby for each bit the surrounding four bits are considered. When at least one of the surronding bits is off, the bit is positioned at a location defined at the outline of the character (provided it is on) and consequently maintains its original status. Otherwise, it is set off. Thus, a blanked character dot pattern is obtained, which has outlines with a thickness of one bit (pixel).

A bit positioned at the border of the bitmap is maintains its original status in the printed outline character.

Further, the present invention provides a method for printing an image onto an image receiving medium, the method comprising the steps of: selecting at least one character and/or symbol to be printed on the image receiving medium; storing font data defining characters and/or symbols printable on said image receiving medium, each character or symbol being defined as a bit map in said first storage means or being convertable into a bit map; selecting whether a selected character and/or symbol is printed in outline shape or in original shape, wherein said selected characters and/or symbol can be printed without or with inner portions; generating print information comprising a plurality of pixels in accordance with the selected characters and/or symbols and the selected shape, the print information for characters in the original shape corresponding to the bit map, and the print information for characters in outline shape corresponding to a converted bit map, each bit of said bit map and the four bits surrounding each bit being used to generate a bit in the converted bit map, and wherein said bit is only set when it is on and simultaneously at least one of the four surrounding bits is off; printing an image onto an image receiving medium in accordance with the generated print information.

Further advantageous features of the invention are disclosed in the subclaims.

For a better understanding of the present invention and as to show how the same may be carried into effect, reference will now be made to the accompagnying drawings in which: Figure 1 is a plan view showing the front of a tape printing apparatus; Figure 2 is a plan view of the underside of the tape printing apparatus of Figure 1; Figure 3 is a simplified block diagram of control circuitry for controlling the tape printing apparatus of Figure 1; Figure 4 shows a diagrammatic representation of a bit of a font which has to be converted into an outline font, with eight surrounding bits; Figure 5 shows the letter A in a 72 dot font; and Figure 6 shows the letter A after conversion in an outline character.

Figure 1 shows a simplified plan view of a tape printing apparatus 2. The tape printing apparatus 2 comprises a keyboard 4.

The keyboard 4 has a plurality of data entry keys and in particular comprises a plurality of numbered, lettered and punctuation keys 6 for inputting data to be printed as a label and function keys 8 for editing the input data. These function keys 8 are arranged for example to change the size or font of the input data. Additionally, these function keys 4 also allow, amongst other functions, outline printing of inputted characters to be achieved. The keyboard 4 also comprises a print key 10 which is operated when it is desired that a label is to be printed as well as tape feeding keys 12. Additionally, the keyboard 4 also has an on/off key 14 for switching the tape printing apparatus 2 on and off. A cursor can be moved over a display 18 by means of cursor keys 12.

The tape printing apparatus 1 also has a liquid crystal display (LCD) 18 which displays the data as it is entered. The display 18 allows the user to view all or part of the label to be printed which facilitates the editing of the label prior to its printing. Additionally, the display 18 can also display messages to the user, for example, error messages or an indication that the print key 14 was pressed. The display 18 is driven by a display driver 28 which can be seen in Figure 3.

On the underside of the tape printing apparatus 1 which can be seen from Figure 2, there is a cassette receiving bay 40. The cassette receiving 40 bay includes a thermal print head 42 and a platen 44 which cooperate to define a print zone 46. The print head 42 is pivotable around a pivot point 48 so that it can be brought into contact with the platen 44 to enable a cas sette to be removed and replaced. A cassette inserted into the cassette bay 40 is denoted generally by reference numeral 50.

The cassette 50 holds a supply spool 52 of image receiving tape 54. The image receiving tape 54 comprises an upper layer for receiving a printed image on one of its surfaces and has its other surface coated with an adhesive layer to which is secured a releasable backing layer. The image receiving tape 54 is guided by a guide mechanism (not shown) through the cassette 50, out of the cassette 50 through an outlet O, past the print zone 46 to a cutting location C. The same cassette 50 also has an ink ribbon supply spool 56 and ink ribbon take up spool 58, and a supply of ink ribbon 60.

The image receiving tape 14 and the ink ribbon 20 are arranged to pass in overlap between the print head 42 and the platen 44.

In particular, the image receiving layer of the image receiving tape 14 is in contact with the ink ribbon 60.

The platen 46 is driven by a motor 30 (see Figure 3), for example a dc motor or a stepper motor so that it rotates to drive the image receiving tape 54 in a direction which is parallel to the lengthwise extent of the image receiving tape 54 through the print zone 46. In this way, an image is printed on the image receiving tape 54 and the image receiving tape 54 is fed from the print zone 46 to the cutting location C which is provided at a location on a portion of the wall of the cassette 50 which is close to the print zone 46. The portion of the wall of the cassette 50 where the cutting location C is defined is denoted by reference 62. A slot 64 is defined in the wall portion 62 and the image receiving tape 54 is fed past the print zone 46 to the cutting location C were it is supported by facing wall portions on either side of the slot 64.

A cutting mechanism 66 is provided and includes a cutter support member 68 which carries a blade 70. The blade 70 cuts the image receiving tape 54 and enters the slot 64. The cutting mechanism is arranged to cut off a portion of the image receiving tape on which an image has been printed by the print head 42 to thereby define a label. The printed label is thus separated from the remaining supply of image receiving tape.

The print head 42 is a thermal print head comprising a column of a plurality of printing elements. The print head 42 is preferably only one printing element wide and the column extends in a direction perpendicular to the lengthwise direction of the image receiving tape 54. The height of the column of printing elements is preferably equal to the width of the image receiving tape 54 to be used with the label printing apparatus 2.

Where more than one width of image receiving tape 14 is used, the print head column will generally have a height equal to the largest width of tape 54. An image is printed on the image receiving tape 54 column by column by the print head 42. It should be appreciated that an image can be printed on the image receiving tape 54 via the ink ribbon 60. Alternatively, if the image receiving tape 54 is of a suitable thermally sensible material, an image can be applied directly by the print head 42 to the image receiving tape 54, without using a ribbon 60.

Figure 3 shows the basic control circuitry for controlling the tape printing apparatus 2 of Figures 1 and 2. There is a microprocessor chip 20 having a read only memory (ROM) 22, a microprocessor 24 and random access memory capacity indicated diagramatically by RAM 26. The microprocessor 24 is controlled by programming stored in the ROM 22 and when so controlled acts as a controller. The microprocessor chip 20 is connected to receive label data input to it from the keyboard 4. The microprocessor chip 20 outputs data to drive the display 18 via the display driver chip 28 to display a label to be printed (or a part thereof) and/or a message or instructions for the user.

Additionally, the microprocessor chip 20 also outputs data to drive the print head 42 which prints an image onto the image receiving tape 54 to form an image on a label. Finally, the microprocessor chip 20 also controls the motor 30 for driving the image receiving tape 54 through the tape printing apparatus 2.

The microprocessor chip 20 may also control the cutting mechanism 66 to allow lengths of image receiving tape 54 to be cut off after an image has been printed thereon to thereby define a label.

Data relating to each character or symbol etc., printable on the image receiving tape 54 is stored in the ROM 22. The data stroed in the ROM 22 is in the form of a n dot font data which represents each character by a n x n bit map, wherein n may be eg. equal to 48 or 72. It should be appreciated that some characters may be stored in other bit map sizes. For example, narrower characters could have a bit map of 48 x 40 bits.

The label printing apparatus 1 allows labels to be composed and displayed on the display 8 using the various keys. In particular, the ROM 22 stores information relating to alphanumeric characters and the like which are associated with respective ones of keys 6 as well as functions associated with the function keys 8. When a key 6 is depressed, data concerning the associated character or the like is retrieved from the ROM 22 and then stored in the RAM 26. The data stored in the RAM 26 may be in the form of a code which identifies the character. The mi croprocessor 24, in accordance with the data stored in the RAM 26 generates pixel data which is transmitted in one form column by column to the print head 42 and to the display 18 in another form. Additionally data concerning a function may be retrieved from the ROM 22 in response to activation of one or more of the function keys 8. That data may take the form of a flag. The pixel data are generated by the microprocessor 24 and sent to the print head 42 and the display 18 will take into account the data relating to one or more functions stored in the RAM 22. As will be appreciated, the keys 6 and 8 of the keyboard 2 have predetermined functions associated therewith which causes predetermined data associated with that function to be retrieved from ROM 22.

When the user wishes to print inputted characters in outlines, ie. such that the inner parts are removed, he selects outline printing by depressing a corresponding function key 8. The printing apparatus then converts the dot pattern data which would be normally sent to the print head 42 into outline printing data (blanked data). The algorithm for the conversion will now be described with reference to Figure 4, which shows a part of a bitmap. Like already mentioned, the ROM 22 stores character data for printing and display purposes, normally in a socalled CGROM (character generator ROM). Such character data are in this embodiment of the invention stored in the form of a bit map of eg. 72 x 72 bits. It should be appreciated that it may be appropriate to store the bit map data in a compressed form, as described eg. in our application EP-A-657 847, or in a Bezier form, as disclosed in EP-A-574 225, the contents of both documents being incorporated herein by reference. Together with the compressed data, data indicating an appropriate expansion algorithm may be stored. Further, the bitmap pattern can be en larged, smoothed and masked (as eg. described in DE-U-29701676, the contents of which are incorporated herein by reference) before it is blanked or sent to the printhead. Figure 4 now indicates a part of the bitmap. The central bit 80 is indicated with E, while A, B, C, D, F, G and H are the eight surrounding bits. In the following, B, D, F and H are referred to as the next neighbours, since they are the bits closest to central bit E.

In order to blank the character, the following method is performed: Each bit of the original bitmap together with the corresponding four next neighbours is subsequently investigated by the microprocessor 24. When all four next neighbours are on, the central bit is set off, otherwise it keeps its original status. Consequently, the dot is only set when it is originally on, and at least one of the four next neighbours is not on. For the bits in Figure 4, this means that E is set to: E' := E AND (NOT (B AND D AND F AND H)) = (E AND (NOT B)) OR (E AND (NOT D)) OR(E AND (NOT F)) OR (E AND (NOT H)).

This simple and effective algorithm has the result that only the bits which are at a position at the outline of a character are set on, while all remaining bits are set off. When the original bit is situated at the border of the original bitmap, it conserves its status, because at least one neighbour is not on (since not present). Thus, a blanked character is easily obtained, which has outlines of one bit and consequently one printhead dot thickness. The bitmap data converted according to the described method are then sent to the printhead and printed, generally without any further intermediate steps.

It should be noted that a method in which every bit is evaluated separately is disadvantageous in that it is relatively slow and requires a respectable amount of program code. Thus, all bits of a print column of the print head can be evaluated at the same time. It should be noted that it is the whole print column that is processed in this way, ie. by loading data defining three printhead columns at one time into the RAM 26, and converting them simultanously as described above, and finally sending them column wise to the print head 42. Hereby, the central column is being converted, and the status of the bits in the other two columns is required in order to investigate the status of the left and right bits adjacent to a bit in the central column. It is thus not necessary to evaluate and store the bitmap of the entire character or label simultanously in RAM 26, thus reducing the required space in RAM 26. For a two line label the algorithm operates on the whole print column and so outlines both lines of characters at the same time without any extra effort.

When additional enhancements like underline, box or shading are selected by the user, they are added to the character data by application of appropriate algorithms to the data which have already been converted into outline data.

A sample of the result of the described method is given in Figures 5 and 6. Figure 5 shows a bitmap of 72 x 72 dots with the character A. After the described method is performed subsequently for each column of the bitmap, only the bits forming the outline of the character are remaining on, such that the bitmap of Figure 6 is obtained. Thus, the character has been effectively blanked and the tape printer is capable of printing a label with outline characters.

Claims (10)

Claims

1. A printer for printing on an image receiving medium, the printer comprising: input means for receiving input data defining an image comprising at least one character and/or symbol to be printed on the image receiving medium; first storage means for holding font data defining characters and/or symbols printable on said image receiving medium, each character or symbol being defined as a bit map in said first storage means or being convertable into a bit map; second storage means for holding a outline conversion algorithm, said printing apparatus being operable to print characters and/or symbols selectively in a first form as characters defined by the bitmap, and in a second form as an outline character; processing means connected to receive said input data, said font data and outline selection data and operable to generate therefrom print information comprising a plurality of pixels, wherein each bit of said bit map and the four bits surrounding each bit are used to generate a bit in the printed outline character, and wherein said bit is only set when it is on and simultaneously at least one of the four surrounding bits is off; and printing means for selectively printing the image on the image receiving medium in accordance with the print information.

2. A printer as claimed in claim 1, wherein the processing means is operable such that a bit positioned at the border of the bitmap is maintains its original status in the printed outline character.

3. A printer as claimed in claim 1 or 2, wherein cutting means are provided for separating the image receiving medium on which an image has been printed from the supply of image receiving medium.

4. A printer as claimed in any one of claims 1 to 3, wherein said printing apparatus is a tape printing apparatus, said tape printing apparatus comprising means for receiving a supply of image receiving tape on which said printing means, which is a print head, is operable to print an image to thereby define a label.

5. A printer as claimed in any one of claims 1 to 4, wherein the processing means are operable to convert an entire column of data, said column of data being printable by said printing means at one time, simultaneously into outline print data, and the processing means being operable to send said column of data to said printing means.

6. A method for printing an image onto an image receiving medium, the method comprising the steps of: selecting at least one character and/or symbol to be printed on the image receiving medium; storing font data defining characters and/or symbols printable on said image receiving medium, each character or symbol being defined as a bit map in said first storage means or being convertable into a bit map; selecting whether a selected character and/or symbol is printed in outline shape or in original shape, wherein said se lected characters and/or symbol can be printed with or without inner portions; generating print information comprising a plurality of pixels in accordance with the selected characters and/or symbols and the selected shape, the print information for characters in the original shape corresponding to the bit map, and the print information for characters in outline shape corresponding to a converted bit map, each bit of said bit map and the four bits surrounding each bit being used to generate a bit in the converted bit map, and wherein said bit is only set when it is on and simultaneously at least one of the four surrounding bits is off; printing an image onto an image receiving medium in accordance with the generated print information.

7. A method as claimed in claim 6, wherein a bit positioned at the border of the bit map is maintains its original status in the converted bit map.

8. A method as claimed in claim 6 or 7, comprising the step of cutting the image receiving medium on which an image has been printed from a supply of image receiving medium.

9. A method as claimed in any one of claims 6 to 8, wherein the image is printed onto an image receiving tape to thereby define a label.

10. A method as claimed in any one of claims 6 to 9, wherein an entire column of data, which is printable by the printing means at one time, is simultaneously converted into outline print data, and printed.