GB2137856A

GB2137856A - Image processing system

Info

Publication number: GB2137856A
Application number: GB08408114A
Authority: GB
Inventors: Richard John Taylor; Paul Roderick Noel Kellar; Anthony David Searby
Original assignee: Quantel Ltd
Current assignee: Quantel Ltd
Priority date: 1983-04-06
Filing date: 1984-03-29
Publication date: 1984-10-10
Also published as: GB8408114D0; GB2137856B

Abstract

A character generator (20) provides video signals representing desired characters which may be held in a store (21) capable of rapid access. The character information is processed in a manipulator (22) to provide a change in shape, size or orientation for example. Field stores (26,27) receive this manipulated information via switches (24,25) as well as reference information from a generator (29). Read out from the respective field stores is arranged to occur when information is not being received by that store. After read out, the information is replaced by reference information, prior to the receipt of further manipulated character information. The reference information may be configured so as to include a portion of previously derived image data or may include any desired background. <IMAGE>

Description

SPECIFICATION Image processing system The invention relates to image processing and more specifically to systems capable of providing manipulated character generation.

In known character-generation systems it is normal for the synthetically generated digital signals representing characters to be written into a frame store so as to be available for display for example. Such known system is shown in Figure 1. The computer 10 is capable of generating signals representing many different characters.

The desired character -- e.g. symbol, number or letter, and its position within the image frame is selected via keyboard 11 and the momentarily generated signal data indicative of this character is received by frame store 12 for retention. In addition, a write address is also generated and the data is written into the correct group of addresses within the frame store 12 under the control of write/read control 13, typically during the line blanking period. The addresses are selected so that the order of the signals in the image raster, when they are read out for reproduction, cause them to be displayed in a desired position in the image. Data stored in the frame store 12 is cyclically read out every field period to a display monitor 14 so as to effectively produce a continuous display of the store content on monitor 14.New characters generated via keyboard 11 are written into their appropriate store addresses, by accessing the relevant designated addresses via control 1 3. The data already stored at other frame store addresses is retained unless new data is written over the earlier character data as when a new character is desired to be stored in the same store address.

Whilst this system works well, its use is limited as there is no provision for flexibility of operation required if the operator wished to manipulate one character relative to another for example.

The present system is directed to producing system flexibility so that character manipulation is possible.

According to the invention there is provided an image processing system comprising: input means for providing a sequence of video signals in a first configuration representing a spatial arrangement of one or more characters; output storage means having storage locations for storing video signals; processing means for manipulating video signals from said input means so as to write them selectively in storage locations of said output storage means to produce a configuration different from said first configuration; reading means for reading video signals from said output storage means in said different configuration, representing a different spatial arrangement of said one or more characters;; sequencing means for said processing means and said reading means for causing manipulated video signals to be written in a first group of storage locations and to be read from a second group of storage locations during spaced time intervals, and for causing manipulated video signals to be written in said second group of storage locations and to be read from said first group of storage locations during intervening time intervals; and referencing means for restoring storage locations in said output storage means to a reference state after video signals are read therefrom and before further video signals are written therein.

In our co-pending United Kingdom Patent Application No. 8306789, UK Publication 2119594, there is described a system for manipulating video signals in which video signals ordered in accordance with an input image raster are re-ordered by writing the video signals in addresses in storage means which are selected to produce a change in the shape, orientation position, size or other characteristic of the image, when the signals are read from the store in a predetermined order, and subsequently reproduced. The manipulating means in systems according to the present invention are preferably systems such as described in the aforesaid patent application, the subject matter of which is incorporated herein by reference.

The invention will now be described by way of example with reference to the accompanying drawings in which: FIGURE 1 shows a known character generation system; FIGURE 2 shows an embodiment of the present invention; FIGURE 3 shows a more detailed arrangement concerned with typeface generation; FIGURE 4 shows a suitable arrangement for the manipulator therein; and FIGURE 5 shows a preferred modification of the Figure 2 embodiment.

The system of Figure 2 shows an arrangement suitable for character manipulation.

The video signals representing desired characters are provided by a generator 20 relatively slowly and they are held in a temporary high speed character store 21. Instead of merely being displayed, they are passed to a character manipulator 22 which effects processing of the character information into a new configuration, involving, for example, a size shape or orientation change. The manipulator in this example is a system such as described in the aforesaid copending patent application. The video signal output from manipulator 22 passes via switches 24 or 25 selectively to the group of storage locations in field stores 26 and 27 in which they are stored in the order determined by the manipulator 22 to produce the new configuration.

The stores 26 and 27 include address generators responsive to the manipulator 22, as described in the aforesaid Patent Application 2119594. The field store output are available for display via switch 31. The sequencing of the switches is provided by sequencer 30.

A reference generator 29 is also provided having an output available to field stores 26 and 27 via switches 24 and 25. As shown, each of the switches 24, 25 is a three position switch. In a first position the field stores receives no information via the respective switch, in the second switch position, the field stores receive reference data from the generator 29 and in the third position the field store receives character signals from the manipulator 22. It can be seen that whilst switch 25 is in the first position, the output of the relevant field store 27 is available via switch 31, so that its stored content can be read out. Read out occurs in the order appropriate to the eventual image raster, being effected by a read out circuit of known construction.After read out, switch 31 moves to the other (upper) position to receive stored data from the other field store 26, whilst switch 24 rotates clockwise to the first position where no data is received. Switch 25 moves to its second position to receive the incoming data from reference generator 29 and this data is written into all the store locations. This switch 25 then moves to the uppermost (third) position to write the manipulated characters signals from manipulator 22 into the store 27.

These stored character signals are available for read out when switch 31 moves into its lower position once more. The writing of the reference signals into each field store preferably occurs during the same field period as that in which the read out of character signals occurs, but at a time when such reading is not actually occurring.

In this manner, each of the field stores is updated with newly manipulated character signals, once during each frame, the update being preceded by the restoration of all the locations in the store to a reference value using the reference data. The reference data is typically fixed (e.g. it may comprise a binary signal equivalent to peak black level) and it is written in all store positions.

This allows great flexibility to be achieved as each entire field store is referenced and re-written with updated manipulated character signals. For example if the manipulation causes a reduction of the character size, the characters will appear as if moving away into the distance, which is very useful for filting effects. If desired, the signal data in one field store can be such that the respective image appears to overiap the image produced from the signals in the other field store, this effect being produced by a suitable choice of the update rate and by relying on persistence of vision of the human eye. For this effect, at least some of the 'neighbouring' addresses in the two field stores 26 and 27 will receive identical character signals.

Although the system is shown, for ease of understanding, having three position switches 24 and 25, in practice it is preferable to employ switches 24 and 25 which are capable of writing the reference data on a pixel by pixel basis, immediatelt following the reading of the respective signal data for a store position. Thus as the character signal on any pixel is read out from a field store, the location is immediately written into with data from the reference generator. This ensures that the reference data is written witnin the same field period as that in which the character signals are read out, which allows the fields to alternate.

In the Figure 3 system an arrangement is shown which includes additional devices to allow increased processing speeds to be achieved. This arrangement is shown as dealing with typeface characters.

A library of typeface sets or fonts is stored electronically on disc 40. The operator can access one of a whole variety of sets of characters and this selected set is fed into typeface store 21 (typically 512 x 512 pixels). Each typeface from the set will be equivalent to several pixels high and wide and can for convenience be considered as comprising a typeface 'tile'. A whole set of such tiles can be retained in the typeface store 21.

To write the typeface data from store 40 into store 21, a linear address generator 41 is operated to read the typeface set into the appropriate addresses in the store 21, the selected tile including a character can then be read into the manipulator 22 for processing as described above with reference to Figure 2. In the present arrangement, cache stores 50 and 51, each with the capacity to store one tile of a predetermined size are provided associated with the manipulator 22 to allow the character data relating to an individual tile to be manipulated rapidly, the data in its new configuration being written into one or other of the cache stores.

Cache stores 50 and 51 are small fast access stores (e.g., 20 x 20 pixels) to provide greater access speeds than the standard MOS dynamic RAM chips used to fabricate the typeface store.

During or after manipulation (e.g., to produce a size change or rotation) the character data is passed to cache store 50 or 51 via switch 47 and is written into addresses selected by the manipulator as determined by a random address generator 44. Thereafter this data can be sequentially accessed in an order related to the eventual image raster as determined by a linear address generator 46 and it is passed via switch 48 for entry into field stores 26 and 27 of Figure 2 via switches 24 or 25. Switch 49 is provided to allow signal data within cache store 50 and 51 to be available for processing together with incoming information in manipulator 22. During manipulation in 22 of data associated with cache store 50, data within cache store 51 is available for readout to the desired field store 26 or 27. The addressing circuits for stores 26 and 27, as already indicated, can be similar to generators 46 and 41. The sequencer 30 of Figure 2 can be used to control all the various switches.

The provision of the fast access cache stores, and the use of a fast manipulator such as described in our aforesaid patent application, allows many characters to be manipulated within a single field read cycle. Part of the manipulator 22 is shown in Figure 4.

This part includes a multiplier 60, an address mechanism 62 and adder 61. As shown, manipulated data signals within cache store 50 or 51 are fed back to form a second input to adder 61. Switching between the cache stores has been omitted for ease of understanding. Character signals from typeface store 21 and Figure 3 are received by multiplier 60 and the numerical information is multiplied by a factor less than 1 and then added to previously stored information in adder 61. The address mechanism defines the x, y address in the cache store from which the signal data is read back to the adder 61 and at which the sum from the adder is written. The z parameter used for multiplication (in this case between 0--1) is also related to the address.As indicated above, the manipulator system described in our aforesaid Patent Application No. 8306789, operates by selecting new addresses for video signals which are to be displaced in relation to the address of the video signals as originally positioned in the image raster. The new address for a video signal will not, in general, coincide with the address of any storage location in the store in which the readdressed video signals are written. It will, rather, lie within a rectangle defined by four storage locations and to achieve correct readdressing, different proportions of the video signal should be assigned to each one of said four locations, the proportions being determined by the position of the address within the rectangle. As a corollary to this, each storage location will in general receive contributions from at least four video signals.The multiplier 60, shown in Figure 4, is arranged to produce the aforesaid proportions of the video signal before being re-written in the addresses of the cache store 50 or 51, z being the factor of proportionality which is variable from address to address. The feedback from the cache store to the adder 61 ensures that a new contribution to a storage location in the cache store is added to any contribution previously made by another video signal.

The character signals provided by the generator 20 or the store 40 may be intensity signals or fuli colour signals, typically for R, G, B or colour difference coding (e.g., Y, I and 0 for NTSC systems). If the colour signals are provided, the appropriate number of signals channels will be required in the system.

Referring now to Figure 5, this illustrates a modification of the Figure 2 embodiment and corresponding parts in the two figures are denoted by the same references. In Figure 5, there are in addition to the field stores 26 and 27 for manipulated character signals, two further field stores 70 and 71. Input video signals can be applied alternately to these field stores during successive field periods by way of a switch 72, and such signals can be derived from a source of background signals which may be for example a video graphic device such as described in our corresponding UK Patent Application No.

8207084 (Patent Publication 2116407).

Alternatively fixed character signals can be used as the input signals to the switch 72. Signals can be read alternately from the stores 70 and 71 in known manner via a switch 73 and applied to one input of a switch 74. A second input of the switch 24 is connected to the output of the reference generator 29. The two field stores 26 and 27 in this example have a second output port which feeds a switch 75 and the output of this can be applied to one input of yet another switch 76, a second input of which is connected to the output of the character generator 29. The switch 31 in the Figure 5 arrangement can be preset so as to read output signals alternately either from the stores 26 and 27 or from the stores 70 and 71.

Presetting of the switch 31 and also of the switches 74 and 76 is performed by the operator via a suitable keyboard or other control instrument.

The signals selectea by the switches 74 and 76 are applied to a logic circuit 77 of a known kind.

Denoting the two inputs to the circuit 77 as A and B respectively, the logic circuit is arranged to produce an output represented respectively by KA + (1 - K)B, where K denotes a factor of between 0 and 1, which can also be selected by the operator. The output of the logic circuit 77 takes the place of the direct output of the reference generator 29 in Figure 2 and is applied to the stores 26 and 27 via the switches 24 and 25 so as to restore the storage locations to a reference state after video signals are read therefrom by the switch 31. The switches 24, 25 and 26 are sequenced by the sequencer 30 as in Figure 2, and the sequencer is also arranged to control the operation of the switch 72, 73 and 75.

It will be appreciated that the Figure 5 arrangement gives greater flexibility of operation than Figure 2, since different modes of operation can be selected by the switches 31, 74 and 76 and the factor K. In one such mode, a complex background, say a coloured scene, represented by video signals applied to the stores 70 and 71 can be used to reset the field stores 26 and 27 after each read out via the switch 31. In another mode, in which the feedback from the stores 26 and 27 contributes to the signals used to reset these stores, together with the output of the generator 29, a decaying trail of characters appears in the image represented by the output signals. In yet another mode, in which fixed character signals are stored in the stores 70 and 71, fixed frozen characters appear on the output image as background, having superimposed on them the moving characters created by the signals from the manipulator 22. The mode of operation described in relation to Figure 2 can also be obtained, and other modes of operation will be apparent. The Figure 5 arrangement can of course also be used in an arrangement using cache stores, as illustrated in Figure 3.

Claims

1. An image processing system comprising: a) input means for providing a sequence of video signals in a first configuration representing a spatial arrangement of one or more characters; b) output storage means having storage locations for storing video signals; c) processing means for manipulating video signals from said input means so as to write them selectively in storage locations of said output storage means to produce a configuration different from said first configuration; d) reading means for reading video signals from said output storage means in said different configuration, representing a different spatial arrangement of said one or more characters;; e) sequencing means for said processing means and said reading means for causing manipulated video signals to be written in a first group of storage locations and to be read from a second group of storage locations during spaced time intervals, and for causing manipulated video signals to be written in said second group of storage locations and to be read from said first group of storage locations during intervening time intervals and f) referencing means for restoring storage locations in said output storage means to a reference state after video signals are read therefrom and before further video signals are written therein.

2. A system according to Claim 1 in which said first and second groups of storage location of said output storage means constitute respective field stores.

3. A system according to Claim 1 or 2 in which said input means comprises a source of video signals representing different characters.

4. A system according to Claim 3 in which said source comprises a video signal generator for generating synthetic characters.

5. A system according to Claim 3 in which said source comprises a library store for video signals representing a plurality of different characters.

6. A system according to Claim 5 in which said library store has the capacity to store video signals representing the characters of a plurality of typeface fonts.

7. A system according to any preceding claim further comprising an intermediate store for video signals representing a plurality of characters to be displayed, said store being arranged to receive signals provided by said input means and to pass said signals to said processing means.

8. A system according to Claim 7 in which said intermediate store has the capacity to store video signals representing a typeface font.

9. A system according to any preceding claim including at least two small capacity cache stores arranged to receive alternately, manipulated groups of video signals from said processing means representing individual character areas, said cache stores being connected to said output storage means so that a plurality of said groups of video signals can be passed sequentially to said output storage means to be stored therein.

1 0. A system according to Claim 1 in which said processing means includes means for multiplying video signals received from said input means for particular store addresses, by factors of less than unity related to the addresses, and means for adding to each signal before writing it at the respective address, a video signal previously stored at said address.

11. A system according to Claim 1 in which said reference means can be selectively arranged to restore the storage locations in said output storage means to a uniform reference state or a non-uniform reference state after video signals are read therefrom.

1 2. A system according to Claim 11 in which said reference means can be selectively arranged to restore said storage locations to a reference state by applying signals representing a graphic image.

13. A system according to Claim 11 in which said reference means can be selectively arranged to restore said storage locations to a reference state by applying signals including a proportion of signals previously stored in said storage locations.

14. An image processing system substantially as described herein with reference to any one of the examples shown in Figures 2 to 5 of the accompanying drawings.