Video graphics systems

Abstract: A video graphics system is provided with a framestore 3 and a viewing store 10. The framestore 3 is arranged to receive new image data created by a processor 6 in response to user manipulations of a stylus/touch tablet device 1. The framestore 3 and the viewing store 10 both have the capacity to store a high definition image and to facilitate display of the image on a high definition monitor 13 the framestore is arranged to transfer only portions of its data contents to the viewing store 10 during a frame period. The portion transferred is determined by the position of the stylus on the touch tablet at the beginning of a frame period. Data in the viewing store 10 is output in faster sequence for display on the monitor 13.

Description: The present invention relates to an electronic graphic apparatus and a method of processing an image. One example of a video graphics system is described in our British Patent No. 2 089 625 and corresponding United States Patent No. 4 514 818. This system includes a touch tablet and stylus combination for generating position signals designating the position of the stylus relative to the touch tablet. The user or operator paints or draws (hereinafter referred to simply as "paints") by selecting a colour and a so called brush distribution from a range of predefined colours and distribution functions. Movement of the stylus relative to the touch tablet causes the generation of a series of position signals. The system also includes a pixel processing circuit and a frame storage means which can store an array of pixels representing a picture. On moving the stylus to designate different positions, a patch of pixels in the frame storage means referenced by each designated position is modified in response to the selected colour and distribution. All the pixels in the frame storage means, representing the picture, can moreover be read repeatedly and applied to a monitor to display the picture as it is built up by the operator. The frame storage means for a system such as referred to in the preceding paragraph requires three ports, one for reading back pixels from the frame storage means to the processing circuit, one for writing the modified pixels from the processing circuit into the frame storage means and the third for repeatedly reading the pixels from the frame storage means to the monitor for display. Serial access is sufficient for reading the pixels as a video signal to the monitor, but random access is required via the first and second ports. These requirements make it difficult to transfer pixels to the monitor at high rates, such as would be needed for example to refresh a monitor displaying a picture of high definition, say HDTV standard. EP-A-202014 describes an electronc graphic apparatus comprising a high resolution image store for storing data defining a high resolution image and a viewing store for storing data representing the image for display on a lower resolution monitor. A filter is provided between the store and the viewing store and operates so as either to enable a portion of the image data to be transferred unfiltered from the viewing store to the image store for display of the image portion on the monitor, or to enable the image data from the image store to be filtered for display of a low resolution version of the image on the monitor. According to the present invention in one of its aspects there is provided an electronic graphic apparatus comprising: an image store having a multiplicity of storage locations for storing data representing a multiplicity of pixels which together form an image; a user operable input circuit for inputting position data identifying a succession of positions in said image store; a first addressing circuit for addressing at a processing rate successive patches of storage locations in the image store determined by said positions identified by said position data; and a processor for processing data at each said patch of storage locations addressed by the first addressing circuit in order to effect a modification to said image represented by said data in the image store at each said patch of storage locations; characterised by: a display store having a multiplicity of storage locations for storing data representing a multiplicity of pixels which together form an image of high resolution for display, said data stored in the display store representing substantially the same image as that represented by said data stored in the image store; a reading circuit for repeatedly reading at a display rate greater than said processing rate data in said display store for output and display of the image represented thereby during a display frame period; and a second addressing circuit for addressing an area of storage locations in the image store including the patches of data processed by the processor during a first frame period, and for addressing a corresponding area of storage locations in said display store, said area in the image store and said corresponding area in the display store being determined by the position represented by position data input by the input circuit at the beginning of the first frame period and for transferring during a second frame period immediately following said first frame period at a rate corresponding to said processing rate data in said addressed area of storage locations in the image store to said corresponding storage locations in said addressed area in the display store, the image data in the display store thereby being updated during said second frame period with data from the image store processed during said first frame period. According to another aspect of the invention there is provided a method of processing an image, the method comprising: storing in an image store having a multiplicity of storage locations data representing a multiplicity of pixels which together form the image; identifying a succession of positions in the image store; addressing at a processing rate successive patches of storage locations in the image store determined by said identified positions; and processing data at each said addressed patch of storage locations in order to effect a modification to the image represented by the data in the image store at each said patch of storage locations; characterised by: storing in a display store having a multiplicity of storage locations data representing a multiplicity of pixels which together form an image of high resolution for display, said data stored in the display store representing substantially the same image as that represented by said data stored in the image store; repeatedly reading at a display rate greater than said processing rate data in said display store for output and display of the image represented thereby during a display frame period; addressing an area of storage locations in said image store including the patches of data processed by the processor during a first frame period; addressing a corresponding area of storage locations in said display store, said area in the image store and said corresponding area in the display store being determined by the position identified at the beginning of the first frame period; and transferring during a second frame period immediately following the first frame period at a rate corresponding to said processing rate data in said area of address locations in said image store to said corresponding storage locations in said addressed area in the display store, the image data in the display store thereby being updated during said second frame period with data from the image store processed during said first frame period. Preferably the operator responsive means includes a stylus for referencing picture points in said further storage means at which pixel modification occurs, and the system is such that movement of the area of said further storage means from which pixels are read is stylus responsive. The above and further features of the invention are set forth with particularity in the appended claims and together with advantages thereof will become clearer from consideration of the following detailed description of an exemplary embodiment of the invention given with reference to the accompanying drawings. In the drawings, Figure 1 is a schematic diagram representing a video graphics system embodying the invention; and Figure 2 is a schematic diagram illustrating the manner in which image data is transferred in the system of Figure 1. Referring now to Figure 1 of the accompanying drawings, there is shown a video graphics system comprising a stylus/touch tablet combination 1 which is arranged such that as the stylus is drawn across the touch tablet, signals XY representing the instantaneous position of the stylus on the touch tablet are output. The XY signals are applied to a patch address generator 2. Picture point data representing an image is stored in a framestore 3 and for each XY position of the stylus, the patch address generator 2 generates, serially, a patch of picture point addresses in the framestore 3, which patch of addresses is related to the XY position of the stylus. In addition to generating XY signals, the stylus/touch tablet combination may be arranged to generate date representing the pressure applied via the stylus to the touch tablet, such pressure related data being stored in a pressure register 4. Notional drawing implements are used to draw image data into the framestore 3 and data representing the distribution of a selected drawing implement is held in a distribution store 5b. Similarly, data representing a user selected colour is held in a colour register or store 5a. The distribution register or store 5b is arranged to provide a distribution signal for each picture point in the patch in the framestore 3 addressed by the generator 2. During painting each addressed picture point is read from the framestore 3 and applied to a processor 6. The processor 6, which may be of the kind described in our above mentioned patents, receives also the colour and distribution data from the respective stores 5a and 5b. The processor 6 is responsive to the pressure exerted on the stylus by the operator as represented by the pressure data in the pressure registers and uses the colour and distribution data to modify each pixel in the currently identified patch, the resulting modified pixel data being written back to their respective locations in the framestore 3. In this way pixel data representing a picture can be created in the framestore 3, or data therein can be touched up, or otherwise processed as described in the aforementioned Patents. In the exemplary system shown in Figure 1, the framestore 3 is formed from four normal television standard three-port framestore devices which are combined to form an enlarged storage field having four quadrants, one quadrant for each of the framestore devices. Thus, the framestore 3 has the capacity to store pixel data representing up to four pictures at the resolution of the normal television standard, for example 625 lines, or to store one picture at four times normal resolution, for example HDTV standard. A read address generator 7 generates addresses to enable the reading of pixels serially from an area in the framestore 3 sufficient to accommodate one picture at normal television resolution, which pixels are output from the framestore 3 via an output bus 8. A scroll data generator 9 also receives the XY signals from the touch tablet 1 and is arranged to generate data that causes the read address generator 7 to shift, horizontally and vertically, the area corresponding to the picture which is read from the framestore 3 to cause the area to occupy a desired position in the enlarged storage field. Thus, whilst the framestore 3 has the capacity to store an image in an enlarged storage field, the read address generator 7 is arranged to generate addresses such that only an area corresponding to an image at normal TV resolution is read from the framestore 3 during a frame period. The exact rate at which data is read from the framestore 3 will of course depend on external influences such as the standards adopted in the country in which the system is to be used, but by way of example the address generator 7 will typically generate addresses such that pixels are read from the area in the framestore 3 at a rate of say 13.5 MHz. The picture point data or pixels read from the framestore 3 are applied to a high definition viewing store 10 which has the capacity to store pixels representing a picture of high resolution relative to the normal television standard mentioned above, for example HDTV standard. The pixels read from the framestore 3 are addressed to picture points in the viewing store 10 under the control of an address generator 11. The operation of both the read address generator 7 and the write address generator 11 is controlled by a timing circuit 12. The address generator 11 at any one time addresses only an area of the viewing store 10 occupying approximately one quarter of the storage field of this store. That is to say, the write address generator 11 addresses an area in the viewing store 11 which area is defined by a number of pixels corresponding to that in the picture read from the framestore 3. The write address generator 11 also receives scrolling data from the scroll data generator 9 and thus the address data generated by the read address generator 7 and the write address generator 11 is coordinated so that the area in the viewing store 10 to which pixel data is written tracks the area in the framestore 3 from which the reading of pixel data occurs. The areas in the framestore 3 and the viewing store 10 are determined by the position of the stylus on the touch tablet at the beginning of each frame period, ie area reading cycle. The stylus can designate any position in the framestore 3, that is to say it can generate signals that designate any address in any of the four three-port framestore devices. At the beginning of each frame period the current address designated by the stylus is used by the scroll data generator 9 to identify the mid point of the areas in both the framestore 3 and the viewing store 10. Once the mid point has been identified the areas remain stationary until the reading cycle is completed ie until the end of the frame period and at the beginning of the next frame period. The areas are then moved by the scroll data generator 9 to the new current stylus position. As successive picture points in the viewing store 10 are addressed, the corresponding pixels output from the framestore 3 are written into the viewing store at that picture point. A high definition read address generator 14 is arranged to generate read addresses to cause the reading of pixels from the high definition viewing store 10 for display of the high definition image on a high definition monitor 13. Figure 2 of the accompanying drawings illustrates the way in which the position of the area addressed by the read address generator 7 changes from frame period to frame period. When the stylus is brought into contact with the touch tablet the address in the framestore 3 corresponding to the point 15 is identified and this point is used to define the centre of the area, as represented by the broken line 16-1. Movement of the stylus on the touch tablet causes data representing the stroke 17 to be drawn into the store by the processor (see Figure 1) and at the same time data is read from the area 16-1 to the corresponding area of the viewing store 10 replacing the data previously in that area. At the beginning of the next frame period t=2, the point 18 is identified as the next centre of the next area 16-2. During this next frame period t=2 data is read from the area 16-2 to a new corresponding area of the viewing store 10 replacing the data previously in that area. At the same time, further movement of the stylus results in the stroke 19 being drawn into the framestore 3. During the next frame period t=3 the point 20 is identified as the centre of the area 16-3, and during creation of a stroke 21, data in the area 16-3 is written to its corresponding area in the viewing store 10. This process is repeated during each frame period with the image gradually being built up in the framestore 3 and transferred in the manner described to the viewing store 10. At the end of the fourth frame period, in the example given in Figure 2, data representing the line 22 will be held in the viewing store 10 for display on the monitor 13. It will thus be appreciated that painting into the framestore 3 is done in the normal way by random access read-modify-write operations at normal TV rates, eg 13.5 MHz, and a portion of the image data including the modified data is transferred to the viewing store 10 also at that rate for display at high definition TV rates, eg 54 MHz. The portion or area of the image that is transferred is always centred on the position of the stylus at the beginning of a frame period and the area is sufficiently large to ensure that no normal movement of the stylus in the ensuing frame period will carry the stylus outside the defined area. Returning now to Figure 1, it should be noted that the viewing store 10 is a two port store and it may comprise suitable Random Access Memory (RAM) devices such as a video RAM having a serial output. There is no need to provide a random access output to read from the viewing store 10. The serial output that provides the video data to the monitor 13 can therefore be rapid enough to refresh the high definition monitor 13 at the rates associated with high definition television. Thus reading may be effected to provide definition at 54 MHz for example. Indeed the monitor 13 may even be an HDTV monitor capable of accepting a video waveform at 74.25 MHz, and a definition of this order can be achieved by providing the stores 3 and 10 with sufficient picture point capacity to accommodate six images at the normal television definition. The number of pixels in the two stores 3 and 10 need not correspond and a digital filter may be included in the bus 8, to compress the picture if the number of pixels in store 3 exceeds that in store 10, or to expand the picture if the situation is reversed. It will be appreciated that in the example described, when painting is being effected, the updating of the picture in the store 10 is carried out within an area which moves with the stylus, the area being centred periodically (at the frame rate) at the current position of the stylus, so that updating is carried out at the area of picture within which the operator is working. For other operations, or for picture composition effects, it may be desirable to update the entire picture in the store 10 from time to time. Updating in store 10 can then be effected in four passes, occupying four frame periods and covering respectively the four quadrants of the picture. Having thus described the present invention by reference to a preferred embodiment it is to be well understood that the embodiment in question is exemplary only and that modifications and variations such as will occur to those possessed of appropriate knowledge and skills may be made without departure from the scope of the invention as set forth in the appended claims.

Claims: An electronic graphic apparatus comprising: an image store (3) having a multiplicity of storage locations for storing data representing a multiplicity of pixels which together form an image; a user operable input circuit (1, 2) for inputting position data identifying a succession of positions in said image store; a first addressing circuit (2) for addressing at a processing rate successive patches of storage locations in the image store determined by said positions identified by said position data; and a processor (6) for processing data at each said patch of storage locations addressed by the first addressing circuit in order to effect a modification to said image represented by said data in the image store at each said patch of storage locations; characterised by: a display store (10) having a multiplicity of storage locations for storing data representing a multiplicity of pixels which together form an image of high resolution for display, said data stored in the display store representing substantially the same image as that represented by said data stored in the image store (3) ; a reading circuit (14) for repeatedly reading at a display rate greater than said processing rate data in said display store for output and display of the image represented thereby during a display frame period; and a second addressing circuit (7, 11) for addressing an area of storage locations in the image store (3) including the patches of data processed by the processor during a first frame period, and for addressing a corresponding area of storage locations in said display store (10), said area in the image store and said corresponding area in the display store being determined by the position represented by position data input by the input circuit (1) at the beginning of the first frame period and for transferring during a second frame period immediately following said first frame period at a rate corresponding to said processing rate data in said addressed area of storage locations in the image store to said corresponding storage locations in said addressed area in the display store, the image data in the display store thereby being updated during said second frame period with data from the image store processed during said first frame period. An electronic graphic apparatus as claimed in claim 1, wherein said user operable input circuit comprises a stylus and touch tablet device (1). An electronic graphic apparatus as claimed in claim 2, wherein the stylus and touch tablet device comprises a pressure sensor for providing pressure data (4) representing instantaneous pressure applied by the stylus to the touch tablet, the processor (6) processing said data at said addressed patch of storage locations in dependence on said pressure data. An electronic graphic apparatus as claimed in any preceding claim, wherein said processor (6) is adapted to process said data at said patch of storage locations in the image store (3) addressed by the first addressing circuit (7) by reading data from the patch of storage locations in the image store, modifying said read data to create modified data and writing said modified data to said addressed patch of storage locations to replace said data previously stored therein. An electronic graphic apparatus as claimed in claim 4, further comprising a store (5a, 5b) for storing color data representing a user selected color and for storing distribution data representing a drawing implement, the processor (6) being arranged to modify the read data by the color data and the distribution data. An electronic graphic apparatus as claimed in any preceding claim, wherein the second addressing circuit comprises a read address generator (7) for generating addresses identifying each of the storage locations comprising said area in the image store (3) and a write address generator (11) for generating addresses identifying each of the storage locations comprising said corresponding area in the display store (10). An electronic graphic apparatus as claimed in claim 6, wherein the storage locations in both the image store (3) and the display store (10) are arranged in an array with each location being addressable in terms of a horizontal and a vertical component, and the second addressing circuit comprises a scroll data generator (9) for generating data, with the read address generator (7) and the write address generator (11) both being responsive to said data from the scroll data generator such that said addresses generated by the read address generator and the write address generator scroll horizontally and vertically through storage locations in the image store and the display store. An electronic graphic apparatus as claimed in claim 7, wherein the scroll data generator (9) is responsive to said position data to generate scroll data for causing said read address generator (7) and said write address generator (11) to generate addresses such that said area and corresponding area of storage locations changes in accordance with changes in the position identified by the position data. An electronic graphic apparatus as claimed in any preceding claim, wherein the second addressing circuit is arranged such that said area in the image store (3) is centered over said position identified by said position data. An electronic graphic apparatus as claimed in any preceding claim, further comprising a monitor (13) for receiving said data output by said reading circuit and for displaying the image represented thereby. A method of processing an image, the method comprising: storing in an image store having a multiplicity of storage locations data representing a multiplicity of pixels which together form the image; identifying a succession of positions in the image store; addressing at a processing rate successive patches of storage locations in the image store determined by said identified positions; and processing data at each said addressed patch of storage locations in order to effect a modification to the image represented by the data in the image store at each said patch of storage locations; characterised by: storing in a display store having a multiplicity of storage locations data representing a multiplicity of pixels which together form an image of high resolution for display, said data stored in the display store representing substantially the same image as that represented by said data stored in the image store; repeatedly reading at a display rate greater than said processing rate data in said display store for output and display of the image represented thereby during a display frame period; addressing an area of storage locations in said image store including the patches of data processed by the processor during a first frame period; addressing a corresponding area of storage locations in said display store, said area in the image store and said corresponding area in the display store being determined by the position identified at the beginning of the first frame period; and transferring during a second frame period immediately following the first frame period at a rate corresponding to said processing rate data in said area of address locations in said image store to said corresponding storage locations in said addressed area in the display store, the image data in the display store thereby being updated during said second frame period with data from the image store processed during said first frame period. The method as claimed in claim 11, wherein said processing is effected by reading data from the addressed patch of storage locations in the image store and modifying the read data to create modified data to the addressed patch of storage locations to replace the data previously stored therein. The method as claimed in claim 12, further comprising: selecting a color and storing color data representative thereof; selecting a drawing implement and storing distribution data representative thereof; and modifying the read data by the color data and the distribution data. The method as claimed in any of claims 11 to 13, further comprising changing the addressing of said area of storage locations in said image store and said corresponding area of storage locations in said display store in response to changes in the identified position. The method as claimed in any of claims 11 to 14, wherein the addressing of the image store and the display store is such that said area of storage locations in the image store is centered over the position identified by the position data. The method as claimed in any of claims 11 to 15, further comprising displaying the image represented by said data read from said display store.

Inventors: NONWEILER BRIAN ROBERT, SEARBY ANTHONY DAVID, NONWEILER, BRIAN ROBERT, SEARBY, ANTHONY DAVID
Applicants: QUANTEL LTD, QUANTEL LIMITED
Application year: 1991
Main classification: G06F3
IPC codes: G06F3, G09G5