GB2238214A - Electronic graphic system combines images using variable density stencil - Google Patents

Abstract

The system includes a stylus and touch tablet 2 by which image data is drawn into a store 3. The image data store 3 may be used as control data or stencil for controlling the combining of images. In one embodiment the system is arranged to enable the density of the control image to be variable up to a predefined maximum and in another embodiment to enable a control image of uniform density to be created. Stylus pressure is used to control the density of the control image. In a further embodiment transfer of images between a bulk storage device (16, Fig 2) and first and second framestores (17, 19, Fig 2) is facilitated. <IMAGE>

Description

LMBRO#NTS IN OR RELATING TO ELECTRONIC GRAPHIC SYSTEMS The invention relates to electronic graphic systems.

BACKGROUND OF THE INVENTION Electronic graphic or image systems in which the painting or drawing of a colour picture can be achieved by electronic means are known. One such system is included in our electronic graphic equipment sold under the trademark "PAINTBOX" and described in our British Patent No. 2,098,625 and corresponding US Patent No. 4,514,818, the teachings of which are incorporated herein by reference. This equipment includes user operable means, in the form of a stylus and touch tablet and a menu of facilities displayed on a display monitor, by which the user can select from a range of colours and a range of notional drawing implements for use in painting or drawing a picture.

The stylus and touch tablet combination includes means for generating position signals representing the position of the stylus on the touch tablet. When such a position signal is produced new picture elements (pixels) are derived for every element in a patch covered by the user selected drawing implement. A picture store is provided and each new pixel is written at the appropriate picture point in the store.

The equipment also includes a processing circuit which derives the new pixels in accordance with the distribution of the selected implement, the colour selected by the user and the value of each pixel previously stored at the respective location in the store and also, as described in the above mentioned patents, in response to pressure applied to the stylus by the user. The user paints or draws by choosing a desired colour and implement, and then manipulating the stylus on the touch tablet and thereby causing the touch tablet to generate a series of position signals defining the path or position of the stylus. The processing circuit derives pixels for a patch of points in the picture and these derived pixels are written back to the picture store.To enable the user to observe the picture being created, the store is read repeatedly and the pixels are applied to a TVtype colour monitor, thus enabling the build-up of the picture to be observed.

Another system which includes additional means to enable a user to perform picture composition in addition to painting is described in our British Patent No. 2,113,950 and corresponding US Patent No. 4,602,286 the teachings of which are also incorporated herein. In this system, storage means are provided for storing two independent pictures which are combined under the users control by way of a control image or stencil held in a stencil store. A picture is produced by drawing pixels into the stencil store and using these pixels as an interpolation coefficient to control the combining of the two independent pictures.

The build-up of the picture should be viewable in real time in order to facilitate use of the equipment.

For this reason the processing circuit must be capable of completing the processing of all pixel patches and writing the processed pixels to the store without interfering with reading from the store to the monitor in a frame period of the monitor, at least when averaged over a few frame periods.

The above discussed systems each provide electronic means by which a user can create image data for display on a monitor and/or for subsequent printing.

OBJECTS AND STATENENTS OF THE INVENTION The invention aims to provide an improved electronic graphic system in which there is a greater degree of control over the creation of a control image for use in selectively combining two independent images. To this end, the system includes means by which the required density of the control image can be set before the control image is drawn. In one mode of operation, the required density can be set to a maximum so that when a control image is drawn it has uniform density and in another mode of operation the required density can be sent to an intermediate value such that when a control image is drawn no part of it has a density greater than the intermediate value.

The invention also aims to provide an improved electronic graphic system in which original images to be modified can be extracted quickly from any arbitrary location in a bulk storage device.

The invention also aims to provide an improved electronic graphic system in which proposed modifications to an image can be reviewed before those modifications are finally made. To this end the system of the invention includes a viewing store which holds pixel data defining the combined image for display on a monitor.

The above and further features of the invention 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.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic block diagram showing the drawing circuitry which forms part of the system according to the present invention; and Figure 2 is a schematic block diagram showing further functional units of the system used in the transfer and manipulation of image data in the system.

DETAILED DESCRIPTION OF THE EMBODIMENT Referring now to Figure 1 of the accompanying drawings an embodiment of an electronic graphic system 1 shown therein includes a stylus/touch tablet device 2 by which the artist may create an image in a store 3 which is read by processor 4 and displayed on a monitor 6. As the stylus is drawn across the tablet by the artist a number of signals are output from the device. Signals XY representative of the instantaneous position of the stylus on the tablet are output to a patch address generator 7. The patch address generator 7 converts the XY co-ordinate information from the tablet into a corresponding location, i.e. picture point, address in the framestore 3.

Notional drawing implements are used to draw images into the frames tore 3 and the system may be arranged such that after each update of the framestore incremental movements of the stylus over the touch tablet are integrated until they exceed one picture point or similar spacing and then the framestore is again updated by stamping a modified patch of pixels in the framestore 3. A signal representing the instantaneous pressure of the stylus on the touch tablet is also delivered to a stylus pressure register 9.

As in the systems described in our abovementioned patents, a set of artist selectable notional drawing implements are each stored in a brush shape memory 10 as a numerical representation of a continuous three dimensional shape which covers a patch of image pixels. The address signal output from the patch address generator 7 is also used to synchronise addressing of the stylus pressure register 9 and the brush shape memory 10. Selection means (not shown in Figure 1) are provided to allow the artist to select one of the drawing implements from the set. The selection means for example may be a menu driven arrangement displayed on the monitor 6.

The manner in which position signals from the touch tablet 2 are generated will depend upon the particular notional drawing implement selected by the artist. For example where the selected implement is say a paint brush, position signals are generated only when the integrated stylus movement is for instance the distance between picture points as above described, whilst for say an airbrush position signals are generated at regular time intervals, even if the stylus is held stationary on the touch tablet.

In normal use data output from the stylus pressure register 9 and the brush shape memory 10 as the artist moves the stylus across the touch tablet are multiplied together to produce a coefficient K for use by a brush processor circuit 11.

The brush processor circuit 11 performs a continuously cycling read-modify-write operation on the image data in the framestore 8 on a pixel-by-pixel basis. Image data is extracted from the framestore 3 and is negatively summed with, i.e. subtracted from, a preset image intensity value held in an intensity register 12 by a summing unit 13 (e.g. a 745381 device). The resulting sum output from the summing unit 13 is multiplied with the coefficient K by way of a multiplying unit 14 (e.g. a MPY-8HuJ/TRW device) and the resulting product is then added to the data extracted from the framestore 3 by way of an adding unit 15 (e.g. a 74S38i device). The data output from the adding unit is then written back into the framestore 3, replacing the original data in the framestore 3.

Although the read-modify-write process is executed in a continuous cycle on the data held in the framestore, it should be apparent to those possessed of the appropriate skills that the data will only be modified when the artist is drawing on the touch tablet with the stylus. K is the product of brush shape and stylus pressure and when the artist is not using the stylus/touch tablet device under pressure the data in the framestore 3 will remain unaltered and no read-modify-write cycles are performed.

The degree of modification of the data normally depends substantially on the brush shape, which it will be recalled is predefined in the brush shape memory as a continuous three dimensional shape, and on the instantaneous stylus pressure. It should be appreciated that each time a picture point in the predefined brush shape notionally moves over a new pixel in the store 8, the value of the image pixel is recalculated by the brush processor 11. Thus, where only the edge of the brush shape moves over a particular image pixel, the value of K will be relatively low.In contrast, for the case where the center of the brush shape moves over a particular image pixel, the contribution to that pixel from the brush will start at a relatively low value of X at the forward edge of the brush shape, will increase to a high value of K at the center of the brush shape, and will then decrease to a low value of K at the trailing edge of the brush. Thus, in this latter case the total summed contribution of the brush to the image pixel will be more substantial than in the previous case. This method of processing data drawn into the framestore 3 avoids the problem of jagged lines by producing non-stepped stencil boundary profiles.

The framestore 3 can be used to store colour image data representing a picture drawn by the user or it can be used as a control plane to store a control image or stencil for use in controlling the combining of data representing two independent images. In the following it will be assumed that the store 3 is being used to store control image data.

The pressure sensitivity of the system as provided by the pressure sensitive stylus and the instantaneous pressure values held in the stylus pressure register 9 helps to give the user a more realistic feel for what is being "painted". Increased pressure will result in a higher value of K which will cause more paint to be transferred to the image being drawn in the framestore 3 and reduced pressure will similarly result in less "paint" being transferred. However, when a control image is being created for use as a stencil it is often important that the stencil is of uniform density or opacity throughout an area and that no thin patches are left in said area.Under these circumstances pressure sensitivity can be a disadvantage and in order to avoid this the system according to the present invention provides a means by which pressure signals from the stylus are ignored and the content of the pressure register 9 is instead set to a maximum value.

This feature is selected from a menu of options (not shown) displayed on the monitor 6 and once selected any further drawing using the stylus will cause corresponding pixels in the stencil store 3 to be flooded with data in accordance with the user selected brush shape. This is because, with stylus pressure set to a maximum, i.e. unity, the coefficient K for a patch of pixels is defined only by the values representing the brush shape over that patch of pixels.

In other circumstances, for example when transparently combining one picture with another, it may be important to the user that the density, i.e.

opacity, of the control image data should not exceed a user determined value. In order to enable the user to limit the maximum density of the control image data or an area of control image data. In our previous electronic graphic systems we have hitherto arranged for the intensity value to be set only to one of two values, namely zero and unity. The intensity value in the intensity register 12 was set to unity when a control image was being drawn and user control over the intensity of the image being drawn was achieved by applying greater or lesser pressure to the stylus.

The intensity value in the intensity register 12 was set to zero when the user wished to erase parts of a control image and again control was achieved by pressure applied to the stylus.

The system according to the present invention also provides a means by which the intensity i.e.

opacity of the control image data being drawn can be set to an intermediate value by the user. This opacity control feature can also be selected from the abovementioned menu of options. With the opacity control feature selected the user is able to set the intensity value in the intensity register 12 either numerically by inputting a number via a suitable means such as a keyboard (not shown) or by selecting an existing point in a control image in the stencil store 3.

In the latter case, a cursor (not shown) is moved over the image as displayed on the monitor 6 by way of the stylus and the touch tablet 2 until the desired point is covered by the cursor. The system is arranged such that pressing down hard on the stylus causes the value of the picture point identified by the cursor to be read from the stencil store 3 and written to the intensity register 12. In this way areas of uniform intensity in the control image can be easily defined and new control image data can be blended seamlessly (i.e. without any changes in opacity) to existing control image data.

Thus the present system provides for a greater degree of control over the creation of a control image for use in selectively combining two independent images.

Once the stencil has been created to the users satisfaction it can be used to combine data representing an initial image with other data for example representing another initial image.

Turning now to Figure 2 of the accompanying drawings, image data representing a first initial image stored in a bulk storage device 16 is read therefrom and held in a first framestore 17 for modification by the user. A second initial image also stored in the bulk storage device 16 can also be read therefrom and stored in a second framestore 19. The manner in which image data can be read to and from the bulk store using the present system will be described in greater detail hereinafter.Control image data drawn into the stencil framestore 3, in the manner already described in relation to Figure 1 of the accompanying drawings, is used to control the processor 4 which performs an interpolation to combine on a pixel-by-pixel basis the image data from the second framestore 19 with the image data from the first frames tore 17 and to write the thus combined image data back to the first framestore 17. The control image data in the stencil framestore 3 is used as an interpolation coefficient on a pixel-by-pixel basis. Interpolation is performed in such a manner that the two images are weighted by the coefficient to determine the contribution that each image makes to the final combined image.

As mentioned above, the system 1 can also be configured such that image data is drawn directly into the first or second framestore without the use of an intermediate control image as described in our abovementioned British Patent No. 2,098,625 and corresponding US Patent No. 4,515, 818.

Furthermore, in our previous electronic graphic systems we have provided means by which the user may transform colour components of pixels in the initial image to give a modified image having corresponding pixels with different RGB colour components. The means by which this is achieved is a transforming circuit which comprises a matrix of arithmetic units that include look up tables, at least one for each colour component. Each look up table holds data describing a colour curve which defines the relationship between the input colour component and the output colour component. In the case where no colour transformation is to occur, the colour curve held in the look up table will be linear such that the output colour component is the same as the input colour component.Coefficients associated with the functions performed by these look up tables can be changed by the user such that when initial colour pixel data is processed by the transforming circuit, it is transformed to define pixel data representing a new colour in accordance with the user defined coefficients. Two framestores are used, one for storing the initial image data and one for storing the transformed image data, and once an image has been transformed in a desired way the transformed image can be selectively combined, or superimposed, on the initial image. The transformed image can also be used to replace, i.e. substitute for, the initial image if so desired.

The present system also includes transforming matrices in the processor 4 to enable the user to modify the colour content of an initial image.

When the framestores are being loaded, the first image data is read from the storage device 16 by selecting a "fetch" option from a menu of options (not shown) displayed on the monitor 6. The "fetch" option is per se well known and is selected by use of the stylus and touch tablet combination 2 which causes the processor 4 to control the transfer of data from the bulk store 16 to the first framestore 17. The bulk storage device may for example be a multi-disc store or the like. The second image data, say image data represented by box A in the bulk store 16, is first transferred to a temporary store area TS in the bulk store 16 and is then transferred from the temporary store area TS to the second framestore 19 all under the control of the stylus 2 and processor 4.

This approach can be adopted by the user in the present system 1 for initial transfer of the second image data to the second framestore 19 if so desired.

During the process of modifying an image in the first framestore 17 by painting new colours or selectively combining it with a second image held in the second framestore 19 it is often convenient to be able to save temporarily the image data of either the first framestore 17 or the second framestore 19. In our previous systems image data from the first framestore 17 can be written to any desired location in the bulk store 16 but the image data from the second frames tore 18 has always been saved in the temporary store TS of the bulk store 16. This approach has previously been adopted to facilitate use of the system by the user.However, it has been found that where the data in the second framestore 19 is to be replaced by data defining a different image this forced requirement to use the temporary save area TS results in an undue amount of time being spent in transferring files to and from the temporary store area TS and other areas, such areas A and B, in the bulk store 16.

This time wasting problem can be avoided in the present system by use of an alternative option selected from the menu (not shown) displayed on the monitor 6. This alternative option enables the user to "restore" the image data in the second framestore 19 with any of the images in the bulk store 16 without having first to transfer the selected image to the temporary store area TS.

When the "restore" option is selected, information identifying the images held in the store 16 is output under the control of the processor 4 and displayed on the monitor 6. The user can then select the required image which, once selected, causes the processor 4 to control the transfer of the image to the second framestore 19.

Thus, the present system provides a means by which original images to be modified can be extracted quickly from any arbitrary location in the bulk storage device 16.

When modifications are made to an image data is read from both the first framestore 17 and the second framestore 19 and combined by the processor 4 under the control of the control image data in the stencil framestore 3. Normally, the thus combined image data is then written back to the first framestore 17 replacing the data originally stored there. Whilst this arrangement provides for fast modifications to an image it means that if the user makes a mistake during the modification, that mistake will immediately appear on the image in the first framestore 17 and, depending on its nature, may only be correctable by retrieving the unmodified image from the bulk store 16 and starting again. The present system includes means which enable the user to view a proposed combination of images before the combined image data is written to the first framestore 17.

Image data is initially stored in the first and second framestores 17, 19 and the user then selects a "view" option from the menu of options displayed on the monitor 6. With this option selected, the processor 4 is inhibited from writing combined data back to the first framestore 17. The combined image data is instead written to a viewing framestore 18 for display on the monitor 6. The user is then free to experiment with the control image drawn in the stencil framestore 3 and so to view on the monitor 6 the effect that such experimental control images have on the combining of the first and second images. The viewing framestore 18 is continually updated by the processor 4 so that any changes can be seen on the monitor substantially as soon as they are made.

A further refinement of this "view" feature is to make the display of images on the monitor 6 dependent on the pressure applied to the stylus. The value representing the pressure applied to the stylus and held in the stylus pressure register 9 (see Figure 1) is interpreted by the processor 4. If no or only low pressure is applied to the stylus then only the first image from the first framestore 17 is transferred to the viewing store 18 and displayed on the monitor 6, whereas when high pressure is applied to the stylus only the second image from the second framestore 19 is transferred to the viewing framestore 18 and displayed on the monitor 6. In the case where a mid range pressure is applied to the stylus, the processor reads the image data from both framestores 17, 19 and combines both images for transfer to the viewing store 18 displayed on the monitor 6.Both images may be combined with equal or another predetermined weighting for display.

Once a "viewed" image satisfactory to the user has been created, image data from the two stores 17, 19 is combined on a pixel-by-pixel basis to produce modified image data which is written back to the first store 17 replacing the data previously stored there.

The system thus described provides the user with a greater degree of control over the creation of a control image by enabling the opacity to be defined by the user. In one arrangement the density of the drawing implement is set to maximum by the user by ignoring the pressure applied to the stylus and in another arrangement the intensity of the image being drawn is set not to exceed a user defined level.

The above described system also provides the user with the means to extract any image from any location in a bulk storage device and to transfer images between the framestores and the bulk storage device without the need to use a temporary store location first.

The system also includes a viewing framestore and means for preventing combined image data from being written over initial image data held in a framestore.

Instead, the combined image data is written only to the viewing framestore and from there displayed on the monitor. This enables the user to view proposed modifications before they are made.

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 spirit and scope of the invention and equivalents thereof.

Claims (12)

CLAIMS:

1. An electronic graphic system for use in for example modifying data defining an. original image, in which system control data representing a control image is used to control the combining of other image data with the original image data to produce data defining a combined image, the control image being definable by a user by way of a user operable control means comprising a drawing input means for converting drawing actions of the user into input data, a modifier for selectively modifying previously stored control image data with the input data to produce new control image data for storage, and density defining means for predefining the desired density of the drawn control image.

2. An electronic graphic system as claimed in claim 1, wherein the density defining means is arranged such that the control data representing the drawn control image has a uniform value.

3. An electronic graphic system as claimed in claim 1, wherein the density defining means is arranged such that the control data representing the drawn image does not exceed a predetermined value less than the maximum possible value.

4. An electronic graphic system as claimed in any preceding claim, wherein the user operable control means comprises implement defining means for defining the notional profile of at least one user selectable drawing implement.

5. An electronic graphic system as claimed in claim 4, wherein the implement defining means comprises a brush store for storing data defining the profile of said at least one implement.

6. An electronic graphic system as claimed in any preceding claim, wherein the drawing input means comprises a stylus and a touch tablet, the stylus being adapted to output values representing the pressure applied to the stylus on the touch tablet which pressure values are used in determining the density of the drawn image subject to the operation of the density defining means, and the touch tablet being adapted to output co-ordinate data which is used to identify the position of control image data to be modified.

7. An electronic graphic system as claimed in any preceding claim, wherein the other image data defines another original image or a portion of another original image.

8. An electronic graphic system for use in for example modifying data defining an original image held in a first store in which system user creatable control data representing a control image is used to control the combining of other image data from a second store with the original image data from the first store to produce data representing a combined image, wherein the combined image data is stored in a viewing store for viewing on a monitor during creation of the control image to enable the user to preview modifications to the original image and, once a desired combined image has been achieved, modifications in accordance with the control image data are effected to the original image data in the first store.

9. An electronic graphic system as claimed in claim 8, wherein the control image is created by way of user operable control means comprising a drawing input means for converting drawing actions of the user into input data, a modifier for selectively modifying previously stored control image data with the input data to produce new control image data for storage, and density defining means for predefining the desired density of the drawn control image.

10. An electronic graphic system as claimed in claim 9, wherein the drawing input means comprises a stylus and a touch tablet, the stylus being adapted to output values representing the pressure applied to the stylus on the touch tablet and wherein the modifier is responsive to the pressure values from the stylus for transferring either the original image data or the other image data or a combination of the data of both images to the viewing store for display.

11. An electronic graphic system as claimed in any of claims 8 to 10, further comprising a bulk store for storing data including data representing at least said initial image said other image and said combined image, the bulk store being arranged such that both said initial image and said other image can be extracted directly from any arbitrary location therewithin.

12. An electronic graphic system substantially as described herein with reference to the accompanying drawings.