Computer graphics processing and selective visual display system – Display peripheral interface input device
Reexamination Certificate
1998-05-28
2001-09-18
Liang, Regina (Department: 2674)
Computer graphics processing and selective visual display system
Display peripheral interface input device
C345S156000, C345S440000
Reexamination Certificate
active
06292167
ABSTRACT:
The invention relates to an electronic graphic system.
Electronic graphic or image systems in which the painting or drawing of a colour image can be simulated, or a portion of one image can be merged into another by electronic means are well known. One such graphic system is described in our British patent number GB-B-2,089,625 and corresponding U.S. Pat. No. 4,514,818, the teachings of which are incorporated herein by reference. This system includes a user operable input device which may be used by the user to select from a range of colours and a range of intensities and to choose from a set of notional drawing implements for use in the painting or drawing.
When a colour is chosen by the user, values representing the components of the selected colour are stored in a colour register. An implement is chosen by selecting from among different implement representations displayed on a display screen and the selected implement is defined by parameters conforming to a three-dimensional surface representing the profile of the implement. Generally speaking the implement profile will have a high centre falling away to a lower value toward the periphery of the profile although other profiles may, of course, be defined. The implement profile represents the notional distribution of colour which would be applied by the implement to the image over the area of the image which it covers.
The user operable input device is preferably a touch tablet and stylus combination. The touch tablet is arranged to generate position signals designating the position of the stylus relative to the touch tablet when the stylus is brought into proximity. When the stylus is applied to the touch tablet a pressure signal representing the pressure applied via the stylus to the touch tablet is output from the stylus and stored in a pressure signal register. Position signals are output at regular intervals from the stylus/touch tablet device. For some implements, representing say paint brushes, implement data is generated for each movement of the stylus by the distance between picture points or similar distance, whilst for other implements, say air brushes, implement data is generated at regular time intervals, even if the stylus is held stationary on the touch tablet.
When a position signal is produced, new video signals (pixels) are derived for every picture point in the patch covered by the selected implement. An image store is provided and each new pixel is written at the appropriate picture point in the store. Such new pixels are derived by a processing circuit in accordance with the selected colour data and the distribution of the selected implement, and in response also to the pressure applied to the stylus and to the value of the pixel previously stored at the respective picture point in the store.
The user, who it is envisaged would normally be an artist lacking experience in the use of computer based systems, paints or draws by choosing a desired colour and implement and then manipulating the stylus, causing the touch tablet to generate a series of position signals which define the path or positioning of the stylus. The processing circuit reads pixels from the image store for a patch of picture points in response to each position signal and these pixels are blended by the processor with signals representing the chosen colour in proportions depending upon the respective values of the brush profile and pressure. The blend is then written back to the picture store replacing the pixels previously stored therein.
In general, the blending process is carried out a number of times for each picture point in the image store whether the implement is moving or stationary (assuming in the case of the moving implement that the patch covered by the implement is larger than the spacing between picture points). The final proportion will depend on the number of processing operations performed per pixel.
To enable the user to observe his creation, the stored picture is read repeatedly and the pixels are applied to a TV-type colour monitor, so that the build-up of the picture can be observed. Of course such systems are not limited to TV-type formats and any suitable video format may be adopted. The system described avoids the problem of jagged edges in the image, an unpleasant stepping appearance normally associated with lines not lying horizontally or vertically in a raster display.
In electronic graphic systems an image is represented by data defining a multiplicity of pixels that together form the image. Each pixel is defined by the data as a value which typically represents a colour in a colour space (RGB, CMY, YUV for example). The data is input to the monitor where it is converted into voltage signals which are used to drive the monitor. In response to the voltage signals light is output from the screen of the monitor at points corresponding to the positions of respective pixels in the image. Thus the image is displayed on the screen of the monitor.
The relationship between the driving voltage signals and the light output from the screen of the monitor in response thereto is not linear and therefore the relationship between the data and the light output also is not linear. In fact the relationship between the value of light output (L) and the pixel colour value (P) defined by the data is of the form
L=P
&ggr;
(1)
where &ggr;=the “gamma” value of the monitor. Typically &ggr;=2.2.
In the graphic system described in the aforementioned GB-B-2,089,625 and U.S. Pat. No. 4,514,818 new pixel data P
NEW
is created from colour data C combined with the pixel data P
OLD
initially stored in the store in accordance with the equation
P
NEW
=KC+
(1−
K
)
P
OLD
(2)
where K is a value determined on a pixel-by-pixel basis for example by user manipulation of the input device.
It can be seen from equations (1) and (2) that the image as represented by the processed data will not correspond with the image as displayed on the screen of the monitor. Substituting light output values L for pixel colour values (P) in equation (2) and rearranging gives the equation
L
NEW
=(
KC
&ggr;
+(1
−K
)
L
OLD
&ggr;
)
1/&ggr;
(3)
In other words changes in the processed data do not result in identical changes in the image as displayed.
Painting is primarily a visual operation and depends on the user interacting with the image as displayed in order to achieve a desired effect. It is of no concern to the user that the relationship is not linear between the colour value of a given pixel as defined by data within the system and the value of light output for that pixel from the monitor. If the user is not satisfied with the image displayed on the monitor he can simply adjust the colours until an acceptable result is achieved. Furthermore, because colour perception is relative, the difference between what would be achievable with a linear relationship and the result actually achieved will largely go unnoticed.
However, electronic graphic systems are not solely concerned with simulating painting in an electronic environment. Such systems are used in the processing of print-quality images (photographs) prior to the printing of those images for example in a magazine or other publication. A print quality image is an image of a resolution similar to that of a quality photograph obtained using a conventional camera, and may be represented in an electronic environment by data defining 8,000×10,000 pixels or more.
In the processing of photographs it is often desirable to achieve photo-realistic effects. For example the user may wish to simulate the effect of illuminating a scene with, say, a blue light. In the real world illuminating a scene with a blue light source will increase the intensity of blues in the scene, will change colours with a blue content closer to blue and will leave other colours substantially unaltered. In hitherto known systems this effect has been difficult to achieve. “Painting” a blue over the image electronically is equivalent to applying paint or
Cooper & Dunham LLP
Liang Regina
Quantel Limited
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