GB2140660A

GB2140660A - Colour graphics device

Info

Publication number: GB2140660A
Application number: GB08314616A
Authority: GB
Inventors: James Larsson
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-05-26
Filing date: 1983-05-26
Publication date: 1984-11-28
Also published as: GB8314616D0

Abstract

A device 1 which may be interposed between a microcomputer 2 and a colour television receiver 3 is used to extend or alter the range of colours which can be displayed on the TV 3 in response to the commands from the microcomputer 2. This is achieved by means of a random access memory acting as a look-up table. RGB colour logic signals output from the microcomputer 2 are used to address this look-up table, in which the desired corresponding output colour logic signals have previously been stored under the control of the microcomputer 2. <IMAGE>

Description

SPECIFICATION Colour Graphics Device The present invention relates to a colour graphics device and more particularly to a device, for use with a computer and a colour graphics output device for altering the colours output from the colour graphics output device in respect to commands from the computer.

Many computers, particularly in the microcomputer field have a facility to output colour graphic information to a colour TV monitor or colour printer. Often, particularly on the simpler microcomputers, the number of colours which can be displayed at any one time is very limited, often between 2 and 8. Making more colours available simultaneously carries a very high overhead in terms of the memory required, particularly where the graphics are bit-mapped.

Broadly, my invention is concerned with altering or extending the range of colours which can be displayed. A basic concept of my invention is to provide a device which can modify the colour information so as to replace each output colour by another so that although the number of colours which can be used simultaneously stays the same, the particular colours used can be altered by the user.

Thus according to my invention there is provided, for use-with a computer and a colour graphics output device, a device for altering the colours output from the colour graphics output device in response to commands from the computer, comprising means for receiving colour logic signals from the computer and transforming them into output colour logic signals, in accordance with a pre-defined, user-alterable, transformation which can then be delivered to the colour graphics output device. The transformation may be achieved by incorporating in the device a look-up table, for example a random access memory of which particular memory locations are addressed using the input colour logic signals and the values read from the addressed locations are used to produce the output colour logic signals, the contents of the memory locations having been preset in advance by the user.

The invention will be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic diagraph showing the use of one embodiment of device according to the invention between a microcomputer and a colour television receiver; Figure 2 is a block diagram of one embodiment of the present invention; and Figure 3 shows an interface which may be incorporated within the device.

Figure 1 shows schematically the manner in which a device 1 according to the present invention is interposed between a microcomputer 2 and colour television receiver 3. The device 1 may be in the form of a stand-alone adaptor with its own power supply which might be either from a battery or, for example, an in-line mains power supply unit. The principal functional part of the device 1 are shown in Figure 2. For the purposes of explanation, it will be assumed that the microcomputer 2 has available the following outputs: 1. Eight data lines DO to D7-these may be available as parallel lines at the user-or communication port of the microcomputer or may be available in serial form, the device 1 then including a serial to parallel converter to reconvert the data to parallel form; 2. R, G and B logical colour signals; 3.A composite video synchronizing signal CS; 4. A handshake signal HS; and 5. A data valid signal DV.

The composite synchronising signal CS is applied to a synchronisation pulse processor 10 which produces at its output 12 a train of pulses corresponding to the frame synchronising signals FS. These signals are used to control the timing of the operation of the device.

An 8x256 bit high speed random access memory 14 is used to store data which is read out using the input RGB logic signals as an address word to produce the desired colour output signals, The read-out data is applied via a 3-state inverter 1 6 to a PAL encoder and UHF modulator which may be of a standard type and is not shown in the drawings. Instead of, or as well as incorporating the PAL encoder and UHF modulator, the device may be adapted to provide R, G 8 B video signals to drive a colour monitor having R, G s B inputs, e.g. by providing a suitable digital to analogue conversion arrangement.

A 3-of-6 data selector 18 which is controlled by the frame sync signal FS can select either the RGB signals or the 3 outputs of a 3-bit transparent latch 20 which samples the 3 low order bits of the data word DO--D7 to be delivered as an address signal AO, Al, A2 to the ram 14.

The encoder requires 4 bits of data for each of the 3 colours, namely two chrominance bits and two luminance bits and, as can be seen from Figure 2, the respective luminance bits for each colour are derived from common outputs of the 3state inverter 1 6.

The data and handshake lines are under the software control of the microcomputer. Broadly, to set the device to carry out the desired transformations of colour the first input colour logic signal is output as an address word on lines DO--D2 and the handshake line HS then strobed to latch the address into the latch 20. The required output colour logic signal is then placed on the bus, the data-valid signal is taken high/low to indicate there is valid data on the bus and thus when the next frame pulse FS occurs, the data is written into the addressed location in RAM 14.

This process is repeated for each pair of input and output colour logic signals; the memory write operations always occurring during a video blanking interval.

A NAND gate 22 connected to the sync processor 10, the handshake line and the data valid controls the right/read state of the RAM 14 so that when HS, FS and DV are all high the data on the data-lines DO-D7 are written into the memory location addressed via the data selector 18. While the frame synchronising signal FS is high, the output of the octal inverter 16 is disabled, thus cutting off colour data from the encoder.

Thus, by causing the microcomputer to output suitable data on the data lines DO--D7 and by appropriately controlling the handshake line signal HS, the user can alter the data which is read from the RAM 14 in response to each combination of the RGB logical colour signals and so control the actual displayed colour into which any particular combination is transformed.

When no alterations to the contents of the memory are required, the handshake line HS is left low.

Figure 3 illustrates a universal interface which may be incorporated in the device of Figure 1 which operates so that data is transferred from the microcomputer's data bus and applied to the lines DO-D7 when the microcomputer's address bus carries a particular address. Thus an octal latch 26 buffers the data, writing into the latch 26 under the control of the output of a digital comparator 28 which compares the current address bus signal with a preset value. This value may be preset, for example, using a DIL switch 30.

It will be apparent that there are many other circuit configurations which will achieve the desired effect of transforming the displayed colours in the desire effect. For example, the userdefined colours transformations could be set using switches rather than a RAM set up as a look-up table or even using analogue means such as patentometers in a suitable circuit configuration e.g. a matrix.

Claims

1. A device, for use with a computer and a colour graphics output device, for altering the colours output from the colour graphics device in response to commands from the computer, comprising means for receiving colour logic signals from the computer and transforming them into output colour logic signals in accordance with a pre-defined, user alterable, transformation which can then be delivered to the colour graphics output device.

2. A device according to claim 1 wherein the arrangement is such that the transformation data are stored electronically.

3. A device according to claim 1 or 2 wherein means are provided whereby the transformation data is set up under the control of signals received from the computer.

4. A device according to claim 1, 2 or 3 and including means defining a look-up table, the table being addressed by reference to the input colour logic signals and arranged to store, at each address, data relating to the desired corresponding output colour logic signals.

5. A device according to any one of the preceding claims wherein the transformation data are stored in a random-access memory having a read/write control, means being provided to read the memory when the transformation of input colour logic signals into output colour logic signals is required and to write into the memory to set up the output colour logic signals which are to correspond with the input colour logic signals.

6. A device according to claim 5 and including a data selector to select as address signals for the random access memory input colour logic signals or at least some of the data signals applied to the random access memory for write operations.

7. A device according to any one of the preceding claims wherein arrangement is such that the transformation data are loaded during video blanking intervals.

8. A device according to any one of the preceding claims and including interfacing means including means for receiving data signals and address signals from the computer and for transferring received data signals to said colour logic signal receiving means when predetermined address signals are received.

9. A device constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.