JPH0528393B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION This invention relates to smoothing circuits for graphic display devices. [Prior art and its problems] The resolution of a raster scan type graphic display device (CRT display device) increases in proportion to the number of dots in the horizontal and vertical directions. However, if the number of dots is increased, the capacity of the display memory will naturally increase, resulting in an increase in cost. For example, a CRT is a graphic display device that displays 512 colors using 3 bits each of R (red), G (green), and B (blue).
If the screen is composed of 192 x 256 dots, each of R, G, and B is 6K x 3 bytes, so the total is 54K.
Bytes of display memory are required, but if we try to double the horizontal resolution, the configuration will be 192 x 512 dots, so (12K x 3) x 3 = 108K bytes of display memory will be required, which means In this example, the capacity is doubled, and an additional 54K bytes of display memory must be provided. [Object of the Invention] An object of the invention is to provide a graphic display device that improves horizontal resolution without significantly increasing memory capacity. [Key Points of the Invention] A smoothing memory that has a one-to-one relationship with each bit on the CRT display screen is provided, and this smoothing memory contains data that controls ON/OFF of half dots at the end of the straight line portion (horizontal direction) of the displayed figure. is calculated and written, and the horizontal resolution is apparently doubled. [Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 9. FIG. 1 is a block diagram of a graphic display device. 1 in the figure is an input device,
Input data from this input device 1 is input to a CPU (central processing unit) 2. A main storage device 3 is connected to this CPU 2, and data is exchanged therewith, and a machine clock generated by a clock generator 4 is inputted thereto. Further, data for controlling the figures processed and output by the CPU 2 and their brightness are written to a video memory 5 and a smoothing memory 6, which are comprised of RAM (random access memory). Therefore, the video memory 5 is red,
It consists of memories 5A, 5B, and 5C for each color of green and blue, into which the above-mentioned graphic data is written. Also, the smoothing memory 6 is connected to the video memory 5 (memory 5A).
~5C), and data for brightness control is written therein. Each memory 5A to 5C and smoothing memory 6
The display data outputted in parallel from the display data is applied to shift registers 7, which are provided in four corresponding series. The data output from this shift register 7 is processed by a smoothing circuit 8 provided with three series.
The signal is inputted to the DA converter circuit 9 and subjected to smoothing processing, and the signal is applied to three series of DA converter circuits 9. This D
-A conversion circuit 9 controls the brightness of the input signal and converts it into a video signal for a raster scan type CRT.
The data is output to the display device 10 to display the figure. On the other hand, other clock signals output from the clock generator 4 are input to the display address control circuit 11 and the synchronization signal generation circuit 12. Display address control circuit 11 outputs an address control signal to video memory 5 and reads data from video memory 5. Also, the synchronization signal generation circuit 12
outputs horizontal and vertical synchronizing signals to the CRT display device 10. Furthermore, the clock signals output by the clock generator 4 are the load clock and shift clock supplied to the shift register 7. FIG. 2 shows the same smoothing circuit 8 and D-A conversion circuit 9 for the three series mentioned above, and shows the shift registers 7 provided for the memories 5A, 5B, 5C, and 6, respectively.
A, 7B, 7C, 7D, and the signals output from each shift register 7A, 7B, 7C, 7D are J ₁ , J ₂ , J ₃ , J ₄ , these signals J ₁ , J ₂ , J ₃ are respectively input to the smoothing circuits 8A, 8B, and 8C of the corresponding series, and the signal _J4 is commonly input to the smoothing circuits 8A, 8B, and 8C. Furthermore, each smoothing circuit 8A, 8
Signals n ₁ , o ₁ , output from B and 8C, respectively
n ₂ , o ₂ , n ₃ , and o ₃ are input to corresponding series of DA conversion circuits 9A, 9B, and 9C, respectively.
If the outputs of the D-A conversion circuits 9A, 9B, and 9C are signals l ₁ , l ₂ , and l _{3 ,} respectively, the signals are red,
Green and blue video signals. FIG. 3 shows a specific circuit configuration of the smoothing circuit 8A (same as 8B and 8C).
The output J ₁ of the shift register (SR) 7A is input to the delay circuit 15, and its output signal a is further input to the delay circuit 16 and output to the OR gate 17 as a signal b. Also, this OR gate 17 has the above-mentioned signal.
J ₁ is also entered. The output signal c of this OR gate 17 is sent to an AND gate 18 which has one end inputted with the output _J4 from the shift register 7D.
is input to the other end of the . The output signal d of this AND gate 18 is connected to the output signal a of the delay circuit 15 at one end.
is input to the other end of an open collector OR gate 19, and the other end of an AND gate 21 to which the output signal a of the delay circuit 15 is input via an inverter 20. Thus, the output of the OR gate 19 and the output of the AND gate 21 are supplied as a signal n ₁ and a signal o ₁ to the DA converter 9A, respectively. FIG. 4 shows three systems of D-A converter circuits 9 (e.g. 9
The configuration of A) is shown. The above signal n ₁ is a resistance
The signal o 1 is input to the base of the NPN transistor T _r via R _B , and the signal o ₁ is input via the inverter 26 to the input terminal of the OR gate 27 of the oven collector. On the other hand, voltage +Vcc is applied to switch SW, one end of which is grounded, via resistor R _D. This switch SW is used to adjust brightness for smoothing, and the other end is connected to the input end of the OR gate 27, and all three systems are commonly connected to a video amplifier (not shown). Also, or gate 27
The output of is connected to the base of the transistor _Tr through a resistor _RC . the base of the transistor T _r ,
A resistor R _A is connected between the collectors, and the emitter is grounded via a resistor _RE . A voltage Vcc is supplied to the collector. The emitter output of transistor T _r is connected to CRT via capacitor C.
It is sent to the display device 9. However, the above resistance R _B ,
The resistance value of R _C is R _B <R _C. Next, the operation of the above embodiment will be explained with reference to FIGS. 5 to 9. Assuming that a straight line is to be drawn on the screen of the CRT display device 10, the general operation will be explained first. First, the coordinate data of the starting point and ending point of a straight line to be drawn is inputted from the input device 1. The CPU 2 uses the main memory circuit 3 to calculate straight line data and brightness control data to be drawn based on the coordinate data, and calculates the data for each of the red, green, and blue memories 5A, 5B of the video memory 5, respectively.
Display data is written to 5C and brightness control data is written to smoothing memory 6. For example, if you want to display a straight line in red, use red memory 5A, if you want to display it in green, use green memory 5B, and if you want to display it in white, use all memories 5A, 5B, 5C.
Write linear data to. The display data from the video memory 5 is outputted word by word to the shift register 7 in accordance with the load clock, and sent out bit by bit from the shift register 7 to the smoothing circuit 8 in accordance with the shift clock. However, if you want to display a yellow diagonal straight line,
Taking the case where 9 bits of a certain raster are written to the video memory 5 as an example, yellow is a composite color of red and green, so if 4 dots out of the 9 dots are to be displayed in yellow, the 5th As shown in the figure, the red and green data are the same, for example "001111000"
becomes. On the other hand, the blue data is data "0000000000" with all 9 bits "0". Furthermore, the brightness control data written to the smoothing memory 6 to perform smoothing processing on this straight line is "001000100". Note that a method for creating this brightness control data will be described later. Now, the data written in the video memory 5 and the smoothing memory 6 are supplied to the smoothing circuit 8 via the shift register 7, but in FIG. 3, the red display data J ₁ is supplied to the red smoothing circuit 8A. and brightness control data J ₄
is supplied. J ₁ , J ₄ , a to d in the same figure
and the output signals J ₁ and o ₁ are as shown in the time chart of FIG. That is, "001111000" of the red display data J ₁ is delayed by half a clock in the delay circuit 15 and becomes a signal a, and further delayed by a half clock in the delay circuit 16 and becomes a signal b. Furthermore, the signal J ₁ and the signal b pass through the OR gate 17 to become the signal c, and the signal c and the signal J ₄ pass through the AND gate 18 to become the signal d. Therefore, the output signal n ₁ becomes the OR output of the signal a and the signal d, and the output signal n ₁ becomes the AND output of the inverted signal of the signal a and the signal d. The signal n ₁ is input to the resistor R _B of the DA converter circuit 9A shown in FIG. 4, and the signal o ₁ is input to the inverter 26. In this D-A conversion circuit 9A, if the output terminal of the OR gate 27 is ○A, and the base of the transistor _Tr is ○RO, the potentials of points ○A and ○RO and the output signal l with respect to signals n ₁ and o ₁ are as follows. It will look like the table.

[Table] Therefore, when SW is ON, display data 4
A half-brightness display is obtained with half-dots at the front and rear ends of the straight line portion of the dot, and diagonal straight lines do not become step-like.
It is displayed smoothly. Also switch
When the SW is turned OFF, the above half-dot display will be displayed at full brightness, as is clear from the previous table. On the other hand, in the case of blue display data J ₃ in FIG. 3, the data output from the shift register 7C is
As shown in Figure 7, it is all “0” data,
Therefore, each of the signals a to d becomes "0", and the signals n ₃ and o ₃ also become "0". That is, D-A
The output of the conversion circuit 9C also becomes "0". Next, the calculation that the CPU 2 performs when inputting the coordinate data of two points and drawing a straight line, that is, the calculation method (algorithm) for the straight line data and brightness control data.
will be explained with reference to FIGS. 8 and 9. As shown in Figure 9A, the starting point (x ₁ , y ₁ )=
Let us take as an example the case where a diagonal straight line is drawn between the end points (x ₂ , y ₂ )=(13, 7) shown by (2, 3) and 12. In addition,
The directions indicated by arrows in the figure are defined as positive x and y directions. 9B shows the state of data written to the video memories 5A to 5C, FIG. 9C shows the state of data written to the smoothing memory 6, FIG. 9D shows the actual display state, and FIG. 9E shows the state of the data written to the smoothing memory 6. A conventional display state corresponding to FIG. 9D is shown. In the flowchart of FIG. 8, first, in the preprocessing of step _S1 , the smoothing memory 6 is completely cleared, and the starting point (x ₁ , y ₁ ) and ending point (x ₂ , y ₂ ) are input from the input device 1. input. Furthermore, specify and input color data. Next, in steps S ₂ and S ₃ , the x displacement and y displacement are compared to determine whether the inclination is 45° or less. Specifically, DX=|x ₁ −x ₂ |=11, DY=|
y ₁ −y ₂ |=4, and the inclination is determined to be 45° or less when DX>DY. In the case of this example, since the smoothing process is only in the horizontal direction, |DX|<|DY
If | is larger than 45°, the line is not subject to processing, and post-processing in step _S34 , such as input waiting processing for displaying the next straight line, painting processing based on the drawn straight line, etc., is executed and the process ends. Next, in step _S4 , the magnitude relationship between x ₁ and x ₂ is determined, and since the x direction is processed from left to right, if X ₁ > x ₂ , proceed to step S ₅ . x ₁
The coordinates of x ₂ , y ₁ and y ₂ are exchanged, and the starting point and ending point are exchanged. In this case, since x ₂ >x ₁ , the above coordinate exchange is not performed and the process proceeds to step _S6 . Next, in step _S6 , .DELTA.y, which represents the displacement of the y coordinate when the x coordinate advances by one dot, is obtained by dividing DY/DX, and .DELTA.y=4/11. This △ again
A sign S=SGN(Δy) is determined such that S=1 when y is positive, S=−1 when y is negative, and S=0 when y is 0. In this case, S=1. Next, in step _S7 , video memories 5, 5A to
At the starting point (x ₁ , y ₁ ) of 5C, color data according to the preprocessing of step S ₁ is written. For example, if it is red, the color data " ₁ ", " ₀ ",
“0” (This expression is changed in the order of R, G, B (1,
0,0). Same below). If it is white, write ( _{1, 1} , 1) in (x 1 , y ₁ ). Next, in step _S8 , the variable M for x step is set to 0 and initialized. Next, in step _S9 , the variable x representing the distance of x until the displacement of y occurs
(X ₀ , x ₁ , and x ₀ for point A in Figure 9
=2, and x ₁ =3 for the points , _, , etc.). Next, in step _S10 , the variable M is incremented by 1 to 1, and by incrementing in the x direction from the starting point, the process enters the processing position of the point A in FIG. In the next step _S11 , x=x ₁ +M ₁ y=y ₁ +f(M△y)
In this case, x=2+1=3,
y=3+f(4/11)=3. Note that the function f
is rounded off to the nearest whole number. Next, in step _S12 , F=f(△y)-f(M-
1) △y) is calculated, and in this case, F=
(4/11)-f(0)=0. That is, △y is x1
Although it is smaller than a dot, when x is incremented by 1 dot and y exceeds 1 dot, the above function F
becomes 1. And in the next step S ₁₃ |F|=
1, that is, whether a displacement of 1 dot has occurred in y, and in this case, |F|=0
Then, proceed to step _S14 . In step S ₁₄ , the current coordinates (3, 3)
The previous color data is stored in the register C', and the color data is written into the video memory 5 at the coordinates (3, 3). The reason for saving the above color data to C' is that it can be used to cancel a previously drawn point, for example, when comparing X ₀ and X ₁ later by processing steps S ₂₇ to _{S 32} (described later). This is to do so. Next, proceed to step _S15 , and check whether x=x ₂ or not, that is,
It is determined whether the processing up to the end point has been completed or not, and in this case it has not been completed, so proceed to step _S16 .
Incremental processing is performed in which X ₀ is increased by 1, so that X ₀ =1. Next, return to step _S10 , M = 1 + 1 = 2, and in step S ₁₁ , x = 2 + 2 = 4, y = 3 +
f(2×4/11)=4, and the point at coordinates (4, 4) is found. And in step _S12 , F=
f(8/11)-f(4/11)=1-0=1, and the movement from the point, that is, the increment of Δy by one dot is determined. Therefore, in the next step _S13 , |F|=1 is determined, and the process advances to step _S17 . In step _S17 , the coordinates when the y displacement occurs are stored in the X, Y registers (X, Y),
X=4, Y=4. In order to save the coordinates to (X, Y), the length of the straight line in the x direction after displacement (in this case, the above X ₁ = 3) is determined, and the length before displacement is determined as X ₀ = Compare with 2 (step
_S27 to _S32 ) This is for processing displacement points. Then, in step _S18 , the previous color data at that time is saved in C'', and the color data is also written into the color memory 5.The reason for saving the previous color data in C'' is that the previous color data is saved in C''. In the same way as in step S ₁₄ where color data was saved, step
When executing S ₂₇ to S ₃₂ , after finding X ₁ , calculate X ₀ and
This is a storage process until comparison with X ₁ is performed and displacement points are processed. Next, in steps S ₁₉ to S ₂₂ , the above steps S ₉ to
The same processing as S ₁₂ is performed, and as a result, X ₁ = 0 (step S ₁₉ ), M = 3 (step S ₂₀ ), x = 2 + 3
= 5, y = 3 + f (3 x 4/11) = 4 (step
S ₂₁ ), F = f (3 x 4/11) - f (2 x 4/11) = 0
(Step S ₂₂ ), and point 4 at coordinates (4, 5) is found. Then, the process advances to step _S23 , and while in step _S13 the length of _X0 was determined by looking at the displacement of y, the answer is NO after looking at the displacement of y to find the length of _X1 , and the process advances to step _S24 . . Next, in the same manner as in steps S ₁₄ and S ₁₈ described above, the color data before the point at that time is stored in C, and the color data is written to the point in the video memory 5. The reason for saving the previous color data in C is that, similarly to C' and C'', the lengths before and after the displacement point are compared by the processing in steps _S27 to _S32 , and when the lengths before and after the displacement are equal, , in order to start processing with this point as a new displacement point.Next, in step _S25 , the result is NO, and in step _S26
Then, X ₁ =0+1=1, and the process returns to step _S20 . Therefore, M=4, and step S ₂₁
Then x=2+4=6, y=3+f(4×4/11)=
4, and the point with coordinates (4, 6) is found.
And in step _S22 , F=f(4×4/11)−
f(3×4/11)=1−1=0 is obtained. Also, at step S ₂₃ , |F|≠, and step S ₂₄
Proceed to C

Claims (1)

[Claims] 1 In a graphic display device, a means for calculating the horizontal increment and vertical increment of a display dot, and when the result of this calculation is displaced by one dot in the vertical direction, a continuous display in the horizontal direction of the raster immediately before the point of displacement. A method for comparing the number of dots with the number of consecutively displayed dots in the horizontal direction of the raster immediately after the displacement point, and a method for displaying an additional half dot on the dot facing the displacement point of the continuously displayed dots with a short number of dots based on the result of this comparison. 1. A graphic display device comprising: means for erasing half a dot facing a displacement point of a long number of consecutively displayed dots.