JPH0446391A - Picture display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image display device, and more particularly to an image display device that simultaneously displays a grayscale image and a character.

[Prior Art] FIG. 4 is a block diagram of essential parts of an example of a conventional image display device.

In this image display device (51), (2) is an image memory that stores and outputs a grayscale image expressed in 8 bits;
3) is a character brain memory that stores and outputs characters expressed in character codes such as ASCII codes or Kanji codes, and (4) is a character pattern corresponding to the character code input from the character plane memory (3). A character generator that outputs a parallel character signal, (5) a shifter that converts the parallel character signal from the character generator (4) from parallel to serial and sequentially outputs it as a character signal pixel by pixel; A display selection circuit (57) generates a control signal for selecting either a grayscale image signal or a character signal based on the logic value of each pixel of the character signal output from the shifter (5), and (57) is for the grayscale image signal. (58) is a tri-state buffer for character signals, (9) is a D/A conversion circuit that converts a manually generated grayscale image signal or character signal into an analog signal and outputs it to the monitor, (10) is a read signal for outputting a grayscale image signal or a parallel character signal from the image memory (2) or the character plane memory (3), and a read signal for outputting a parallel character signal corresponding to the display line from the character generator (4). This is a control circuit that generates a line address signal to operate the shifter (5) and a clock signal to operate the D/A conversion circuit (9).

FIG. 5(a) is an exemplary diagram of a display image of the image display device (51). P indicates a pixel.

FIG. 5(b) shows the density of the grayscale image signal on the i-line of the display image of FIG. 5(a). The density on the vertical axis ranges from 0 to 255 because the density of the grayscale image signal is expressed in 8 bits.

The horizontal axis corresponds to each pixel on the i-line of the display image.

FIG. 5(c) shows a character signal in one line of the display image of FIG. 5(a).

A pixel whose character signal has a logical value of “1” has a density r
255J, and pixels with a logical value of "0" have a density of "
0".

FIG. 5(d) shows the input signal of the D/A conversion circuit (9). In FIG. 5(C), a character signal is selected and inputted at the pixel where the character signal=1, and a grayscale image signal is selected and inputted at the pixel where the character signal=0.

The D/A conversion circuit (9) converts the input signal shown in FIG. 5(d) into an analog signal, outputs it to a monitor (not shown),
An i-line display as shown in Figure (a) is obtained.

Note that other conventional image display devices include
125886, ``Masking the grayscale image portion adjacent to the character'', and JP-A No. 125886,
There is a device that calculates and displays the density of a character from the average value of the density of a grayscale image around the character, which is disclosed in Japanese Patent No. 249588.

[Problems to be Solved by the Invention] The conventional image display device 51 described above has a problem in that when the density of the grayscale image around the character is the same as or close to the density of the character, the character becomes extremely difficult to see.

In addition, all conventional image display devices have a problem in that their configurations are complicated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image display device that has a simple configuration and can display characters in an easy-to-see manner.

[Means for Solving the Problems] In a first aspect, the present invention provides an image display method for simultaneously displaying a grayscale image and a character, in which the density of a pixel of a grayscale image corresponding to a pixel of a character is set to a predetermined reference value. An image display method is provided, which is characterized in that the image density is compared and the density is changed from the original density based on the comparison result.

In a second aspect, the present invention provides an image display device that simultaneously displays a grayscale image and a character, comprising a comparison means for comparing the density of a pixel of a grayscale image corresponding to a pixel of a character with a predetermined reference value, and the comparison means The present invention is characterized by comprising a density changing means for changing the density image from the original density based on the comparison result, and a display means for displaying the density image changed from the original density by the density changing means. Provides an image display device.

[Operation] In the image display device of the present invention, the density of the pixel of the grayscale image corresponding to the pixel of the character is compared with a predetermined reference value, and the density is changed from the original density based on the comparison result and displayed.

In other words, in a grayscale image where the density of numerically neighboring pixels does not suddenly change, the density of the pixel in the grayscale image corresponding to the character pixel changes from the original density,
As a result, the characters appear to stand out.

[Example] Hereinafter, the present invention will be described in more detail based on the example shown in the drawings. Note that this invention is not limited to this.

FIG. 1 is a block diagram of essential parts of an image display device according to an embodiment of the present invention.

In this image display device (1), (2) is an image memory that stores a grayscale image expressed in 8 bits, and (3) is an A
A character brain memory (4) stores characters expressed in character codes such as SCII codes or Kanji codes;
), a character generator (5) outputs a parallel character signal having a character pattern corresponding to the character code inputted from the character generator (5), which performs parallel/serial conversion of the parallel character signal from the character generator (4) and converts the parallel character signal from the character generator (4) into one pixel as a character signal. The shifter (6) outputs the image memory (2) in order for each image.
), an exclusive OR circuit that takes the exclusive OR of the most significant bit of the gray image signal from the shifter (5) and the character signal from the shifter (5); (9) is a circuit other than the most significant bit of the gray image signal; A D/A conversion circuit (10) is a D/A conversion circuit that converts a total of 8 bits of input, that is, the bit of the image memory (2) and one bit of the output of the exclusive OR circuit (6), into an analog signal and outputs it to the monitor. or the character brain memory (
A read signal for outputting a grayscale image signal and a parallel character signal from 3), a line address signal for outputting a parallel character signal according to the display line from the character generator (4), and 1 the shifter (5). This is a control circuit that generates a clock signal for operating the D/A conversion circuit (9), and a clock signal for operating the D/A conversion circuit (9).

FIG. 2(a) is an exemplary diagram of a display image of the image display device (1). P indicates a pixel. The operation will be explained below based on this display image.

In response to a read signal from the control circuit (10), the image memory (2) outputs a grayscale image signal for each pixel.

Figure 2 (b) is Figure 2 (a) when there is no character.
This shows the density of the grayscale image signal on the i-line of the displayed image. The density on the vertical axis indicates that the density of the grayscale image signal is 8.
Since it is expressed in bits, it is 0 to 255. The horizontal axis corresponds to each pixel on the i-line of the displayed image in FIG. 2(a).

On the other hand, upon receiving a read signal from the control circuit (10), a character code is output from the character brain memory (3).

A character generator (4) sends a parallel character signal corresponding to the character code to a control circuit (1).
Output is performed line by line according to the line address signal from 0).

The shifter (5) performs parallel/serial conversion on the parallel character signal in synchronization with the clock signal from the control circuit (10), and outputs a character signal for each pixel.

FIG. 2(C) shows a character signal on the i-line of the display image of FIG. 2(a), and the logical value of the character signal is a pixel of "1" or a pixel of a character.

The exclusive OR circuit (6) calculates the exclusive OR of the most significant bit of the grayscale image signal outputted from the image memory (2) and the character signal outputted from the shifter (5). Replace with the most significant bit.

Figure 3 shows the density of the grayscale image signal (hereinafter referred to as the new grayscale image signal) whose most significant bit has been replaced with the output of the exclusive OR circuit (6) and the source output from the 1-image memory (2). FIG. 3 is a conceptual diagram showing the relationship between the density and the density of the grayscale image signal.

In other words, for a pixel where the logic value of the character signal input to the exclusive OR circuit (6) is "1", the output of the exclusive OR circuit (6) will be the logic value of the most significant bit of the input grayscale image signal. As a result, the density of the new grayscale image signal changes to the density of the original grayscale image signal minus rl 28J if rl 28J or more, as shown by the solid line in FIG. The concentration changes by adding only

Furthermore, for pixels where the logical value of the character signal input to the exclusive OR circuit (6) is rOJ, the output of the exclusive OR circuit (6) is equal to the logical value of the most significant bit of the input grayscale image signal. , the density of the new grayscale image signal remains the same as the density of the original grayscale image signal, as indicated by the dashed-dotted line in FIG.

In this way, the signal input to the D/A conversion circuit (9) is
As shown in FIG. 2(d), a new grayscale image signal is obtained in which the density of the grayscale image signal corresponding to the pixel of the character is changed by "128". This new grayscale image signal is converted into an analog signal and output to a monitor (not shown) to obtain a display image as shown in FIG. 2(a).

As is clear from a comparison between FIG. 2(a) and FIG. 5(a), the characters are easier to see in this embodiment.

Also, as is clear from comparing Figures 1 and 4,
This embodiment has a simpler configuration.

Another example is one in which bits other than the most significant bit of the grayscale image signal are used as inputs to the exclusive OR circuit. In this case, the density of the pixel of the grayscale image corresponding to the pixel of the character is displayed changed from the density of the original grayscale image by the density corresponding to the bit of the grayscale image signal input to the exclusive OR circuit.

Still another embodiment is one in which a plurality of exclusive OR circuits are provided and the exclusive OR of a plurality of bits of the grayscale image signal is performed.

[Effects of the Invention] According to the image display device of the present invention, the density of pixels of a grayscale image corresponding to pixels of a character is displayed while being changed from the original density.

Therefore, in a grayscale image where the density of numerically neighboring pixels does not suddenly change, only the density of the pixel of the grayscale image corresponding to the character pixel changes from the original density, so the character appears to stand out. It becomes like this.

Also, the configuration becomes simpler.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of main parts of an image display device according to an embodiment of the present invention, FIG. 2(a) is an illustration of a display image of the image display device according to an embodiment of the present invention, and FIG. 2(b) is shown in Figure 2(a)
FIG. 2(C) is an explanatory diagram of the i-line character signal of FIG. 2(a).
Figure (d) is an explanatory diagram of the new gray scale image signal of one line in Figure 2 (a), Figure 3 is a relationship diagram between the original gray scale image signal and the new gray scale image signal, and Figure 4 is a diagram of the conventional image display device. FIG. 5(a) is an exemplary diagram of a display image of a conventional image display device; FIG. 5(b) is an explanatory diagram of the i-line grayscale image signal of FIG. 5(a). , FIG. 5(C) is i in FIG. 5(a)
An explanatory diagram of the line character signal, Fig. 5(d) is the 5th line character signal.
FIG. 3 is an explanatory diagram of a composite signal of the i-line grayscale image signal and character signal in FIG. In the figure, (1) is an image display device, (2) is an image memory, (3) is a character brain memory, (5) is a shifter, (6) is an exclusive OR circuit, and (9) is a D/A conversion It is a circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In an image display method for simultaneously displaying a grayscale image and a character, the density of a pixel of a grayscale image corresponding to a pixel of a character is compared with a predetermined reference value, and the original value is determined based on the comparison result. An image display method characterized by displaying an image by changing its density from . 2. An image display device that simultaneously displays a grayscale image and a character, comprising: a comparison means for comparing the density of a pixel of the grayscale image corresponding to a pixel of the character with a predetermined reference value; An image display device comprising: a density changing means for changing the density of an image from its original density; and a display means for displaying a grayscale image whose density has been changed from the original density by the density changing means.