JP2548269B2 - Bitmap display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bitmap display device for converting image information stored in a bitmap memory into a video signal using a look-up table and displaying the video signal.

2. Related Art For example, a pixel value is looked up in a look-up table
In a bitmap display device that performs multicolor display by converting color information according to (abbreviated), the number of colors that can be used at the same time is limited to 2 ⁿ colors when the information amount of each pixel is n bits.

Therefore, if the colors to be registered in the LUT are randomly selected, it is often impossible to obtain an image that satisfies the requirements.

Therefore, efforts are sometimes made to make the color combinations registered in the LUT the most appropriate combination for the image to be displayed. This most suitable color combination is a unique combination for each image, and generally, different images have different most suitable color combinations. Therefore, when the image is stored, this color combination is also stored. When displaying the stored image, the color combination stored together is written in the LUT.

However, considering that a multi-window display is performed using a bitmap display device, a plurality of images may be displayed simultaneously as shown in FIG. In such a case, one of the plurality of images must be displayed in a color combination different from the stored color combination, and the quality of the image is significantly impaired.

In order to deal with the above-mentioned problem, conventionally, a method has been used in which one of a plurality of windows is designated by a pointing device or the like, and a coloring right is given only to the designated window to change the contents of the LUT. .

Also, a window area is set in a part of the one-sided display screen having a plurality of LUTs, and different LUTs are used inside and outside the area.
There is also an attempt to use.

However, in the conventional method, there is no difference in that only one image is correctly displayed at a time, the advantage of multi-window is not utilized, and the coloring right is moved to another window. If this is done, the color tone of the entire screen, including the part outside the window, may change significantly, which is unsightly.

Further, in an attempt to set a window area in a part of the display screen, a relatively large area setting means is required to give flexibility to the number, position, size and shape of windows.

In view of such a point, the present invention is a relatively small-scale means,
An object is to obtain a bitmap display device that can use different LUTs in a part of the display screen.

Means for Solving the Problems The present invention includes a bitmap memory that holds bitmap image information, and a plurality of lookup tables that convert image information obtained from the bitmap memory into video signals for each pixel, From the image information obtained from the bit map memory, trigger detection means for detecting a pixel or a combination of pixels that is a trigger for switching the lookup table to be used, and the trigger detection means for detecting the trigger. In response, a key pixel storage unit that receives and holds a key pixel that determines a lookup table to be used from the bitmap memory, and a pixel that the key pixel storage unit holds is used as a lookup table. A lookup table that translates into information to be determined and selects only one from the plurality of lookup tables. And a table selecting means.

Action In addition to the target image to be displayed, the trigger that triggers the switching of the lookup table to be used is written in advance in the bitmap memory. Here, the trigger is defined in advance as a pixel or a combination of pixels having a specific value. The trigger detection means detects this and notifies the key pixel storage means of the detection. Upon receiving the notification, the key pixel storage means obtains the key pixel from the bitmap memory and holds it. Which pixel is the key pixel is determined separately.

The look-up table selection means always refers to the pixel held by the key pixel storage means, determines the look-up table to be used from among the plurality of look-up tables, and the look-up table decided to be used. Only the table is activated and the other lookup tables are deactivated. In this way, a plurality of look-up tables are switched and used.

Embodiments The operation of the present invention will be described by taking a bit map display device in which each pixel has a color identified by 4 bits as an example. This is shown in FIG. Since it is 4 bits, color numbers 0 to 15 are applied. Further, in this example, there are 16 LUTs from 0 to 15.

Now, in this bitmap display device, the bitmap memory 1 is raster-scanned for display, and 4-bit information per pixel is read out accordingly. Then, the LUT is searched with the read 4 bits to obtain the color of the pixel. Each entry in the LUT represents 4 bits of red, blue, and green, and 12 bits in total to represent the color. Here, which of the 16 LUTs is used is determined by the lookup table selection means 5, but at the beginning of each raster row, it is determined as a specific LUT. In this example, this is the 0th LUT
And

The image information converted into the color by the LUT is selected by the look-up table selection means 5, converted into an analog signal by the D / A converter 6, and displayed on the CRT display 7. The 4-bit information per pixel read by the raster scan is also given to the trigger detection means 3 and the key pixel storage means 4 in parallel with the LUT.

In this example, the number 15 pixel is 2 in each raster line.
Continuing triggers, the pixels following the triggers are the key pixels (key pixels), the pixel after the key pixel is the switching area,
That is, the area where the LUT can be switched. The color number of the key pixel is the same as the LUT used in the switching area.
Number.

At this time, when the pixels are arranged in the raster line as shown in FIG. 2, the trigger 8 is first detected by the trigger detecting means 3 and the key pixel storing means 4 is notified of that fact. In order to detect a trigger, two 4-bit registers are arranged to hold the latest two scanned pixels, and this can be compared with the set (15,15) defined as a trigger. . In response to the detection of the trigger, the key pixel storage means 4 holds the key pixel 9, that is, the pixel of color number 8. Then, the look-up table selection means 5 comes to select the 8th LUT, and the 8th LUT is applied to the pixels after A.

An example of forming a window in such a bitmap display device is shown in FIG. The vertical boundary line 12 of the window 11 has a width of 3 pixels. An enlarged view of the vertical border 12 of the window is shown in FIG. Of the two vertical boundary lines 12, the left one, that is, the one to be scanned first, has the color numbers 15, 15, and 8 arranged in order, and the right one has the color numbers 15, 15, and 0 arranged in order. Therefore, LUT number 8 is applied inside this window, but number 0 is applied outside this window.

The same thing holds even if there are multiple windows, and the maximum
Up to 15 windows, each window and the part outside the window can set LUT independently.

Further, the vertical boundary line 12 looks like a line segment drawn to make it easier to identify the window, and does not give a strange feeling.

By the way, a trigger may be accidentally included in the display image. In this case, the value of the key pixel is changed so that unnecessary switching of the LUT does not occur. Since the key pixel is a small area, it does not matter so much visually.

EFFECTS OF THE INVENTION As described above, according to the present invention, the user writes the trigger and the key pixel at an appropriate position in the bitmap memory, so that an arbitrary look-up table in an arbitrary area within the same display screen is displayed. Can be applied. Moreover, since the number of times the lookup table is switched is not limited, its practical value is great.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of a positional relationship between a trigger, a key pixel, and a switching area, and FIG. 3 is an explanatory diagram in which a window is formed in the above embodiment, The figure is the third
FIG. 5 is an enlarged view of the vertical boundary line of the window in the figure, and FIG. 5 is an explanatory view of displaying a plurality of images at the same time. 1 ... Bitmap memory, 2 ... Plural look-up tables, 3 ... Trigger detection means, 4 ... Key pixel storage means, 5 ... Lookup table selection means, 6 ... D / A
Converter, 7 ... CRT display, 8 ... Trigger, 9 ...
Key pixel, 10 …… Switching area, 11 …… Window, 12 …… Vertical border line, 13 …… Outside window.

Claims (1)

(57) [Claims] 1. A bitmap memory for holding bitmap image information, a plurality of lookup tables for converting the image information obtained from the bitmap memory into a video signal for each pixel, and the bitmap memory. Trigger detection means for detecting a pixel or a combination of pixels which is a trigger for switching the look-up table to be used from the image information to be used, and should be used in response to the trigger detection means detecting the trigger. A key pixel storage unit that receives and holds a key pixel that determines a lookup table from the bitmap memory, and a pixel that the key pixel storage unit holds is translated into information that determines a lookup table to be used. And a look-up table selection means for selecting only one from the plurality of look-up tables. That bit map display device.