JP2003189178A - On-screen display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an on-screen display device that can set a transparency or a coefficient denoting the transparency in a prescribed number of bits to set a ratio of mixing between an original image and on-screen display (OSD) information by each pixel or each character similarly to the conventional case and reduce the memory capacity having conventionally been required to set the transparency. <P>SOLUTION: An argument in 4-bits denoting the transparency by each character or each pixel configuring the OSD information is set to an argument memory area 28B. Since the argument has a smaller number of bits that of the transparency in 8-bits, the capacity of the argument memory area 28B will do with a half of that with the case of writing the transparency. The argument read from the argument memory area 28B is converted into the transparency in 8-bits by a conversion table 42B and an α value computing element 43 calculates a coefficient α (0≤α≤1) denoting the transparency. Multipliers 44, 46 and an adder 48 mix the original image with the OSD information on the basis of the coefficient α. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-screen display device, and more particularly to an on-screen display device used for image display devices such as televisions and digital cameras.

[0002]

2. Description of the Related Art A conventional on-screen display device simply adds on-screen display (OSD) information such as character information output from a character generator to an original image (Japanese Patent Laid-Open No. 11-338454).

An OSD device shown in FIG. 4 is also known in the past. This OSD device 10 has a coefficient α indicating transparency.
By (0 ≦ α ≦ 1), the mixing ratio of the original image and the OSD information is set, and the OSD information is superimposed on the original image.

That is, the original image input to the OSD device 10 is multiplied by (1-α) by the multiplier 18, and the adder 1
Added to 4. Further, OSD information such as character information output from the character generator 16 is multiplied by a coefficient α indicating transparency by a multiplier 18 and added to an adder 14. The adder 14 adds (mixes) the original image multiplied by (1-α) and the OSD information multiplied by the coefficient α indicating transparency and outputs the OSD information.

The transparency is a certain number of bits (for example, 8 bits) for each character or each pixel in one screen.
Is set by.

[0006]

The conventional O shown in FIG.
The SD device 10 sets the transparency with a certain number of bits (for example, 8 bits) for each character or for each pixel in one screen, so that the memory capacity required to set the transparency becomes large. There is.

The present invention has been made in view of the above circumstances, and a transparency having a predetermined number of bits for setting the mixing ratio of the original image and the OSD information for each pixel or each character, or the transparency. It is an object of the present invention to provide an on-screen display device capable of setting the coefficient indicating the same as in the conventional case and reducing the memory capacity required for the conventional transparency setting.

[0008]

In order to achieve the above object, the invention according to claim 1 sets an original image and on-screen information such as characters for each character or each pixel constituting the on-screen information. In the on-screen display device that mixes based on the transparency, the storage means for reading and writing an argument indicating the transparency for each character or each pixel that constitutes the on-screen information, and having a transparency of a predetermined number of bits A storage unit in which an argument having a smaller number of bits is written, and a corresponding argument is read according to the position information of the pixel of the original image, and the transparency corresponding to the argument or a coefficient indicating the transparency is stored, and the storage is performed. A conversion table for reading the corresponding transparency or coefficient based on the argument read from the means, and reading from the conversion table. It is characterized by mixing the original image and on-screen information based on the transparency or coefficients.

Since the storage means writes an argument having a smaller number of bits than the transparency having a predetermined number of bits, the storage capacity can be reduced as compared with the case where the transparency is written as it is. On the other hand, since the argument read from the storage means is converted into the transparency of a predetermined number of bits or the coefficient indicating the transparency through the conversion table, the transparency or the coefficient can be set as in the conventional case. .

As described in claim 2, the transparency or the coefficient corresponding to the argument stored in the conversion table can be freely rewritten. This allows
The relationship between the argument and the transparency or the coefficient can be made non-linear. For example, when the original image is bright, the transparency can be finely set for the argument that darkens the on-screen information.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of an on-screen display device according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram of a main part of an image display device such as a television and a digital camera including an on-screen display device according to the present invention.

As shown in the figure, this image display device is
A CPU (central processing unit) 20, which is a control unit that controls the apparatus as a whole, a DMA (Direct Memory Access) controller 22, a signal that performs various signal processing such as sharpness correction, gamma correction, contrast correction, and white balance correction Processing circuit 24, encoder 26, SDRA
An M (Synchronous DRAM) 28, an OSD information including a device control program, a font, an icon, etc., and an R storing a plurality of types of data of a conversion table described later.
An OM 30 and an OSD circuit 32 that performs a process of combining an original image and OSD information are connected to a common bus 34.

As shown in FIG. 2, the SDRAM 28 has a bitmap memory area 28A as a frame memory for temporarily storing OSD information such as characters and icons, and an argument memory area 2 corresponding to the bitmap memory area 28A.
8B and. Bitmap memory area 28A
Is, for example, 640 × 480 pixel size, and the bit depth is 8 bits, and the argument memory area 28B is, for example,
The size is 640 × 480 pixels and the bit depth is 4 bits, which is half the memory capacity of the bitmap memory area 28A.

CPU 20 or DMA controller 22
Reads the OSD information stored in the ROM 30 as appropriate, writes the OSD information in the bitmap memory area 28A of the SDRAM 28, and writes an argument indicating the transparency of the OSD information in the argument memory area 28B. OS
The information of 1 pixel (8 bits) of the D information is address information indicating any one of the 256 colors of the color palette. The argument set for each pixel or character is a 4-bit (0 to 15) value indicating the transparency (transparency represented by 8 bits) of the OSD information of the pixel or character.

The OSD circuit 32 includes a latch circuit 40A, 40B and a color palette table 42 as shown in FIG.
A, a conversion table 42B, an α value calculator 43, multipliers 44 and 46, and an adder 48.

The latch circuit 40A of the OSD circuit 32,
40B, OSD information and arguments are added from the bitmap memory area 28A and the argument memory area 28B of the SDRAM 28 via the common bus 34, and the multiplier 46
The original image is added to. This original image is adapted to be added via an interface (not shown) or via the image pickup means and the signal processing circuit 24.

The OSD information and the argument for each pixel in the bitmap memory area 28A and the argument memory area 28B are the position information on the screen of the original image input to the OSD circuit 32 (in the horizontal and vertical directions of the screen). DMA information is sequentially transferred in correspondence with the position information).

The OSD information and the argument transferred to the OSD circuit 32 are latch circuits 40A and 40B for each pixel.
And is added to the color palette table 42A and the conversion table 42B.

As described above, the OSD information for each pixel is the address information of the color palette table 42A, and the input O from the color palette table 42A.
Information (luminance signal Y and chroma signals C _r , C _b ) indicating any one of 256 colors corresponding to the SD information is read and output to the multiplier 44.

The conversion table 42B is a look-up table in which 8-bit transparency is stored corresponding to a 4-bit argument as shown in FIG. 3. For example, the input / output characteristics A, B and C shown in FIG. One of them has been written. The transparency is a value indicating the mixing ratio of the original image and the OSD information. In the case of the transparency = 255 shown in FIG. 3, the original image: OSD information = 0: 1 and the transparency = 0.
In the case of, the original image: OSD information = 1: 0.

Data indicating the input / output characteristics A, B, or C written in the conversion table 42B shown in FIG.
A table value of input / output characteristics, which is prepared in the OM 30 and is suitable for the type of original image to be combined with OSD information, is set. For example, when synthesizing OSD information in a bright part of the original image, as the argument is increased (the OSD information is displayed darker), the input / output characteristic A whose transparency can be finely set is selected, and the dark part of the original image is selected. When synthesizing OSD information, the input / output characteristic C for which the transparency can be finely set is selected as the argument is made smaller (OSD information is displayed lighter). That is, the table value of the conversion table 42B can be freely rewritten. still,
The table value of the conversion table 42B is not limited to the table value indicating the input / output characteristics A, B, or C in FIG. 3, but can be rewritten to a table value having various characteristics such as a γ characteristic.

The conversion table 42B is a latch circuit 40B.
When an argument of 4 bits (0 to 15) for each pixel is input from, the 8-bit transparency corresponding to the input argument is read and output to the α value calculator 43.

The α value calculator 43 calculates a coefficient α (hereinafter, referred to as a coefficient α) based on the 8-bit transparency input from the conversion table 42B.
"Α value") is calculated by the following formula,

[0025]

## EQU1 ## α = transparency / 255 (0 ≦ α ≦ 1) The α value thus obtained is output to the multiplier 44, and the (1-α) value is output to the multiplier 46.
Is output to.

Information indicating any one of 256 colors from the color palette table 42A is added to the other input of the multiplier 44, and the multiplier 44 multiplies the information indicating the color by the α value. And outputs it to the adder 48. On the other hand, the original image is added to the other input of the multiplier 46, and the multiplier 46 multiplies the original image by the (1−α) value and adds it.
Output to.

The adder 48 adds the two inputs added from the multipliers 44 and 46, thereby mixing the OSD information and the original image, and outputs the mixed image to the encoder 26 (FIG. 2).

In the encoder 26, the O
The luminance signal Y and the chroma signals C _r and C _{b in} which the original image and the OSD information are mixed are input from the SD circuit 32, and the luminance signal Y is input.
Is added with the blanking pulse and the synchronizing signal, and on the other hand, the chroma signals C _r and C _b are each subjected to quadrature two-phase modulation with a color subcarrier of 3.58 MHz and added. Add the burst signals modulated by the _Z color subcarrier. Then, the luminance signal Y to which the blanking pulse and the synchronization signal have been added and the chroma signal to which the burst signal generated by the burst flag pulse have been added are added to generate an NTSC composite video signal.

The composite video signal generated in this manner is output to a television or a liquid crystal monitor and displayed as an image in which OSD information is mixed with the original image.

The bit depth of the argument stored in the argument memory area is not limited to this embodiment, and may be 2 bits or more and smaller than the number of bits of transparency converted by the conversion table. Good. Further, in this embodiment, the conversion table and the α value calculator are provided separately, but these may be combined into one table and the α value may be read directly from the argument.

[0031]

As described above, according to the present invention, the transparency having a predetermined number of bits for setting the mixing ratio of the original image and the OSD information for each pixel or each character is directly stored in the storage means. Since the argument having a smaller number of bits than the transparency is stored instead of being stored, the storage capacity can be reduced. On the other hand, since the argument read from the storage means is converted into the transparency of a predetermined number of bits or the coefficient indicating the transparency by the conversion table, the transparency or the coefficient can be set as in the conventional case. The table value of the conversion table can be freely rewritten, and a conversion table suitable for the brightness of the original image can be used.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of an image display device such as a television and a digital camera including an on-screen display device according to the present invention.

FIG. 2 is a block diagram showing details of an OSD circuit and the like in FIG.

FIG. 3 is a diagram used to explain a conversion table in an OSD circuit.

FIG. 4 is a schematic configuration diagram of a conventional on-screen display device.

[Explanation of symbols]

20 ... Central processing unit (CPU), 22 ... DMA controller, 26 ... Encoder, 28 ... SDRAM, 28A ...
Bitmap memory area, 28B ... Argument memory area, 3
0 ... ROM, 32 ... OSD circuit, 34 ... Common bus, 40
A, 40B ... Latch circuit, 42A ... Color palette table, 42B ... Conversion table, 43 ... α value calculator, 4
4, 46 ... Multiplier, 48 ... Adder

Claims (2)

[Claims] 1. An on-screen display device for mixing an original image and on-screen information such as characters on the basis of transparency set for each character or each pixel constituting the on-screen information, wherein the on-screen information is Storage means for reading and writing an argument indicating transparency for each character or pixel that constitutes
A storage unit in which an argument having a smaller number of bits than the transparency having a predetermined number of bits is written, and a corresponding argument is read according to position information of pixels of the original image; and a transparency corresponding to the argument or the transparency. And a conversion table for reading out the corresponding transparency or coefficient based on the argument read from the storage means, and an original image based on the transparency or coefficient read from the conversion table. An on-screen display device characterized by mixing with on-screen information. 2. The on-screen display device according to claim 1, wherein the transparency or the coefficient corresponding to the argument stored in the conversion table can be freely rewritten.