JPH06333040A - Image processor - Google Patents

Abstract

PURPOSE:To provide an image processor which can perform the conversion of gradation at a high speed and in a simple constitution. CONSTITUTION:An image processor converts the image data shown in N- gradation into the image data of M-gradation and is provided with an image input part 40 which inputs the image data shown in N-gradation in a prescribed unit, a gradation converting part 41 which collectively converts the image data supplied from the part 40 into the image data of M-gradation, and an image output part 42 which outputs the image data M-gradation in a prescribed unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus capable of executing gradation conversion processing for converting an image expressed in N gradations into M gradations.

[0002]

2. Description of the Related Art Generally, an image processing apparatus or a DTP (Desk Top Publishing) capable of inputting an image
In a system or the like, a process of converting the number of gradations of an image may be necessary for the purpose of, for example, combining images having different numbers of gradations or increasing the accuracy during calculation. Conventionally, the following method has been used for this type of processing.

As shown in FIG. 3, four gradation data represented by 2 bits / pixel (see FIG. 3A) is converted into 16 gradation data represented by 4 bits / pixel (see FIG. For example, it is assumed that the processing is performed with the configuration as shown in FIG. 20 is N gradation (4 in this case)
N gradation image storage unit for storing an original image expressed in gradation, 21 is a pixel unit image input unit for reading image data from the N gradation image storage unit 20 in pixel units, and 22 is an N gradation image A pixel-unit gradation conversion unit that converts data into M gradations (16 gradations in this case) in pixel units, and 23 combines the converted data into a bit width that can be input to an M gradation image storage unit described below. And a pixel-synthesized image output unit 24 for outputting the converted image data of M gradations. In this example, the inside of the pixel unit gradation conversion unit 22 has a pixel unit gradation conversion table 221 for converting an input pixel value into an output pixel value in a one-to-one manner, and actual conversion is performed using this table. Pixel unit gradation conversion processing unit 22
It consists of zero. Pixel unit gradation conversion table 22
The contents shown in FIG. 5 are stored inside 1 and the pixel value expressed by 2 bits / pixel can be converted into 4 bits / pixel.

When the image data is read from the N gradation image storage unit 20, since the data is usually handled with a fixed bit width such as 8 bits, the pixel unit image input unit 2 is temporarily operated.
The image data is buffered in 1 and cut out pixel by pixel and sent to the pixel unit gradation conversion unit 22. The pixel-unit gradation conversion unit 22 receives the input data from the pixel-unit gradation conversion processing unit 220, and performs conversion by referring to the pixel-unit gradation conversion table 221. The converted data is the pixel composite image output unit 2
3 and is stored in the M gradation image storage unit 24. M
When the input bit width to the gradation image storage unit is in units of 8 bits, the gradation-converted data is temporarily buffered by the pixel composite image output unit 23, and when the next 4-bit data is output, And stores it in the M gradation image storage unit.

In this example, the pixel-unit gradation conversion table 22
Although the conversion is performed using 1, the operation shown in FIG. 5 is also realized by a comparator or the like, or the condition determination is performed by software.

[0006]

However, the above processing method has the following drawbacks. Normally, the bit width that can be input / output in the image storage means is fixed,
For example, when the bit width is 8 bits, in order to process the data of 2 bits / pixel, it is necessary to read out the data buffered by the pixel-unit image input unit 21 four times while cutting out each two bits. . Further, if the converted image data has 4 bits / pixel, the pixel composite image output unit 23 has to write in 8-bit units even at the time of writing.
It is necessary to provide a buffer in and to perform processing such as synthesizing and writing two pieces of output data, which is a factor of reducing the processing speed. Further, in the case where the bit width is not 1 / integer or an integer multiple of the input / output bit width such as 3 bits / pixel, the control becomes very complicated when located at the boundary between two 8-bit data. I had.

The present invention has been made in view of the above points, and an object of the present invention is to provide an image processing apparatus capable of executing gradation conversion at high speed and having a simple structure.

[0008]

In order to achieve the above object, in the present invention, attention is paid to the fact that gradation conversion can be executed in pixel units irrespective of surrounding pixels, and a plurality of pixels of input image data are collectively processed. A feature is that a table for converting to another gradation is provided. Specifically, for example, as shown in FIG. 2, when converting 2-bit / pixel data into 4-bit / pixel, a gradation conversion table that collectively converts 4 pixels is provided, and a gradation conversion table in the image input unit is provided. The processing can be performed at high speed by collectively converting a plurality of pixels without performing processing such as cutting out in pixel units or combining output data in the image output unit.

[0009]

By converting a plurality of pixels all at once, the number of conversion processes can be reduced, and high-speed processing can be achieved. In addition, there is no need for a buffer for storing the cut-out or read-out data for each pixel in the image input unit, a buffer for storing data in the image output unit or a buffer for storing the previous output data, and the configuration is simple. It has the advantage that it can be realized.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an image processing apparatus according to the present invention. In the figure, 40 is an image input unit for reading out image data of 4 gradations, which is an original image, in units of 8 bits in a unit of 4 pixels, 41 is data of 16 gradations collectively for data inputted in 8 bit units. The gradation conversion unit 42 converts the 16-bit output from the gradation conversion unit 41 to the storage unit in 8-bit units. Inside the gradation conversion unit 41, a gradation conversion table 411 in which the data shown in FIG. 2 is stored, and data of 4 pixels represented by 2 bits using the gradation conversion table 411 are collectively displayed. A gradation conversion processing unit 410 that converts data of 4 pixels represented by 4 bits is included.

The image input section 40 uses N gradations (4 in this case).
8-bit data is read from the gradation image storage unit 20 and input to the gradation conversion unit 41. Inside the gradation conversion unit 41, the gradation conversion processing unit 410 accesses the gradation conversion table 411 based on the input data, and outputs the output to the image output unit 42. For example, using the table of FIG. 2, when the input is 4-pixel data of “10, 11, 10, 11”, the image output unit 42 displays “1010,
The data of 1111, 1010, 1111 "is output. The image output unit 42 outputs this data in M units of 8 bits.
The gradation (16 gradations in this case) is output to the image storage unit 24. By repeating this operation, a 4-gradation image can be converted into a 16-gradation image at high speed in units of 4 pixels.
In this example, the conversion from 4 gradations to 16 gradations has been described as an example, but by adding a means for changing the contents of the conversion table, it is possible to use it in combination with other gradation conversions. can do. For example, when converting a binary image into data of 256 gradations, processing can be performed in units of 8 pixels by configuring a conversion table of 8-bit input-64-bit output. Similarly, in order to convert an image of 8 gradations to 256 gradations, a conversion table of 24-bit input-64-bit output is created although the capacity of the table is considerably large, and the input is performed in units of 8 bits × 3. Output 8 bits ×
By performing the conversion in 8 units, it is possible to perform gradation conversion without processing the data that straddles the byte boundary.

In some cases, the capacity required for the conversion table can be reduced by leaving the mechanism for performing the combining process in the image output unit. For example, when converting a 256-gradation image into a binary value, the output side is normally set to a multiple of 8 bits.
Batch processing is required in units of 8 pixels. In this case, the input becomes 8 bits × 8 pixels = 64 bits, and the capacity of the table for collectively converting this into 8 bits becomes enormous. Therefore, if processing is performed in units of 2 pixels instead of in units of 8 pixels, and the output is synthesized and output so that the output becomes 8 bits, the conversion table becomes 16 bits input-2 bits output, and the required capacity is about 16 Kbytes. can do.

[0014]

As described above, according to the present invention, it is possible to perform high-speed processing by collectively converting the gradation of a plurality of pixels, and cut out or read out data in pixel units in the image input unit. It is also possible to realize an image processing apparatus capable of high-speed processing with a simple configuration, since a buffer for storing data, a data combining operation in the image output unit and a buffer for storing previous output data can be dispensed with. it can.

[Brief description of drawings]

FIG. 1 is a block diagram of an image processing apparatus showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of contents of a gradation conversion table of the present invention.

FIG. 3 is an explanatory diagram of image gradation conversion.

FIG. 4 is a block diagram of an image processing apparatus showing a conventional example.

FIG. 5 is an explanatory diagram of contents of a conventional pixel-unit gradation conversion table.

[Explanation of symbols]

20 ... N gradation image storage unit, 21 ... Pixel unit image input unit,
22 ... Pixel unit gradation conversion unit, 220 ... Pixel unit gradation conversion processing unit, 221 ... Pixel unit gradation conversion table, 23 ... Pixel composite image output unit, 24 ... M gradation image storage unit, 40 ... Image input unit , 41 ... gradation conversion unit, 410 ... gradation conversion processing unit, 411 ... gradation conversion table, 42 ... image output unit

Claims (2)

[Claims] 1. An image processing apparatus for converting image data expressed in N gradations into M gradations, input means for inputting the image data expressed in N gradations in a predetermined unit, and the input means. Gradation conversion means for collectively converting the image data of a predetermined unit inputted from M to gradation, and output means for outputting the image data gradation-converted to M gradation in the predetermined unit. An image processing device characterized by: 2. The gradation conversion means has a storage means for preliminarily tabulating and storing a result of converting image data of a predetermined unit input from the input means into M gradations at a time. The image processing apparatus according to claim 1.