JPH05159049A - Picture processor - Google Patents

Abstract

PURPOSE:To make a picture processing efficient and to prevent the deterioration of picture quality. CONSTITUTION:Picture data 11 is input picture data (D5) which is inputted in the first data system of five bits per picture element. Picture data 12 is picture data (D8) which is enlarged to data on the same number of bits as the second data system of eight bits per picture element. Namely, bit0 to bit4 of input picture data D5 in picture data 11 are connected to bit3 to bit7 of input picture data D8 in picture data 12, and bit2 to bit4 of input picture data D5 in picture data 11 are connected to bit0 to bit2 of input data D8 in picture data 12 so as to enlarge data.

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 for converting a data format of input image data into image data of a data format suitable for a recording apparatus.

[0002]

2. Description of the Related Art Conventionally, it has been practiced to process input image data in a plurality of data formats in a digital image processing apparatus to generate output image data suitable for a recording apparatus connected to the apparatus. As a specific example of the data format, image data (1st color of 1 pixel is represented by 5 bits)
There is a data format). According to this, it is possible to express 32 shades of gray in the case of a monochromatic image, and if each color image is represented by the three primary colors of red (R), green (G) and blue (B), each has 5 bits. 32,768 colors can be expressed.

As a concrete example of another data format (second data format) having a larger number of bits than the above data format, there is image data in which one color of one pixel is represented by 8 bits. If a monochrome image can represent 256 gradations, and a color image represented by the three primary colors of red (R), green (G), and blue (B) has 8 bits, 16777216 Can express colors. Then, in the conventional digital image processing apparatus, the input image data input in the first data format is expanded to 8-bit data and temporarily stored in the storage means. That is, the first
8 times the input image data input in the data format of
It is extended to the same 8-bit data as the second data format.
In the case of color image data, each of red (R), green (G) and blue (B) is multiplied by 8 to obtain red (R), green (G) and blue (B).
Each is expanded to the same 8-bit data as the second data format.

[0004]

[Problems to be solved by the invention] However,
In the conventional image processing apparatus of this type, since the input image data input in the first data format is simply multiplied by 8 and expanded to the same 8-bit data as in the second data format, The possible values of the expanded data are 0 for the minimum value and 248 for the maximum value. On the other hand, the minimum value of the values that the image data input in the second data format can take is 0.
And the maximum value is 255. Therefore, when the input image data input in the first data format is simply multiplied by eight, there is a problem that the contrast ratio decreases compared to the image data input in the second data format.

[0005]

[Means for solving problems] and

The present invention has been made for the purpose of solving the above-mentioned problems, and has the following structure as one means for solving the above-mentioned problems. That is, the number of bits is expanded from the input image data having the first data format in which one pixel is represented by m bits to the image data in the second data format in which one pixel is represented by n (n>m> 0) bits. In the image processing apparatus for recording as described above, the image data D _m having the first data format is recorded.

[0006]

[Equation 7] Then, the expanded image data D _n of the second data format is

[0007]

[Equation 8] It is represented by. With the above configuration, it is possible to improve the efficiency of image processing and prevent deterioration of image quality.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing the arrangement of an image processing apparatus according to an embodiment of the present invention. In the figure, the input data expansion means 1 converts the input image data (D ₅ ) input in a first data format described later into 1
This is an extension means for obtaining the image data (D ₈ ) by expanding to the same number of bits as the second data format of 8 bits per pixel. The switching means 31 switches corresponding to the above-mentioned input data format, and when the image data is input in the first data format in which one pixel is 5 bits, the switching means 3
1 is input to the (1) side, and when the image data is input in the second data format in which one pixel is 8 bits, (2)
Switch to the side. Therefore, regarding the image data that has passed through this switching means 31, there is no distinction as to whether it was input in the first data format or in the second data format.

The storage control means 32 includes a storage means 1 (3
3) and the storage means 2 (34) are controlled so that the storage means 1 (33) and the storage means 2 (34) store the converted input image data in the first data format or the unconverted input image data. The input image data in the second data format is temporarily stored. Then, the storage control unit 32 is the storage unit 1.
(33), 2 (34) has a means (not shown) for generating the write address and the write signal when writing the image data, and the other storage means stores the written image data. A means (not shown) for generating the read address and read signal when reading
Have.

Further, the storage control means 32 stores in the storage means 1 at the time when both the writing process and the reading process are completed.
It has a switching means (not shown) for switching the roles of (33) and 2 (34). That is, the storage means set to the write mode is set to the read mode, and the storage means set to the read mode is set to the write mode. The storage means 1 (32) and the storage means 2 (3
As for the capacity of 3), it is sufficient if the minimum image data is one line,
Specifically, it is determined by the number of bits per pixel of the image data and the number of pixels per line of the recording device 38.

The brightness data converting means 35 is a data converting means for expressing the input image data expressed by the brightness by the density, and the number of bits per pixel of the input image data is 8.
(For color images, the three primary colors red (R), green (G),
When the blue (B) data is 8 bits each, conversion is performed according to the following equation (1). That is, assuming that the input image data is D _i , the density data D _k (in the case of a color image, the data of the three primary colors red (R), green (G), and blue (B) are respectively density data D _r , D _g , D _b ) is converted as follows. D _k = −255 / A _k × log (D _i / 255) (1) However, 0 ≦ D _k ≦ 255, and A _k is a constant.

FIG. 2 is a diagram showing the relationship between input image data and output image data. Specifically, the density data D _k (D _r , D _g , D _{b in} the case of a color image) calculated in advance according to the above equation (1) is stored in the storage means, and the input image data is used as address information. , See them. The density correction means 36 in FIG. 1 corrects the density characteristics of the recording device 38. Usually, in a recording apparatus such as an inkjet, the relationship between input image data and its recording density is
It does not become a straight line as indicated by reference numeral 500 in FIG. 3, but has a characteristic as indicated by reference numeral 501. Therefore, it is necessary to correct the input data and the recording density thereof so as to form a straight line as indicated by reference numeral 500. The correction data is 5
The data represented by 02 is selected so as to be symmetrical with respect to the characteristic indicated by reference numeral 501 with respect to the straight line 500. Here, the correction data (reference numeral 502) is stored in advance in the storage means, and the input image data is referred to as address information.

The pseudo halftone processing means 37 is a processing means for expressing a grayscale image in a pseudo manner by the presence or absence of dots. The recording device 38 is, for example, a device that adopts an inkjet system or a thermal transfer system. Note that the error diffusion method, which has been attracting attention in recent years, is a method that makes it possible to achieve both gradation and resolution. In this method, the difference between the density of the original image and the density of each pixel of the binarized output image, that is, , Calculate the error,
A method is adopted in which the error value that is the result of this calculation is given a specific weight to the peripheral pixels of the pixel of interest according to the coefficient of the weight matrix, and then dispersed.

Further, since this method spatially diffuses an error which is a density difference between pixels of the original image and the output image,
Unlike the dither processing which is another pseudo halftone processing method, the number of gradations is not limited by the matrix size. For this error diffusion method, see R. WFloyd and L. Steinberg "An.
Adaptive Algorithm for Spatial Gray Scale "SID 75 D
Published in igest (1976).

FIG. 4 is a diagram showing a data expansion method in the input data expansion means constituting the image processing apparatus according to this embodiment. In the figure, image data 11 is input image data (denoted as D ₅ ) input in a first data format of 5 bits per pixel, and image data 12 is a second image data of 8 bits per pixel. Image data (denoted as D ₈ ) extended to data having the same number of bits as the data format of.

Here, as shown in FIG. 4, bits 0 to 4 of the input image data D ₅ of the image data 11 are converted to bits ₃ to 7 of the input image data D ₈ of the image data 12.
To the input image data D of the image data 11
Bits 2 to 4 of ₅ are connected to bits 0 to 2 of the input image data D ₈ of the image data 12. The above relationship can be expressed by a mathematical expression as follows. That is, the input image data D ₅ of the image data 11 is

[0017]

[Equation 2] Expressed as, the expanded input image data D ₈ is expressed by the following equation (3).

[0018]

[Equation 3] However, b _i is 0 or 1, and k = (3 + i) / 5, which is rounded down after the decimal point. Further, FIG. 5 shows a part of the input image data D ₅ and the expanded image data D ₈ and is denoted by reference numeral 2.
1 is 0 to 31 as the value of the input image data D ₅ , and reference numeral 22 corresponds to the value of the input image data D ₅ .
The values 0 to 255 of the expanded image data D ₈ are shown.
Generally, when the input image data D _{m in} which one pixel is represented by m bits is expanded to n-bit image data D _n ,
According to the following formula (4). That is,

[0019]

[Equation 4] Becomes However, in the above formula (4), b _i is 0 or 1, n>m> 0, k = (n−m + i) / m, and fractions below the decimal point are truncated.

As described above, according to this embodiment,
Input image data in which one pixel is composed of the bit number m,
When the number of bits is expanded to n (n>m> 0) to form image data in a data format suitable for the recording apparatus, the input image data is not simply expanded according to the difference in the number of bits, and the predetermined value is set. By expanding the number of bits so that the gradation conforms to the non-linear characteristic of, there is an effect that efficiency of image processing and deterioration of image quality can be prevented.

[Modification] A modification of the above embodiment will be described below. FIG. 6 is an extension of the first data format in which one pixel of the input image data is represented by m bits to the second data format in which one pixel of the input image data is represented by n (n>m> 0) bits. 6 is a flowchart showing a control procedure when the is realized by a software program. In step S601 of FIG. 6, it clears the variables D _n for storing data D _n after expansion, in step S602, first
The variable i for counting the number of repetitions of is cleared. Continue,
In step S603, the data D _m before expansion is stored in the arithmetic register AR (not shown). Then, step S60
At 4, the variable j for counting the second number of iterations is cleared.

In step S605, the second iteration count is calculated and stored in the variable k. The calculation formula at that time is k = (int) (nm + i) / m (5). In addition, (int) of the above formula (5) is (n-
After calculating m + i) / m, it indicates that the fractional part is truncated. In step S606, the value of each bit of the pre-expansion data D _m stored in the arithmetic register AR is checked, and if it is not a logical “0”, the flow advances to step S607 to store the value stored in the variable D _n . To 2 ^{(n-m + i-mj)}
Is added and the result is stored in the variable D _n . Then, the value of the variable j that counts the second number of repetitions is incremented by 1 (step S608). In step S609,
The value of the variable j is checked, and steps S607 to
The process of S609 is repeated.

On the other hand, the determination in step S606 is YES.
In the case of, that is, when the corresponding bit of the arithmetic register AR is logical “0”, the processing of steps S607 to S609 is not executed and the process proceeds to step S610. In this step S610, the variable i for counting the first number of iterations is
Increase the value of by 1. Then, in step S611, the value of the variable i is checked, and the processes of steps S604 to S611 are repeated until it becomes larger than m-1. When all the series of processes are executed, the first data D _m represented by m bits becomes n (n>m> 0).
It is expanded into the second data D _n represented in bits and stored in the variable D _n .

[0024]

As described above, according to the present invention,
Image data D _{m in} which one pixel has a data format of m bits
1 pixel is n (n>m> 0) according to a predetermined conversion characteristic.
By expanding the image data D _n with the same number of bits as the data format represented by bits, the efficiency of image processing is improved,
There is an effect that deterioration of image quality can be prevented.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a relationship between input image data and output image data in the embodiment,

FIG. 3 is a diagram showing a relationship between input image data and its recording density in an ordinary recording apparatus,

FIG. 4 is a diagram showing a data expansion method in an input data expansion unit that constitutes the image processing apparatus according to the embodiment.

FIG. 5 is a diagram showing a part of input image data and expanded image data;

FIG. 6 is a flowchart showing a control procedure when a software program realizes a process of expanding the data format of input image data to another data format.

[Explanation of symbols]

1 Input Data Expansion Means, 11 Input Image Data Having First Data Format 12 Data After Expansion of Input Image Data of First Data Format 31 Switching Means 32 Storage Control Means 33, 34 Storage Means 35 Luminance Data Conversion Means 36 Density correction means 37 Pseudo halftone processing means 38 Recording device

Claims (1)

[Claims] 1. Input image data having a first data format in which one pixel is represented by m bits, and one pixel is n (n> n).
In an image processing apparatus for expanding the number of bits and recording the image data of the second data format represented by m> 0) bits, the image data D _m having the first data format is expressed as follows: Then, the expanded image data D _n of the second data format is as follows. An image processing device represented by the following.