JPH11103463A - Picture encoding method and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a picture encoding method and storage medium that selects a picture element sequence on the edge of a block adjacent to a block to be encoded out of a block picture element used for prediction, improves prediction precision by using an average value of the picture element sequence concerned and can improve encoding efficiency. SOLUTION: An input picture is divided into blocks, each block is converted into a DCT coefficient by a two-dimensional DCT transformation and further linear quantified, the DCT coefficient quantified is entropy encoded and made to be code data and, at the same time, decoded and converted to a decoded picture element value, and a local decode block is generated. Then, since blocks 5 and 16 are already completely reconstructed at the time of processing a block 17, it is possible to use an average value of one picture element sequence on the edge part of the blocks 5 and 16 indicated by hatched lines at the time of calculating predicted value, information on a picture element short in distance is reflected upon the predicted value, the precision of prediction is improved and encoding efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image coding method and a storage medium, and more particularly to an image coding method for improving coding efficiency by improving the accuracy of predictive coding in block-based coding. The present invention relates to a method and a storage medium.

[0002]

2. Description of the Related Art Recently, international standardization of multimedia-related image coding has been rapidly advanced. For example, JPEG (Joint Photographic Exper
ts Group), H.264, which is an encoding standard for video communication media. 263, M which is an encoding standard for moving image storage media
PEG (Moving Picture Experts Group) and the like. In each of these encoding methods, an encoding algorithm that realizes a bit rate (transmission rate) suited to each purpose is adopted.

[0003] For example, JPEG has two major classifications.
Compression methods. The first method is DCT (Disc
Rete Cosine Transform: Discrete Cosine Transform) The second method is DPCM in two-dimensional space
(Differential Pulse Code Modulation)
This is a tial method. Since the DCT method includes quantization, generally, the original image is irreversible encoding in which the original image is not completely reproduced. However, a sufficient decoded image quality can be obtained even with a small number of bits. On the other hand, the Spatial method is a reversible coding which has a small compression ratio but can completely reproduce an original image.

In the DCT method, an input image is subjected to DCT conversion, quantization, and entropy coding in an encoder (encoder), and is converted into coded data. First, the encoder divides the input image into 8 × 8 pixel blocks,
Each block is a two-dimensional D according to the following equation (1).
CT conversion is performed.

[0005]

(Equation 1)

The DCT transform converts 8 × 8 (64) pixel data into 8 × 8 (64) DCT coefficients. The coefficient at the upper left corner in the matrix of DCT coefficients is called a DC component and is an average value of block data. The remaining 63 coefficients are called AC components. 64 DC
The T coefficient is linearly quantized with a different step size for each coefficient position using a quantization table that defines a quantization step size for each coefficient.

[0007] The quantized DCT coefficients are entropy-encoded into code data. There are Huffman coding and arithmetic coding as methods of entropy coding, and the procedures differ for DC components and AC components, respectively. Here, D
A case where entropy encoding using DPCM is performed for encoding the C component will be described.

FIG. 10 shows a state in which a plurality of blocks Aij of 8 × 8 pixels as described above are arranged. For example, from the block A00 located at the upper left, A01, A02,
.. A10, A11,..., If the block A11 is encoded, the blocks A00, A11,.
A01, A02, and A10 are in a coded state. At this time, when performing one-dimensional DPCM, the value of block A10 is used as prediction of block A11, and two-dimensional DPCM is performed.
Is performed, for example, (A
10 + A01 + A00) / 3.

[0009]

However, as described above, using the average value (DC component) for each block, D
In the mean value encoding method that performs PCM, when the block size increases, for example, the distance between the block A00 and the block A11 in FIG. 10 increases, and there is a problem that the prediction is not sufficiently performed.

Accordingly, an object of the present invention is to select, from among the pixels of a block used for prediction, a pixel column at the edge of a block adjacent to a block to be encoded, and use the average value of the pixel column. Accordingly, it is an object of the present invention to provide an image coding method and a storage medium capable of improving prediction accuracy and improving coding efficiency.

[0011]

According to the first aspect of the present invention,
In an image encoding method in which an image is divided into a plurality of blocks each including a plurality of pixels and an encoding process is sequentially performed in units of the blocks, when encoding the block, a neighborhood of a block in which the encoding process is performed is performed. And predictive coding is performed using information of some pixels in the block that has already been subjected to the coding process as a predicted value.

According to the image encoding method of the present invention, an image is divided into a plurality of blocks each composed of a plurality of pixels, and the encoding process is sequentially performed in units of the blocks. When coding the block, predictive coding is performed using information of some pixels in the block which has been located near the block to be subjected to the coding process and has already been subjected to the coding process as a predicted value.

According to a fifth aspect of the present invention, there is provided a storage medium storing a computer-executable program, wherein the computer-executable program code for dividing an image into a plurality of blocks constituted by a plurality of pixels, When encoding the block, a computer that performs prediction encoding is located near a block to perform the encoding process, and uses information of some pixels in the already encoded block as a prediction value. Executable program code,
Is stored.

According to a second aspect of the present invention, in the image encoding method according to the first aspect, some pixels in the block for obtaining the predicted value are included in the code in the block. It may be one or more pixel rows adjacent to the block on which the conversion process is performed.

According to the first, second, and fifth aspects of the present invention, it is attempted to encode, for example, a pixel row at one edge of an adjacent block from pixels of a block used for prediction. By selecting some pixels located in the vicinity of the block and using the information of the pixels as predicted values, information of pixels that are close in distance is adopted as predicted values, thereby improving the prediction accuracy of encoding. Thus, the coding efficiency can be improved.

According to a third aspect of the present invention, there is provided an image encoding method for dividing an image into a plurality of blocks each composed of a plurality of pixels and sequentially performing an encoding process on a block-by-block basis. In the vicinity of the block to be subjected to the encoding process, the degree of change of the pixel value in each direction is compared in the image area constituted by the blocks which have already been subjected to the encoding process. The method is characterized in that a direction is calculated, a block corresponding to the calculated direction is selected from the image area, and prediction coding is performed using information of some pixels in the block as a prediction value.

According to a third aspect of the present invention, there is provided an image encoding method for dividing an image into a plurality of blocks each including a plurality of pixels and sequentially performing an encoding process on a block basis. When encoding the block, the degree of change of the pixel value in each direction is compared in an image area which is located in the vicinity of the block to be subjected to the encoding processing and is configured by the blocks which have already been encoded. Then, a direction in which the degree of change is small is calculated, a block corresponding to the calculated direction is selected from within the image area, and information of some pixels in this block is used as a prediction value, and prediction encoding is performed. Do.

According to a sixth aspect of the present invention, there is provided a storage medium storing a computer-executable program, wherein the computer-executable program code for dividing an image into a plurality of blocks constituted by a plurality of pixels, When encoding the block, the degree of change of the pixel value in each direction is compared in an image area which is located in the vicinity of the block to be subjected to the encoding processing and is configured by the blocks which have already been encoded. A program code executable by a computer for calculating a direction in which the degree of change is small, and a block corresponding to the calculated direction is selected from the image area, and information of some pixels in the block is predicted. Computer-executable program code for performing predictive encoding by using as a value, and storing a program including the program code. It is.

According to a fourth aspect of the present invention, in the image encoding method according to the third aspect, the degree of change is compared in a vertical direction and a horizontal direction to obtain the predicted value. May be one or more pixel columns adjacent to the block on which the encoding process is performed in the block.

According to the third, fourth, and sixth aspects of the present invention, it is attempted to encode, for example, a pixel row at the edge of an adjacent block from pixels of a block used for prediction. By selecting some pixels located in the vicinity of the block and in the direction with the smallest prediction error and using the information of the pixels as prediction values, information of pixels that are closer in distance and have smaller prediction errors can be obtained. This is adopted as the prediction value, so that the prediction accuracy of the coding can be improved and the coding efficiency can be improved.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image encoding method according to the present invention will be described below in detail with reference to FIGS.

(First Embodiment) Hereinafter, an image encoding apparatus 1 to which an image encoding method according to the present invention is applied will be described in detail with reference to FIGS.

First, the configuration will be described. FIG. 1 is a block diagram illustrating a configuration of an image encoding device 1 according to the present embodiment. In FIG. 1, an image encoding device 1 includes a control unit 2,
It comprises an input device 3, a RAM 4, a display device 5, a storage device 6, and a storage medium 7, and each unit is connected by a bus 8.

The control unit 2 stores an application program specified from various application programs corresponding to the image encoding device 1 stored in the storage device 6 and various instructions or data input from the input device 3 into the RAM 4. In accordance with the input instruction and the input data, various processes are executed in accordance with the application program stored in the RAM 4, and the processing results are stored in the work memory 4 a in the RAM 4 and the display device 5. To be displayed. Then, the processing result stored in the work memory 4a is stored in a storage destination in the storage device 6 which is instructed to be input from the input device 3.

The control unit 2 executes a process of encoding image data input from the storage device 6 or from an external device (not shown) via a communication line. FIG. 2 is a block diagram illustrating functions of the encoding process performed by the control unit 2.

In FIG. 2, the control unit 2 divides an input image into blocks of, for example, 8 × 8 pixels, and performs a two-dimensional DCT transform on each block according to the equation (1) to obtain an 8 × 8 pixel.
8 × 64 (64) DCTs of 8 (64) pixel data
Convert to coefficients. Then, the control unit 2 has 64 DCTs.
The coefficients are linearly quantized with a different step size for each coefficient position using a quantization table that defines a quantization step size for each coefficient. Here, the input image is 8 × 8
The case of dividing into blocks of pixels has been described as an example, but the size of the blocks is arbitrary.

Next, the control unit 2 entropy-encodes the quantized DCT coefficient to generate code data, decodes the quantized DCT coefficient by a local decoder, converts the quantized DCT coefficient into a decoded pixel value, Generate a decode block. Then, the control unit 2 calculates an average value (DC component of a DCT coefficient) of a pixel row at an edge of the block, which is necessary for calculating a predicted value of image data input later in time from the local decode block. Is obtained and stored in the predicted value memory 4b in the RAM 4.

When encoding image data input later in time, the average value of the pixel row at the edge of the adjacent block is selected from the average values stored in the predicted value memory 4b. If there are a plurality of the average values (e.g., the left side and the upper side), a calculation such as weighting is further performed to obtain a predicted value. The difference between the image data and the DCT coefficient is obtained, the difference data is quantized, and the same processing is repeated thereafter.

The input device 3 includes a keyboard provided with a cursor key, numeric input keys, various function keys, and the like, and a mouse as a pointing device, and outputs a key press signal of the keyboard to the control unit 2. At the same time, an operation signal from the mouse is output to the control unit 2.

A RAM (Random Access Memory) 4 is a work memory 4a for storing a designated application program, input instructions, input data, processing results, and the like, and a temporal memory for predicting a later block in time. It has a predicted value memory 4b for storing the average value of the pixel row at the edge of the previous block.

The display device 5 is a CRT (Cathode Ray Tub).
e) It is constituted by a liquid crystal display device or the like, and displays display data according to a display control signal input from the control unit 2.

The storage device 6 has a storage medium 7 in which programs, data and the like are stored in advance, and this storage medium 7 is constituted by a magnetic or optical recording medium or a semiconductor memory. The storage medium 7 is fixedly provided in the storage device 6 or is detachably mounted. The storage medium 7 includes various application programs, menu display programs, and the like corresponding to the image encoding device 1. The data and the like processed by each processing program are stored.

The program, data, and the like stored in the storage medium 7 may be received and stored from another device connected via a communication line or the like. The storage medium 7 is stored in another connected device.
May be provided so that programs, data, and the like stored in the storage medium 7 are used via a communication line.

Next, the operation will be described. FIG. 3 shows the display device 5.
3 is a diagram showing a state in which divided blocks are sequentially encoded from the upper left to the lower right in the order shown in the figure. Of course, when decoding the encoded data, it is assumed that the image is completely reproduced from the upper left block in the same order.

In such a processing flow, FIG.
When processing the block 17, the blocks 5, 16 have already been completely reconstructed by the local decoder, so that when calculating the predicted values, the edges of the blocks 5, 16 as shown by hatching in FIG. Can be used.

By using the average value of one pixel column at the edge of an adjacent block, information of pixels that are close in distance can be reflected in the predicted value, the prediction accuracy is improved, and the coding efficiency is improved. Can be improved.

Hereinafter, the average value encoding using the average value of one pixel column at the edge of the adjacent block will be described with reference to FIGS. 5 and 6. Here, the principle of the present invention will be described. In order to briefly explain the above, as shown in FIG. 5, a case will be described in which only the average value of one pixel column at the edge of the block immediately before (to the left) is used.

FIG. 6 is a flowchart for explaining mean value encoding by the image encoding apparatus 1 to which the image encoding method of the present invention is applied. In FIG. 6, pre
_Ave represents a predicted value, DCT (DCi) represents a DC component of block i, DCT (ACi) represents an AC component of block i, and Q (X) represents quantized data of X.

First, the controller 2 sets pre_ave = P0
(Initial value of prediction value), after initialization of average coding is performed with i = 1 (step S1), block i (i = 1)
(Step S2).

Next, the control unit 2 determines that Δ = DCT (DC1
) -P0 is calculated to obtain DC component difference data (step S3), and the difference data .DELTA.
The coefficients (a plurality of DCTs (AC1)) are quantized and coded (step S4). The encoded data is stored in the storage medium 7 of the storage device 6 and is decoded by the local decoder function of the control unit 2 to form a local decode block.

That is, the control unit 2 transmits the quantized data Q (DCT (AC1)) and Q (DCT (D
C1)) (= Q (Δ) + Q (pre_ave)) is inversely quantized, and an IDCT operation, which is an inverse transform of DCT, is performed to generate a local decode block (step S).
5).

Conventionally, the average value (DC component) of all pixel values constituting the local decode block is defined as pre_a
However, in the present embodiment, the average value (DC component) of the pixel row on the edge adjacent to the next block, such as the shaded portion in block 16 in FIG.
The value of i is incremented (step S6), and if the incremented value of i is larger than the number of pixels in the block, the processing in the block is determined to be completed, and the encoding processing in the block is terminated. Finished,
Otherwise, the encoding of the next block (step S2
To step S6).

Based on the procedure of the flowchart in FIG. 6, the necessary calculations are performed as needed to
It is also possible to refer to one block. Also, in the present embodiment, DCT is used as a coding method in block units.
, The average value separation type VQ (Ve
Other coding methods such as ctor Quantization (vector quantization) may be used. At this time, 8 × 8, 4 × 4, 2 × 2, etc. may be mixed as the block size. However, if the processing order is appropriately determined, the image can be processed by the image encoding method of the present invention. For example, even when various block sizes are mixed as shown in FIG. 7, the processing can be performed if the processing is performed in the order of the numbers shown in FIG.

As described above, according to the image encoding apparatus of the first embodiment to which the image encoding method of the present invention is applied, the control unit 2 converts the input image into a block of 8 × 8 pixels, for example. The block is divided, and each block is subjected to a two-dimensional DCT transform in accordance with the equation (1) to convert 8 × 8 (64) pixel data into 8 × 8 (64) DCT coefficients.
Then, the control unit 2 linearly quantizes the 64 DCT coefficients with a different step size for each coefficient position, using a quantization table that defines a quantization step size for each coefficient.

Next, the control unit 2 entropy-encodes the quantized DCT coefficient to generate code data, decodes the quantized DCT coefficient by a local decoder, converts the quantized DCT coefficient into a decoded pixel value, Generate a decode block. Then, the control unit 2 calculates an average value (DC component of a DCT coefficient) of a pixel row at an edge of the block, which is necessary for calculating a predicted value of image data input later in time from the local decode block. Is obtained and stored in the predicted value memory 4b in the RAM 4.

When encoding image data input later in time, the average value of the pixel row at the edge of the adjacent block is selected from the average values stored in the predicted value memory 4b. If there are a plurality of the average values (e.g., the left side and the upper side), a calculation such as weighting is further performed to obtain a predicted value. The difference between the image data and the DCT coefficient is obtained, the difference data is quantized, and the same processing is repeated thereafter.

Therefore, by selecting a pixel row at the edge of a block adjacent to the block to be coded from among the pixels of the block used for prediction and utilizing the average value of the pixel row, distance Since the average value of close pixels is adopted as the prediction value, it is possible to realize an image coding method capable of improving the prediction accuracy of the average value coding and improving the coding efficiency.

(Second Embodiment) In the above-described first embodiment, a case has been described in which the prediction value is obtained by using the average value of the pixel row at the edge of the adjacent block. It is also possible to select a block that is most suitable as a prediction value from among them and use the average value of the pixel rows at the edge of the selected block.

Therefore, in the second embodiment, the average value of the pixel row at the edge of the block on the left of the block to be coded is used as the predicted value, or the pixel row at the edge of the block on the upper right is used. The case where the predicted value is calculated by determining whether to perform the calculation by a predetermined calculation will be described.

Hereinafter, an image encoding apparatus according to a second embodiment to which the image encoding method according to the present invention is applied will be described in detail. The image encoding device according to the second embodiment basically has substantially the same configuration as the image encoding device 1 according to the first embodiment. The description will be omitted, and only the portions different from the first embodiment will be described below with reference to FIGS. 1, 8, and 9.

When encoding the image data input later in time, the control unit 2 calculates the average value of the pixel row at the edge of the adjacent block from among the average values stored in the predicted value memory 4b. When a plurality of average values are selected (e.g., left and upper neighbors) by selecting a value, the average value of blocks for which local decode blocks have already been generated is further used, for example, in the horizontal and vertical directions. By comparing the errors in the directions and selecting the average value of the pixel row at the edge of the block in the direction in which the error is smaller, a predicted value is obtained. , The difference data is quantized, and the same processing is repeated thereafter.

Next, the operation will be described. Also in the second embodiment, FIG. 3 shows an image of the entire display screen of the display device 5, in which the divided blocks are sequentially encoded from the upper left to the lower right in the order shown in the figure. FIG. Of course, when decoding the encoded data, it is assumed that the image is completely reproduced from the upper left block in the same order.

In such a processing flow, FIG.
Since blocks 4, 5, and 16 have already been completely reconstructed by the local decoder when processing block 17 of FIG. The error between the pixel row A at the edge and the pixel row B at the upper edge of the block 16 is compared with the error between the pixel row C at the right edge of the block 4 and the pixel row D at the left edge of the block 5 to determine the error. The average value of the pixel row at the edge of the block adjacent in the direction (vertical / horizontal) in which is small can be used.

For example, | CD | ≒ 0 and | AB |>
If> 0, the image is predicted to change greatly in the vertical direction, and it is not desirable to use the pixel row F at the lower edge of the block 5 as the predicted value of the average value of the block 17. Therefore, blocks 16 adjacent in the direction in which the error is small
By using the average value of the pixel row E on the right edge of
Information of pixels that are close in distance and have a small prediction error can be reflected in the prediction value, and the prediction accuracy can be further improved, and the coding efficiency can be further improved.

FIG. 9 is a flowchart for explaining mean value encoding by the image encoding apparatus to which the image encoding method of the present invention is applied. Note that FIG. 9 shows the same processing as steps S1 to S5 in the flowchart of FIG. 6 described for the first embodiment,
The processing performed in place of step S6 is shown. Also,
In FIG. 9, pre_ave represents a predicted value, and Th1
Represents a predetermined threshold at which the error is considered equal to 0;
h2 represents a predetermined threshold value for determining that the error is too large to be used as a predicted value.

The control unit 2 performs the processing in step S shown in FIG.
After executing the processing of steps 1 to S5, the pixel row A shown in FIG.
Of the average value of the pixel row B and the average value of the pixel row B, and the error | CD− of the average value of the pixel row C and the average value of the pixel row D are calculated. , | CD | <Th
1 and | AB |> Th2 is determined (step S11). If the condition to be determined in step S11 is satisfied, that is, if the image does not change largely in the horizontal direction but changes greatly in the vertical direction, pre_ave = E (average of the pixel row E) (Step S12), then the value of i is incremented (Step S18), and the routine goes to Step S7 shown in the flowchart of FIG.

If the condition to be determined is not satisfied in step S11, the control section 2 determines whether or not | AB | <Th1 and | CD |> Th2 (step S13). If the condition to be determined in step S13 is satisfied, that is, if the image does not change greatly in the vertical direction but changes largely in the horizontal direction, pre_ave = F (average of the pixel row F) Value) (step S14), then the value of i is incremented (step S18), and the process proceeds to step S7 shown in the flowchart of FIG.

Further, when the condition to be determined is not satisfied in step S13, the control unit 2 sets | AB | <Th
1 and | CD | <Th1 is determined (step S15). If the condition to be determined in step S15 is satisfied, that is, if the image has not changed greatly in either the vertical direction or the horizontal direction, p
Assuming that re_ave = (E + F) / 2 (the average value of the pixel rows E and F) (step S16), the value of i is incremented (step S18), and the process proceeds to step S7 shown in the flowchart of FIG.

Further, when the condition to be determined is not satisfied in step S15, the control unit 2 calculates pre_ave in accordance with a condition freely set in advance (step S17), and then increments the value of i (step S17). Step S18), Step S shown in the flowchart of FIG.
Move to 7. Conditions set in step S17 include, for example, a method of using an average value of all adjacent blocks as in the related art, a method of calculating a predicted value by performing weighting according to the magnitude of error between adjacent pixel columns, and the like. Various methods are conceivable.

Also, in the present embodiment, as in the first embodiment, a DC
Although the case of T is shown, for example, the average value separation type VQ
Other encoding methods such as (Vector Quantization) may be used. At this time, 8 × 8, 4 × 4, 2 × 2, etc. may be mixed as the block size. However, if the processing order is appropriately determined, the image can be processed by the image encoding method of the present invention.

As described above, according to the image encoding apparatus of the second embodiment to which the image encoding method of the present invention is applied, the control unit 2 encodes image data input later in time. When performing the conversion, the average value of the pixel row at the edge of the adjacent block is selected from the average values stored in the prediction value memory 4b, and when there are a plurality of the average values (the left and Next, for example, an average value of blocks in which local decode blocks have already been generated is used to compare, for example, errors in the horizontal direction and the vertical direction. Is used as a prediction value, for example, by selecting an average value, a difference between the prediction value and the DCT coefficient of the image data input later in time is obtained, the difference data is quantized, and the same processing is repeated thereafter. .

Therefore, a pixel row at an edge of a block adjacent to a block to be coded is selected from the pixels of the block used for prediction, and a pixel having the smallest prediction error is selected from a plurality of pixel rows. By selecting a column and using the average value of the pixel column, the average value of a pixel column that is close in distance and has a small prediction error is adopted as the prediction value, thereby improving prediction accuracy and improving encoding. An image coding method that can improve efficiency can be realized.

In the first and second embodiments,
Although the average value of one pixel column at the edge of the block adjacent to the block to be encoded is adopted as the prediction value, the method of selecting a pixel to be adopted as the prediction value is arbitrary. For example,
A plurality of pixel columns at the edge of a block adjacent to the block to be encoded may be used, or an area such as a rectangular range may be used instead of a column unit.

[0064]

According to the first, second, and fifth aspects of the present invention, a partial pixel located near a block to be encoded is selected from the pixels of a block used for prediction. By using the information of the pixel as the prediction value, the information of the pixel that is close in distance is adopted as the prediction value, so that the prediction accuracy of the coding can be improved and the coding efficiency can be improved.

According to the third, fourth, and sixth aspects of the present invention, one of the pixels of the block used for prediction, which is located near the block to be coded and has the smallest prediction error, By selecting the pixel of the part and using the information of the pixel as the prediction value, the information of the pixel that is close in distance and has a smaller prediction error is adopted as the prediction value, and the prediction accuracy of the encoding is improved. Thus, the coding efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an image encoding device 1 according to an embodiment of the present invention.

FIG. 2 is a block diagram showing functions of an encoding process executed by a control unit 2 shown in FIG. 1;

3 shows an image of the entire display screen of the display device 5 shown in FIG. 1, in which divided blocks are moved from upper left to lower right.
FIG. 4 is a diagram illustrating a state in which encoding is sequentially performed in the order shown in FIG.

4 is an enlarged view of a block around a block 17 in FIG. 3, and illustrates a method of encoding the block 17 using an average value of one pixel column at an edge portion of blocks 5 and 16 (first method);
FIG.

FIG. 5 is a diagram similar to FIG. 4, but illustrating a case in which only the average value of one pixel column at the edge of the immediately preceding (left adjacent) block is used.

FIG. 6 is a flowchart illustrating average value encoding performed by the image encoding apparatus 1 to which the image encoding method according to the first embodiment of the present invention is applied, with reference to FIG.

FIG. 7 shows a block size of 8 × 8, 4 × 4, 2 × 2.
FIG. 11 is a diagram showing an appropriate processing order when the image encoding method of the present invention is applied in a case where the same is mixed.

FIG. 8 is a diagram similar to FIG. 4, comparing an error between a pixel column A and a pixel column B and an error between a pixel column C and a pixel column D, and adjoining in a direction in which the error is small (vertical and horizontal). FIG. 10 is a diagram for explaining a method (second embodiment) of encoding a block 17 using an average value of a pixel row at an edge of the block.

FIG. 9 is a flowchart illustrating average value encoding performed by an image encoding apparatus to which an image encoding method according to a second embodiment of the present invention is applied, with reference to FIG.

FIG. 10 is a diagram for explaining a conventional image encoding method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image encoding device 2 control unit 3 input device 4 RAM 4 a work memory 4 b predicted value memory 5 display device 6 storage device 7 storage medium 8 bus

Claims (6)

[Claims] 1. An image encoding method for dividing an image into a plurality of blocks each composed of a plurality of pixels and sequentially performing an encoding process on a block-by-block basis. Image coding method characterized by performing predictive coding by using, as a predicted value, information of some pixels in a block which has been located near a block where coding is performed and has already been coded. 2. A method according to claim 1, wherein a part of pixels in the block for obtaining the predicted value is one or more rows of pixels adjacent to the block to be subjected to the encoding process in the block. Item 7. The image encoding method according to Item 1. 3. An image coding method for dividing an image into a plurality of blocks constituted by a plurality of pixels and sequentially performing an encoding process on a block-by-block basis. Is located in the vicinity of the block to be performed, and the degree of change in the pixel value in each direction is compared in the image region formed by each block that has already been subjected to the encoding process, and the direction in which the degree of change is small is calculated. An image coding method, wherein a block corresponding to the calculated direction is selected from within an image area, and prediction coding is performed using information of some pixels in the block as a prediction value. 4. The comparison of the degree of change is performed in a vertical direction and a horizontal direction, and some pixels in the block for obtaining the predicted value are adjacent to the block to be subjected to the encoding process in the block. 4. The image encoding method according to claim 3, wherein the number of pixels is one or more. 5. A storage medium storing a computer-executable program, comprising: a computer-executable program code for dividing an image into a plurality of blocks each including a plurality of pixels; and encoding the blocks. At this time, a computer-executable program code that is located in the vicinity of the block to be subjected to the encoding process, uses information of some pixels in the already-encoded block as a prediction value, and performs prediction encoding, and A storage medium storing a program including: 6. A storage medium storing a computer-executable program, comprising: a computer-executable program code for dividing an image into a plurality of blocks each including a plurality of pixels; and encoding the blocks. At this time, the degree of change of the pixel value in each direction is compared in the image area which is located near the block to be subjected to the encoding process and is configured by the blocks which have been already encoded, and A computer code that can be executed by a computer that calculates a small direction, a block corresponding to the calculated direction is selected from the image area, and information of some pixels in the block is used as a prediction value, and a prediction code A storage medium storing a program including: a program code executable by a computer performing the conversion; and