JPH08321944A - Image data interpolation method - Google Patents

Abstract

PURPOSE: To estimate a picture element value of a missing picture element more accurately by extracting normal picture elements used for interpolation from every direction of missing picture elements uniformly so as to use a changing inclination of picture element values in both longitudinal and lateral directions for the interpolation. CONSTITUTION: Coordinates of missing data detected by an error correction decoder 6 are received to check an area of missing data. A picture element in a missing area and a normal reception picture element for interpolation are selected to be a picture element value (g) of the missing picture element and n-sets of normal reception picture elements to surround the picture element (g) are all used. Two normal picture elements are extracted. A point in a 3-dimension space whose coordinate is based on a coordinate of each picture element and its picture element value corresponds to each picture element, and an area of a triangle of three points is obtained as a function of (g). The area is calculated with respect to all values by which the (g) takes and the value (g) minimizing the area is used for a picture element value by the interpolation of the missing picture element (g). The interpolation value of all missing picture elements is calculated by repeating the processing as above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data interpolating method, and particularly when transmitting image data, when partial data is lost due to transmission error, line interruption, etc. The present invention relates to a method for estimating from image data transmitted to a computer by interpolation.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a transmission system of image data. Digitally converted input image data is encoded by an information source encoder 1 to further reduce the influence of transmission code error. The error correction encoder 2 performs error correction encoding. The modulator 3 modulates the encoded data into a signal suitable for the transmission path 4 and transmits the signal.

On the receiving side, the received data input received via the transmission line 4 is demodulated by the demodulator 5 to take out a digital signal. This demodulated signal is error-correction-decoded by the error-correction decoder 6 and then decoded by the information-source decoder 7, thus outputting the output image data.

In such an image data transmission system, among the transmission errors detected by the error correction decoder 6, uncorrectable transmission errors may remain. In this case, the information source decoder 7 discards this uncorrectable error data. Then, the image data interpolator 8 calculates the discarded missing data by interpolation.

FIG. 3 is a flowchart showing the operation of the image data interpolator 8, and FIG. 4 is an explanatory diagram of the interpolation method. In this interpolation, when the pixel coordinates in the horizontal and vertical directions of the screen are represented by (x, y), the normally received pixel values are used to perform interpolation in the x direction or the y direction. That is,
First, since it is known from the information from the error correction decoder 6 which pixel at which coordinate is missing, the missing x or y direction section is obtained (step 301). FIG.
Indicates the case of the x-direction interpolation, and the missing section is between x ₂ and x ₅ . Since the both ends is normally received pixel (pixel g1, g6 of FIG. 4 the x coordinate x _1, x _6), then obtains the equation of a straight line connecting the two points (Step 3
02). Since this expression is a linear expression of x (a linear expression of y in the case of interpolation in the y direction), x or y
By substituting coordinate values (Figure 4, x ₂ ~x _5), and calculates the pixel value of the missing pixel (in FIG. 4 G2～g5) (step 303).

[0006]

5 to 7 show examples of interpolation by the above-described conventional data interpolation method. FIG. 5 shows the original image data, and the screen has 9 × 9 pixels for simplicity. It is assumed that the 9 × 9 pixels in the portion indicated by the double frame A are missing due to a transmission error or interruption. At this time, in the process of FIG. 3, the result of horizontal direction (x direction) interpolation is shown in FIG. 6, and the result of vertical direction (y direction) interpolation is shown in FIG. As can be seen by comparing these interpolation results with the original image data of FIG. 5, there is a problem that the accuracy of interpolation is not good in the conventional method, and the interpolation results differ depending on which interpolation direction is used. There was a problem of being lost.

An object of the present invention is to solve the problem that it is difficult to restore an original image by interpolating image data that has been lost due to a transmission line error, line interruption, etc., and to reproduce an image close to the original image. It is to provide an image data interpolation method that can be performed.

[0008]

According to the present invention, in an image data interpolation method for estimating a pixel value of a missing pixel whose pixel value is missing, among the normal pixels to which the pixel value is given, the above-mentioned missing A plurality of pixels that are close to the pixel are selected, and each pixel is made to correspond to one point on the three-dimensional space having the coordinates on the two-dimensional screen and the pixel value as coordinates, For all two normal pixel sets that can be taken out, the area of a triangle formed by three points in the three-dimensional space corresponding to each normal pixel set and the above-mentioned missing pixel is obtained by using the pixel value of the above-mentioned missing pixel as a variable. , A pixel value of the missing pixel that minimizes the sum of the areas of the triangles corresponding to all the normal pixel sets is obtained as a minimized pixel value, and the minimized pixel value thus obtained is interpolated for the missing pixel. by It discloses an image data interpolation method characterized in that the value.

[0009]

If the normal pixels used for the interpolation are taken uniformly from the respective directions of the missing pixels, the interpolation is performed by using the changing tendency of the pixel values in both vertical and horizontal directions, and more accurate interpolation is performed. Data is obtained.

[0010]

EXAMPLES Examples of the present invention will be described in detail below. FIG. 1 is a flowchart showing an embodiment of the image data interpolation method according to the present invention. The process shown in this flowchart is executed by the image data interpolator 8 of the transmission system as shown in FIG. In the present embodiment, first, the error data detected by the error correction decoder 6 that is uncorrectable, that is, the coordinates of the missing data are taken in, and the area of the missing data is checked (step 101). This area is the portion of the double frame A in the original image data of the conventional example. FIG. 8 shows a more generalized missing area A (inside the double frame), and its periphery is surrounded by normal reception pixels g1 to g28.

When the missing area is changed, one missing pixel for obtaining the pixel value by interpolation is then selected from the missing area, and at the same time, a normal receiving pixel for the interpolation is selected (step 102). If the missing pixel selected here is g in FIG. 8, it is assumed in the present embodiment that all 28 pixels g1 to g28 in FIG. 8 are used as normal receiving pixels for interpolating this. In general, assuming that the number of normally-received pixels including the missing area is n, all of them are used.

Next, two pixels are taken out from the normal reception pixels selected as described above and designated as gi and gj (step 103). The coordinates are (xi, yi) and (xj, y
j), the pixel values are gi and gj, the coordinates of the selected missing pixel are (x, y), and the pixel value is g (this is a variable),
In a three-dimensional space composed of pixel coordinates and pixel values, three points Pi
(Xi, yi, gi), Pj (xj, yj, gj), P
An expression expressing the area Δ _ij of a triangle spanning 0 (x, y, g)

[Equation 1] Is calculated (step 104). However

[Equation 2] Is. Further, here, the pixel and its pixel value are represented by the same signals g, gi, ... For convenience. Therefore, as the points Pi and Pj corresponding to the normal reception pixel, for all the combinations taken out two by two from the n selected in step 102, there are two points of each combination and a point P0 corresponding to the missing pixel g. The area of the stretched triangle is calculated as above, and the total sum Δ is

(Equation 3) Is. This is the _sum of _n C ₂ = n (n−1) / 2 terms, and in the case of n = 28 in FIG. 8, it is the sum of 378 terms. This Δ is a function of the pixel value g of the missing pixel.
Therefore, the value of Δ is calculated for all possible values of g, and the value of g that minimizes it is used as the pixel value by interpolation of the missing pixel g (steps 105 and 106). For example, when the pixel value is 256 levels, Δ of (Equation 3) is calculated for each value of g = 0 to 255, and g giving the minimum value of the 256 values is set as the correction pixel value. Step 1 above
The processing of 02 to 106 is repeated (step 107), and the interpolated values of all the missing pixels are calculated.

FIG. 9 shows an interpolation result obtained by the method of this embodiment for the missing pixel in the double frame A of the original image data of FIG. Comparing this result with the original image data of FIG. 5, it can be seen that interpolation data better than the conventional results of FIGS. 6 and 7 is obtained. This is because, while the conventional method is one-dimensional interpolation, x,
This is because it is a two-dimensional interpolation method that takes into consideration the change tendency of pixel values in both y directions, and that an average interpolation result is obtained using many normal reception points.

Although a three-dimensional space composed of pixel coordinates and pixel values is used in the above embodiment, when the pixel value and the coordinate value are significantly different from each other, in the above embodiment, In some cases, calculation errors may occur and appropriate results may not be obtained. In such a case, a pixel value or coordinate value multiplied by an appropriate coefficient and standardized may be used as a coordinate value of a point in the three-dimensional space.

Further, in the above-mentioned embodiment, the interpolation is performed by using all the normal reception pixels in the periphery of the missing area, but if this is done, the amount of calculation becomes large. Therefore, as a simple method, only the vertical direction of the currently selected missing pixel, only the diagonal direction of 45 °, or only 4 or 8 of the normal receiving pixels closest to the missing pixel in both directions are interpolated. May be used for. In the example of FIG. 8, for example, for the pixel g, pixels g1, g4, g7, g11, g1
There are eight of 5, g19, g23, and g26. Even with this, sufficient accuracy can be obtained, and the amount of calculation can be significantly reduced.

[0016]

According to the present invention, the accuracy of estimation by interpolation of missing image data can be greatly improved, and at the same time, the problem that the result differs depending on the interpolation direction can be eliminated.

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of an image data interpolation method of the present invention.

FIG. 2 is a block diagram of an image data transmission system having an interpolation function.

FIG. 3 is a flowchart showing a conventional image data interpolation method.

FIG. 4 is an explanatory diagram of a conventional image data interpolation method.

FIG. 5 is a diagram showing an example of image data.

6 is a diagram showing an interpolation result of the image data of FIG. 5 by a conventional method (horizontal direction).

7 is a diagram showing an interpolation result of the image data of FIG. 6 by a conventional method (vertical direction).

FIG. 8 is a diagram showing how to select a normal reception pixel in the embodiment of FIG.

9 is a diagram showing an interpolation result of the image data of FIG. 5 by the method of the present invention.

[Explanation of symbols]

 1 Information Source Encoder 2 Error Correction Encoder 3 Modulator 4 Transmission Line 5 Demodulator 6 Error Correction Decoder 7 Information Source Decoder 8 Image Data Interpolator

Claims (4)

[Claims] 1. An image data interpolation method for estimating a pixel value of a missing pixel, the pixel value of which is missing, of normal pixels to which the pixel value is given, which are close to the missing pixel. Two normals that can be extracted from the selected normal pixels by selecting a plurality of pixels and making each pixel correspond to one point in a three-dimensional space having coordinates on the two-dimensional screen and pixel values as coordinates. For all of the normal pixel sets, the area of a triangle formed by three points in the three-dimensional space corresponding to each normal pixel set and the missing pixel is obtained by using the pixel value of the missing pixel as a variable, and A feature is that the pixel value of the missing pixel that minimizes the total area of the corresponding triangles is obtained as a minimized pixel value, and the thus obtained minimized pixel value is used as an estimated value by interpolation of the missing pixel. Image data interpolation method to be. 2. The normal pixel adjacent to the missing pixel is selected by selecting all the normal pixels adjacent to the periphery of the missing pixel area including the missing pixel. The described image data interpolation method. 3. A normal pixel that is close to the missing pixel is selected from one or both of a normal pixel that is closest to the missing pixel in the vertical and horizontal directions and a normal pixel that is closest to the missing pixel in the 45 ° direction. 2. The image data interpolation method according to claim 1, wherein is selected. 4. The coordinates of a point in the three-dimensional space are standardized by multiplying a pixel value or a coordinate of a pixel corresponding to the point by a constant coefficient. An image data interpolating method according to any one of the above.