JPS6195478A - Coordinate conversion processing device of picture - Google Patents

Abstract

PURPOSE:To rotate a picture by 45 deg. simply and by an angle of an integral times thereof by reading successively a picture element data in a right angle direction with respect to a moving direction of a scanning reference point every main scanning period when reading a picture data from a picture data memory. CONSTITUTION:In the figure, a picture data memory M(x,y) is shown in a thick line. Herein, as shown by dotted lines, N(x,y) having an address space of a 45 deg. inclined rectangular shape circumscribing to the picture data memory M(x,y) is set. In order to rotate by 45 deg., in the address space of N(x,y), a reference point of a reading scanning is selected to (-1,3). Then, every main scanning period, by making increment (+1) an x address and decrement (-1) a y address, a subscanning in a right inclined downward direction is carried out and the scanning reference point is moved. By carrying out such reading and scanning, an output image rotated clockwise by 45 deg. is obtained. Namely, the address space N(x,y) of the picture data memory is set, and in order to incline a reading scanning by 45 deg., a rotation of 45 deg. can be done easily.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image coordinate transformation processing method for rotating a digital image.

2. Description of the Related Art Structures of Conventional Examples and Their Problems In recent years, digital image processing has reached the stage of practical use due to the increase in density and speed of semiconductor integrated circuit devices such as memories. Incidentally, in digital image processing, image coordinate transformation is one of the very basic processes and is frequently used.

In general, coordinate transformation such as rotation and inversion of a digital image involves processing an input image with a two-dimensional spread stored in memory at F(x, y) and converting it to coordinates (x, y). It can be put into practice by applying it.

However, in such a general-purpose coordinate transformation method, it is necessary to perform arithmetic processing including multiple multiplications and additions as shown in equation (1) for each pixel, and then write it to memory again. be. Further, if the output coordinates (x', y') are not integers, it becomes necessary to create output pixel data by interpolation processing. For that reason, as mentioned above,
In the coordinate transformation method, the processing speed is slow and the scale of the processing device tends to increase.

Therefore, conventionally, coordinate transformation has been easily realized by controlling the read address of the image data memory.

FIG. 1 shows an explanatory diagram of a conventional coordinate transformation processing method.

Figure 1 (→ indicates an image data memory M(x, y) having isometric two-dimensional addresses;
To write and read data, follow the arrows shown in the figure.
The scanning is performed pixel by pixel according to the main scanning in the x direction and the sub scanning in the y direction. If the scanning of the read address matches the scanning of the address during writing, the input image is reproduced as is.

In order to rotate one input image by 90 degrees and reproduce it, please refer to Figure 1 (
As shown by the arrow in the middle, the read address of the image data memory is scanned in the main scan direction in the y direction and in the -x direction.

This is possible by reading out according to the sub-scanning.

In this way, in the conventional coordinate conversion processing method, when reading the image data memory, the main scanning of the read address,
Image rotation or inversion processing was performed by switching the sub-scanning direction or scanning in the positive and negative directions.

However, in the above example, one image can only be rotated by 90 degrees or an angle that is an integral multiple of 9o0.

OBJECTS OF THE INVENTION In view of these conventional problems, it is an object of the present invention to provide an image coordinate transformation processing method that can realize image rotation processing finer than 90° without increasing the number of processing devices.

Structure of the Invention The present invention provides a scanning reference point for each sub-scanning period in an expanded address space when reading out image data from an image data memory stored in accordance with the scanning of a single image. At the same time, the scanning base is moved every main scanning period.

This method provides a method for

DESCRIPTION OF THE EMBODIMENTS FIG. 2 is an explanatory diagram of an image coordinate transformation processing apparatus in an embodiment of the present invention.

To simplify the explanation, the number of pixels in a two-dimensional image is assumed to be 6 x 5. In other words, it is assumed that the input image is stored in an address in the image data memory M (x, y) according to scanning. .

By controlling the read address in such an image data memory, 450 rotations are performed.

In FIG. 2(a), image data memory M(x,y)
is shown within the thick line. Here, as shown by the dotted line in FIG. 2(a), N(x, y) has a rectangular address space inclined at 45 degrees circumscribing the image data memory M(x, y).
Set. N(x, y) has an address area as shown in the figure, and when the x, y address exceeds the rumored expression, the pixel data is assumed to give a constant value such as the black level or white level. , (N(x
+ y )=M(xv y ).

As shown above, in order to perform a 46° rotation, in the address space of N (x, y) as described above, the reference point of the read scan is selected at (-1, 3), and every main scan period , the air address is incremented (+1) and the ty address is decremented (-1), whereby main scanning is performed diagonally upward to the right. In addition, the X and 7 addresses of the scanning reference point are each incremented (+1
), sub-scanning is performed diagonally downward to the right, and the scanning reference point moves. By performing such a readout scan, an output image rotated clockwise by 45 degrees as shown in FIG.

In order to set a new address space N(x, y) and tilt the read scan by 46 degrees, the air address and y address are controlled simultaneously for each main scan and sub scan. At this time, the scanning line spacing is increased by 6 times, and since every other pixel is scanned, the output image is reduced, but the output image is 4 times larger without causing image distortion.
It is rotated by 5 degrees and played back, and does not require any processing such as interpolation.
Can easily rotate 45°.

Above, in order to simplify the explanation, the image size is set to 5.
×5, but it is clear that the present invention can be applied to images of a size that is large enough.

In addition, in controlling the X address and y address, by combining increment and decrement processing, 4
Needless to say, it is possible to rotate and invert the image by an angle that is an integral multiple of 5 degrees, and it is also possible to move the image by changing the initial value of the scanning reference point.

The operation of one embodiment of the present invention has been described above, but in order to realize the present invention, it can be realized by software processing by a CPU and dedicated hardware processing, and the software scale or hardware scale may be increased. This can be achieved without any problems.

Effects of the Invention As described above, the present invention provides an image coordinate transformation processing method that can easily realize image rotation, inversion, and movement of 45 degrees and integral multiples thereof by controlling the read address of the image memory. This is what we provide.

[Brief explanation of the drawing]

Fig. 1 (→, crest is an explanatory diagram of a conventional image coordinate transformation processing method, and Fig. 2 (, ), (yen is an explanatory diagram of an image coordinate transformation processing method of an embodiment of the present invention. Person's name Patent attorney Toshio Nakao Haga1 person No.1
Drawing 2nd drawing

Claims (1)

[Claims] When reading image data from the image data memory stored in accordance with image scanning, the scanning reference point is moved diagonally to an adjacent pixel in a certain direction in each sub-scanning period in the expanded address space, and the scanning reference point is moved diagonally to an adjacent pixel in a certain direction in each sub-scanning period in the expanded address space. Coordinate transformation of an image, comprising means for rotating the image by an angle of 45° and an integral multiple of 45° by sequentially reading out pixel data in a direction orthogonal to the moving direction of the scanning reference point. Processing equipment.