Image analysis – Image transformation or preprocessing – Changing the image coordinates
Reexamination Certificate
2002-03-19
2003-07-01
Mariam, Daniel G. (Department: 2621)
Image analysis
Image transformation or preprocessing
Changing the image coordinates
C382S237000, C382S299000, C382S300000, C345S660000, C345S670000, C345S671000, C348S561000, C348S581000, C358S445000, C358S451000, C358S525000, C708S208000
Reexamination Certificate
active
06587602
ABSTRACT:
TECHNICAL BACKGROUND
This invention is related to a resolution conversion system for converting digital graphical information of still pictures and moving pictures including characters, line drawings, natural pictures and the like into another graphical information having a different number of pixels so as to display converted pictures on a display device. More specifically, the invention is related to a resolution conversion system and the method thereof which allows input image information of a particular number of pixels to be displayed on the display device or a screen in a window environment having a different resolution when displaying the multimedia moving pictures.
DESCRIPTION OF BACKGROUND ART
In the conversion of digital images, when the number of pixels of an original image is reduced, another image of a reduced scale from the original image can be obtained on the same display device. Accordingly, it is useful when displaying a reduced image in a window or the like to reduce the number of the pixels of the original image. In addition, it is possible to display images on a screen of a display device capable of lower resolution than that of the original image.
In order to reduce the number of pixels of the original image, the simplest way is to thin some pixels out. Alternatively, there is another way to reduce the number of the pixels of the original image by simply calculating the mean of luminance values of 3×3=9 pixels (e.g. if each pixel has 8 bits of luminance information, the luminance value falls within a 256 level gray scale) and by assigning it to a luminance of one pixel.
Furthermore, in Japanese Patent Application Laid-Open No. Hei 6-124189, there is disclosed a method for reducing the number of the pixels of the original image by taking averages of the image data of the original image in a horizontal direction and a vertical direction. In this method, lines are drawn using a line drawing algorithm known as a conventional art, and the horizontal line of the original image is shown as a set of a plural dots (y dots) of a horizontal component. The length of each horizontal line may be considered to be indicative of the number of input pixel data sets corresponding to one pixel data set after scaling-down to be stored in VRAM. Although the lengths of the horizontal lines may be different from each other or they may be identical to each other, the horizontal scaling-down is accomplished by taking the average of the pixel data for n dots. The vertical scaling-down can also be similarly accomplished.
On the contrary, if the number of pixels of the original image is increased, an enlarged image of the original image can be obtained on the same display device. Accordingly, it is useful for displaying an enlarged image in a window or the like to increase the number of the pixels of the original image. In addition, it is possible to display images on a screen of a display device capable of higher resolution than that of the original image.
In order to increase the number of the pixels of the original image, the simplest way is to surround a pixel in the original image, in horizontal and vertical directions, with pixels of the same gray scale level.
Alternatively, instead of simply placing the pixels having the same gray scale level, there is another way of increasing the number of pixels of the original image by calculating interpolation pixels whose gray scale level is positioned on a line extending between adjacent pixels of the original image between which the pixels are interpolated so as to use the calculated interpolation pixels.
Furthermore, a method for arbitrarily converting the resolution of the original image is shown in FIG.
1
. In
FIG. 1
,
2001
designates original image data,
2002
designates a process for multiplying the original data by L
1
in a vertical direction and by M
1
in a horizontal direction, and
2003
designates the image data subjected to the L
1
×M
1
multiplication processing. Reference numeral
2004
designates a process for multiplying the enlarged image data by 1/L
2
in the vertical direction and by 1/M
2
in the horizontal direction, and
2005
designates the image data subjected to the (1/L
2
)×(1/M
2
) multiplication processing, wherein L
1
, L
2
, M
1
and M
2
are positive integers. In the multiplication processes of L
1
×M
1
and (1/L
2
)×(1/M
2
), if L
1
>L
2
and M
1
>M
2
, then the image is enlarged, whereas if L
1
<L
2
and M
1
<M
2
, then the image is reduced. In this way, the size of the image are arbitrarily modified in accordance with the combination of the enlarging and reducing processes.
If the same pixels as one pixel of the original image are placed in the horizontal and vertical directions so as to increase the number of pixels in accordance with the above mentioned method, the obtained image may include very noticeable aliasing, and therefore the quality of the obtained image may be degraded.
Instead of simply placing the same pixels, if the number of pixels are increased using the interpolation pixels whose gray scale levels are positioned on the line which links gray scale levels of the adjacent pixels of the original image, a very noticeable aliasing mosaic image is prevented from occurring. However, since high frequency components in a portion of the original image where a boundary between light and shade is clearly recognized may be reduced so as to smooth that portion, the obtained image becomes faded or blurred.
Furthermore, according to the method for arbitrarily converting the size of the image using the combination of the enlarging and reducing processes, since the reducing processing is executed after the completion of the enlarging processing, the processing is time consuming. In addition, according to this method, since the image is enlarged prior to the reducing processing, it is necessary to provide a memory for storing data of the enlarged image, which makes the hardware large.
SUMMARY OF THE INVENTION
The first object of the present invention is to prevent an image having noticeable mosaic aliasing so as to realize a high quality image, in resolution conversion increasing the number of pixels of an original image.
In addition, the second object of the present invention is to store a high frequency component of a contour portion of an original image where a boundary between light and shade is clearly recognized, so as to realize a high quality image, in resolution conversion increasing the number of pixels of the original image.
Furthermore, the third object of the present invention is to realize a high speed resolution conversion processing which can be used for a digital moving picture processing, in a resolution conversion increasing the number of pixels of an original image.
In addition, the fourth object of the present invention is to realize arbitrary resolution conversion processing in a minimum size of hardware, in resolution conversion increasing the number of pixels of an original image.
The above and the other objects of the present invention are accomplished by a resolution conversion apparatus for converting an original digital image into a digital image having a different number of pixels in accordance with an instructed conversion magnification factor comprising a determination circuit for determining, for each block including a predetermined number of pixels of the original digital image, the number of interpolation pixels and positions where the interpolation pixels are interpolated in the block of the original digital image, and a converted image generation circuit for generating pixel data for the interpolation pixels to be interpolated in each of the blocks in accordance with the number of interpolation pixels and the positions, so as to obtain a converted digital image based upon pixel data for the pixels in the original digital image and of the generated pixels to be interpolated, wherein the converted image generation circuit is arranged such that when a difference between two pixel values in the original digital image
Kasai Naruhiko
Koizumi Hiroyuki
Sato Hiroko
Wakisawa Shinji
Watanabe Youichi
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