Method and apparatus for resizing images using discrete cosine transform
First Claim
Patent Images
1. A method of resizing an image using a resizing ratio, comprising:
- receiving a DCT (Discrete Cosine Transform) coefficient matrix Y×
X of an input image;
calculating a transformation matrix for transforming the DCT coefficient matrix Y×
X of the input image using an integer aspect ratio closest to the target resizing ratio;
performing a coarse resizing on the DCT coefficient matrix Y×
X of the input image in a DCT domain using the transformation matrix;
obtaining a spatial image by performing an IDCT (Inverse Discrete Cosine transform) on the coarse-resized image; and
forming an output image having a coefficient matrix y×
x by performing a fine resizing on the spatial image in a spatial domain, whereinthe calculating of the transformation matrix includes;
calculating N′
that satisfies Y;
y=N;
N′ and
calculating M′
that satisfies X;
x=M;
M′
, where N and M are the number of vertical direction coefficients and the number of horizontal direction coefficients in a coefficient matrix of an DCT filter;
selecting integers N″ and
M″
closest to the calculated decimal fractions N′ and
M′
; and
calculating an N″
×
N″
transformation matrix and an M″
×
M″
transformation matrix using N″ and
M″
,Y denotes the number of pixels in a vertical direction of the input image, X demotes the number of pixels in a horizontal direction of the input image, y denotes the number of pixels in a vertical direction of the output image, an x denotes the number of pixel in a horizontal direction of the output image, andthe performing of the coarse resizing includes calculating an N″
×
M″
transformation matrix of the input image using the N″
×
N″
transformation matrix and the M″
×
M″
transformation matrix.
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Abstract
A method for resizing an image using a resizing ratio may include receiving DCT (Discrete Cosine Transform) coefficients of an input image; calculating a transformation matrix for transforming the input image to an integer aspect ratio closest to the resizing ratio; performing a coarse resizing on the input image in a DCT domain using the transformation matrix; obtaining a spatial image by performing an IDCT (Inverse Discrete Cosine Transform) on the coarse-resized domain; and forming an output image by performing a fine resizing on the spatial image in a spatial domain.
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Citations
20 Claims
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1. A method of resizing an image using a resizing ratio, comprising:
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receiving a DCT (Discrete Cosine Transform) coefficient matrix Y×
X of an input image;calculating a transformation matrix for transforming the DCT coefficient matrix Y×
X of the input image using an integer aspect ratio closest to the target resizing ratio;performing a coarse resizing on the DCT coefficient matrix Y×
X of the input image in a DCT domain using the transformation matrix;obtaining a spatial image by performing an IDCT (Inverse Discrete Cosine transform) on the coarse-resized image; and forming an output image having a coefficient matrix y×
x by performing a fine resizing on the spatial image in a spatial domain, whereinthe calculating of the transformation matrix includes; calculating N′
that satisfies Y;
y=N;
N′ and
calculating M′
that satisfies X;
x=M;
M′
, where N and M are the number of vertical direction coefficients and the number of horizontal direction coefficients in a coefficient matrix of an DCT filter;selecting integers N″ and
M″
closest to the calculated decimal fractions N′ and
M′
; andcalculating an N″
×
N″
transformation matrix and an M″
×
M″
transformation matrix using N″ and
M″
,Y denotes the number of pixels in a vertical direction of the input image, X demotes the number of pixels in a horizontal direction of the input image, y denotes the number of pixels in a vertical direction of the output image, an x denotes the number of pixel in a horizontal direction of the output image, and the performing of the coarse resizing includes calculating an N″
×
M″
transformation matrix of the input image using the N″
×
N″
transformation matrix and the M″
×
M″
transformation matrix. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus for resizing an input image using a resizing ratio, comprising:
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a receiver for receiving a DCT (discrete cosine transform) coefficients matrix Y×
X of an input image;a transformation matrix calculation unit for calculating a transformation matrix for transforming the DCT coefficient matrix Y×
X of the input image using an integer aspect ratio closest to the resizing ratio;a coarse resizing unit for performing a coarse resizing on the DCT coefficient matrix Y×
X of the input image in a DCT domain using the transformation matrix;an IDCT (inverse discrete cosine transform) unit for obtaining a spatial image by performing an IDCT on the coarse-resized image; and a fine resizing unit for forming an output image having a coefficient matrix y×
x by performing a fine resizing on the spatial image in a spatial domain, whereinthe transformation matrix calculation unit calculates N′
that satisfies Y;
y=N;
N′ and
calculates M′
that satisfies X;
x=M;
M′
, wherein N and M are the number of vertical direction coefficients and the number of horizontal direction coefficients in a coefficient matrix of an DCT filter, selects integers N″ and
M″
closest to the calculated decimal fractions N′ and
M′
, and calculates an N″
×
N″
transformation matrix an M″
×
M″
transformation matrix using N″ and
M″
,Y denotes the number of pixels in a vertical direction of the input image, X denotes the number of pixels in a horizontal direction of the input image, y denotes the number of pixels in a vertical direction of the output image, and x denotes the number of pixels in a horizontal direction of the output image, and the coarse resizing unit calculates an N″
×
M″
transformation matrix of the input image using the N″
×
N″
transformation matrix and the M″
×
M″
transformation matrix. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method of resizing an image using a resizing ratio, comprising:
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receiving a DCT (Discrete Cosine Transform) coefficient matrix Y×
X of an input image;calculating a transformation matrix for transforming the DCT coefficient matrix Y×
X of the input image using an integer aspect ratio closest to the target resizing ratio;performing a coarse resizing on the DCT coefficient matrix Y×
X of the input image in a DCT domain using the transformation matrix;obtaining a spatial image by performing an IDCT (Inverse Discrete Cosine transform) on the coarse-resized image; and forming an output image having a coefficient matrix y×
x by performing a fine resizing on the spatial image in a spatial domain, whereinthe calculating of the transformation matrix includes; calculating N′
that satisfies Y;
y=N;
N′ and
calculating M′
that satisfies X;
x=M;
M′
, where N and M are the number of vertical direction coefficients and the number of horizontal direction coefficients in a coefficient matrix of an DCT filter;selecting integers N″ and
M″
closest to the calculated decimal fractions N′ and
M′
; andcalculating an N″
×
N″
transformation matrix and an M″
×
M″
transformation matrix using N″ and
M″
,Y denotes the number of pixels in a vertical direction of the input image, X demotes the number of pixels in a horizontal direction of the input image, y denotes the number of pixels in a vertical direction of the output image, an x denotes the number of pixel in a horizontal direction of the output image. - View Dependent Claims (18, 19, 20)
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Specification