Resolution conversion upon hierarchical coding and decoding

• US 7,558,441 B2
• Filed: 10/22/2003
• Issued: 07/07/2009
• Est. Priority Date: 10/24/2002
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Owada, Mitsuru
• Primary Examiner(s): Bella; Matthew C
• Assistant Examiner(s): CHU, RANDOLPH I
• Application Number:
  US10/689,781
• Publication Number:
  US 20040086188A1
• Time in Patent Office: 2,085 Days
• Field of Search: 382/240, 382/298, 341/79, 709/203, 375/240.19
• US Class Current: 382/299
• CPC Class Codes: G06T 9/00 Image coding bandwidth or redundancy reduction for static pictures H04N1/41; coding or decoding of static colour picture signals H04N1/64; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/134 characterised by the element, parameter or criterion affecting or controlling the adaptive coding
• CPC Class Codes: H04N 19/187 the unit being a scalable video layer
• CPC Class Codes: H04N 19/44 Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• CPC Class Codes: H04N 19/635 characterised by filter definition or implementation details

Abstract

In a decoding method of decoding encoded image data which has been hierarchically encoded in advance, a size of an image to be outputted is determined, and then the encoded image data is decoded up to a layer of hierarchy which is at least one layer more than a minimum number of layer/layers of hierarchy necessary to acquire an image of the determined size.

Claims

1. A decoding method of decoding encoded image data which has been hierarchically encoded in advance by a discrete wavelet transform method, comprising:

using a processor to perform the following;

determining a size of an image to be output;

judging a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

determining whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy of the encoded image data;

decoding, if the determination proves true, all the layers of hierarchy of the encoded image data, and otherwise decoding the encoded image data up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy; and

reducing the size of the decoded image to the determined size,

wherein, in said judging step, the number n satisfies a condition of

1/2ⁿ>

Sout/Sin>

1/2⁽ⁿ⁺¹⁾

 

where Sout is an output image size, and Sin is the input image size, n is an integer equal to or greater than 1, and is judged as the minimum number of layer/layers of hierarchy, and in said decoding step, image data is decoded up to a hierarchy until an input-output ratio of image size becomes

1/2<sup>(n−

1)</sup>.

4. The decoding method according to claim 1, wherein the determined size includes horizontal pixel number information and vertical pixel number information.

5. The decoding method according to claim 1, wherein an encoding method used conforms to JPEG2000.

2. A decoding method of decoding encoded image data which has been hierarchically encoded in advance by a discrete wavelet transform method, comprising:

using a processor to perform the following;

determining a size of an image to be outputted;

judging a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

determining whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy of the encoded image data;

decoding, if the determination proves true, all the layers of hierarchy of the encoded image data, and otherwise decoding the encoded image data up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy; and

reducing the size of the decoded image to the determined size,

wherein, in said judging step, the number n satisfies a condition of

X=Sin/Sout

n=INT(log₂X)

 

where Sout is an output image size, and Sin is the input image size, and is judged as the minimum number of layer/layers of hierarchy; and

in said decoding step, image data is decoded up to a hierarchy which satisfies a condition of

Number of Layer/Layers to Be Decoded=(Total Number of Layers)−

n+1.

13. The decoding method according to claim 2, wherein the determined size includes horizontal pixel number information and vertical pixel number information.

3. A decoding method of decoding encoded image data which has been hierarchically encoded in advance by a discrete wavelet transform method, comprising:

using a processor to perform the following;

determining a size of an image to be outputted;

judging a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

determining whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy of the encoded image data;

decoding, if the determination proves true, all the layers of hierarchy of the encoded image data, and otherwise decoding the encoded image data up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy; and

reducing the size of the decoded image to the determined size,

wherein said decoding the encoded image data up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy further includes;

decoding a lowest layer of hierarchy of encoded image data among layer/layers which has/have not been decoded, and repeating the decoding of a lowest layer of hierarchy of the encoded image data among the layer/layers which has/have not been decoded until it is determined that the size of the decoded image is equal to or larger than the determined size of the image to be outputted; and

decoding a next lowest layer of hierarchy of the encoded image data.

14. The decoding method according to claim 3, wherein the determined size includes horizontal pixel number information and vertical pixel number information.

6. A decoding apparatus for decoding encoded image data which has been hierarchically encoded in advance, comprising:

a first determination unit that determines a size of an image to be outputted;

a judging unit that judges a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

a second determination unit that determines whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy of the encoded image data;

a decoding unit that, if the determination proves true, encodes all the layers of hierarchy of the enclosed image data, and otherwise decodes the encoded image data up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy; and

a reduction unit that reduces the size of the decoded image to the determined size,

wherein, in said judging step, the number n satisfies a condition of

1/2ⁿ≧

Sout/Sin>

1/2⁽ⁿ⁺¹⁾

 

where Sout is an output image size, and Sin is the input image size, n is an integer equal to or greater than 1, and is judged as the minimum number of layer/layers of hierarchy, and

wherein, in said decoding step, image data is decoded up to a hierarchy until an input-output ratio of image size becomes

1/2<sup>(n−

1)</sup>.

7. An encoding method of hierarchically encoding image data by a discrete wavelet transform method, comprising:

using a processor to perform the following;

determining a size of an image to be outputted;

judging a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

determining whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy to which the image data can be encoded; and

encoding, if the determination proves true, all the layers of hierarchy of the image data, and otherwise encoding the image data up to a layer of hierarchy which is one more layer higher than the minimum number of layer/layers of hierarchy,

wherein, in said judging step, the number n satisfies a condition of

1/2ⁿ>

Sout/Sin>

1/2⁽ⁿ⁺¹⁾

 

where Sout is an output image size, and Sin is the input image size, n is an integer equal to or greater than 1, and is judged as the minimum number of layer/layers of hierarchy, and

wherein, in said encoding step, image data is decoded up to a hierarchy until an input-output ratio of image size becomes

1/2<sup>(n−

1)</sup>.

10. The encoding method according to claim 7, wherein the determined size includes horizontal pixel number information and vertical pixel number information.

11. The encoding method according to claim 7, wherein an encoding method conforms to JPEG2000.

8. An encoding method of hierarchically encoding image data by a discrete wavelet transform method, comprising:

using a processor to perform the following;

determining a size of an image to be outputted;

judging a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

determining whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy to which the image data can be encoded; and

encoding, if the determination proves true, all the layers of hierarchy of the encoded image data, and otherwise encoding the image data up to a layer of hierarchy which is one more layer higher than the minimum number of layer/layers of hierarchy,

wherein, in said judging step, the number n satisfies a condition of

X=Sin/Sout

n=INT(log₂X)

 

where Sout is an output image size, and Sin is the input image size, and is judged as the minimum number of layer/layers of hierarchy, and

wherein, in said encoding step, image data is encoded up to a hierarchy which satisfies a condition of

Number of Layer/Layers to Be Decoded=(Total Number of Layers)−

n+1.

9. An encoding method of hierarchically encoding image data by a discrete wavelet transform method, comprising:

using a processor to perform the following;

determining a size of an image to be outputted;

judging a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

determining whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy to which the image data can be encoded; and

encoding, if the determination proves true, all the layers of hierarchy of the image data, and otherwise encoding the image data up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy,

wherein said encoding the image data up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy further includes;

encoding a lowest layer of hierarchy of an image among layer/layers which has/have not been encoded, and repeating encoding of a lowest layer of hierarchy of the image among the layer/layers which has/have not been encoded until it is determined that the size of the encoded image is equal to or larger than the determined size of the image to be outputted; and

encoding a next lowest layer of hierarchy of the image.

12. An encoding apparatus for hierarchically encoding an image, comprising:

a first determination unit that determines a size of an image to be outputted;

a judging unit that judges a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

a second determination unit that determines whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy to which the image data can be encoded;

an encoding unit that, if the determination proves true, encodes all the layers of hierarchy of the image data, and otherwise encodes the image up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy; and

reducing the size of the decoded image to the determined size,

wherein, in said judging step, the number n satisfies a condition of

1/2ⁿ>

Sout/Sin_—

1/2⁽ⁿ⁺¹⁾

 

where Sout is an output image size, and Sin is the input image size, n is an integer equal to or greater than 1, and is judged as the minimum number of layer/layers of hierarchy, and

wherein, in said encoding step, image data is decoded up to a hierarchy until an input-output ratio of image size becomes

1/2<sup>(n−

1)</sup>.

15. A decoding apparatus for decoding encoded image data which has been hierarchically encoded in advance, comprising:

a first determination unit that determines a size of an image to be outputted;

a judging unit that judges a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

a second determination unit that determines whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy of the encoded image data;

a decoding that, if the determination proves true, encodes all the layers of hierarchy of the encoded image data, and otherwise decoding the encoded image data up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy; and

a reducing unit that reduces the size of the decoded image to the determined size,

wherein, in said judging unit, the number n satisfies a condition of

X=Sin/Sout

n=INT(log₂X)

 

where Sout is an output image size, and Sin is the input image size, and is judged as the minimum number of layer/layers of hierarchy; and

in said decoding unit, image data is decoded up to a hierarchy which satisfies a condition of

Number of Layer/Layers to Be Decoded=(Total Number of Layers)−

n+1.

16. A decoding apparatus for decoding encoded image data which has been hierarchically encoded in advance, comprising:

a first determining unit that determines a size of an image to be outputted;

a judging unit that judges a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

a second determining unit that determines whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy of the encoded image data;

a decoding unit that, if the determination proves true, decodes all the layers of hierarchy of the encoded image data, and otherwise decodes the encoded image data up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy; and

a reducing unit that reduces the size of the decoded image to the determined size,

wherein when said decoding unit decodes the encoded image data up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy, the decoding further includes;

decoding a lowest layer of hierarchy of encoded image data among layer/layers which has/have not been decoded, and repeating the decoding of a lowest layer of hierarchy of the encoded image data among the layer/layers which has/have not been decoded until it is determined that the size of the decoded image is equal to or larger than the determined size of the image to be outputted; and

decoding a next lowest layer of hierarchy of the encoded image data.

17. An encoding apparatus for hierarchically encoding image data by a discrete wavelet transform method, comprising:

a first determining unit that determines a size of an image to be outputted;

a judging unit that judges a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

a second determining unit that determines whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy to which the image data can be encoded;

an encoding unit that, if the determination proves true, encodes all the layers of hierarchy of the encoded image data, and otherwise encodes the image data up to a layer of hierarchy which is one more layer higher than the minimum number of layer/layers of hierarchy,

wherein, in said judging unit, the number n satisfies a condition of

X=Sin/Sout

n=INT(log₂X)

 

where Sout is an output image size, and Sin is the input image size, and is judged as the minimum number of layer/layers of hierarchy, and

wherein, in said encoding step, image data is encoded up to a hierarchy which satisfies a condition of

Number of Layer/Layers to Be Decoded=(Total Number of Layers)−

n+1.

18. An encoding apparatus for hierarchically encoding image data by a discrete wavelet transform method, comprising:

a first determining unit that determines a size of an image to be outputted;

a judging unit that judges a minimum number of layer/layers of hierarchy needed to obtain a decoded image of size equal to or exceed the determined size;

a second determining unit that determines whether the minimum number of layer/layers of hierarchy corresponds to all the layers of hierarchy to which the image data can be encoded;

an encoding unit that, if the determination proves true, encodes all the layers of hierarchy of the image data, and otherwise encodes the image data up to a layer of hierarchy which is one layer higher than the minimum number of layer/layers of hierarchy,

wherein said encoding the image data up to a layer of hierarchy which is one or more layers higher than the minimum number of layer/layers of hierarchy further includes;

encoding a lowest layer of hierarchy of an image among layer/layers which has/have not been encoded, and repeating encoding of a lowest layer of hierarchy of the image among the layer/layers which has/have not been encoded until it is determined that the size of the encoded image is equal to or larger than the determined size of the image to be outputted; and

encoding a next lowest layer of hierarchy of the image.