Resolution changing method and apparatus

• US 20050201632A1
• Filed: 03/01/2005
• Published: 09/15/2005
• Est. Priority Date: 03/09/2004
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Sakakima, Eito
• Granted Patent: US 7,567,723 B2
• Time in Patent Office: Days
• US Class Current: 382/254
• CPC Class Codes: G06T 3/403 Edge-driven scaling; Edge-based scaling

Abstract

When a plurality of reference pixels do not include the boundary of a block, the pixel data of an interpolation pixel is computed by performing the first kind of interpolation processing by use of a plurality of the pixel data of the reference pixels. When a plurality of reference pixels include the boundary of a block, the pixel data of an interpolation pixel is computed by performing the second kind of interpolation processing by use of a plurality of the pixel data of the reference pixels. The second kind of interpolation processing is such that produces a smaller effect of enhancing the edge of an image as compared with the first kind of interpolation processing.

Claims

1. A resolution changing method for changing the resolution of image data subjected to a predetermined image processing involving block split, the method comprising:

a reference pixel selection step of selecting a plurality of reference pixels to be supplied to an operation of an interpolation pixel from the image data;

a determination step of determining whether or not the plurality of reference pixels include a boundary of the block; and

an interpolation pixel data computation step

of computing pixel data of an interpolation pixel by performing a first kind of interpolation processing by the use of a plurality of pixel data of the reference pixels when the plurality of reference pixels do not include the boundary of the block and

of computing pixel data of an interpolation pixel by performing a second kind of interpolation processing by the use of a plurality of pixel data of the reference pixels when the plurality of reference pixels include the boundary of the block,

wherein the second kind of interpolation processing produces a smaller effect of enhancing an edge of an image as compared with the first kind of interpolation processing.

3. A resolution changing method according to claim 1, wherein the predetermined image processing is orthogonal transformation encoding processing.

4. A resolution changing method according to claim 1, wherein the first kind of interpolation processing is interpolation processing by a bicubic interpolation.

5. A resolution changing method according to claim 1, wherein the second kind of interpolation processing is interpolation processing by a bilinear interpolation.

2. A resolution changing method for changing the resolution of image data subjected to a predetermined image processing involving block split, the method comprising:

a reference pixel selection step of selecting a plurality of reference pixels to be supplied to an operation of an interpolation pixel from the image data;

a determination step of determining whether or not the plurality of reference pixels include a boundary of the block; and

an interpolation pixel data computation step

of computing pixel data of an interpolation pixel by performing a first kind of interpolation processing by the use of a plurality of pixel data of the reference pixels when the plurality of reference pixels do not include the boundary of the block and

of computing pixel data of an interpolation pixel by performing a second kind of interpolation processing by the use of a plurality of pixel data of the reference pixels when the plurality of reference pixels include the boundary of the block,

wherein the first kind of interpolation processing produces a smaller effect of smoothing a discontinuous portion of the boundary of the block as compared with the second kind of interpolation processing.

6. A resolution changing method according to claim 2, wherein the predetermined image processing is orthogonal transformation encoding processing.

7. A resolution changing method according to claim 2, wherein the first kind of interpolation processing is interpolation processing by a bicubic interpolation.

8. A resolution changing method according to claim 2, wherein the second kind of interpolation processing is interpolation processing by a bilinear interpolation.

9. A resolution changing apparatus for changing the resolution of image data subjected to a predetermined image processing involving block split, the apparatus comprising:

a reference pixel selection unit that selects a plurality of reference pixels to be supplied to an operation of an interpolation pixel from the image data;

a block boundary determination unit that determines whether or not the plurality of selected reference pixels include a boundary of the block;

a pixel computation mode switching unit that determines a mode of computing pixel data of an interpolation pixel from pixel data of the selected reference pixels according to determination result by the block boundary determination unit;

a pixel extraction unit that extracts pixel data of the selected reference pixels; and

an interpolation pixel computation unit that computes pixel data of an interpolation pixel from the extracted pixel data of the reference pixels according to a mode determined by the pixel computation mode switching unit,

wherein the pixel computation mode switching unit determines a first mode for computing pixel data when the block boundary determination unit determines that the plurality of reference pixels do not include the boundary of the block, and determines a second mode for computing pixel data that produces a smaller effect of enhancing an edge of an image as compared with the first mode when the block boundary determination unit determines that the plurality of reference pixels include the boundary of the block.

11. A resolution changing apparatus according to claim 9, wherein the predetermined image processing is orthogonal transformation encoding processing.

10. A resolution changing apparatus for changing the resolution of image data subjected to a predetermined image processing involving block split, the apparatus comprising:

a reference pixel selection unit that selects a plurality of reference pixels to be supplied to an operation of an interpolation pixel from the image data;

a block boundary determination unit that determines whether or not the plurality of selected reference pixels include a boundary of the block;

a pixel computation mode switching unit that determines a mode of computing pixel data of an interpolation pixel from pixel data of the selected reference pixels according to determination result by the block boundary determination unit;

a pixel extraction unit that extracts pixel data of the selected reference pixels; and

an interpolation pixel computation unit that computes pixel data of an interpolation pixel from the extracted pixel data of the reference pixels according to a mode determined by the pixel computation mode switching unit,

wherein the pixel computation mode switching unit determines a first mode for computing pixel data when the block boundary determination unit determines that the plurality of reference pixels do not include the boundary of the block, and determines a second mode for computing pixel data that produces a larger effect of smoothing a discontinuous portion of the boundary of the block as compared with the first mode when the block boundary determination unit determines that the plurality of reference pixels include the boundary of the block.

12. A resolution changing apparatus according to claim 10, wherein the predetermined image processing is orthogonal transformation encoding processing.