An adaptive image interpolation algorithm for image/video processing Author : Cheng-Soon Chuah,...

An adaptive image interpolation algorithm

for image/video processing

Author : Cheng-Soon Chuah, Jin-Jang LeouSource : Pattern Recognition 34 (2001) 2383-2393Speaker : Yi - Ping Lu Adviser : Ku-Yaw Chang

2007/12/17 Digital Image Processing 2

OutlineOutline►Introduction►Proposed adaptive image interpolation al

gorithm►Simulation results►Concluding remarks


Introduction►Image interpolation is one of the key tech

nologies in image/video processing►A new adaptive image interpolation algori

thm is proposed


Introduction►The main purposes of image interpolation

include: Image expansion or zooming Achieving higher compression ratio for image

sequence compression


Introduction►Based on the experimental results

PSNR (peak signal-to-noise ratio) in dB Subjective measure of the quality of the inter

polated images


Adaptive image interpolation algorithm



►A cubic B-spline function The low-resolution image frame is first interp

olated into a coarsely up-sampled image frame

►Pixel classification Edge and non-edge pixels by analyzing the loc

al image characteristics



► 1-difference filter and 2-D edge sensitive filter Iteratively improve the coarsely (cubic B-spline) inter

polated image frame until the termination criterion is satisfied

► 1-difference filter Recover high-frequency components lost within the d

ecimation procedure ► 2-D edge sensitive filter

Reconstruct sharp edges and image details►Blocking artifacts

Reduced by a smoothing operator



image resolution-low in the pixel a of valuePixel Lk：blockExpansion Bk：

z*z Size z：iterationrth r ：

operation Rounding )( Round ：‧kji, Bblock expantion whithin j)(i, valuepixel The f ：



►2.1. Proposed 1-difference filter Increases or decreases the pixel value of a pix

el to be interpolated Define dif(r) as the absolute difference betwee

n Lk and the mean of pixel values of all pixels in expansion block Bk within the rth iteration



► new pixel value Each in expansion block Bk within the (r+1)th iterati

on is then pre-computed by (3) Mean

►Pixel values of all the 9 pixels in the 3*3 window centered at pixel (i, j)

►All the pixel values in expansion block Bk are changed into their corresponding new pixel values

only if <

1)(rji,f

(r)ji,f

1)(rji,f

1)(rdif (r)dif



► 2.2. Proposed 2-D edge-sensitive filter Human eyes are more sensitive to high-contrast edge

s than smooth areas Applying bilinear and cubic B-spline functions

►Smooths image data►Blurs the discontinuities

To cope with this problem►An edge-sensitive filter is employed in this study to compens

ate the over-smoothing effect



► 2.2. Proposed 2-D edge-sensitive filter Based on the direction and the relative position of a p

ixel within a 5*5 window The Prewitt operators

►Determine the existences and orientations of edge pixels

)(,rjif



►2.3. Postprocessing: Blocking Artifacts Reduction Because the proposed approach is performed

in a block-by-block fashion, blocking artifacts are inevitable



► To measure the seriousness of blocking artifacts An expansion block is defined as the mean of the absolute pixel

value difference between the expansion block and its four neighboring expansion blocks

y visibilitartifacts blocking The ： V ji,


Simulation results►The proposed adaptive image interpolatio

n algorithm has been implemented On a Pentium 133 PC C programming language Three test image

►“Salesman”, “Football”, and “Flower Garden”

►Three different decimation/expansion ratios are employed z = 2, 3, 4


Simulation results►Three existing approaches for comparison

Zero-order (Zero-O) Bilinear interpolation (Bilinear) Cubic B-spline interpolation (Cubic)


Simulation results


Concluding remarks►A new adaptive image interpolation algorithm is

proposed. ► In the proposed approach

A low-resolution image frame is first interpolated into a coarsely interpolated image frame using the cubic B-spline function

All the pixels in each coarsely interpolated image frame are then classified into non-edge and edge pixels

1-difference filter 2-D edge-sensitive filter Blocking artifacts-reducing


Concluding remarks►Based on the experimental results

PSNR in dB Subjective measure of the quality of the inter

polated images The proposed approach are better than that b

y the three existing interpolation approaches ►This shows the feasibility of the proposed

approach

The End

An adaptive image interpolation algorithm for image/video processing Author : Cheng-Soon Chuah,...

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