Edge enhancement, using transform of subtracted smoothing image
F. Cheevasuvit, K. Dejhan,A. Somboonkaew
Faculty of Engineering, King Mongkut’s Institute of Technology
Ladkrabang,
Ladkrabag, Bangkok 10520, Thailand.
Abstract
The detail of edges in an image can be obtained by subtracting a smoothed image from the original. Since the resultant subtracted image contains not only the real edges, but also the spurious edges. The eliminate these spurious edges, the inverse Butterworth transform function has been proposed in this paper to transform the subtracted image. Therefore, an edge enhancement image can be performed by adding back the transformed image to the original.
Introduction
The satellite images always have low contrast, by consequence, the difficulty will be appeared in image interpretation. Therefore, the edge enhancement technique has been used to overcome this problem. The aim of edge enhancement. is to modify the appearance of an image to make it visually more attractive or to improve the visibility of certain features [1]. The edge enhancement technique leads to enhance all high spatial frequency detail in an image including edges, lines and points of high gradients [2]. The subtractive smoothing method has been used as the simplest way to obtain high spatial frequency image. By this method the detail of edges in the image can be performed by subtracting a smoothed image from the original. Some smoothing templates as shown in Fig. I will be selected for the convolution operation which will give a smoothed image. The smoothing process smoothes the detail in the image and also reduces the image contrast. These effects will cause the attenuation of high spatial frequency components. in the image. Therefore, the resultant smoothed image becomes blurred.
Then, the subtraction of smoothed image from the original gives an image with only edge detail. Thus, the edge enhancement image can be achieved by adding back the subtracted image back to the original. The block diagram of edge enhancement process as mentioned above can be shown as in the Fig. 2, while the Fig. 3 presents the resultant example result of edge enhancement image.
Fig. 2 Block diagram of edge enhancement by subtractive smoothing
