This applet obtains the edge of the 2-d image using the wavelet decomposition.
The bases of the wavelet decomposition can be selected from Haar, Daubechies (N=3), and Daubechies (N=5).
As shown in the page of "wavelet decomposition of image",
the low-freq. components and the high-freq.components of the image are successively obtained by applying the wavelet decomposition to the image.
Moreover, the original image is reconstructed from the low-freq. and high-freq. components.
This procedure is called the inverse wavelet transform.
By reconstructing the image from only the high-freq. components (without low-freq. components),
the high-freq. image is obtained, and this image can be used to detect the edge of the original image.