The invention disclosed a method for digital image interpolation and
sharpness enhancement, said method includes the following steps: 1)
Inputting an image signal Xij to a first interpolation low pass filter FIR
1, said FIR 1 is a cubic interpolation filter having filter coefficient
hi(n); 2) inputting an image signal Xij to at least one of second
interpolation low pass filters FIR 2, said FIR 2 is an interpolation
filter having filter coefficient hi'(n), wherein said FIR 2 has a cut-off
frequency lower than that of said FIR 1; 3) making FIR 1 outputted via a
band pass filter to obtain an image signal tij; 4) making FIR 2 outputted
via a delay buffer to obtain an image signal tij'; 5) inputting said image
signal tij and tij' to a subtractor to get a differential signal tij-tij';
and 6) obtaining an output of image signal Yij by means of the following
equation: Yij=tij+S.multidot.(tij-tij'), where S is a sharpness level
control coefficient.
