% changes for DDTONE.WEB to enhance contrasts
@x
@!new_row:array[-3..nn+4] of real; {densities in row being input}
@y
@!new_row:array[-3..nn+4] of real; {densities in row being input}
@!row_buf:array[0..2,0..nn+1] of real; {`actual' data before enhancement}
@z
@x
@!t:eight_bits; {byte of input}
begin for j←-3 to 0 do new_row[j]←0.0;
if i>mm then for j←1 to nn do new_row[j]←0.0
else for j←1 to nn do
	begin read(bytes_in,t); new_row[j]←(255.5-t)/256.0;
	end;
@y
@!t:eight_bits; {byte of input}
begin if i=1 then
	begin for j←1 to nn do
		begin read(bytes_in,t); row_buf[2,j]←(255.5-t)/256.0;
		end;
	row_buf[2,0]←row_buf[2,1]; row_buf[2,nn+1]←row_buf[2,nn];
	for j←0 to nn+1 do row_buf[1,j]←row_buf[2,j];
	end;
for j←0 to nn+1 do
	begin row_buf[0,j]←row_buf[1,j]; row_buf[1,j]←row_buf[2,j];
	end;
if i<mm then
	begin for j←1 to nn do
		begin read(bytes_in,t); row_buf[2,j]←(255.5-t)/256.0;
		end;
	row_buf[2,0]←row_buf[2,1]; row_buf[2,nn+1]←row_buf[2,nn];
	end;
for j←-3 to 0 do new_row[j]←0.0;
for j←1 to nn do new_row[j]←9*row_buf[1,j]-row_buf[0,j-1]-row_buf[0,j]
 -row_buf[0,j+1]-row_buf[1,j-1]-row_buf[1,j+1]-row_buf[2,j-1]
 -row_buf[2,j]-row_buf[2,j+1];
@z