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-- $Date: 2003/12/30 04:54:08 $
-- $Revision: 1.4 $
-- $Author: jcrocholl $
package body PNM is
-------------------
-- Internal reading
-------------------
-- Read one character from a stream.
function Read_Character
(Stream : in Stream_Access) -- Read from this stream.
return Character -- The character.
is
Result : Character;
begin
Character'Read(Stream, Result);
return Result;
end Read_Character;
-- Read a PNM file type's magic number from a stream.
function Read_Magic
(Stream : in Stream_Access) -- Read from this stream.
return String2 -- The magic number.
is
Result : String2;
begin
String2'Read(Stream, Result);
return Result;
end Read_Magic;
-- Convert a character from '0' to '9' to a natural number.
function Character_To_Natural
(C : in Character) -- Convert this character.
return Natural is -- Result of conversion.
begin
return Character'Pos(C) - Character'Pos('0');
end Character_To_Natural;
-- Read a natural number from a stream. Ignore leading white space
-- and comments.
function Read_Natural
(Stream : in Stream_Access) -- Read from this stream.
return Natural -- The natural number.
is
Result : Natural;
C : Character;
begin
loop
C := Read_Character(Stream);
if C = '#' then
while C /= ASCII.LF loop
C := Read_Character(Stream);
end loop;
end if;
exit when C >= '0' and C <= '9';
end loop;
Result := Character_To_Natural(C);
loop
C := Read_Character(Stream);
exit when C < '0' or C > '9';
Result := Result * 10 + Character_To_Natural(C);
end loop;
return Result;
end Read_Natural;
-------------------
-- Internal writing
-------------------
-- Write a PNM file type's magic number to a stream.
procedure Write_Magic
(Stream : in Stream_Access; -- Write to this stream.
Magic : in String2) is -- Write this magic number.
begin
String2'Write(Stream, Magic);
end Write_Magic;
-- Write one white space and a natural number to a stream.
procedure Write_Natural
(Stream : in Stream_Access; -- Write to this stream.
N : in Natural) is -- Write this number.
begin
String'Write(Stream, Natural'Image(N));
end Write_Natural;
----------------------
-- Headers with Maxval
----------------------
-- Read a PNM file header, with Maxval (for PGM and PPM).
procedure Read_Header
(Stream : in Stream_Access; -- Read from this stream.
Magic : out String2; -- Magic number for PNM file type.
Width : out Positive; -- Width of the image in pixels.
Height : out Positive; -- Height of the image in pixels.
Maxval : out Positive) is -- Maximum pixel component value.
begin
Magic := Read_Magic(Stream);
Width := Read_Natural(Stream);
Height := Read_Natural(Stream);
Maxval := Read_Natural(Stream);
end Read_Header;
-- Write a PNM file header, with Maxval (for PGM and PPM).
procedure Write_Header
(Stream : in Stream_Access; -- Write to this stream.
Magic : in String2; -- Magic number for PNM file type.
Width : in Positive; -- Width of the image in pixels.
Height : in Positive; -- Height of the image in pixels.
Maxval : in Positive) is -- Maximum pixel component value.
begin
Write_Magic(Stream, Magic);
Write_Natural(Stream, Width);
Write_Natural(Stream, Height);
Write_Natural(Stream, Maxval);
Character'Write(Stream, Character'Val(10));
end Write_Header;
-------------------------
-- Headers without Maxval
-------------------------
-- Read a PNM file header, without Maxval (for PBM).
procedure Read_Header
(Stream : in Stream_Access; -- Read from this stream.
Magic : out String2; -- Magic number for PNM file type.
Width : out Positive; -- Width of the image in pixels.
Height : out Positive) is -- Height of the image in pixels.
begin
Magic := Read_Magic(Stream);
Width := Read_Natural(Stream);
Height := Read_Natural(Stream);
end Read_Header;
-- Write a PNM file header, without Maxval (for PBM).
procedure Write_Header
(Stream : in Stream_Access; -- Write to this stream.
Magic : in String2; -- Magic number for PNM file type.
Width : in Positive; -- Width of the image in pixels.
Height : in Positive) is -- Height of the image in pixels.
begin
Write_Magic(Stream, Magic);
Write_Natural(Stream, Width);
Write_Natural(Stream, Height);
Character'Write(Stream, Character'Val(10));
end Write_Header;
end PNM;