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From: griest-tom@cs.yale.edu (Tom Griest)
Subject: Re: .PCX parser. In Ada of course...
Date: 1996/03/23
Message-ID: <4j28cqINNbke@RA.DEPT.CS.YALE.EDU>#1/1
X-Deja-AN: 143959595
references: <4ius06INNcpe@faatcrl.faa.gov>
organization: Yale University Computer Science Dept., New Haven, CT 06520-2158
cc: thompsor@admin.tc.faa.gov
keywords: PCX, Ada95
newsgroups: comp.lang.ada
Date: 1996-03-23T00:00:00+00:00
List-Id: <comp.lang.ada>

ron thompson <thompsor@admin.tc.faa.gov> writes:
>

[snip]

>Any brave and fearless Ada programmers out there got an Ada
>written .pcx parser? Know anyone that does? 

Here are a couple snippets from an Ada-based PCX (graphics format) parser.  
I would send you all the code, but it is pretty tightly intermixed
with display code for Win32.  [There is a lot of scaling and zooming, etc.
that is not really related to PCX].   I didn't write this BTW, but it
is LabTek property and you can do what you want with it (providing
you assume all responsibilty).

-Tom

-----------------------------------------------------------------------------
--
-- This is the PCX header and associated types/constants for processing the
-- file.
--
repeat_signature  : constant := 16#C0#;
repeat_count_mask : constant := 16#3F#;

type PALETTE_TYPE is array(0..47) of BYTE;
type RESERVED_TYPE is array(0..57) of BYTE;

type PCX_HEADER_RECORD is record  -- should use a rep spec to be safe!
  MANUFACTURER        : BYTE;
  VERSION             : BYTE;
  ENCODING            : BYTE;
  BITS_PER_PIXEL      : BYTE;
  XMIN                : SHORT;  -- always 16 bits
  YMIN                : SHORT;
  XMAX                : SHORT;
  YMAX                : SHORT;
  HRES                : SHORT;
  VRES                : SHORT;
  PALETTE             : PALETTE_TYPE;
  RESERVED_1          : BYTE;
  NUM_PLANES          : BYTE;
  BYTES_PER_LINE      : SHORT;
  TYPE_OF_PALETTE     : SHORT;
  RESERVED_2          : RESERVED_TYPE;
end record;


-- main PCX decode loop

  INDEX := 0;
  for ROW in 0..Y_LIMIT loop
    WY := Scale(ROW - Y_OFFSET, Y_SCALE);
    X := 0;
    loop
      VALUE := PCX_BYTES(INDEX);
      INDEX := INDEX + 1;
      if (VALUE and repeat_signature) = repeat_signature then
        COUNT := VALUE and repeat_count_mask;
        if ROW >= Y_OFFSET then
          VALUE := PCX_BYTES(INDEX);
          for I in 1..COUNT loop
            if X >= X_OFFSET and
               X < X_LIMIT then
              Display_Byte(DISPLAY_HDC,
                           INSTANCE_INDEX,
                           VALUE,
                           X - X_OFFSET,
                           WY);
            end if;
            X := X + 8;
          end loop;
        else                        -- not in the Y_OFFSET range yet
          X := X + 8 * INT(COUNT);
        end if;
        INDEX := INDEX + 1;
      else
        if ROW >= Y_OFFSET and
           X >= X_OFFSET and
           X < X_LIMIT then
          Display_Byte(DISPLAY_HDC,
                       INSTANCE_INDEX,
                       VALUE,
                       X - X_OFFSET,
                       WY);
        end if;
        X := X + 8;
      end if;
      exit when X >= BITS_PER_LINE;
    end loop;
  end loop;