Loading .GIF and .PCX

 BBS: Inland Empire Archive
Date: 12-13-92 (18:57)             Number: 386
From: PETER BARNEY                 Refer#: NONE
  To: CRUZ MONCIVAIS                Recvd: NO  
Subj: Loading .GIF and .PCX          Conf: (2) Quik_Bas

 >  PB> Your reply chain got tangled.  You should've sent the reply to Harry
 >  PB> Gish. He did post some code for 256-pcx though.  Did you get it?

 >  No I did not get that code?   Is it possible to re-post?

I don't have the EXACT original code (it was written in
ZBASIC, I converted to QB), hope you don't mind Harry.

'(1127)  Sat 21 Nov 92  1:56p
'By: Harry Gish
'To: All
'Re: 256 color PCX reader
'St:
'


DEFINT A-Z
SCREEN 13

FileName$ = "256COLOR.PCX"  'fill in the blank
OPEN FileName$ FOR BINARY AS #2 LEN = 11
'Size# must be set to actual PCX file size in bytes
Size# = LOF(2)

'The first 128 bytes in the file are a header.
'Much of it is unused, or of no practical use.
'For simplicity we'll cover the important ones only.

header$ = SPACE$(128)
GET #2, , header$: CLS

'The first position is a PCX 'signature'.

Sig$ = LEFT$(header$, 1)
IF Sig$ <> CHR$(10) THEN PRINT "Invalid PCX file, no ZSoft header found": END

'The next header byte specifies the version.
'For 256 color it must be 5.

Ver$ = MID$(header$, 2, 1): Ver = ASC(Ver$)
IF Ver <> 0 AND Ver <> 2 AND Ver <> 3 AND Ver <> 5 THEN
PRINT "Invalid version number": END

'The next header byte specifies the color bits.
'For 256 color it must be 8.

ColorBits$ = MID$(header$, 4, 1): ColorBits = ASC(ColorBits$)
IF ColorBits <> 1 AND ColorBits <> 8 THEN PRINT "Invalid
number of color bits": END

'The image size is contained in 4 bytes
'starting at position 9 of the header.

XRes$ = MID$(header$, 9, 2)
XRes1$ = LEFT$(XRes$, 1): XRes2$ = RIGHT$(XRes$, 1)
XRes = ASC(XRes1$) + ASC(XRes2$) * 256 + 1

YRes$ = MID$(header$, 11, 2)
YRes1$ = LEFT$(YRes$, 1): YRes2$ = RIGHT$(YRes$, 1)
YRes = ASC(YRes1$) + ASC(YRes2$) * 256 + 1

'256 Color PCX

Bytes# = 128
Pointer = 0

'The palette information (definitions of the 256 colors)
'is contained in the last 768 bytes of the file. There
'is a "leading check-byte" of 0C (hex) preceding it.
'Here we're positioning to that check-byte.

SEEK #2, Size# - 769
a$ = " "
GET #2, , a$

'Now we read the next 768 bytes {256 x 3 for Red,
'Green and Blue definitions respectively}. Current
'paletting for PCX requires division by 4. If there
'is a "true-color" PCX format {and there may be and
'I don't know about it} I'd expect it to simply drop
'the division by 4 and make it the actual number.

FOR X = 0 TO 255
    a$ = "   "
    GET #2, , a$
    R = (ASC(MID$(a$, 1, 1)) / 4) AND 63
    G = (ASC(MID$(a$, 2, 1)) / 4) AND 63
    B = (ASC(MID$(a$, 3, 1)) / 4) AND 63
    PALETTE X, R + G * 256 + B * 65536
NEXT

'Now we position at the 128th byte,
'which is where the data begins.

SEEK #2, 128

'Read a byte

DecodeGroup:
X$ = " "
IF EOF(2) THEN GOTO done
GET #2, , X$: X = ASC(X$): Bytes# = Bytes# + 1

'Now we must see if the byte represents a single color
'value or if it is a multiplier value. A quirk of 256
'COLOR PCX's is that a single value of the top 64 colors
'must be encoded as a multiplier of 1 times the color.
'You can't say COLOR 255, you must say 1 times 255. This
'makes many 256 color PCX files actually larger than a
'simple value dump. In this case if the byte value is
'less than 193 then it is an actual value.

'LONGIF ? - Harry, what the heck does LONGIF mean?
IF X < 193 THEN
    PSET (Pointer, LineNo), X
    Pointer = Pointer + 1
END IF

'Otherwise we interpret it as a multiplier.
'Multiplier value can be as large as 63.

'LONGIF ? - again?
IF X > 192 THEN
    X = X - 192:
    X$ = " "
    GET #2, , X$: y = ASC(X$): Bytes# = Bytes# + 1
    LINE (Pointer, LineNo)-(Pointer + X - 1, LineNo), y
    Pointer = Pointer + X
END IF

'Pointer notes the current position in the X line scan.
'When the line is done Pointer gets reset to zero.

IF Pointer < XRes GOTO DecodeGroup
Pointer = 0

'If we're at end of line now we need to see if all lines are decoded.
'If so we end, otherwise we start processing the next line.

IF LineNo = YRes GOTO done

LineNo = LineNo + 1
GOTO DecodeGroup

done:
BEEP
WHILE INKEY$ = "": WEND
SCREEN 2, 1: SCREEN 0, 0: COLOR 15, 1, 4: CLS : END

--- FMail 0.92