Please consider a donation to the Higher Intellect project. See https://preterhuman.net/donate.php or the Donate to Higher Intellect page for more info.

PCX Technical Reference Manual

From Higher Intellect Vintage Wiki
Jump to navigation Jump to search
The following is culled from a USENET posting by [email protected]

Technical Reference Manual

Including Information For:
Publisher's Paintbrush~
PC Paintbrush~ Plus
PC Paintbrush
FRIEZE Graphics~

ZSoft Corporation
450 Franklin Rd. Suite 100
Marietta, GA  30067
(404) 428-0008

Copyright 1988 ZSoft Corporation


Table of Contents

Introduction
Image File (.PCX) Format
Decoding the .PCX File Format
Palette Information Description
PC Paintbrush Bitmap Font Format
Sample "C" Routines
FRIEZE Technical Information
Pre-7.00 FRIEZE Specifications
Pre-7.00 FRIEZE Function Calls
Pre-7.00 FRIEZE Error Codes
7.00 and later FRIEZE Specifications
7.00 and later FRIEZE Function Calls
7.00 and later FRIEZE Error Codes
The .PCX Programmer's Toolkit



Introduction

This booklet was designed to aid developers and users in understanding
the technical aspects of the .PCX file format and the use of FRIEZE.
Any comments, questions or suggestions about this booklet should be
sent to:

   ZSoft Corporation Technical Support Department
   ATTN: Technical Reference Manual
   450 Franklin Rd. Suite 100
   Marietta, GA 30067
   USA


IMAGE FILE (.PCX) FORMAT

The information in this section will be useful if you want to write a
program to read or write PCX files (images).  If you want to write a
special case program for one particular image format you should be
able to produce something that runs twice as fast as "Load from..." in
PC Paintbrush.  Image files used by PC Paintbrush product family and
FRIEZE (those with a .PCX extension) begin with a 128 byte header.
Usually you can ignore this header, since your images will all have
the same resolution.  If you want to process different resolutions or
colors, you will need to interpret the header correctly.  The
remainder of the image file consists of encoded graphic data.  The
encoding method is a simple byte oriented run-length technique.  We
reserve the right to change this method to improve efficiency.  When
more than one color plane is stored in the file, each line of the
image is stored by color plane (generally ordered red, green, blue,
intensity), as shown below.

Scan line 0:    RRR...
                GGG...
                BBB...
                III...
Scan line 1:    RRR...
                GGG...
                BBB...
                III...
(etc.)

The encoding method is:

   FOR  each  byte,  X,  read from the file
        IF the top two bits of X are  1's then
                count = 6 lowest bits of X
                data = next byte following X
        ELSE
                count = 1
                data = X

Since the overhead this technique requires is, on average, 25% of the
non-repeating data and is at least offset whenever bytes are repeated,
the file storage savings are usually considerable.  The format of the
file header is shown below.



ZSoft .PCX FILE HEADER FORMAT

Byte    Item            Size    Description/Comments

0       Manufacturer    1       Constant Flag  10 = ZSoft .PCX
1       Version         1       Version information:
                                0 = Version 2.5
                                2 = Version 2.8 w/palette information
                                3 = Version 2.8 w/o palette information
                                5 = Version 3.0
2       Encoding        1       1 = .PCX run length encoding
3       Bits per pixel  1       Number of bits/pixel per plane
4       Window          8       Picture Dimensions 
                                (Xmin, Ymin) - (Xmax - Ymax)
                                in pixels, inclusive
12      HRes            2       Horizontal Resolution of creating device
14      VRes            2       Vertical Resolution of creating device
16      Colormap        48      Color palette setting, see text
64      Reserved        1
65      NPlanes         1       Number of color planes
66      Bytes per Line  2       Number of bytes per scan line per 
                                color plane (always even for .PCX files)
68      Palette Info    2       How to interpret palette - 1 = color/BW,
                                2 = grayscale
70      Filler          58      blank to fill out 128 byte header

All variables of size 2 are integers.



Decoding .PCX Files

First, find the pixel dimensions of the image by calculating [XSIZE =
Xmax - Xmin + 1] and [YSIZE = Ymax - Ymin + 1].  Then calculate how
many bytes are required to hold one complete uncompressed scan line:
TotalBytes = NPlanes * BytesPerLine Note that since there are always
an integral number of bytes, there will probably be unused data at the
end of each scan line.  TotalBytes shows how much storage must be
available to decode each scan line, including any blank area on the
right side of the image.  You can now begin decoding the first scan
line - read the first byte of data from the file.  If the top two bits
are set, the remaining six bits in the byte show how many times to
duplicate the next byte in the file.  If the top bits are not set, the
first byte is the data itself, with a count of one.  Continue decoding
the rest of the line.  Keep a running subtotal of how many bytes are
moved and duplicated into the output buffer.  When the subtotal equals
TotalBytes, the scan line is complete.  There will always be a
decoding break at the end of each scan line.  But there will not be a
decoding break at the end of each plane within each scan line.  When
the scan line is completed, there may be extra blank data at the end
of each plane within the scan line.  Use the XSIZE and YSIM values to
find where the valid image data is.  If the data is multi-plane
BytesPerLine shows where each plane ends within the scan line.
Continue decoding the remainder of the scan lines.  There may be extra
scan lines at the bottom of the image, to round to 8 or 16 scan lines.


Palette Information Description

EGA/VGA 16 Color Palette Information

The palette information is stored in one of two different formats.  In
standard RGB format (IBM EGA, IBM VGA) the data is stored as 16
triples.  Each triple is a 3 byte quantity of Red, Green, Blue values.
The values can range from 0-255 so some interpre tation into the base
card format is necessary.  On an IBM EGA, for example, there are 4
possible levels of RGB for each color.  Since 256/4 = 64, the
following is a list of the settings and levels:

Setting         Level
0-63            0
64-127          1
128-192         2
193-254         3


VGA 256 Color Palette Information

ZSoft has recently added the capability to store palettes containing
more than 16 colors in the .PCX image file.  The 256 color palette is
formatted and treated the same as the 16 color palette, except that it
is substantially longer.  The palette (number of colors x 3 bytes in
length) is appended to the end of the .PCX file, and is preceded by a
12 decimal.  To determine the VGA BIOS palette you need only divide
the values read in the palette by 4.  To access a 256 color palette:
First, check the version number in the header, if it contains a 5
there is a palette.  Second, read to the end of the file and count
back 769 bytes.  The value you find should be a 12 decimal, showing
the presence of a 256 color palette.  CGA Color Palette Information
For a standard IBM CGA board, the palette settings are a bit more
complex.  Only the first byte of the triple is used.  The first triple
has a valid first byte which represents the background color.  To find
the background, take the (unsigned) byte value and divide by 16.  This
will give a result between 0-15, hence the background color.  The
second triple has a valid first byte, which represents the foreground
palette.  PC Paintbrush supports 8 possible CGA palettes, so when the
foreground setting i ded between 0 and 255, there are 8 ranges of
numbers and the divisor is 32.


CGA Color Map

Header Byte #16 
Background color is determined in the upper four bits.
Header Byte #19
Only upper 3 bits are used, lower 5 bits are ignored.  The first three
bits that are used are ordered C, P, I.  These bits are interpreted as
follows:

c: color burst enable - 0 = color; 1 = monochrome
p: palette - 0 = yellow; 1 = white
i: intensity - 0 = dim; 1 = bright


PC Paintbrush Bitmap Character Format

The bitmap character fonts are stored in a particularly simple format.
The format of these characters is as follows:

Header (2 bytes)
font width      db      0a0h + character width (in dots)
font height     db      character height (in dots)
Character Widths (256 bytes)
char widths     db      256 dup(each char's width +1)
Character Images
(remainder of the file)

The characters are stored in ASCII order and as many as 256 may be
provided.  Each character is left justified in the character block,
all characters take up the same number of bytes.  Bytes are organized
as N strings, where each string is one scan line of the character.
See figure 2.  For example, each character in a 5x7 font requires 7
bytes.  A 9x14 font uses 28 bytes per character (stored two bytes per
scan line in 14 sets of 2 byte packets).  Custom fonts may be any size
up to the current maximum of 10K bytes allowed for a font fil e.



Sample "C" Routines

The following is a simple set of C subroutines to read data from a .PCX file.

/* This procedure reads one encoded block from the image file and
stores a count and data byte. Result:
  0 = valid data stored
  EOF = out of data in file */

encget(pbyt, pcnt, fid)
int *pbyt;     /* where to place data */
int *pcnt;     /* where to place count */
FILE *fid;     /* image file handle */
{
int i;
        *pcnt = 1;     /* safety play */
        if(EOF    ==    (i    =    getc(fid))) return(EOF);
        if(0xc0 == (0xc0 & i))   {
        *pcnt = 0x3f&i;
        if(EOF == (i=getc(fid)))
                        return(EOF);
}
*pbyt = i;
return(0);
}


/* Here's a program fragment using encget.  This reads an entire file
and stores it in a (large) buffer, pointed to by the variable "bufr".
"fp" is the file pointer for the image */

while (EOF != encget(&chr, &cnt, fp))
                for (i = 0; i ~                 *bufr++ = chr;


The following is a set of C subroutines to write data to a .PCX file.

 /* This subroutine encodes one scanline and writes it to a file */

encLine(inBuff, inLen, fp)
unsigned char *inBuff;  /* pointer to scanline data */
int inLen;                      /* length of raw scanline in bytes */
FILE *fp;                       /* file to be written to */
{  /* returns number of bytes written into outBuff, 0 if failed */
        unsigned char this, last;
int srcIndex, i;
register int total;
register unsigned char runCount; /* max single runlength is 63 */
total = 0;
last = *(inBuff);               runCount = 1;

for (srcIndex = 1; srcIndex  inLen; srcIndex++) {
        this = *(++inBuff);
        if (this == last)       {
                 runCount++;    /* it encodes */
                if (runCount == 63)     {
                        if (!(i=encput(last, runCount, fp)))
                                return(0);
                        total += i;
                        runCount = 0;
                        }
                }
        else    {   /* this != last */
                if (runCount)   {
                        if (!(i=encput(last, runCount, fp)))
                                return(0);
                        total += i;
                        }
                last = this;
                runCount = 1;
                }
        }       /* endloop */
if (runCount)   {               /* finish up */
        if (!(i=encput(last, runCount, fp)))
                return(0);
        return(total + i);
        }
return(total);
}

/* subroutine for writing an encoded byte pair 
(or single byte  if it doesn't encode) to a file */
encput(byt, cnt, fid) /* returns count of bytes written, 0 if err */
unsigned char byt, cnt;
FILE *fid;
{
if(cnt) {
        if( (cnt==1) && (0xc0 != (0xc0&byt)) )  {
                if(EOF == putc((int)byt, fid))
                        return(0); /* disk write error (probably full) */
                return(1);
                }
        else            {
                if(EOF == putc((int)0xC0 | cnt, fid))
                        return(0);      /* disk write error */
                if(EOF == putc((int)byt, fid))
                        return(0);      /* disk write error */
                return(2);
                }
        }
return(0);
}



FRIEZE Technical Information


FRIEZE Information

FRIEZE is a memory resident utility that allows you to capture and
save graphic images from other programs.  You can then bring these
images into PC Paintbrush for editing and enhancement.  FRIEZE was
rewritten for use in PC Paintbrush Plus, and so the technical
information about FRIEZE has changed dramatically.  To easily provide
technical information for all versions of FRIEZE, we have split this
section of the manual into two parts, one about PRE-7.00 versions of
FRIEZE, and one about the current versions (7.00 or higher).  FRIEZE
7.10 and later can be removed from memory (this can return you almost
85K of DOS RAM, depending on your configuration).  To do this, you can
choose to release FRIEZE from memory in the PCINSTAL menu, or at any
time by changing directories to your P C PAINTBRUSH product directory
and typing the word "FRIEZE."


Pre-7.00 FRIEZE Specifications


FRIEZE Print Option Settings

FRIEZE can easily adapt to incomplete printer cables (missing IBM
specified status lines) and will drive either serial or parallel
devices.  Note that FRIEZE always uses the standard BIOS calls, so a
non-handshaking device will time out, but can be told to ignore such
things as paper out.  The FRIEZE command syntax is: FRIEZE Xnaarr
Where: X = either Parallel or Serial n = port number aa = a two digit
hexadecimal code for which return bits cause an abort rr = a two digit
hexadecimal code for which return bits cause a retry Examples: FRIEZE
P1 - use the default settings of Parallel output, port number 1, abort
mask of 28h, and retry mask of 01h FRIEZE P2 - use printer port #2
FRIEZE S1 - use serial port #1, and Xon/Xoff handshaking FRIEZE P10028
- use printer port #1, abort mask of 00 (nothing is read as an error)
and retry mask of 28h Interpreting the codes: On return from the
parallel printer call, the bit interpretations are: 80h - busy signal
(0=busy) 40h - acknowledge 20h - out of paper 10h - selected 08h - I/O
error 04h - unused 02h - unused 01h - time out


FRIEZE Function Calls

FRIEZE is operated using software interrupt number 10h (the video
interrupt call).  To make a FRIEZE function call, load 75 (decimal)
into the AH register, the function call number into the CL register
and then, either load AL with the function argument or load ES and BX
with a segment and offset which point to the function argument the n
do an int 10h.  FRIEZE will return a result code number in AX--zero
means success, other values show error conditions.  All other
registers are unchanged.

No.     Definition      Arguments
0       Print Window    AL = mode: 0 - character,
                        1 - normal, 2 - sideways
1       Read Window     ES:BX - string
                        (filename to read from)
2       Write Window    ES:BX - string
                        (filename to write to)
3       Print Width     AL = width in 1/4 inches
4       Print Height    AL = height in 1/4 inches
5       Reserved
6       Set Left Margin AL = printout margin in 
                        1/4 inches
7       Set Window Size ES:BX - 4 element word
                        vector of window settings:
                        Xmin, Ymin, Xmax, Ymax
8       Reserved
9       Set Patterns    ES:BX - 16 element vector
                        of byte values containing the
                        screen-to-printer color
                        correspondence
10      Get Patterns    ES:BX - room for 16 bytes as
                        above
11      Set Mode        AL = mode number
                        (See SETMODE command)
12      Reserved
13      Reserved
14      Reserved
15      Get Window      ES:BX - room for 4 words of
                        the current window settings
16      Set Print Options       ES:BX - character string of
                        printer options.  Same format
                        as for the FRIEZE command.
17      Initialize      ES:BX - 3 word array
                        containing data from 
                        PC Paintbrush Disk 1 file
                        CARDS.DAT (Hres, Vres,
                        optional code number)
All character strings are ended by a zero byte (ASCIIZ format).


FRIEZE Error Codes

When FRIEZE is called using interrupt 10 hex, it will return an error
code in the AX register.  A value of zero shows that there was no
error.  A nonzero result means there was an error.  These error codes
are explained below.

0       No Error
1       Printout was stopped by user with the ESC key
2       Reserved
3       File read error
4       File write error or printer error
5       File not found
6       Invalid Header or can't create file
        (not a picture or wrong screen mode)
7       File close error
8       Disk error - usually drive door open
9       Not used
10      Invalid command - CL was set to call a nonexistent 
        FRIEZE function
11      Not used
12      Not used


7.00 and Later FRIEZE

The newer versions of FRIEZE have a different number of parameters on
its command line.  The new FRIEZE command line format is:

FRIEZE {PD} {Xnaarr} {flags} {video} {hres} {vres} {vnum}

Where:

{PD}    Printer driver filename (without the .PDV extension)
{Xnaarr}
                X=S for Serial Printer X=P for Parallel Printer
                n = port number
                aa = Two digit hex code for which return bits cause
                         an abort
                rr = Two digit hex code for which return bits cause
                        a retry
{flags} Four digit hex code
                        First Digit controls Length Flag
                        Second Digit controls Width Flag
                        Third Digit controls Mode Flag
                        Fourth Digit controls BIOS Flag
NOTE:   The length, width and mode flags are printer driver specific.
                See PRINTERS.DAT on disk 1 for correct use.  In 
                general width flag of 1 means wide carriage, and 
                0 means standard width.  Length flag of 0 and 
                mode flag of 0 means use standard printer driver 
                settings.
{video} Video driver combination, where the leading digit
                signifies the high level video driver and the rest
                signifies the low level video driver
                Example = 1EGA - uses DRIVE1 and EGA.DEV
{hres}  Horizontal resolution of the desired graphics mode
{vres}  Vertical resolution of the desired graphics mode
{vnum}  Hardware specific parameter (usually number of color planes)
Note: The last four parameters can be obtained from the CARDS.DAT file, on Disk
 1 of your PC Paintbrush diskettes.
Parallel printer return codes:
        80h - Busy Signal (0=busy)
        40h - Acknowledge
        20h - Out of paper
        10h - Selected
        08h - I/O error
        04h - Unused
        02h - Unused
        01h - Time out


FRIEZE Function Calls

FRIEZE is operated using software interrupt number 10h (the video
interrupt call).  To make a FRIEZE function call, load 75 (decimal)
into the AH register, the function number into the CL register and
then, either load AL with the function argument or load ES and BX with
a segment and offset which point to the function argument then do an
int 10h.  FRIEZE will return a result code number in AX--zero means
success, other values show error conditions.  All other registers are
unchanged.

No.     Definition      Arguments
0       Reserved
1       Load Window     ES:BX - string
                        (filename to read from)
2       Save Window     ES:BX - string
                        (filename to write to)
3       Reserved
4       Reserved        
6       Reserved        
7       Set Window Size ES:BX - 4 element word
                        vector of window settings:
                        Xmin, Ymin, Xmax, Ymax
8       Reserved
9       Set Patterns    ES:BX - 16 element vector
                        of byte values containing the
                        screen-to-printer color
                        correspondence
10      Get Patterns    ES:BX - room for 16 bytes as
                        above
11      Set Mode        AL = mode number
                        (See SETMODE command)
12      Reserved
13      Reserved
14      Reserved
15      Get Window      ES:BX - room for 4 words of
                        the current window settings
16      Set Print Options       ES:BX - character string of
                        printer options.  Same format
                        as for the FRIEZE command.
17      Reserved
18      Reserved
19      Reserved
20      Get FRIEZE Version.     AH gets the whole number portion 
                        and AL gets the decimal portion of
                        the version number.  If AH=0, it
                        can be assumed that it is a 
                        pre-7.00 version of FRIEZE.
21      Set Parameters  ES:BX points to an 8 word table 
                        (16 bytes) of parameter settings: 
                        TopMargin, LeftMargin, HSize,VSize,
                        Quality/Draft Mode, PrintHres, 
                        PrintVres, Reserved.    
                        Margins and sizes are specified in 
                        hundredths of inches.
                        Q/D mode parameter values:
                        0 - draft print mode
                        1 - quality print mode
                        2 - use Hres, Vres for output 
                        resolution.  Print resolutions are 
                        specified in DPI.  Any parameter
                        which should be left unchanged may      
                        be filled with a (-1) (0FFFF hex).  
                        The reserved setting should be filled
                        with a (-1).
22      Get Parameters  ES:BX points to an 8 word table 
                        (16 bytes) where parameter settings
                        are held.
23      Get Printer Res ES:BX points to a 12 word table
                        (24 bytes) where printer resolution
                        pairs (6 pairs) are held.
NOTE: All character strings are ended by a zero byte 
        (ASCIIZ format).


FRIEZE Error Codes

When FRIEZE is called using interrupt 10 hex, it will return an error
code in the AX register.  A value of zero shows that there was no
error.  A nonzero result means there was an error.  These error codes
are explained below.

0       No Error
1       Printout was stopped by user with the ESC key
2       Reserved
3       File read error
4       File write error
5       File not found
6       Invalid Header - not an image, wrong screen mode
7       File close error
8       Disk error - usually drive door open
9       Printer error - printer is off or out of paper
10      Invalid command - CL was set to call a nonexistent 
        FRIEZE function
11      Can't create file - write protect tab or disk is full
12      Wrong video mode - FRIEZE cannot capture text screens.



The PCX Programmer's Toolkit

The .MDBO/PCX Programmer's Toolkit.MDNM/, by Genus Microprogramming,
allows developers to create applications with the ability to display,
save, capture, and manipulate PCX format images.  Because it supports
the most common display adapters and compilers , the toolkit can be
used in a wide variety of areas.  Besides the library interfaces, many
utility programs are provided for displaying and capturing screens,
creating windows, inspecting image headers and locating coordinates.
Over 35 routines for displaying and saving images from buffers and
files, setting palettes, accessing image headers, and more.

   Written in Assembler for maximum display speed

   Fast enough for animation

   Image library manager saves disk space and makes portability easy
   (group multiple PCX images in a single library file)

   Display images within database applications

Displays Supported:

    All Modes of the Hercules, CGA, EGA, and VGA graphics adapters.

Compilers Supported:

    Linkable libraries are provided for Microsoft C, Turbo C, QuickC,
    Lattice C, QuickBasic, Turbo Pascal, and Clipper.  Quick libraries
    are provided for the Microsoft integrated compilers, and a unit is
    provided for Turbo Pascal.  Small, Medium, and Large model
    libraries are included for compilers that support multiple memory
    models.

Software Supported:

    Paint packages such as ZSoft's PC Paintbrush and Microsoft
    Paintbrush are directly compatible.  Desktop Publishing packages
    supported include Xerox Ventura Publisher and Aldus PC PageMaker.

What the Toolkit Requires:

    An IBM PC/XT/AT or 100% compatible, 120disk drive, an IBM
    CGA/EGA/VGA, or Hercules adapter (or 100% compatible), and DOS 2.0
    or above.


Only $89.95!!!

Order direct from:
ZSoft Corporation
450 Franklin Rd., Suite 100
Marietta, GA.  30057
(404) 428-0008

Microsoft, Microsoft C, QuickC, QuickBasic, and Microsoft Paintbrush
are trademarks of Microsoft Corporation. Turbo C, Turbo Basic, and
Turbo Pascal are trademarks of Borland International.  Clipper is a
trademark of Nantucket Software.  Lattice C is a trademark of Lattice
Corporation.  Hercules is a trademark of Hercules Corporation.  Other
software packages are trademarks of their respective companies.