imagpcx.cpp

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/////////////////////////////////////////////////////////////////////////////
// Name:        imagpcx.cpp
// Purpose:     wxImage PCX handler
// Author:      Guillermo Rodriguez Garcia <[e-mail]>
// Version:     1.1
// CVS-ID:      $Id: imagpcx.cpp,v 1.40 2005/03/17 23:19:06 VZ Exp $
// Copyright:   (c) 1999 Guillermo Rodriguez Garcia
// Licence:     wxWindows licence
/////////////////////////////////////////////////////////////////////////////

#if defined(__GNUG__) && !defined(NO_GCC_PRAGMA)
#pragma implementation "imagpcx.h"
#endif

// For compilers that support precompilation, includes "wx.h".
#include "wx/wxprec.h"

#ifdef __BORLANDC__
#pragma hdrstop
#endif

#ifndef WX_PRECOMP
#  include "wx/defs.h"
#  include "wx/palette.h"
#endif

#if wxUSE_IMAGE && wxUSE_PCX

#include "wx/imagpcx.h"
#include "wx/wfstream.h"
#include "wx/module.h"
#include "wx/log.h"
#include "wx/intl.h"

#include "wx/hash.h"
#include "wx/list.h"
#include "wx/object.h"

//-----------------------------------------------------------------------------
// wxPCXHandler
//-----------------------------------------------------------------------------

IMPLEMENT_DYNAMIC_CLASS(wxPCXHandler,wxImageHandler)

#if wxUSE_STREAMS

//-----------------------------------------------------------------------------
// RLE encoding and decoding
//-----------------------------------------------------------------------------

void RLEencode(unsigned char *p, unsigned int size, wxOutputStream& s)
{
    unsigned int data, last, cont;

    // Write 'size' bytes. The PCX official specs say there will be
    // a decoding break at the end of each scanline, so in order to
    // force this decoding break use this function to write, at most,
    // _one_ complete scanline at a time.

    last = (unsigned char) *(p++);
    cont = 1;
    size--;

    while (size-- > 0)
    {
        data = (unsigned char) *(p++);

        // Up to 63 bytes with the same value can be stored using
        // a single { cont, value } pair.
        //
        if ((data == last) && (cont < 63))
        {
            cont++;
        }
        else
        {
            // need to write a 'counter' byte?
            if ((cont > 1) || ((last & 0xC0) == 0xC0))
                s.PutC((char) (cont | 0xC0));

            s.PutC((char) last);
            last = data;
            cont = 1;
        }
    }

    // write the last one and return;
    if ((cont > 1) || ((last & 0xC0) == 0xC0))
        s.PutC((char) (cont | 0xC0));

    s.PutC((char) last);
}

void RLEdecode(unsigned char *p, unsigned int size, wxInputStream& s)
{
    unsigned int i, data, cont;

    // Read 'size' bytes. The PCX official specs say there will be
    // a decoding break at the end of each scanline (but not at the
    // end of each plane inside a scanline). Only use this function
    // to read one or more _complete_ scanlines. Else, more than
    // 'size' bytes might be read and the buffer might overflow.

    while (size > 0)
    {
        data = (unsigned char)s.GetC();

        // If ((data & 0xC0) != 0xC0), then the value read is a data
        // byte. Else, it is a counter (cont = val & 0x3F) and the
        // next byte is the data byte.

        if ((data & 0xC0) != 0xC0)
        {
            *(p++) = (unsigned char)data;
            size--;
        }
        else
        {
            cont = data & 0x3F;
            data = (unsigned char)s.GetC();
            for (i = 1; i <= cont; i++)
                *(p++) = (unsigned char)data;
            size -= cont;
        }
    }
}


//-----------------------------------------------------------------------------
// PCX reading and saving
//-----------------------------------------------------------------------------

// PCX header
#define HDR_MANUFACTURER    0
#define HDR_VERSION         1
#define HDR_ENCODING        2
#define HDR_BITSPERPIXEL    3
#define HDR_XMIN            4
#define HDR_YMIN            6
#define HDR_XMAX            8
#define HDR_YMAX            10
#define HDR_NPLANES         65
#define HDR_BYTESPERLINE    66
#define HDR_PALETTEINFO     68

// image formats
enum {
    wxPCX_8BIT,             // 8 bpp, 1 plane (8 bit)
    wxPCX_24BIT             // 8 bpp, 3 planes (24 bit)
};

// error codes
enum {
    wxPCX_OK = 0,           // everything was OK
    wxPCX_INVFORMAT = 1,    // error in pcx file format
    wxPCX_MEMERR = 2,       // error allocating memory
    wxPCX_VERERR = 3        // error in pcx version number
};


// ReadPCX:
//  Loads a PCX file into the wxImage object pointed by image.
//  Returns wxPCX_OK on success, or an error code otherwise
//  (see above for error codes)
//
int ReadPCX(wxImage *image, wxInputStream& stream)
{
    unsigned char hdr[128];         // PCX header
    unsigned char pal[768];         // palette for 8 bit images
    unsigned char *p;               // space to store one scanline
    unsigned char *dst;             // pointer into wxImage data
    unsigned int width, height;     // size of the image
    unsigned int bytesperline;      // bytes per line (each plane)
    int bitsperpixel;               // bits per pixel (each plane)
    int nplanes;                    // number of planes
    int encoding;                   // is the image RLE encoded?
    int format;                     // image format (8 bit, 24 bit)
    unsigned int i, j;

    // Read PCX header and check the version number (it must
    // be at least 5 or higher for 8 bit and 24 bit images).

    stream.Read(hdr, 128);

    if (hdr[HDR_VERSION] < 5) return wxPCX_VERERR;

    // Extract all image info from the PCX header.

    encoding     = hdr[HDR_ENCODING];
    nplanes      = hdr[HDR_NPLANES];
    bitsperpixel = hdr[HDR_BITSPERPIXEL];
    bytesperline = hdr[HDR_BYTESPERLINE] + 256 * hdr[HDR_BYTESPERLINE + 1];
    width        = (hdr[HDR_XMAX] + 256 * hdr[HDR_XMAX + 1]) -
                   (hdr[HDR_XMIN] + 256 * hdr[HDR_XMIN + 1]) + 1;
    height       = (hdr[HDR_YMAX] + 256 * hdr[HDR_YMAX + 1]) -
                   (hdr[HDR_YMIN] + 256 * hdr[HDR_YMIN + 1]) + 1;

    // Check image format. Currently supported formats are
    // 8 bits (8 bpp, 1 plane) and 24 bits (8 bpp, 3 planes).

    if ((nplanes == 3) && (bitsperpixel == 8))
        format = wxPCX_24BIT;
    else if ((nplanes == 1) && (bitsperpixel == 8))
        format = wxPCX_8BIT;
    else
        return wxPCX_INVFORMAT;

    // If the image is of type wxPCX_8BIT, then there is
    // a palette at the end of the image data. If we were
    // working with a file, we could seek at the end to the
    // end (SeekI(-769, wxFromEnd) and read the palette
    // before proceeding. Unfortunately, this would prevent
    // loading several PCXs in a single stream, so we can't
    // do it. Thus, 8-bit images will have to be decoded in
    // two passes: one to read and decode the image data,
    // and another to replace 'colour indexes' with RGB
    // values.

    // Resize the image and allocate memory for a scanline.

    image->Create(width, height);

    if (!image->Ok())
        return wxPCX_MEMERR;

    if ((p = (unsigned char *) malloc(bytesperline * nplanes)) == NULL)
        return wxPCX_MEMERR;

    // Now start reading the file, line by line, and store
    // the data in the format required by wxImage.

    dst = image->GetData();

    for (j = height; j; j--)
    {
        if (encoding)
            RLEdecode(p, bytesperline * nplanes, stream);
        else
            stream.Read(p, bytesperline * nplanes);

        switch (format)
        {
            case wxPCX_8BIT:
            {
                for (i = 0; i < width; i++)
                {
                    // first pass, just store the colour index
                    *dst = p[i];
                    dst += 3;
                }
                break;
            }
            case wxPCX_24BIT:
            {