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zrleencodetemplate.c

/*
 * Copyright (C) 2002 RealVNC Ltd.  All Rights Reserved.
 * Copyright (C) 2003 Sun Microsystems, Inc.
 *
 * This is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this software; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
 * USA.
 */

/*
 * Before including this file, you must define a number of CPP macros.
 *
 * BPP should be 8, 16 or 32 depending on the bits per pixel.
 * GET_IMAGE_INTO_BUF should be some code which gets a rectangle of pixel data
 * into the given buffer.  EXTRA_ARGS can be defined to pass any other
 * arguments needed by GET_IMAGE_INTO_BUF.
 *
 * Note that the buf argument to ZRLE_ENCODE needs to be at least one pixel
 * bigger than the largest tile of pixel data, since the ZRLE encoding
 * algorithm writes to the position one past the end of the pixel data.
 */

#include <zrleoutstream.h>
#include <zrlepalettehelper.h>
#include <assert.h>

/* __RFB_CONCAT2 concatenates its two arguments.  __RFB_CONCAT2E does the same
   but also expands its arguments if they are macros */

#ifndef __RFB_CONCAT2E
#define __RFB_CONCAT2(a,b) a##b
#define __RFB_CONCAT2E(a,b) __RFB_CONCAT2(a,b)
#endif

#ifdef CPIXEL
#define PIXEL_T __RFB_CONCAT2E(zrle_U,BPP)
#define zrleOutStreamWRITE_PIXEL __RFB_CONCAT2E(zrleOutStreamWriteOpaque,CPIXEL)
#define ZRLE_ENCODE __RFB_CONCAT2E(zrleEncode,CPIXEL)
#define ZRLE_ENCODE_TILE __RFB_CONCAT2E(zrleEncodeTile,CPIXEL)
#define BPPOUT 24
#else
#define PIXEL_T __RFB_CONCAT2E(zrle_U,BPP)
#define zrleOutStreamWRITE_PIXEL __RFB_CONCAT2E(zrleOutStreamWriteOpaque,BPP)
#define ZRLE_ENCODE __RFB_CONCAT2E(zrleEncode,BPP)
#define ZRLE_ENCODE_TILE __RFB_CONCAT2E(zrleEncodeTile,BPP)
#define BPPOUT BPP
#endif

#ifndef ZRLE_ONCE
#define ZRLE_ONCE

static const int bitsPerPackedPixel[] = {
  0, 1, 2, 2, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4
};

static zrlePaletteHelper paletteHelper;

#endif /* ZRLE_ONCE */

static void ZRLE_ENCODE_TILE (PIXEL_T* data, int w, int h, zrleOutStream* os);

static void ZRLE_ENCODE (int x, int y, int w, int h,
                   zrleOutStream* os, void* buf
                   EXTRA_ARGS)
{
  int ty;
  for (ty = y; ty < y+h; ty += rfbZRLETileHeight) {
    int tx, th = rfbZRLETileHeight;
    if (th > y+h-ty) th = y+h-ty;
    for (tx = x; tx < x+w; tx += rfbZRLETileWidth) {
      int tw = rfbZRLETileWidth;
      if (tw > x+w-tx) tw = x+w-tx;

      GET_IMAGE_INTO_BUF(tx,ty,tw,th,buf);

      ZRLE_ENCODE_TILE((PIXEL_T*)buf, tw, th, os);
    }
  }
  zrleOutStreamFlush(os);
}


static void ZRLE_ENCODE_TILE (PIXEL_T* data, int w, int h, zrleOutStream* os)
{
  /* First find the palette and the number of runs */

  zrlePaletteHelper *ph;

  int runs = 0;
  int singlePixels = 0;

  rfbBool useRle;
  rfbBool usePalette;

  int estimatedBytes;
  int plainRleBytes;
  int i;

  PIXEL_T* ptr = data;
  PIXEL_T* end = ptr + h * w;
  *end = ~*(end-1); /* one past the end is different so the while loop ends */

  ph = &paletteHelper;
  zrlePaletteHelperInit(ph);

  while (ptr < end) {
    PIXEL_T pix = *ptr;
    if (*++ptr != pix) {
      singlePixels++;
    } else {
      while (*++ptr == pix) ;
      runs++;
    }
    zrlePaletteHelperInsert(ph, pix);
  }

  /* Solid tile is a special case */

  if (ph->size == 1) {
    zrleOutStreamWriteU8(os, 1);
    zrleOutStreamWRITE_PIXEL(os, ph->palette[0]);
    return;
  }

  // Try to work out whether to use RLE and/or a palette.  We do this by
  // estimating the number of bytes which will be generated and picking the
  // method which results in the fewest bytes.  Of course this may not result
  // in the fewest bytes after compression...

  useRle = FALSE;
  usePalette = FALSE;

  estimatedBytes = w * h * (BPPOUT/8); // start assuming raw

  plainRleBytes = ((BPPOUT/8)+1) * (runs + singlePixels);

  if (plainRleBytes < estimatedBytes) {
    useRle = TRUE;
    estimatedBytes = plainRleBytes;
  }

  if (ph->size < 128) {
    int paletteRleBytes = (BPPOUT/8) * ph->size + 2 * runs + singlePixels;

    if (paletteRleBytes < estimatedBytes) {
      useRle = TRUE;
      usePalette = TRUE;
      estimatedBytes = paletteRleBytes;
    }

    if (ph->size < 17) {
      int packedBytes = ((BPPOUT/8) * ph->size +
                         w * h * bitsPerPackedPixel[ph->size-1] / 8);

      if (packedBytes < estimatedBytes) {
        useRle = FALSE;
        usePalette = TRUE;
        estimatedBytes = packedBytes;
      }
    }
  }

  if (!usePalette) ph->size = 0;

  zrleOutStreamWriteU8(os, (useRle ? 128 : 0) | ph->size);

  for (i = 0; i < ph->size; i++) {
    zrleOutStreamWRITE_PIXEL(os, ph->palette[i]);
  }

  if (useRle) {

    PIXEL_T* ptr = data;
    PIXEL_T* end = ptr + w * h;
    PIXEL_T* runStart;
    PIXEL_T pix;
    while (ptr < end) {
      int len;
      runStart = ptr;
      pix = *ptr++;
      while (*ptr == pix && ptr < end)
        ptr++;
      len = ptr - runStart;
      if (len <= 2 && usePalette) {
        int index = zrlePaletteHelperLookup(ph, pix);
        if (len == 2)
          zrleOutStreamWriteU8(os, index);
        zrleOutStreamWriteU8(os, index);
        continue;
      }
      if (usePalette) {
        int index = zrlePaletteHelperLookup(ph, pix);
        zrleOutStreamWriteU8(os, index | 128);
      } else {
        zrleOutStreamWRITE_PIXEL(os, pix);
      }
      len -= 1;
      while (len >= 255) {
        zrleOutStreamWriteU8(os, 255);
        len -= 255;
      }
      zrleOutStreamWriteU8(os, len);
    }

  } else {

    // no RLE

    if (usePalette) {
      int bppp;
      PIXEL_T* ptr = data;

      // packed pixels

      assert (ph->size < 17);

      bppp = bitsPerPackedPixel[ph->size-1];

      for (i = 0; i < h; i++) {
        zrle_U8 nbits = 0;
        zrle_U8 byte = 0;

        PIXEL_T* eol = ptr + w;

        while (ptr < eol) {
          PIXEL_T pix = *ptr++;
          zrle_U8 index = zrlePaletteHelperLookup(ph, pix);
          byte = (byte << bppp) | index;
          nbits += bppp;
          if (nbits >= 8) {
            zrleOutStreamWriteU8(os, byte);
            nbits = 0;
          }
        }
        if (nbits > 0) {
          byte <<= 8 - nbits;
          zrleOutStreamWriteU8(os, byte);
        }
      }
    } else {

      // raw

#ifdef CPIXEL
      PIXEL_T *ptr;
      for (ptr = data; ptr < data+w*h; ptr++) {
        zrleOutStreamWRITE_PIXEL(os, *ptr);
      }
#else
      zrleOutStreamWriteBytes(os, (zrle_U8 *)data, w*h*(BPP/8));
#endif
    }
  }
}

#undef PIXEL_T
#undef zrleOutStreamWRITE_PIXEL
#undef ZRLE_ENCODE
#undef ZRLE_ENCODE_TILE
#undef BPPOUT

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