/*
 * Image Scaling Functions
 * Copyright (c) 2005 David A. Schleef <ds@schleef.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <glib.h>
#include <string.h>

#include "vs_scanline.h"
#include "vs_image.h"

#define ROUND_UP_2(x)  (((x)+1)&~1)
#define ROUND_UP_4(x)  (((x)+3)&~3)
#define ROUND_UP_8(x)  (((x)+7)&~7)

void
vs_image_scale_nearest_RGBA (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  int i;
  int j;
  int x;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  acc = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    xacc = 0;
    vs_scanline_resample_nearest_RGBA (dest->pixels + i * dest->stride,
        src->pixels + j * src->stride, dest->width, &xacc, x_increment);

    acc += y_increment;
  }
}

void
vs_image_scale_linear_RGBA (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  guint8 *tmp1;
  guint8 *tmp2;
  int y1;
  int y2;
  int i;
  int j;
  int x;
  int dest_size;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  dest_size = dest->width * 4;

  tmp1 = tmpbuf;
  tmp2 = tmpbuf + dest_size;

  acc = 0;
  xacc = 0;
  y2 = -1;
  vs_scanline_resample_linear_RGBA (tmp1, src->pixels, dest->width, &xacc,
      x_increment);
  y1 = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    if (x == 0) {
      if (j == y1) {
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      } else if (j == y2) {
        memcpy (dest->pixels + i * dest->stride, tmp2, dest_size);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_RGBA (tmp1, src->pixels + j * src->stride,
            dest->width, &xacc, x_increment);
        y1 = j;
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      }
    } else {
      if (j == y1) {
        if (j + 1 != y2) {
          xacc = 0;
          vs_scanline_resample_linear_RGBA (tmp2,
              src->pixels + (j + 1) * src->stride, dest->width, &xacc,
              x_increment);
          y2 = j + 1;
        }
        vs_scanline_merge_linear_RGBA (dest->pixels + i * dest->stride,
            tmp1, tmp2, dest->width, x);
      } else if (j == y2) {
        if (j + 1 != y1) {
          xacc = 0;
          vs_scanline_resample_linear_RGBA (tmp1,
              src->pixels + (j + 1) * src->stride, dest->width, &xacc,
              x_increment);
          y1 = j + 1;
        }
        vs_scanline_merge_linear_RGBA (dest->pixels + i * dest->stride,
            tmp2, tmp1, dest->width, x);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_RGBA (tmp1, src->pixels + j * src->stride,
            dest->width, &xacc, x_increment);
        y1 = j;
        xacc = 0;
        vs_scanline_resample_linear_RGBA (tmp2,
            src->pixels + (j + 1) * src->stride, dest->width, &xacc,
            x_increment);
        y2 = (j + 1);
        vs_scanline_merge_linear_RGBA (dest->pixels + i * dest->stride,
            tmp1, tmp2, dest->width, x);
      }
    }

    acc += y_increment;
  }
}


void
vs_image_scale_nearest_RGB (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  int i;
  int j;
  int x;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  acc = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    xacc = 0;
    vs_scanline_resample_nearest_RGB (dest->pixels + i * dest->stride,
        src->pixels + j * src->stride, dest->width, &xacc, x_increment);

    acc += y_increment;
  }
}

void
vs_image_scale_linear_RGB (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  guint8 *tmp1;
  guint8 *tmp2;
  int y1;
  int y2;
  int i;
  int j;
  int x;
  int dest_size;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  dest_size = dest->width * 3;

  tmp1 = tmpbuf;
  tmp2 = tmpbuf + dest_size;

  acc = 0;
  xacc = 0;
  y2 = -1;
  vs_scanline_resample_linear_RGB (tmp1, src->pixels, dest->width, &xacc,
      x_increment);
  y1 = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    if (x == 0) {
      if (j == y1) {
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      } else if (j == y2) {
        memcpy (dest->pixels + i * dest->stride, tmp2, dest_size);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_RGB (tmp1, src->pixels + j * src->stride,
            dest->width, &xacc, x_increment);
        y1 = j;
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      }
    } else {
      if (j == y1) {
        if (j + 1 != y2) {
          xacc = 0;
          vs_scanline_resample_linear_RGB (tmp2,
              src->pixels + (j + 1) * src->stride, dest->width, &xacc,
              x_increment);
          y2 = j + 1;
        }
        vs_scanline_merge_linear_RGB (dest->pixels + i * dest->stride,
            tmp1, tmp2, dest->width, x);
      } else if (j == y2) {
        if (j + 1 != y1) {
          xacc = 0;
          vs_scanline_resample_linear_RGB (tmp1,
              src->pixels + (j + 1) * src->stride, dest->width, &xacc,
              x_increment);
          y1 = j + 1;
        }
        vs_scanline_merge_linear_RGB (dest->pixels + i * dest->stride,
            tmp2, tmp1, dest->width, x);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_RGB (tmp1, src->pixels + j * src->stride,
            dest->width, &xacc, x_increment);
        y1 = j;
        xacc = 0;
        vs_scanline_resample_linear_RGB (tmp2,
            src->pixels + (j + 1) * src->stride, dest->width, &xacc,
            x_increment);
        y2 = (j + 1);
        vs_scanline_merge_linear_RGB (dest->pixels + i * dest->stride,
            tmp1, tmp2, dest->width, x);
      }
    }

    acc += y_increment;
  }
}

/* YUYV */

void
vs_image_scale_nearest_YUYV (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  int i;
  int j;
  int x;
  int xacc;
  int n_quads;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  n_quads = ROUND_UP_2 (dest->width) / 2;
  acc = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    xacc = 0;
    vs_scanline_resample_nearest_YUYV (dest->pixels + i * dest->stride,
        src->pixels + j * src->stride, n_quads, &xacc, x_increment);

    acc += y_increment;
  }
}

void
vs_image_scale_linear_YUYV (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  guint8 *tmp1;
  guint8 *tmp2;
  int y1;
  int y2;
  int i;
  int j;
  int x;
  int dest_size;
  int n_quads;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  dest_size = ROUND_UP_4 (dest->width * 2);
  n_quads = ROUND_UP_2 (dest->width) / 2;

  tmp1 = tmpbuf;
  tmp2 = tmpbuf + dest_size;

  acc = 0;
  xacc = 0;
  y2 = -1;
  vs_scanline_resample_linear_YUYV (tmp1, src->pixels, n_quads, &xacc,
      x_increment);
  y1 = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    if (x == 0) {
      if (j == y1) {
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      } else if (j == y2) {
        memcpy (dest->pixels + i * dest->stride, tmp2, dest_size);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_YUYV (tmp1, src->pixels + j * src->stride,
            n_quads, &xacc, x_increment);
        y1 = j;
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      }
    } else {
      if (j == y1) {
        if (j + 1 != y2) {
          xacc = 0;
          vs_scanline_resample_linear_YUYV (tmp2,
              src->pixels + (j + 1) * src->stride, n_quads, &xacc, x_increment);
          y2 = j + 1;
        }
        vs_scanline_merge_linear_YUYV (dest->pixels + i * dest->stride,
            tmp1, tmp2, n_quads, x);
      } else if (j == y2) {
        if (j + 1 != y1) {
          xacc = 0;
          vs_scanline_resample_linear_YUYV (tmp1,
              src->pixels + (j + 1) * src->stride, n_quads, &xacc, x_increment);
          y1 = j + 1;
        }
        vs_scanline_merge_linear_YUYV (dest->pixels + i * dest->stride,
            tmp2, tmp1, n_quads, x);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_YUYV (tmp1, src->pixels + j * src->stride,
            n_quads, &xacc, x_increment);
        y1 = j;
        xacc = 0;
        vs_scanline_resample_linear_YUYV (tmp2,
            src->pixels + (j + 1) * src->stride, n_quads, &xacc, x_increment);
        y2 = (j + 1);
        vs_scanline_merge_linear_YUYV (dest->pixels + i * dest->stride,
            tmp1, tmp2, n_quads, x);
      }
    }

    acc += y_increment;
  }
}

/* UYVY */

void
vs_image_scale_nearest_UYVY (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  int i;
  int j;
  int x;
  int xacc;
  int n_quads;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  n_quads = (dest->width + 1) / 2;
  acc = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    xacc = 0;
    vs_scanline_resample_nearest_UYVY (dest->pixels + i * dest->stride,
        src->pixels + j * src->stride, n_quads, &xacc, x_increment);

    acc += y_increment;
  }
}

void
vs_image_scale_linear_UYVY (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  guint8 *tmp1;
  guint8 *tmp2;
  int y1;
  int y2;
  int i;
  int j;
  int x;
  int dest_size;
  int n_quads;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  dest_size = ROUND_UP_4 (dest->width * 2);
  n_quads = ROUND_UP_2 (dest->width) / 2;

  tmp1 = tmpbuf;
  tmp2 = tmpbuf + dest_size;

  acc = 0;
  xacc = 0;
  y2 = -1;
  vs_scanline_resample_linear_UYVY (tmp1, src->pixels, n_quads, &xacc,
      x_increment);
  y1 = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    if (x == 0) {
      if (j == y1) {
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      } else if (j == y2) {
        memcpy (dest->pixels + i * dest->stride, tmp2, dest_size);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_UYVY (tmp1, src->pixels + j * src->stride,
            n_quads, &xacc, x_increment);
        y1 = j;
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      }
    } else {
      if (j == y1) {
        if (j + 1 != y2) {
          xacc = 0;
          vs_scanline_resample_linear_UYVY (tmp2,
              src->pixels + (j + 1) * src->stride, n_quads, &xacc, x_increment);
          y2 = j + 1;
        }
        vs_scanline_merge_linear_UYVY (dest->pixels + i * dest->stride,
            tmp1, tmp2, n_quads, x);
      } else if (j == y2) {
        if (j + 1 != y1) {
          xacc = 0;
          vs_scanline_resample_linear_UYVY (tmp1,
              src->pixels + (j + 1) * src->stride, n_quads, &xacc, x_increment);
          y1 = j + 1;
        }
        vs_scanline_merge_linear_UYVY (dest->pixels + i * dest->stride,
            tmp2, tmp1, n_quads, x);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_UYVY (tmp1, src->pixels + j * src->stride,
            n_quads, &xacc, x_increment);
        y1 = j;
        xacc = 0;
        vs_scanline_resample_linear_UYVY (tmp2,
            src->pixels + (j + 1) * src->stride, n_quads, &xacc, x_increment);
        y2 = (j + 1);
        vs_scanline_merge_linear_UYVY (dest->pixels + i * dest->stride,
            tmp1, tmp2, n_quads, x);
      }
    }

    acc += y_increment;
  }
}

/* greyscale */

void
vs_image_scale_nearest_Y (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  int i;
  int j;
  int x;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  acc = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    xacc = 0;
    vs_scanline_resample_nearest_Y (dest->pixels + i * dest->stride,
        src->pixels + j * src->stride, dest->width, &xacc, x_increment);

    acc += y_increment;
  }
}

void
vs_image_scale_linear_Y (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  guint8 *tmp1;
  guint8 *tmp2;
  int y1;
  int y2;
  int i;
  int j;
  int x;
  int dest_size;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  dest_size = dest->width;

  tmp1 = tmpbuf;
  tmp2 = tmpbuf + dest_size;

  acc = 0;
  xacc = 0;
  y2 = -1;
  vs_scanline_resample_linear_Y (tmp1, src->pixels, dest->width, &xacc,
      x_increment);
  y1 = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    if (x == 0) {
      if (j == y1) {
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      } else if (j == y2) {
        memcpy (dest->pixels + i * dest->stride, tmp2, dest_size);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_Y (tmp1, src->pixels + j * src->stride,
            dest->width, &xacc, x_increment);
        y1 = j;
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      }
    } else {
      if (j == y1) {
        if (j + 1 != y2) {
          xacc = 0;
          vs_scanline_resample_linear_Y (tmp2,
              src->pixels + (j + 1) * src->stride, dest->width, &xacc,
              x_increment);
          y2 = j + 1;
        }
        vs_scanline_merge_linear_Y (dest->pixels + i * dest->stride,
            tmp1, tmp2, dest->width, x);
      } else if (j == y2) {
        if (j + 1 != y1) {
          xacc = 0;
          vs_scanline_resample_linear_Y (tmp1,
              src->pixels + (j + 1) * src->stride, dest->width, &xacc,
              x_increment);
          y1 = j + 1;
        }
        vs_scanline_merge_linear_Y (dest->pixels + i * dest->stride,
            tmp2, tmp1, dest->width, x);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_Y (tmp1, src->pixels + j * src->stride,
            dest->width, &xacc, x_increment);
        y1 = j;
        xacc = 0;
        vs_scanline_resample_linear_Y (tmp2,
            src->pixels + (j + 1) * src->stride, dest->width, &xacc,
            x_increment);
        y2 = (j + 1);
        vs_scanline_merge_linear_Y (dest->pixels + i * dest->stride,
            tmp1, tmp2, dest->width, x);
      }
    }

    acc += y_increment;
  }
}

/* RGB565 */

void
vs_image_scale_nearest_RGB565 (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  int i;
  int j;
  int x;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  acc = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    xacc = 0;
    vs_scanline_resample_nearest_RGB565 (dest->pixels + i * dest->stride,
        src->pixels + j * src->stride, dest->width, &xacc, x_increment);

    acc += y_increment;
  }
}

void
vs_image_scale_linear_RGB565 (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  guint8 *tmp1;
  guint8 *tmp2;
  int y1;
  int y2;
  int i;
  int j;
  int x;
  int dest_size;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  dest_size = dest->width * 2;

  tmp1 = tmpbuf;
  tmp2 = tmpbuf + dest_size;

  acc = 0;
  xacc = 0;
  y2 = -1;
  vs_scanline_resample_linear_RGB565 (tmp1, src->pixels, dest->width, &xacc,
      x_increment);
  y1 = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    if (x == 0) {
      if (j == y1) {
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      } else if (j == y2) {
        memcpy (dest->pixels + i * dest->stride, tmp2, dest_size);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_RGB565 (tmp1, src->pixels + j * src->stride,
            dest->width, &xacc, x_increment);
        y1 = j;
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      }
    } else {
      if (j == y1) {
        if (j + 1 != y2) {
          xacc = 0;
          vs_scanline_resample_linear_RGB565 (tmp2,
              src->pixels + (j + 1) * src->stride, dest->width, &xacc,
              x_increment);
          y2 = j + 1;
        }
        vs_scanline_merge_linear_RGB565 (dest->pixels + i * dest->stride,
            tmp1, tmp2, dest->width, x);
      } else if (j == y2) {
        if (j + 1 != y1) {
          xacc = 0;
          vs_scanline_resample_linear_RGB565 (tmp1,
              src->pixels + (j + 1) * src->stride, dest->width, &xacc,
              x_increment);
          y1 = j + 1;
        }
        vs_scanline_merge_linear_RGB565 (dest->pixels + i * dest->stride,
            tmp2, tmp1, dest->width, x);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_RGB565 (tmp1, src->pixels + j * src->stride,
            dest->width, &xacc, x_increment);
        y1 = j;
        xacc = 0;
        vs_scanline_resample_linear_RGB565 (tmp2,
            src->pixels + (j + 1) * src->stride, dest->width, &xacc,
            x_increment);
        y2 = (j + 1);
        vs_scanline_merge_linear_RGB565 (dest->pixels + i * dest->stride,
            tmp1, tmp2, dest->width, x);
      }
    }

    acc += y_increment;
  }
}

/* RGB555 */

void
vs_image_scale_nearest_RGB555 (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  int i;
  int j;
  int x;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  acc = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    xacc = 0;
    vs_scanline_resample_nearest_RGB555 (dest->pixels + i * dest->stride,
        src->pixels + j * src->stride, dest->width, &xacc, x_increment);

    acc += y_increment;
  }
}

void
vs_image_scale_linear_RGB555 (const VSImage * dest, const VSImage * src,
    guint8 * tmpbuf)
{
  int acc;
  int y_increment;
  int x_increment;
  guint8 *tmp1;
  guint8 *tmp2;
  int y1;
  int y2;
  int i;
  int j;
  int x;
  int dest_size;
  int xacc;

  y_increment = ((src->height - 1) << 16) / (dest->height - 1);
  x_increment = ((src->width - 1) << 16) / (dest->width - 1);

  dest_size = dest->width * 2;

  tmp1 = tmpbuf;
  tmp2 = tmpbuf + dest_size;

  acc = 0;
  xacc = 0;
  y2 = -1;
  vs_scanline_resample_linear_RGB555 (tmp1, src->pixels, dest->width, &xacc,
      x_increment);
  y1 = 0;
  for (i = 0; i < dest->height; i++) {
    j = acc >> 16;
    x = acc & 0xffff;

    if (x == 0) {
      if (j == y1) {
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      } else if (j == y2) {
        memcpy (dest->pixels + i * dest->stride, tmp2, dest_size);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_RGB555 (tmp1, src->pixels + j * src->stride,
            dest->width, &xacc, x_increment);
        y1 = j;
        memcpy (dest->pixels + i * dest->stride, tmp1, dest_size);
      }
    } else {
      if (j == y1) {
        if (j + 1 != y2) {
          xacc = 0;
          vs_scanline_resample_linear_RGB555 (tmp2,
              src->pixels + (j + 1) * src->stride, dest->width, &xacc,
              x_increment);
          y2 = j + 1;
        }
        vs_scanline_merge_linear_RGB555 (dest->pixels + i * dest->stride,
            tmp1, tmp2, dest->width, x);
      } else if (j == y2) {
        if (j + 1 != y1) {
          xacc = 0;
          vs_scanline_resample_linear_RGB555 (tmp1,
              src->pixels + (j + 1) * src->stride, dest->width, &xacc,
              x_increment);
          y1 = j + 1;
        }
        vs_scanline_merge_linear_RGB555 (dest->pixels + i * dest->stride,
            tmp2, tmp1, dest->width, x);
      } else {
        xacc = 0;
        vs_scanline_resample_linear_RGB555 (tmp1, src->pixels + j * src->stride,
            dest->width, &xacc, x_increment);
        y1 = j;
        xacc = 0;
        vs_scanline_resample_linear_RGB555 (tmp2,
            src->pixels + (j + 1) * src->stride, dest->width, &xacc,
            x_increment);
        y2 = (j + 1);
        vs_scanline_merge_linear_RGB555 (dest->pixels + i * dest->stride,
            tmp1, tmp2, dest->width, x);
      }
    }

    acc += y_increment;
  }
}