bool test (int height)
{
bool ok = true;
std::set<int> encoded, decoded;
for (int l = 0; l < height; l++) {
int d = decode_line_number (l, height);
ok &= 0 <= d && d < height;
decoded.insert (d);
int e = encode_line_number (l, height);
ok &= 0 <= e && e < height;
encoded.insert (e);
ok &= (l == encode_line_number(decode_line_number(l, height), height));
ok &= (l == decode_line_number(encode_line_number(l, height), height));
}
ok &= decoded.size() == height;
ok &= encoded.size() == height;
return ok;
}
bool
GIFInput::read_native_scanline (int _y, int z, void *data)
{
if (_y < 0 || _y > m_spec.height)
return false;
bool interlacing = m_spec.get_int_attribute ("gif:Interlacing") != 0;
// decode scanline index if image is interlaced
int gif_y = interlacing ? decode_line_number (_y) : _y;
if (interlacing) { // gif is interlaced so cache the scanlines
int scanlines_cached = m_cached_data.size() / m_spec.width;
if (gif_y >= scanlines_cached) {
// scanline is not cached yet, read the scanline and preceding ones
m_cached_data.resize (m_spec.width * (gif_y + 1));
int delta_size = m_spec.width * (gif_y - scanlines_cached + 1);
if (DGifGetLine (m_gif_file,
&m_cached_data[scanlines_cached * m_spec.width],
delta_size) == GIF_ERROR) {
report_last_error ();
return false;
}
}
translate_scanline (&m_cached_data[gif_y * m_spec.width], data);
} else { // no interlacing, thus no scanlines caching
if (m_next_scanline > gif_y) {
// requested scanline is located before the one to read next
// random access is not supported, so reopen the file, find
// current subimage and skip preceding image data
ImageSpec dummyspec;
if (! close () ||
! open (m_filename, dummyspec) ||
! seek_subimage (m_subimage, 0, dummyspec)) {
return false;
}
int remaining_size = m_spec.width * gif_y;
boost::scoped_array<unsigned char> buffer
(new unsigned char[remaining_size]);
if (DGifGetLine (m_gif_file, buffer.get(), remaining_size)
== GIF_ERROR) {
report_last_error ();
return false;
}
} else if (m_next_scanline < gif_y) {
// requested scanline is located after the one to read next
// skip the lines in between
int delta_size = m_spec.width * (gif_y - m_next_scanline);
boost::scoped_array<unsigned char> buffer
(new unsigned char[delta_size]);
if (DGifGetLine (m_gif_file,
buffer.get(),
delta_size) == GIF_ERROR) {
report_last_error ();
return false;
}
}
// read the requested scanline
boost::scoped_array<unsigned char> fscanline
(new unsigned char[m_spec.width]);
if (DGifGetLine (m_gif_file,
fscanline.get(),
m_spec.width) == GIF_ERROR) {
report_last_error ();
return false;
}
translate_scanline (fscanline.get(), data);
}
m_next_scanline = gif_y + 1;
return true;
}
