static void _ccv_read_png_fd(FILE* in, ccv_dense_matrix_t** x, int type)

{

  png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);

  png_infop info_ptr = png_create_info_struct(png_ptr);

  if (setjmp(png_jmpbuf(png_ptr)))

  {

    png_destroy_read_struct(&png_ptr, &info_ptr, 0);

    return;

  }

  png_init_io(png_ptr, in);

  png_read_info(png_ptr, info_ptr);

  png_uint_32 width, height;

  int bit_depth, color_type;

  png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, 0, 0, 0);

  ccv_dense_matrix_t* im = *x;

  if (im == 0)

    *x = im = ccv_dense_matrix_new((int) height, (int) width, (type) ? 
type18
 : 
CCV_8U | (23
((color_type & PNG_COLOR_MASK_COLOR) == PNG_COLOR_TYPE_GRAY)23
 ? 
CCV_C10
 : 
CCV_C323
), 0, 0);

  png_set_strip_16(png_ptr);

  png_set_strip_alpha(png_ptr);

  if (color_type == PNG_COLOR_TYPE_PALETTE)

    png_set_palette_to_rgb(png_ptr);

  if (color_type == PNG_COLOR_TYPE_GRAY && 
bit_depth < 80
)

    png_set_expand_gray_1_2_4_to_8(png_ptr);

  if (CCV_GET_CHANNEL(im->type) == CCV_C3)

    png_set_gray_to_rgb(png_ptr);

  else if (CCV_GET_CHANNEL(im->type) == CCV_C1)

    png_set_rgb_to_gray(png_ptr, 1, -1, -1);

  png_read_update_info(png_ptr, info_ptr);

  unsigned char** row_vectors = (unsigned char**)alloca(im->rows * sizeof(unsigned char*));

  int i;

  for (i = 0; i < im->rows; 
i++21.4k
)

    row_vectors[i] = im->data.u8 + i * im->step;

  png_read_image(png_ptr, row_vectors);

  png_read_end(png_ptr, 0);

  int ch = CCV_GET_CHANNEL(im->type);

  // empty out the padding

  if (im->cols * ch < im->step)

  {

    size_t extra = im->step - im->cols * ch;

    unsigned char* ptr = im->data.u8 + im->cols * ch;

    for (i = 0; i < im->rows; 
i++, ptr += im->step173
)

      memset(ptr, 0, extra);

  }

  png_destroy_read_struct(&png_ptr, &info_ptr, 0);

}

static int _ccv_write_png_fd(ccv_dense_matrix_t* mat, FILE* fd, void* conf)

{

  png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);

  png_infop info_ptr = png_create_info_struct(png_ptr);

  if (setjmp(png_jmpbuf(png_ptr)))

  {

    png_destroy_write_struct(&png_ptr, &info_ptr);

    return -1;

  }

  png_init_io(png_ptr, fd);

  int compression_level = 0;

  if (conf != 0)

    compression_level = ccv_clamp(*(int*)conf, 0, MAX_MEM_LEVEL);

  if(compression_level > 0)

  {

    png_set_compression_mem_level(png_ptr, compression_level);

  } else {

    // tune parameters for speed

    // (see http://wiki.linuxquestions.org/wiki/Libpng)

    png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, PNG_FILTER_SUB);

    png_set_compression_level(png_ptr, Z_BEST_SPEED);

  }

  png_set_compression_strategy(png_ptr, Z_HUFFMAN_ONLY);

  png_set_IHDR(png_ptr, info_ptr, mat->cols, mat->rows, 
(mat->type & CCV_8U)2
 ? 
83
 : 16, 
(2
CCV_GET_CHANNEL2
(mat->type) == CCV_C1) ? PNG_COLOR_TYPE_GRAY : PNG_COLOR_TYPE_RGB, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);

  unsigned char** row_vectors = (unsigned char**)alloca(mat->rows * sizeof(unsigned char*));

  int i;

  for (i = 0; i < mat->rows; 
i++1.80k
)

    row_vectors[i] = mat->data.u8 + i * mat->step;

  png_write_info(png_ptr, info_ptr);

  png_write_image(png_ptr, row_vectors);

  png_write_end(png_ptr, info_ptr);

  png_destroy_write_struct(&png_ptr, &info_ptr);

  return 0;

}