//-----------------------------------------------------------------//
bool jpeg_io::probe(utils::file_io& fin)
{
unsigned char sig[2];
long pos = fin.tell();
size_t l = fin.read(sig, 1, 2);
fin.seek(pos, utils::file_io::seek::set);
if(l == 2) {
if(sig[0] == 0xff && sig[1] == 0xd8) {
return true;
}
}
return false;
}
//-----------------------------------------------------------------//
bool jpeg_io::info(utils::file_io& fin, img::img_info& fo)
{
if(!probe(fin)) {
return false;
}
struct jpeg_decompress_struct cinfo;
struct jpeg_error_mgr errmgr;
long pos = fin.tell();
// エラーのハンドリング
cinfo.err = jpeg_std_error(&errmgr);
errmgr.error_exit = error_exit_task;
// 構造体の初期設定
jpeg_create_decompress(&cinfo);
// file_io クラス設定
fio_jpeg_file_io_src(&cinfo, &fin);
// ファイルの情報ヘッダの読込み
error_code_ = 0;
jpeg_read_header(&cinfo, TRUE);
fin.seek(pos, utils::file_io::seek::set);
if(error_code_) {
/// std::endl << "JPEG decode error: 'header'(" << static_cast<int>(error_code_) << ")" << std::endl;
jpeg_destroy_decompress(&cinfo);
return false;
}
fo.width = cinfo.output_width;
fo.height = cinfo.output_height;
fo.mipmap_level = 0;
fo.multi_level = 0;
fo.i_depth = 0;
if(cinfo.output_components == 4) {
fo.r_depth = 8;
fo.g_depth = 8;
fo.b_depth = 8;
fo.a_depth = 8;
fo.grayscale = false;
} else if(cinfo.output_components == 3) {
fo.r_depth = 8;
fo.g_depth = 8;
fo.b_depth = 8;
fo.a_depth = 0;
fo.grayscale = false;
} else if(cinfo.output_components == 2) {
fo.r_depth = 8;
fo.g_depth = 8;
fo.b_depth = 8;
fo.a_depth = 8;
fo.grayscale = true;
} else if(cinfo.output_components == 1) {
fo.r_depth = 8;
fo.g_depth = 8;
fo.b_depth = 8;
fo.a_depth = 0;
fo.grayscale = true;
} else {
fo.r_depth = 0;
fo.g_depth = 0;
fo.b_depth = 0;
fo.a_depth = 0;
fo.grayscale = false;
return false;
}
return true;
}