jpeg2k 0.5.2

JPEG 2000 image loader.
Documentation 
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use super::*;

/// Magic bytes for JP2 RFC3745.
pub const JP2_RFC3745_MAGIC: &'static [u8] = &[
  0x00, 0x00, 0x00, 0x0c, 0x6a, 0x50, 0x20, 0x20, 0x0d, 0x0a, 0x87, 0x0a
];
/// Magic bytes for J2K Codestream.
pub const J2K_CODESTREAM_MAGIC: &'static [u8] = &[
  0xff, 0x4f, 0xff, 0x51
];

/// Supported Jpeg 2000 formats.
#[derive(Debug, Clone, Copy)]
pub enum J2KFormat {
  JP2,
  J2K,
}

/// Detect Jpeg 2000 format from magic bytes.
pub fn j2k_detect_format(buf: &[u8]) -> Result<J2KFormat> {
  if buf.starts_with(JP2_RFC3745_MAGIC) {
    Ok(J2KFormat::JP2)
  } else if buf.starts_with(J2K_CODESTREAM_MAGIC) {
    Ok(J2KFormat::J2K)
  } else {
    Err(Error::UnknownFormatError("Can't detect image format from bytes".into()))
  }
}

/// Detect Jpeg 2000 format from file extension.
pub fn j2k_detect_format_from_extension(ext: Option<&std::ffi::OsStr>) -> Result<J2KFormat> {
  let lower_ext = ext
    .and_then(|e| e.to_str())
    .map(|e| e.to_ascii_lowercase());
  match lower_ext.as_ref().map(|s| s.as_str()) {
    Some("jp2") => Ok(J2KFormat::JP2),
    Some("j2k") | Some("j2c") | Some("jpc") => Ok(J2KFormat::J2K),
    Some(ext) => Err(Error::UnknownFormatError(format!("Unknown file extension: {}", ext))),
    None => Err(Error::UnknownFormatError("No file extension".into())),
  }
}