Struct IfdEntry 

pub struct IfdEntry {
    pub tag_id: u16,
    pub field_type: Option<FieldType>,
    pub field_type_raw: u16,
    pub count: u64,
    pub value_offset_bytes: Vec<u8>,
    pub is_inline: bool,
}

A single entry in an IFD (Image File Directory).

Each entry describes one piece of metadata about the image. The value may be stored inline (in the value_offset field) or at a separate offset in the file.

Classic TIFF Entry Layout (12 bytes)

Bytes 0-1:  Tag ID (u16)
Bytes 2-3:  Field type (u16)
Bytes 4-7:  Count (u32)
Bytes 8-11: Value or offset (u32)

BigTIFF Entry Layout (20 bytes)

Bytes 0-1:   Tag ID (u16)
Bytes 2-3:   Field type (u16)
Bytes 4-11:  Count (u64)
Bytes 12-19: Value or offset (u64)

Fields

tag_id: u16

The tag ID (may be a known TiffTag or unknown)

field_type: Option<FieldType>

The field type (None if unknown type)

field_type_raw: u16

Raw field type value (for error reporting)

count: u64

Number of values (not bytes!)

value_offset_bytes: Vec<u8>

Raw bytes of the value/offset field. For classic TIFF: 4 bytes, for BigTIFF: 8 bytes. Contains either the actual value (if inline) or an offset to the value.

is_inline: bool

Whether the value is stored inline (true) or at an offset (false)

Implementations

impl IfdEntry

pub fn tag(&self) -> Option<TiffTag>

Get the known TiffTag for this entry, if recognized.

pub fn value_offset(&self, byte_order: ByteOrder) -> u64

Get the offset to the value data (for non-inline values).

Arguments

• byte_order - The byte order to use for reading

Returns

The offset, or 0 if the value is inline (check is_inline first).

pub fn inline_u16(&self, byte_order: ByteOrder) -> Option<u16>

Read inline value as a single u16.

Arguments

• byte_order - The byte order to use for reading

Returns

The value, or None if not inline or count != 1 or wrong type.

pub fn inline_u32(&self, byte_order: ByteOrder) -> Option<u32>

Read inline value as a single u32.

Arguments

• byte_order - The byte order to use for reading

Returns

The value, or None if not inline or count != 1 or wrong type.

pub fn inline_u64(&self, byte_order: ByteOrder) -> Option<u64>

Read inline value as a single u64.

Arguments

• byte_order - The byte order to use for reading

Returns

The value, or None if not inline or count != 1 or wrong type.

pub fn value_byte_size(&self) -> Option<u64>

Calculate total byte size of the value data.

Trait Implementations

impl Clone for IfdEntry

fn clone(&self) -> IfdEntry

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for IfdEntry

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.