Struct DecodeOptions

impl DecodeOptions

fn new() -> Self

Creates a new decoder builder

fn set_color_output(&mut self, color: ColorOutput)

Configure how color data is decoded.

fn set_memory_limit(&mut self, limit: MemoryLimit)

Configure a memory limit for decoding.

fn check_frame_consistency(&mut self, check: bool)

Configure if frames must be within the screen descriptor.

The default is false.

When turned on, all frame descriptors being read must fit within the screen descriptor or otherwise an error is returned and the stream left in an unspecified state.

When turned off, frames may be arbitrarily larger or offset in relation to the screen. Many other decoder libraries handle this in highly divergent ways. This moves all checks to the caller, for example to emulate a specific style.

fn skip_frame_decoding(&mut self, skip: bool)

Configure whether to skip decoding frames.

The default is false.

When turned on, LZW decoding is skipped. Decoder::read_next_frame will return compressed LZW bytes in frame's data. Decoder::next_frame_info will return the metadata of the next frame as usual. This is useful to count frames without incurring the overhead of decoding.

fn check_lzw_end_code(&mut self, check: bool)

Configure if LZW encoded blocks must end with a marker end code.

The default is false.

When turned on, all image data blocks—which are LZW encoded—must contain a special bit sequence signalling the end of the data. LZW processing terminates when this code is encountered. The specification states that it must be the last code output by the encoder for an image.

When turned off then image data blocks can simply end. Note that this might silently ignore some bits of the last or second to last byte.

fn allow_unknown_blocks(&mut self, check: bool)

Configure if unknown blocks are allowed to be decoded.

The default is false.

When turned on, the decoder will allow unknown blocks to be in the BlockStart position.

When turned off, decoded block starts must mark an Image, Extension, or Trailer block. Otherwise, the decoded image will return an error. If an unknown block error is returned from decoding, enabling this setting may allow for a further state of decoding on the next attempt.

This option also allows unknown extension blocks. The decoder assumes the follow the same block layout, i.e. a sequence of zero-length terminated sub-blocks immediately follow the extension introducer.

fn read_info<R: Read>(self, r: R) -> Result<Decoder<R>, DecodingError>

Reads the logical screen descriptor including the global color palette

Returns a Decoder. All decoder configuration has to be done beforehand.