Trait ScanlineDecoder 

pub trait ScanlineDecoder {
    // Required methods
    fn width(&self) -> u32;
    fn height(&self) -> u32;
    fn comps_count(&self) -> u8;
    fn bpc(&self) -> u8;
    fn row_stride(&self) -> usize;
    fn decode_scanline(&mut self) -> Result<Option<&[u8]>, DecodeError>;
    fn reset(&mut self) -> Result<(), DecodeError>;
    fn current_line(&self) -> Option<usize>;

    // Provided methods
    fn get_width(&self) -> u32 { ... }
    fn get_height(&self) -> u32 { ... }
    fn count_comps(&self) -> u8 { ... }
    fn get_bpc(&self) -> u8 { ... }
    fn skip_to_scanline(&mut self, target: usize) { ... }
    fn src_offset(&self) -> Option<usize> { ... }
    fn get_src_offset(&self) -> Option<usize> { ... }
}

A scanline-based image decoder that yields one row of pixels at a time.

After construction, call decode_scanline repeatedly to get each row. Returns Ok(None) after the last row. Call reset to restart from the first row.

Mirrors PDFium’s ScanlineDecoder base class interface, including the image-geometry accessors GetWidth(), GetHeight(), CountComps(), and GetBPC().

Required Methods

fn width(&self) -> u32

Image width in pixels. Mirrors PDFium’s GetWidth().

fn height(&self) -> u32

Image height in pixels. Mirrors PDFium’s GetHeight().

fn comps_count(&self) -> u8

Number of color components per pixel (e.g. 1 for gray, 3 for RGB, 4 for CMYK). Mirrors PDFium’s CountComps().

fn bpc(&self) -> u8

Bits per color component (e.g. 1, 8, 16). Mirrors PDFium’s GetBPC().

fn row_stride(&self) -> usize

Number of bytes per row: (width * comps_count * bpc + 7) / 8.

fn decode_scanline(&mut self) -> Result<Option<&[u8]>, DecodeError>

Decode and return the next scanline.

Returns Ok(Some(data)) for each row, Ok(None) when all rows are done.

fn reset(&mut self) -> Result<(), DecodeError>

Reset the decoder to the first scanline.

fn current_line(&self) -> Option<usize>

Current line index (0-based), or None if no lines have been read yet.

Provided Methods

fn get_width(&self) -> u32

Upstream alias for width(). Mirrors PDFium’s GetWidth().

fn get_height(&self) -> u32

Upstream alias for height(). Mirrors PDFium’s GetHeight().

fn count_comps(&self) -> u8

Upstream alias for comps_count(). Mirrors PDFium’s CountComps().

fn get_bpc(&self) -> u8

Upstream alias for bpc(). Mirrors PDFium’s GetBPC().

fn skip_to_scanline(&mut self, target: usize)

Skip ahead to scanline target by decoding and discarding intermediate lines.

After this call, current_line() will be >= Some(target) if the decoder has at least target + 1 scanlines available.

The upstream SkipToScanline() accepted a PauseIndicatorIface pause parameter; rpdfium omits pause/resume since the library is synchronous.

fn src_offset(&self) -> Option<usize>

Returns the byte offset of the current source position in the compressed stream, if available.

Upstream GetSrcOffset() is used for progressive decode bookkeeping not needed in rpdfium’s synchronous model.

fn get_src_offset(&self) -> Option<usize>

Upstream alias for src_offset(). Mirrors PDFium’s GetSrcOffset().

Implementors

impl ScanlineDecoder for RunLengthScanlineDecoder

impl ScanlineDecoder for DctScanlineDecoder

impl ScanlineDecoder for FlateScanlineDecoder