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package decoder
import (
"image"
"gitee.com/coodder/unipdf/internal/jbig2/bitmap"
"gitee.com/coodder/unipdf/internal/jbig2/document"
"gitee.com/coodder/unipdf/internal/jbig2/errors"
"gitee.com/coodder/unipdf/internal/jbig2/reader"
)
// Decoder is the structure used to decode JBIG2 encoded byte streams.
type Decoder struct {
inputReader reader.StreamReader
document *document.Document
currentDecodedPage int
parameters Parameters
}
// DecodePage decodes jbig2 encoded page for provided 'pageNumber' in the document.
func (d *Decoder) DecodePage(pageNumber int) ([]byte, error) {
return d.decodePage(pageNumber)
}
// DecodePageImage decodes page with 'pageNumber' from the document and stores it's result
// within go image.Image.
func (d *Decoder) DecodePageImage(pageNumber int) (image.Image, error) {
const processName = "decoder.DecodePageImage"
i, err := d.decodePageImage(pageNumber)
if err != nil {
return nil, errors.Wrap(err, processName, "")
}
return i, nil
}
// DecodeNextPage decodes next jbig2 encoded page and returns decoded byte stream
func (d *Decoder) DecodeNextPage() ([]byte, error) {
d.currentDecodedPage++
pageNumber := d.currentDecodedPage
return d.decodePage(pageNumber)
}
// PageNumber returns
func (d *Decoder) PageNumber() (int, error) {
const processName = "Decoder.PageNumber"
if d.document == nil {
return 0, errors.Error(processName, "decoder not initialized yet")
}
return int(d.document.NumberOfPages), nil
}
func (d *Decoder) decodePage(pageNumber int) ([]byte, error) {
const processName = "decodePage"
if pageNumber < 0 {
return nil, errors.Errorf(processName, "invalid page number: '%d'", pageNumber)
}
if pageNumber > int(d.document.NumberOfPages) {
return nil, errors.Errorf(processName, "page: '%d' not found in the decoder", pageNumber)
}
// get the page from the document.
page, err := d.document.GetPage(pageNumber)
if err != nil {
return nil, errors.Wrap(err, processName, "")
}
// get bitmap from this page.
bm, err := page.GetBitmap()
if err != nil {
return nil, errors.Wrap(err, processName, "")
}
// inverse the color by default.
bm.InverseData()
if !d.parameters.UnpaddedData {
return bm.Data, nil
}
return bm.GetUnpaddedData()
}
func (d *Decoder) decodePageImage(pageNumber int) (image.Image, error) {
const processName = "decodePageImage"
if pageNumber < 0 {
return nil, errors.Errorf(processName, "invalid page number: '%d'", pageNumber)
}
if pageNumber > int(d.document.NumberOfPages) {
return nil, errors.Errorf(processName, "page: '%d' not found in the decoder", pageNumber)
}
// get the page from the document.
page, err := d.document.GetPage(pageNumber)
if err != nil {
return nil, errors.Wrap(err, processName, "")
}
// get bitmap from this page.
bm, err := page.GetBitmap()
if err != nil {
return nil, errors.Wrap(err, processName, "")
}
return bm.ToImage(), nil
}
// Decode prepares decoder for the jbig2 encoded 'input' data,
// with optional 'parameters' and optional Globally encoded
// data segments - 'globals'.
func Decode(input []byte, parameters Parameters, globals *document.Globals) (*Decoder, error) {
r := reader.New(input)
doc, err := document.DecodeDocument(r, globals)
if err != nil {
return nil, err
}
return &Decoder{inputReader: r, document: doc, parameters: parameters}, nil
}
// Parameters are the parameters used by the jbig2 decoder.
type Parameters struct {
UnpaddedData bool
Color bitmap.Color
}
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