unipdf/pdf/contentstream/contentstream.go

/*
 * This file is subject to the terms and conditions defined in
 * file 'LICENSE.md', which is part of this source code package.
 */

// The content stream parser provides functionality to parse the content stream into a list of
// operands that can then be processed further for rendering or extraction of information.
// The contentstream package uses the core and model packages.

package contentstream

import (
	"fmt"

	. "github.com/unidoc/unidoc/pdf/core"
)

type ContentStreamOperation struct {
	Params  []PdfObject
	Operand string
}

// Parses and extracts all text data in content streams and returns as a string.
// Does not take into account Encoding table, the output is simply the character codes.
func (this *ContentStreamParser) ExtractText() (string, error) {
	operations, err := this.Parse()
	if err != nil {
		return "", err
	}
	inText := false
	txt := ""
	for _, op := range operations {
		if op.Operand == "BT" {
			inText = true
		} else if op.Operand == "ET" {
			inText = false
		}
		if op.Operand == "Td" || op.Operand == "TD" || op.Operand == "T*" {
			// Move to next line...
			txt += "\n"
		}
		if inText && op.Operand == "TJ" {
			if len(op.Params) < 1 {
				continue
			}
			paramList, ok := op.Params[0].(*PdfObjectArray)
			if !ok {
				return "", fmt.Errorf("Invalid parameter type, no array (%T)", op.Params[0])
			}
			for _, obj := range *paramList {
				if strObj, ok := obj.(*PdfObjectString); ok {
					txt += string(*strObj)
				}
			}
		} else if inText && op.Operand == "Tj" {
			if len(op.Params) < 1 {
				continue
			}
			param, ok := op.Params[0].(*PdfObjectString)
			if !ok {
				return "", fmt.Errorf("Invalid parameter type, not string (%T)", op.Params[0])
			}
			txt += string(*param)
		}
	}

	return txt, nil
}