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PDF data extraction in Kotlin (images, text, paths)

Sample Kotlin code for using PDFTron SDK to extract text, paths, and images from a PDF. The sample also shows how to do color conversion, image normalization, and process changes in the graphics state. Learn more about our PDF Parsing & Content Extraction Library.

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//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2019 by PDFTron Systems Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------

package com.pdftron.android.pdfnetsdksamples.samples

import com.pdftron.android.pdfnetsdksamples.OutputListener
import com.pdftron.android.pdfnetsdksamples.PDFNetSample
import com.pdftron.android.pdfnetsdksamples.R
import com.pdftron.android.pdfnetsdksamples.util.Utils
import com.pdftron.common.PDFNetException
import com.pdftron.filters.FilterReader
import com.pdftron.pdf.*
import java.util.*

class ElementReaderAdvTest : PDFNetSample() {
    init {
        setTitle(R.string.sample_elementreaderadv_title)
        setDescription(R.string.sample_elementreaderadv_description)
    }

    override fun run(outputListener: OutputListener?) {
        super.run(outputListener)
        mOutputListener = outputListener
        mFileList.clear()
        printHeader(outputListener!!)

        // string output_path = "../../TestFiles/Output/";

        try
        // Extract text data from all pages in the document
        {
            mOutputListener!!.println("__________________________________________________")
            mOutputListener!!.println("Extract page element information from all ")
            mOutputListener!!.println("pages in the document.")

            val doc = PDFDoc(Utils.getAssetTempFile(PDFNetSample.INPUT_PATH + "newsletter.pdf")!!.absolutePath)
            doc.initSecurityHandler()

            val pgnum = doc.pageCount
            val page_begin = doc.pageIterator

            val page_reader = ElementReader()

            val itr: PageIterator

            itr = page_begin
            while (itr.hasNext())
            //  Read every page
            {
                val nextPage = itr.next()!!
                mOutputListener!!.println("Page " + nextPage.getIndex() +
                        "----------------------------------------")
                page_reader.begin(nextPage)
                ProcessElements(page_reader)
                page_reader.end()
            }

            //Close the open document to free up document
            //memory sooner than waiting for the
            //garbage collector
            doc.close()
            mOutputListener!!.println("Done")
        } catch (e: Exception) {
            mOutputListener!!.printError(e.stackTrace)
        }

        for (file in mFileList) {
            addToFileList(file)
        }
        printFooter(outputListener)
    }

    companion object {

        private var mOutputListener: OutputListener? = null

        private val mFileList = ArrayList<String>()

        internal var m_buf: String? = null

        @Throws(PDFNetException::class)
        internal fun ProcessPath(reader: ElementReader, path: Element) {
            if (path.isClippingPath) {
                mOutputListener!!.println("This is a clipping path")
            }

            val pathData = path.pathData
            val data = pathData.points
            val opr = pathData.operators

            var x1: Double
            var y1: Double
            var x2: Double
            var y2: Double
            var x3: Double
            var y3: Double
            // Use path.getCTM() if you are interested in CTM (current transformation matrix).

            mOutputListener!!.print(" Path Data Points := \"")
            var data_index = 0
            for (opr_index in opr.indices) {
                when (opr[opr_index]) {
                    PathData.e_moveto.toByte() -> {
                        x1 = data[data_index]
                        ++data_index
                        y1 = data[data_index]
                        ++data_index
                        mOutputListener!!.print("M$x1 $y1")
                    }
                    PathData.e_lineto.toByte() -> {
                        x1 = data[data_index]
                        ++data_index
                        y1 = data[data_index]
                        ++data_index
                        mOutputListener!!.print(" L$x1 $y1")
                    }
                    PathData.e_cubicto.toByte() -> {
                        x1 = data[data_index]
                        ++data_index
                        y1 = data[data_index]
                        ++data_index
                        x2 = data[data_index]
                        ++data_index
                        y2 = data[data_index]
                        ++data_index
                        x3 = data[data_index]
                        ++data_index
                        y3 = data[data_index]
                        ++data_index
                        mOutputListener!!.print(" C$x1 $y1 $x2 $y2 $x3 $y3")
                    }
                    PathData.e_rect.toByte() -> {
                        x1 = data[data_index]
                        ++data_index
                        y1 = data[data_index]
                        ++data_index
                        val w = data[data_index]
                        ++data_index
                        val h = data[data_index]
                        ++data_index
                        x2 = x1 + w
                        y2 = y1
                        x3 = x2
                        y3 = y1 + h
                        mOutputListener!!.print("M$x1 $y1 L$x2 $y2 L$x3 $y3 L$x1 $y3 Z")
                    }
                    PathData.e_closepath.toByte() -> mOutputListener!!.println(" Close Path")
                    else -> throw PDFNetException("Invalid Element Type", 0, "", "", "")
                }
            }

            mOutputListener!!.print("\" ")

            val gs = path.gState

            // Set Path State 0 (stroke, fill, fill-rule) -----------------------------------
            if (path.isStroked) {
                mOutputListener!!.println("Stroke path")

                if (gs.strokeColorSpace.type == ColorSpace.e_pattern) {
                    mOutputListener!!.println("Path has associated pattern")
                } else {
                    // Get stroke color (you can use PDFNet color conversion facilities)
                    var rgb = ColorPt()
                    rgb = gs.strokeColor
                    var v = rgb.get(0)
                    rgb = gs.strokeColorSpace.convert2RGB(rgb)
                    v = rgb.get(0)
                }
            } else {
                // Do not stroke path
            }

            if (path.isFilled) {
                mOutputListener!!.println("Fill path")

                if (gs.fillColorSpace.type == ColorSpace.e_pattern) {
                    mOutputListener!!.println("Path has associated pattern")
                    val pat = gs.fillPattern
                    val type = pat.type
                    if (type == PatternColor.e_shading) {
                        mOutputListener!!.println("Shading")
                        val shading = pat.shading
                        if (shading.type == Shading.e_function_shading) {
                            mOutputListener!!.println("FUNCT")
                        } else if (shading.type == Shading.e_axial_shading) {
                            mOutputListener!!.println("AXIAL")
                        } else if (shading.type == Shading.e_radial_shading) {
                            mOutputListener!!.println("RADIAL")
                        }
                    } else if (type == PatternColor.e_colored_tiling_pattern) {
                        mOutputListener!!.println("e_colored_tiling_pattern")
                    } else if (type == PatternColor.e_uncolored_tiling_pattern) {
                        mOutputListener!!.println("e_uncolored_tiling_pattern")
                    } else {
                        mOutputListener!!.println("?")
                    }
                } else {
                    var rgb = ColorPt()
                    rgb = gs.fillColor
                    var v = rgb.get(0)
                    rgb = gs.fillColorSpace.convert2RGB(rgb)
                    v = rgb.get(0)
                }
            } else {
                // Do not fill path
            }

            // Process any changes in graphics state  ---------------------------------

            val gs_itr = reader.changesIterator
            while (gs_itr.hasNext()) {
                when (gs_itr.next()!!.toInt()) {
                    GState.e_transform -> {
                    }
                    GState.e_line_width -> {
                    }
                    GState.e_line_cap -> {
                    }
                    GState.e_line_join -> {
                    }
                    GState.e_flatness -> {
                    }
                    GState.e_miter_limit -> {
                    }
                    GState.e_dash_pattern -> {
                        //double[] dashes;
                        //dashes=gs.getDashes();
                        //gs.getPhase();
                    }
                    GState.e_fill_color -> {
                        if (gs.fillColorSpace.type == ColorSpace.e_pattern && gs.fillPattern.type != PatternColor.e_shading) {
                            //process the pattern data
                            reader.patternBegin(true)
                            ProcessElements(reader)
                            reader.end()
                        }
                    }
                }// Get transform matrix for this element. Unlike path.GetCTM()
                // that return full transformation matrix gs.GetTransform() return
                // only the transformation matrix that was installed for this element.
                //
                //gs.getTransform();
                //gs.getLineWidth();
                //gs.getLineCap();
                //gs.getLineJoin();
                //gs.getMiterLimit();
            }
            reader.clearChangeList()
        }

        @Throws(PDFNetException::class)
        internal fun ProcessText(page_reader: ElementReader) {
            // Begin text element
            mOutputListener!!.println("Begin Text Block:")

            var element: Element?
            while (true) {
                element = page_reader.next()
                if (element == null) {
                    break
                }
                when (element.type) {
                    Element.e_text_end -> {
                        // Finish the text block
                        mOutputListener!!.println("End Text Block.")
                        return
                    }

                    Element.e_text -> {
                        val gs = element.gState

                        val cs_fill = gs.fillColorSpace
                        val fill = gs.fillColor

                        val out: ColorPt
                        out = cs_fill.convert2RGB(fill)

                        val cs_stroke = gs.strokeColorSpace
                        val stroke = gs.strokeColor

                        val font = gs.font

                        mOutputListener!!.println("Font Name: " + font.name)
                        //font.isFixedWidth();
                        //font.isSerif();
                        //font.isSymbolic();
                        //font.isItalic();
                        // ...

                        //double font_size = gs.getFontSize();
                        //double word_spacing = gs.getWordSpacing();
                        //double char_spacing = gs.getCharSpacing();
                        //String txt = element.getTextString();

                        if (font.type == Font.e_Type3) {
                            //type 3 font, process its data
                            val itr = element.charIterator
                            while (itr.hasNext()) {
                                page_reader.type3FontBegin(itr.next(), null)
                                ProcessElements(page_reader)
                                page_reader.end()
                            }
                        } else {
                            val text_mtx = element.textMatrix
                            var x: Double
                            var y: Double
                            var char_code: Long

                            val itr = element.charIterator
                            while (itr.hasNext()) {
                                val data = itr.next()!!
                                char_code = data.getCharCode()
                                //mOutputListener.print("Character code: ");

                                mOutputListener!!.print(char_code.toString())

                                x = data.getGlyphX()        // character positioning information
                                y = data.getGlyphY()

                                // Use element.getCTM() if you are interested in the CTM
                                // (current transformation matrix).
                                val ctm = element.ctm

                                // To get the exact character positioning information you need to
                                // concatenate current text matrix with CTM and then multiply
                                // relative positioning coordinates with the resulting matrix.
                                //
                                val mtx = ctm.multiply(text_mtx)
                                val t = mtx.multPoint(x, y)
                                x = t.x
                                y = t.y
                                //mOutputListener.println(" Position: x=" + x + " y=" + y );
                            }

                            mOutputListener!!.println()
                        }
                    }
                }
            }
        }

        @Throws(PDFNetException::class)
        internal fun ProcessImage(image: Element) {
            val image_mask = image.isImageMask
            val interpolate = image.isImageInterpolate
            val width = image.imageWidth
            val height = image.imageHeight
            val out_data_sz = width * height * 3

            mOutputListener!!.println("Image: " +
                    " width=\"" + width + "\""
                    + " height=\"" + height)

            // Matrix2D& mtx = image->GetCTM(); // image matrix (page positioning info)

            // You can use GetImageData to read the raw (decoded) image data
            //image->GetBitsPerComponent();
            //image->GetImageData();	// get raw image data
            // .... or use Image2RGB filter that converts every image to RGB format,
            // This should save you time since you don't need to deal with color conversions,
            // image up-sampling, decoding etc.

            val img_conv = Image2RGB(image)    // Extract and convert image to RGB 8-bpc format
            val reader = FilterReader(img_conv)

            // A buffer used to keep image data.
            val buf = ByteArray(out_data_sz)
            val image_data_out = reader.read(buf)
            // &image_data_out.front() contains RGB image data.

            // Note that you don't need to read a whole image at a time. Alternatively
            // you can read a chunk at a time by repeatedly calling reader.Read(buf)
            // until the function returns 0.
        }

        @Throws(PDFNetException::class)
        internal fun ProcessElements(reader: ElementReader) {
            var element: Element?
            // Read page contents
            while (true) {
                element = reader.next()
                if (element == null) {
                    break
                }
                when (element.type) {
                    Element.e_path                        // Process path data...
                    -> {
                        ProcessPath(reader, element)
                    }
                    Element.e_text_begin                // Process text block...
                    -> {
                        ProcessText(reader)
                    }
                    Element.e_form                        // Process form XObjects
                    -> {
                        reader.formBegin()
                        ProcessElements(reader)
                        reader.end()
                    }
                    Element.e_image                        // Process Images
                    -> {
                        ProcessImage(element)
                    }
                }
            }
        }
    }

}
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