Identifying the text based on the output in PDF using PDFBOX

Question

Iam using the PDF BOX for getting color information of the text in PDF. I could able to get the output by using the following code. But my doubt is what StrokingColor repres

Answer 1

According to the clarifications in comments the OP wants to

compare the font colors of one pdf page to another pdf page [...] if there is a text "Sample" in black color and some other text "sample1" in grey color....i need to know that sample--> black color, sample1-->grey color like this..i want the full text and its color

PDFBox has a text extraction engine, the PDFTextStripper. There are some challenges in using it for the task at hand, though, among them:

• Originally it is not designed for extracting color information alongside the text; the TextPosition objects it uses don't even have any attribute for color. Thus, we will have to extend it somewhat.

  • We will first register listeners for color operations to keep track of colors at all.

  • We will furthermore store the color information for a TextPosition object in another structure (I would prefer to extend text position accordingly but due to several inaccessible private members that would have meant quite some hassle).

  • This has already been shown in details in this answer; for the backgrounds, look there.

• PDF allows many ways of drawing text. The letters may be filled with one color and its border may be stroked with another. Their border may even serve as clipping path for following drawing operations. We will only consider filling and stroking colors.

• Text drawn may later on be covered by other drawings, either completely hiding it or changing its apparent color. We will ignore this for now.

For PDFBox 1.8.x

As indicated, we extend the PDFTextStripper like this:

import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.pdfbox.util.PDFTextStripper;
import org.apache.pdfbox.util.TextPosition;

public class ColorTextStripper extends PDFTextStripper
{
    public ColorTextStripper() throws IOException
    {
        super();
        setSuppressDuplicateOverlappingText(false);

        registerOperatorProcessor("CS", new org.apache.pdfbox.util.operator.SetStrokingColorSpace());
        registerOperatorProcessor("cs", new org.apache.pdfbox.util.operator.SetNonStrokingColorSpace());
        registerOperatorProcessor("SC", new org.apache.pdfbox.util.operator.SetStrokingColor());
        registerOperatorProcessor("sc", new org.apache.pdfbox.util.operator.SetNonStrokingColor());
        registerOperatorProcessor("SCN", new org.apache.pdfbox.util.operator.SetStrokingColor());
        registerOperatorProcessor("scn", new org.apache.pdfbox.util.operator.SetNonStrokingColor());
        registerOperatorProcessor("G", new org.apache.pdfbox.util.operator.SetStrokingGrayColor());
        registerOperatorProcessor("g", new org.apache.pdfbox.util.operator.SetNonStrokingGrayColor());
        registerOperatorProcessor("RG", new org.apache.pdfbox.util.operator.SetStrokingRGBColor());
        registerOperatorProcessor("rg", new org.apache.pdfbox.util.operator.SetNonStrokingRGBColor());
        registerOperatorProcessor("K", new org.apache.pdfbox.util.operator.SetStrokingCMYKColor());
        registerOperatorProcessor("k", new org.apache.pdfbox.util.operator.SetNonStrokingCMYKColor());
    }

    @Override
    protected void processTextPosition(TextPosition text)
    {
        renderingMode.put(text, getGraphicsState().getTextState().getRenderingMode());
        strokingColor.put(text, getGraphicsState().getStrokingColor().getColorSpaceValue());
        nonStrokingColor.put(text, getGraphicsState().getNonStrokingColor().getColorSpaceValue());

        super.processTextPosition(text);
    }

    Map<TextPosition, Integer> renderingMode = new HashMap<TextPosition, Integer>();
    Map<TextPosition, float[]> strokingColor = new HashMap<TextPosition, float[]>();
    Map<TextPosition, float[]> nonStrokingColor = new HashMap<TextPosition, float[]>();

    final static List<Integer> FILLING_MODES = Arrays.asList(0, 2, 4, 6);
    final static List<Integer> STROKING_MODES = Arrays.asList(1, 2, 5, 6);
    final static List<Integer> CLIPPING_MODES = Arrays.asList(4, 5, 6, 7);

    @Override
    protected void writeString(String text, List<TextPosition> textPositions) throws IOException
    {
        for (TextPosition textPosition: textPositions)
        {
            Integer charRenderingMode = renderingMode.get(textPosition);
            float[] charStrokingColor = strokingColor.get(textPosition);
            float[] charNonStrokingColor = nonStrokingColor.get(textPosition);

            StringBuilder textBuilder = new StringBuilder();
            textBuilder.append(textPosition.getCharacter())
                       .append("{");

            if (FILLING_MODES.contains(charRenderingMode))
            {
                textBuilder.append("FILL:")
                           .append(toString(charNonStrokingColor))
                           .append(';');
            }

            if (STROKING_MODES.contains(charRenderingMode))
            {
                textBuilder.append("STROKE:")
                           .append(toString(charStrokingColor))
                           .append(';');
            }

            if (CLIPPING_MODES.contains(charRenderingMode))
            {
                textBuilder.append("CLIP;");
            }

            textBuilder.append("}");
            writeString(textBuilder.toString());
        }
    }

    String toString(float[] values)
    {
        if (values == null)
            return "null";
        StringBuilder builder = new StringBuilder();
        switch(values.length)
        {
        case 1:
            builder.append("GRAY"); break;
        case 3:
            builder.append("RGB"); break;
        case 4:
            builder.append("CMYK"); break;
        default:
            builder.append("UNKNOWN");
        }
        for (float f: values)
        {
            builder.append(' ')
                   .append(f);
        }

        return builder.toString();
    }
}

You can call it like this:

PDFTextStripper stripper = new ColorTextStripper();

PDDocument document = PDDocument.load(SOURCE_FILE);

String text = stripper.getText(document);

The resulting text contains something like this:

P{FILL:RGB 0.803 0.076 0.086;}e{FILL:RGB 0.803 0.076 0.086;}l{FILL:RGB 0.803 0.076 0.086;}l{FILL:RGB 0.803 0.076 0.086;}e{FILL:RGB 0.803 0.076 0.086;}

and

G{FILL:RGB 0.102 0.101 0.095;}r{FILL:RGB 0.102 0.101 0.095;}a{FILL:RGB 0.102 0.101 0.095;}z{FILL:RGB 0.102 0.101 0.095;}i{FILL:RGB 0.102 0.101 0.095;}e{FILL:RGB 0.102 0.101 0.095;}

for the Pelle and Grazie from this

or

K{FILL:RGB 0.0 0.322 0.573;}E{FILL:RGB 0.0 0.322 0.573;}Y{FILL:RGB 0.0 0.322 0.573;}

and

C{FILL:GRAY 0.0;}o{FILL:GRAY 0.0;}m{FILL:GRAY 0.0;}b{FILL:GRAY 0.0;}i{FILL:GRAY 0.0;}n{FILL:GRAY 0.0;}e{FILL:GRAY 0.0;}d{FILL:GRAY 0.0;}

for KEY and Combined from this:

Instead of serializing all the information into a String result, you can of course also create some class containing both the color and the character information in a structured way. Just like now the String result is created in writeString, you can change this method to add instances of such a class to some list in it.

Requirements

At least PDFBox version 1.8.4 is required to make this work. I tested it using 2.0.0-SNAPSHOT but 1.8.4 should suffice. 1.8.3, on the other hand, has a bug which sometimes forwards the wrong TextPosition objects to writeString, cf. PDFBOX-1804, and earlier versions don't provide a TextPosition collection to writeString at all.

For PDFBox 2.x

There were multiple refactorings and other changes in PDFBox 2.x which also concern the code above.

Ported to PDFBox 2.x it may look like this:

public class ColorTextStripper extends PDFTextStripper {
    public ColorTextStripper() throws IOException {
        super();
        setSuppressDuplicateOverlappingText(false);

        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetStrokingColorSpace());
        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetNonStrokingColorSpace());
        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetStrokingColor());
        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetNonStrokingColor());
        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetStrokingColorN());
        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetNonStrokingColorN());
        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetStrokingDeviceGrayColor());
        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetNonStrokingDeviceGrayColor());
        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetStrokingDeviceRGBColor());
        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetNonStrokingDeviceRGBColor());
        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetStrokingDeviceCMYKColor());
        addOperator(new org.apache.pdfbox.contentstream.operator.color.SetNonStrokingDeviceCMYKColor());
    }

    @Override
    protected void processTextPosition(TextPosition text) {
        renderingMode.put(text, getGraphicsState().getTextState().getRenderingMode());
        strokingColor.put(text, getGraphicsState().getStrokingColor().getComponents());
        nonStrokingColor.put(text, getGraphicsState().getNonStrokingColor().getComponents());

        super.processTextPosition(text);
    }

    Map<TextPosition, RenderingMode> renderingMode = new HashMap<TextPosition, RenderingMode>();
    Map<TextPosition, float[]> strokingColor = new HashMap<TextPosition, float[]>();
    Map<TextPosition, float[]> nonStrokingColor = new HashMap<TextPosition, float[]>();

    final static List<RenderingMode> FILLING_MODES = Arrays.asList(RenderingMode.FILL, RenderingMode.FILL_STROKE, RenderingMode.FILL_CLIP, RenderingMode.FILL_STROKE_CLIP);
    final static List<RenderingMode> STROKING_MODES = Arrays.asList(RenderingMode.STROKE, RenderingMode.FILL_STROKE, RenderingMode.STROKE_CLIP, RenderingMode.FILL_STROKE_CLIP);
    final static List<RenderingMode> CLIPPING_MODES = Arrays.asList(RenderingMode.FILL_CLIP, RenderingMode.STROKE_CLIP, RenderingMode.FILL_STROKE_CLIP, RenderingMode.NEITHER_CLIP);

    @Override
    protected void writeString(String text, List<TextPosition> textPositions) throws IOException {
        for (TextPosition textPosition: textPositions) {
            RenderingMode charRenderingMode = renderingMode.get(textPosition);
            float[] charStrokingColor = strokingColor.get(textPosition);
            float[] charNonStrokingColor = nonStrokingColor.get(textPosition);

            StringBuilder textBuilder = new StringBuilder();
            textBuilder.append(textPosition.getUnicode()).append("{");

            if (FILLING_MODES.contains(charRenderingMode)) {
                textBuilder.append("FILL:").append(toString(charNonStrokingColor)).append(';');
            }

            if (STROKING_MODES.contains(charRenderingMode)) {
                textBuilder.append("STROKE:").append(toString(charStrokingColor)).append(';');
            }

            if (CLIPPING_MODES.contains(charRenderingMode)) {
                textBuilder.append("CLIP;");
            }

            textBuilder.append("}");
            writeString(textBuilder.toString());
        }
    }

    String toString(float[] values)
    {
        if (values == null)
            return "null";
        StringBuilder builder = new StringBuilder();
        switch(values.length) {
        case 1:
            builder.append("GRAY"); break;
        case 3:
            builder.append("RGB"); break;
        case 4:
            builder.append("CMYK"); break;
        default:
            builder.append("UNKNOWN");
        }
        for (float f: values) {
            builder.append(' ')
                   .append(f);
        }

        return builder.toString();
    }
}

(ColorTextStripper)