ASCII85CompressionStrategy.java

/*
    This file is part of the iText (R) project.
    Copyright (c) 1998-2026 Apryse Group NV
    Authors: Apryse Software.

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    following permission added to Section 15 as permitted in Section 7(a):
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package com.itextpdf.rups.io.encoders;

import com.itextpdf.kernel.pdf.IStreamCompressionStrategy;
import com.itextpdf.kernel.pdf.PdfName;
import com.itextpdf.kernel.pdf.PdfObject;
import com.itextpdf.kernel.pdf.PdfStream;

import java.io.OutputStream;

/**
 * A compression strategy that uses the {@code ASCII85Decode} filter for PDF
 * streams.
 *
 * <p>
 * This strategy implements the {@link IStreamCompressionStrategy} interface
 * and provides {@code ASCII85Decode} encoding.
 *
 * <p>
 * The strategy ensures, that streams are saved using just 7-bit ASCII
 * characters, but it typically increases sizes of streams by 25% compared to
 * just saving them as-is. So calling this a "compression strategy" is a
 * misnomer.
 */
public class ASCII85CompressionStrategy implements IStreamCompressionStrategy {
    /**
     * Constructs a new {@link ASCII85CompressionStrategy} instance.
     */
    public ASCII85CompressionStrategy() {
        // empty constructor
    }

    /**
     * Returns the name of the compression filter.
     *
     * @return {@link PdfName#ASCII85Decode} representing the {@code ASCII85Decode} filter
     */
    @Override
    public PdfName getFilterName() {
        return PdfName.ASCII85Decode;
    }

    /**
     * Returns the decode parameters for the {@code ASCII85Decode} filter.
     * <p>
     * This implementation returns {@code null} as no special decode parameters
     * are required for standard ASCII85 compression.
     *
     * @return {@code null} as no decode parameters are needed
     */
    @Override
    public PdfObject getDecodeParams() {
        return null;
    }

    /**
     * Creates a new output stream with ASCII85 compression applied.
     * <p>
     * This method wraps the original output stream in a {@link ASCII85OutputStream}
     * that applies ASCII85 compression.
     *
     * @param original the original output stream to wrap
     * @param stream   the PDF stream containing compression configuration
     *
     * @return a new {@link ASCII85OutputStream} that compresses data using the ASCII85 algorithm
     */
    @Override
    public OutputStream createNewOutputStream(OutputStream original, PdfStream stream) {
        return new ASCII85OutputStream(original);
    }
}