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Java PDF Box implementation for the veraPDF Validation Java API, generated from an Xtext model.
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/**
 * This file is part of veraPDF PDF Box PDF/A Validation Model Implementation, a module of the veraPDF project.
 * Copyright (c) 2015, veraPDF Consortium 
 * All rights reserved.
 *
 * veraPDF PDF Box PDF/A Validation Model Implementation is free software: you can redistribute it and/or modify
 * it under the terms of either:
 *
 * The GNU General public license GPLv3+.
 * You should have received a copy of the GNU General Public License
 * along with veraPDF PDF Box PDF/A Validation Model Implementation as the LICENSE.GPL file in the root of the source
 * tree.  If not, see http://www.gnu.org/licenses/ or
 * https://www.gnu.org/licenses/gpl-3.0.en.html.
 *
 * The Mozilla Public License MPLv2+.
 * You should have received a copy of the Mozilla Public License along with
 * veraPDF PDF Box PDF/A Validation Model Implementation as the LICENSE.MPL file in the root of the source tree.
 * If a copy of the MPL was not distributed with this file, you can obtain one at
 * http://mozilla.org/MPL/2.0/.
 */
package org.verapdf.model.tools.transparency;

import org.apache.pdfbox.cos.COSArray;
import org.apache.pdfbox.cos.COSBase;
import org.apache.pdfbox.cos.COSDictionary;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.pdmodel.font.encoding.Encoding;
import org.verapdf.model.factory.operator.GraphicState;
import org.verapdf.model.impl.pb.pd.PBoxPDContentStream;
import org.verapdf.model.impl.pb.pd.colors.PBoxPDColorSpace;
import org.verapdf.model.impl.pb.pd.font.PBoxPDFont;
import org.verapdf.model.impl.pb.pd.font.PBoxPDType3Font;
import org.verapdf.model.impl.pb.pd.images.PBoxPDXForm;
import org.verapdf.model.impl.pb.pd.images.PBoxPDXImage;
import org.verapdf.model.impl.pb.pd.images.PBoxPDXObject;
import org.verapdf.model.impl.pb.pd.pattern.PBoxPDTilingPattern;
import org.verapdf.model.pdlayer.PDContentStream;

import java.util.Map;

/**
 * Transparency checker class
 *
 * @author Maksim Bezrukov
 */
public class TransparencyBehaviour {

	private boolean isFillCheck = false;
	private boolean isStrokeCheck = false;
	private boolean isXObjectCheck = false;
	private boolean isColorSpaceCheck = false;
	private boolean isFontCheck = false;

	private TransparencyBehaviour() {
	}

	/**
	 * @return an instance of TransparencyBehaviour class with fill checks
	 */
	public static TransparencyBehaviour createFillInstance() {
		TransparencyBehaviour tb = new TransparencyBehaviour();
		tb.isFillCheck = true;
		return tb;
	}

	/**
	 * @return an instance of TransparencyBehaviour class with fill and XObjects
	 *         checks
	 */
	public static TransparencyBehaviour createFillXObjectInstance() {
		TransparencyBehaviour tb = createFillInstance();
		tb.isXObjectCheck = true;
		return tb;
	}

	/**
	 * @return an instance of TransparencyBehaviour class with fill and patterns
	 *         checks
	 */
	public static TransparencyBehaviour createFillColorSpaceInstance() {
		TransparencyBehaviour tb = createFillInstance();
		tb.isColorSpaceCheck = true;
		return tb;
	}

	/**
	 * @return an instance of TransparencyBehaviour class with fill, patterns
	 *         and font checks
	 */
	public static TransparencyBehaviour createFillColorSpaceFontInstance() {
		TransparencyBehaviour tb = createFillColorSpaceInstance();
		tb.isFontCheck = true;
		return tb;
	}

	/**
	 * @return an instance of TransparencyBehaviour class with stroke and
	 *         patterns checks
	 */
	public static TransparencyBehaviour createStrokeColorSpaceInstance() {
		TransparencyBehaviour tb = new TransparencyBehaviour();
		tb.isStrokeCheck = true;
		tb.isColorSpaceCheck = true;
		return tb;
	}

	/**
	 * @return an instance of TransparencyBehaviour class with stroke, patterns
	 *         and font checks
	 */
	public static TransparencyBehaviour createStrokeColorSpaceFontInstance() {
		TransparencyBehaviour tb = createStrokeColorSpaceInstance();
		tb.isFontCheck = true;
		return tb;
	}

	/**
	 * @return an instance of TransparencyBehaviour class with fill, stroke and
	 *         patterns checks
	 */
	public static TransparencyBehaviour createFillStrokeColorSpaceInstance() {
		TransparencyBehaviour tb = new TransparencyBehaviour();
		tb.isFillCheck = true;
		tb.isStrokeCheck = true;
		tb.isColorSpaceCheck = true;
		return tb;
	}

	/**
	 * @return an instance of TransparencyBehaviour class with fill, stroke,
	 *         patterns and font checks
	 */
	public static TransparencyBehaviour createFillStrokeColorSpaceFontInstance() {
		TransparencyBehaviour tb = createFillStrokeColorSpaceInstance();
		tb.isFontCheck = true;
		return tb;
	}

	/**
	 * Checks the given graphic state for the transparency depends on created
	 * object type
	 * 
	 * @param graphicState
	 *            graphicState object for check
	 * @return true if the given argument object contains transparency depends
	 *         on created object type
	 */
	public boolean containsTransparency(GraphicState graphicState) {
		if (baseCheck(graphicState)) {
			return true;
		}

		if (isFillCheck && graphicState.getCa_ns() < 1.0f) {
			return true;
		}

		if (isStrokeCheck && graphicState.getCa() < 1.0f) {
			return true;
		}

		if (isXObjectCheck && xObjectContainsTransparency(graphicState.getVeraXObject())) {
			return true;
		}

		if (isColorSpaceCheck && colorSpaceCheck(graphicState)) {
			return true;
		}

		if (isFontCheck && fontCheck(graphicState)) {
			return true;
		}

		return false;
	}

	private static boolean fontCheck(GraphicState graphicState) {
		PBoxPDFont font = graphicState.getVeraFont();
		if (font instanceof PBoxPDType3Font) {
			PBoxPDType3Font type3Font = (PBoxPDType3Font) font;
			Encoding encoding = type3Font.getEncodingObject();
			if (encoding != null) {
				boolean result = false;
				Map charProcStreams = type3Font.getCharProcStreams();
				for (byte glyphCode : graphicState.getCharCodes()) {
					String glyphName = encoding.getName(glyphCode);
					PBoxPDContentStream glyphStream = (PBoxPDContentStream) charProcStreams.get(glyphName);
					if (glyphStream != null) {
						result |= glyphStream.isContainsTransparency();
					}
				}
				return result;
			}
		}
		return false;
	}

	private boolean colorSpaceCheck(GraphicState graphicState) {
		if (isFillCheck) {
			PBoxPDColorSpace fillCS = graphicState.getVeraFillColorSpace();
			if (fillCS instanceof PBoxPDTilingPattern && ((PBoxPDTilingPattern) fillCS).isContainsTransparency()) {
				return true;
			}
		}
		if (isStrokeCheck) {
			PBoxPDColorSpace strokeCS = graphicState.getVeraStrokeColorSpace();
			if (strokeCS instanceof PBoxPDTilingPattern && ((PBoxPDTilingPattern) strokeCS).isContainsTransparency()) {
				return true;
			}
		}
		return false;
	}

	private static boolean baseCheck(GraphicState graphicState) {
		COSBase sMask = graphicState.getSMask();
		if (sMask instanceof COSDictionary) {
			return true;
		}

		COSBase bm = graphicState.getBm();
		if (bm instanceof COSName) {
			COSName bmName = (COSName) bm;
			if (!bmName.equals(COSName.getPDFName("Normal"))) {
				return true;
			}
		} else if (bm instanceof COSArray) {
			COSArray bmArray = (COSArray) bm;
			if (bmArray.size() != 1) {
				return true;
			}
			COSBase bmValue = bmArray.get(0);
			if (!(bmValue instanceof COSName && bmValue.equals(COSName.getPDFName("Normal")))) {
				return true;
			}
		} else if (bm != null) {
			return true;
		}
		return false;
	}

	private static boolean xObjectContainsTransparency(PBoxPDXObject xobj) {
		if (xobj instanceof PBoxPDXForm) {
			return ((PBoxPDXForm) xobj).containsTransparency();
		} else if (xobj instanceof PBoxPDXImage) {
			return ((PBoxPDXImage) xobj).containsTransparency();
		}
		return false;
	}
}