# PDHighlightAppearanceHandler.java

    /*
     * Copyright 2018 The Apache Software Foundation.
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     *      http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */

    package org.apache.pdfbox.pdmodel.interactive.annotation.handlers;

    import java.io.IOException;
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.apache.pdfbox.cos.COSDictionary;
    import org.apache.pdfbox.cos.COSName;
    import org.apache.pdfbox.pdmodel.PDFormContentStream;
    import org.apache.pdfbox.pdmodel.PDResources;
    import org.apache.pdfbox.pdmodel.common.PDRectangle;
    import org.apache.pdfbox.pdmodel.graphics.blend.BlendMode;
    import org.apache.pdfbox.pdmodel.graphics.color.PDColor;
    import org.apache.pdfbox.pdmodel.graphics.form.PDFormXObject;
    import org.apache.pdfbox.pdmodel.graphics.state.PDExtendedGraphicsState;
    import org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotation;
    import org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotationHighlight;
    import org.apache.pdfbox.pdmodel.PDAppearanceContentStream;
    import org.apache.pdfbox.pdmodel.PDDocument;

    /**
     *
     * @author Tilman Hausherr
     */
    public class PDHighlightAppearanceHandler extends PDAbstractAppearanceHandler
    {
        private static final Log LOG = LogFactory.getLog(PDHighlightAppearanceHandler.class);

        public PDHighlightAppearanceHandler(PDAnnotation annotation)
        {
            super(annotation);
        }

        public PDHighlightAppearanceHandler(PDAnnotation annotation, PDDocument document)
        {
            super(annotation, document);
        }

        @Override
        public void generateNormalAppearance()
        {
            PDAnnotationHighlight annotation = (PDAnnotationHighlight) getAnnotation();

            float[] pathsArray = annotation.getQuadPoints();
            if (pathsArray == null)
            {
                return;
            }
            PDColor color = annotation.getColor();
            if (color == null || color.getComponents().length == 0)
            {
                return;
            }
            PDRectangle rect = annotation.getRectangle();
            if (rect == null)
            {
                return;
            }
            AnnotationBorder ab = AnnotationBorder.getAnnotationBorder(annotation, annotation.getBorderStyle());

            // Adjust rectangle even if not empty, see PLPDF.com-MarkupAnnotations.pdf
            //TODO in a class structure this should be overridable
            // this is similar to polyline but different data type
            //TODO padding should consider the curves too; needs to know in advance where the curve is
            float minX = Float.MAX_VALUE;
            float minY = Float.MAX_VALUE;
            float maxX = Float.MIN_VALUE;
            float maxY = Float.MIN_VALUE;
            for (int i = 0; i < pathsArray.length / 2; ++i)
            {
                float x = pathsArray[i * 2];
                float y = pathsArray[i * 2 + 1];
                minX = Math.min(minX, x);
                minY = Math.min(minY, y);
                maxX = Math.max(maxX, x);
                maxY = Math.max(maxY, y);
            }

            // get the delta used for curves and use it for padding
            float maxDelta = 0;
            for (int i = 0; i < pathsArray.length / 8; ++i)
            {
                // one of the two is 0, depending whether the rectangle is
                // horizontal or vertical
                // if it is diagonal then... uh...
                float delta = Math.max((pathsArray[i + 0] - pathsArray[i + 4]) / 4,
                                       (pathsArray[i + 1] - pathsArray[i + 5]) / 4);
                maxDelta = Math.max(delta, maxDelta);
            }

            rect.setLowerLeftX(Math.min(minX - ab.width / 2 - maxDelta, rect.getLowerLeftX()));
            rect.setLowerLeftY(Math.min(minY - ab.width / 2 - maxDelta, rect.getLowerLeftY()));
            rect.setUpperRightX(Math.max(maxX + ab.width + maxDelta, rect.getUpperRightX()));
            rect.setUpperRightY(Math.max(maxY + ab.width + maxDelta, rect.getUpperRightY()));
            annotation.setRectangle(rect);

            try (PDAppearanceContentStream cs = getNormalAppearanceAsContentStream())
            {
                PDExtendedGraphicsState r0 = new PDExtendedGraphicsState();
                PDExtendedGraphicsState r1 = new PDExtendedGraphicsState();
                r0.setAlphaSourceFlag(false);
                r0.setStrokingAlphaConstant(annotation.getConstantOpacity());
                r0.setNonStrokingAlphaConstant(annotation.getConstantOpacity());
                r1.setAlphaSourceFlag(false);
                r1.setBlendMode(BlendMode.MULTIPLY);
                cs.setGraphicsStateParameters(r0);
                cs.setGraphicsStateParameters(r1);
                PDFormXObject frm1 = new PDFormXObject(createCOSStream());
                PDFormXObject frm2 = new PDFormXObject(createCOSStream());
                frm1.setResources(new PDResources());
                try (PDFormContentStream mwfofrmCS = new PDFormContentStream(frm1))
                {
                    mwfofrmCS.drawForm(frm2);
                }
                frm1.setBBox(annotation.getRectangle());
                COSDictionary groupDict = new COSDictionary();
                groupDict.setItem(COSName.S, COSName.TRANSPARENCY);
                //TODO PDFormXObject.setGroup() is missing
                frm1.getCOSObject().setItem(COSName.GROUP, groupDict);
                cs.drawForm(frm1);
                frm2.setBBox(annotation.getRectangle());
                try (PDFormContentStream frm2CS = new PDFormContentStream(frm2))
                {
                    frm2CS.setNonStrokingColor(color);
                    int of = 0;
                    while (of + 7 < pathsArray.length)
                    {
                        // quadpoints spec sequence is incorrect, correct one is (4,5 0,1 2,3 6,7)
                        // https://stackoverflow.com/questions/9855814/pdf-spec-vs-acrobat-creation-quadpoints

                        // for "curvy" highlighting, two Bézier control points are used that seem to have a
                        // distance of about 1/4 of the height.
                        // note that curves won't appear if outside of the rectangle
                        float delta = 0;
                        if (Float.compare(pathsArray[of + 0], pathsArray[of + 4]) == 0 &&
                            Float.compare(pathsArray[of + 1], pathsArray[of + 3]) == 0 &&
                            Float.compare(pathsArray[of + 2], pathsArray[of + 6]) == 0 &&
                            Float.compare(pathsArray[of + 5], pathsArray[of + 7]) == 0)
                        {
                            // horizontal highlight
                            delta = (pathsArray[of + 1] - pathsArray[of + 5]) / 4;
                        }
                        else if (Float.compare(pathsArray[of + 1], pathsArray[of + 5]) == 0 &&
                                 Float.compare(pathsArray[of + 0], pathsArray[of + 2]) == 0 &&
                                 Float.compare(pathsArray[of + 3], pathsArray[of + 7]) == 0 &&
                                 Float.compare(pathsArray[of + 4], pathsArray[of + 6]) == 0)
                        {
                            // vertical highlight
                            delta = (pathsArray[of + 0] - pathsArray[of + 4]) / 4;
                        }

                        frm2CS.moveTo(pathsArray[of + 4], pathsArray[of + 5]);

                        if (Float.compare(pathsArray[of + 0], pathsArray[of + 4]) == 0)
                        {
                            // horizontal highlight
                            frm2CS.curveTo(pathsArray[of + 4] - delta, pathsArray[of + 5] + delta,
                                           pathsArray[of + 0] - delta, pathsArray[of + 1] - delta,
                                           pathsArray[of + 0], pathsArray[of + 1]);
                        }
                        else if (Float.compare(pathsArray[of + 5], pathsArray[of + 1]) == 0)
                        {
                            // vertical highlight
                            frm2CS.curveTo(pathsArray[of + 4] + delta, pathsArray[of + 5] + delta,
                                           pathsArray[of + 0] - delta, pathsArray[of + 1] + delta,
                                           pathsArray[of + 0], pathsArray[of + 1]);
                        }
                        else
                        {
                            frm2CS.lineTo(pathsArray[of + 0], pathsArray[of + 1]);
                        }
                        frm2CS.lineTo(pathsArray[of + 2], pathsArray[of + 3]);
                        if (Float.compare(pathsArray[of + 2], pathsArray[of + 6]) == 0)
                        {
                            // horizontal highlight
                            frm2CS.curveTo(pathsArray[of + 2] + delta, pathsArray[of + 3] - delta,
                                           pathsArray[of + 6] + delta, pathsArray[of + 7] + delta,
                                           pathsArray[of + 6], pathsArray[of + 7]);
                        }
                        else if (Float.compare(pathsArray[of + 3], pathsArray[of + 7]) == 0)
                        {
                            // vertical highlight
                            frm2CS.curveTo(pathsArray[of + 2] - delta, pathsArray[of + 3] - delta,
                                           pathsArray[of + 6] + delta, pathsArray[of + 7] - delta,
                                           pathsArray[of + 6], pathsArray[of + 7]);
                        }
                        else
                        {
                            frm2CS.lineTo(pathsArray[of + 6], pathsArray[of + 7]);
                        }

                        frm2CS.fill();
                        of += 8;
                    }
                }
            }
            catch (IOException ex)
            {
                LOG.error(ex);
            }
        }

        @Override
        public void generateRolloverAppearance()
        {
            // No rollover appearance generated
        }

        @Override
        public void generateDownAppearance()
        {
            // No down appearance generated
        }
    }