/**
 * Example written by Bruno Lowagie in answer to
 * http://stackoverflow.com/questions/29152313/fix-the-orientation-of-a-pdf-in-order-to-scale-it
 */
package sandbox.events;

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Image;
import com.itextpdf.text.pdf.PdfArray;
import com.itextpdf.text.pdf.PdfDictionary;
import com.itextpdf.text.pdf.PdfName;
import com.itextpdf.text.pdf.PdfPageEventHelper;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfRectangle;
import com.itextpdf.text.pdf.PdfWriter;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import sandbox.WrapToTest;

/**
 * This solution is suboptimal as it throws away all interactivity.
 * If you want to keep the interactive elements (annotations, form fields,...),
 * you need to do much more work. If you don't need to scale down, but instead
 * only have to scale up, you should try the example that was written in
 * answer to http://stackoverflow.com/questions/21871027/rotating-in-itextsharp-while-preserving-comment-location-orientation
 */
@WrapToTest
public class ScaleDown {
    
    public static final String SRC = "resources/pdfs/orientations.pdf";
    public static final String DEST = "results/events/scaled_down.pdf";
        
    public class ScaleEvent extends PdfPageEventHelper {
        
        protected float scale = 1;
        protected PdfDictionary pageDict;
        
        public ScaleEvent(float scale) {
            this.scale = scale;
        }
        
        public void setPageDict(PdfDictionary pageDict) {
            this.pageDict = pageDict;
        }
        
        @Override
        public void onStartPage(PdfWriter writer, Document document) {
            writer.addPageDictEntry(PdfName.ROTATE, pageDict.getAsNumber(PdfName.ROTATE));
            writer.addPageDictEntry(PdfName.MEDIABOX, scaleDown(pageDict.getAsArray(PdfName.MEDIABOX), scale));
            writer.addPageDictEntry(PdfName.CROPBOX, scaleDown(pageDict.getAsArray(PdfName.CROPBOX), scale));
        }
    }
    
    public static void main(String[] args) throws IOException, DocumentException {
        File file = new File(DEST);
        file.getParentFile().mkdirs();
        new ScaleDown().manipulatePdf(SRC, DEST);
    }
    
    public void manipulatePdf(String src, String dest) throws IOException, DocumentException {
        PdfReader reader = new PdfReader(src);
        float scale = 0.5f;
        ScaleEvent event = new ScaleEvent(scale);
        event.setPageDict(reader.getPageN(1));
        
        int n = reader.getNumberOfPages();
        Document document = new Document();
        PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(dest));
        writer.setPageEvent(event);
        document.open();
        Image page;
        for (int p = 1; p <= n; p++) {
            page = Image.getInstance(writer.getImportedPage(reader, p));
            page.setAbsolutePosition(0, 0);
            page.scalePercent(scale * 100);
            document.add(page);
            if (p < n) {
                event.setPageDict(reader.getPageN(p + 1));
            }
            document.newPage();
        }
        document.close();
    }
    
    public PdfArray scaleDown(PdfArray original, float scale) {
        if (original == null)
            return null;
        float width = original.getAsNumber(2).floatValue()
                - original.getAsNumber(0).floatValue();
        float height = original.getAsNumber(3).floatValue()
                - original.getAsNumber(1).floatValue();
        return new PdfRectangle(width * scale, height * scale);
    }
}