High Resolution HTML to Image Conversion

Question

I am rendering a html file using JEditorPane and painting the pixels to a BufferedImage object. How can I make a higher resolution than 72 dpi.
Here is my current program
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.JEditorPane;
public class Main {
    public static final double WIDTH_INCHES = 11 - 0.5 - 0.5;
    public static final double HEIGHT_INCHES = 11 - 0.5 - 0.5;
    public static final double DPI = 72;
    public static final int WIDTH_PIXELS = (int) (WIDTH_INCHES * DPI);
    public static final int HEIGHT_PIXELS = (int) (HEIGHT_INCHES * DPI);
    public static void main(String[] args) throws FileNotFoundException,
            IOException {
        StringBuilder htmlCode = new StringBuilder();
        FileReader htmlFileReader = new FileReader("test.htm");
        BufferedReader htmlFileBufferedReader =
                new BufferedReader(htmlFileReader);
        String aLine;
        while ((aLine = htmlFileBufferedReader.readLine()) != null) {
            htmlCode.append(aLine + "\n");
        JEditorPane editorPane = new JEditorPane("text/html",
                htmlCode.toString());
        editorPane.setMaximumSize(new Dimension(WIDTH_PIXELS, HEIGHT_PIXELS));
        editorPane.setSize(new Dimension(WIDTH_PIXELS, HEIGHT_PIXELS));
        editorPane.setBackground(Color.WHITE);
        editorPane.setPreferredSize(new Dimension(WIDTH_PIXELS, HEIGHT_PIXELS));
        BufferedImage image = new BufferedImage(WIDTH_PIXELS, HEIGHT_PIXELS,
                Image.SCALE_SMOOTH);
        editorPane.paint(image.getGraphics());
        ImageIO.write(image, "png", new File("test.png"));
}How can I make this program to make a better resolution image?

Answer 1

I was profiling the application and found that iText was copying the whole image and running transparency checks for the 8.5 by 11 that I was doing at 72x4 dpi.
I found a way to do it more efficiently and it happens to take advantage of the vector text.
I used the PdfContentByte.createGraphicsShapes method to get a PDF Graphics2D object and I painted to that instead of painting to the java.awt.image. I did this in combination with disabling double buffering on the JEditorPane
This is my working code example
import com.lowagie.text.*;
import com.lowagie.text.pdf.*;
import java.awt.Dimension;
import java.awt.Insets;
import java.io.*;
import java.util.Date;
import javax.swing.JEditorPane;
import javax.swing.border.EmptyBorder;
public class HtmlConverter {
    public static void main(String[] args) throws FileNotFoundException,
            IOException, DocumentException, BadElementException {
        StringBuilder htmlCode = new StringBuilder();
        FileReader htmlFileReader = new FileReader("test.htm");
        BufferedReader htmlFileBufferedReader =
                new BufferedReader(htmlFileReader);
        String aLine;
        while ((aLine = htmlFileBufferedReader.readLine()) != null) {
            htmlCode.append(aLine + "\n");
        convertToPdf(htmlCode.toString(),
                new FileOutputStream("test.pdf"));
    public static void convertToPdf(String htmlCode, OutputStream output) {
        final long startTime = new Date().getTime();
        try {
            final Rectangle PAGE_SIZE = PageSize.LETTER;
            final float PDF_MARGIN_INCHES = 0.5F;
            final int PDF_MARGIN_PIXELS = (int) (PDF_MARGIN_INCHES * 72);
            final int HTML_DOC_PX_WIDTH = (int) PAGE_SIZE.getWidth();
            final int HTML_DOC_PX_HEIGHT = (int) PAGE_SIZE.getHeight();
            Document document = new Document(PAGE_SIZE);
            JEditorPane htmlEditorPane = new JEditorPane("text/html", htmlCode);
            htmlEditorPane.setDoubleBuffered(false);
            htmlEditorPane.setMaximumSize(
                    new Dimension(HTML_DOC_PX_WIDTH, HTML_DOC_PX_HEIGHT));
            htmlEditorPane.setPreferredSize(
                    new Dimension(HTML_DOC_PX_WIDTH, HTML_DOC_PX_HEIGHT));
            htmlEditorPane.setSize(HTML_DOC_PX_WIDTH, HTML_DOC_PX_HEIGHT);
            htmlEditorPane.setBorder(new EmptyBorder(PDF_MARGIN_PIXELS,
                    PDF_MARGIN_PIXELS, PDF_MARGIN_PIXELS, PDF_MARGIN_PIXELS));
            htmlEditorPane.setMargin(new Insets(PDF_MARGIN_PIXELS,
                    PDF_MARGIN_PIXELS, PDF_MARGIN_PIXELS, PDF_MARGIN_PIXELS));
            PdfWriter writer = PdfWriter.getInstance(document, output);
            document.open();
            PdfContentByte cb = writer.getDirectContent();
            java.awt.Graphics2D g2d =
                    cb.createGraphicsShapes((int) PAGE_SIZE.getWidth(),
                    (int) PAGE_SIZE.getHeight());
            htmlEditorPane.paint(g2d);
            g2d.dispose();
            document.close();
        } catch (Exception ex) {
            throw new RuntimeException("Exception while generating PDF file." +
                    " This may have been caused by a I/O Exception in the" +
                    " output stream", ex);
        final long endTime = new Date().getTime();
        System.out.println("Total Time: " + (endTime - startTime) + "ms");
}