Draw image at mid position using pdfbox Java

Question

I'm trying to add an image to the center of pdf using pdfbox. Below is my code but I'm unable to get the correct position of image in pdf. I followed the following link In PDFBox, how to change the origin (0,0) point of a PDRectangle object? to get the correct position but still image is off from the midpoint position?

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDPageContentStream;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.pdmodel.graphics.image.LosslessFactory;
import org.apache.pdfbox.pdmodel.graphics.image.PDImageXObject;
import org.apache.pdfbox.util.Matrix;

public class imageAppend {
     public static void main (String[] args){

            File file = new File("...pdf file location");
            PDDocument doc = null;
            try 
            {
                doc = PDDocument.load(file);
                PDImageXObject pdImage = PDImageXObject.createFromFile("image file location", doc);

                PDPage page = doc.getPage(0);
                PDPageContentStream contentStream = new PDPageContentStream(doc, page, PDPageContentStream.AppendMode.APPEND, true);

               float x_pos = page.getCropBox().getWidth();
               float y_pos = page.getCropBox().getHeight();

                float x_adjusted = ( x_pos - w ) / 2;
                float y_adjusted = ( y_pos - h ) / 2;

                Matrix mt = new Matrix(1f, 0f, 0f, -1f, page.getCropBox().getLowerLeftX(), page.getCropBox().getUpperRightY());
            contentStream.transform(mt);
            contentStream.drawImage(pdImage, x_adjusted, y_adjusted, w, h);

                doc.save("new pdf file location");
                doc.close();

            } catch (IOException e) 
            {
                e.printStackTrace();
            }
        }
}

At first glance you center the lower left corner of the image. — mkl, Apr 21 '18 at 21:30
hi @mkl i'm able to draw the image at correct position however the image is inverted. I don't know how to correct it? — shanky, Apr 23 '18 at 17:15
Well, your matrix parameters start with `1f, 0f, 0f, -1f`. The -1 implies a mirroring in direction of the **y** coordinate. — mkl, Apr 23 '18 at 18:27
By "invert" do you mean "with inverted colours"? I thought you meant inverted coordinates. Please share the image — mkl, Apr 23 '18 at 18:53

score 5 · Accepted Answer · answered Apr 24 '18 at 09:07

I reproduced your problem, with my test data (unfortunately you did not share yours) I get

The fix is simple, I removed the two lines

Matrix mt = new Matrix(1f, 0f, 0f, -1f, page.getCropBox().getLowerLeftX(), page.getCropBox().getUpperRightY());
contentStream.transform(mt);

and now get

For the general case you should also add the coordinates of the lower left corner of the crop box to your x_adjusted and y_adjusted

float x_adjusted = ( x_pos - w ) / 2 + page.getCropBox().getLowerLeftX();
float y_adjusted = ( y_pos - h ) / 2 + page.getCropBox().getLowerLeftY();

(AddImage test method testImageAppendNoMirror)

Draw image at mid position using pdfbox Java

1 Answers1