ImageJ how do I write strings on an image?

Question

I need to write some text on an image, before centering it or put it in some paragraphs I wanted to get used to the library step by step so I've written this code found on a tutorial:

import ij.IJ;
import ij.ImagePlus;
import ij.process.ImageProcessor;
import java.awt.*;

    public void prova(String nome) {
            ImagePlus image = IJ.openImage(myimagepath);
            Font font = new Font("Arial", Font.BOLD, 30);
            ImageProcessor ip = image.getProcessor();
            ip.setColor(Color.BLACK);
            ip.setFont(font);
            ip.drawString(nome, 20, 20);
        }

I expected the file on the path to be already edited but it isn't, am I missing something? it's a .jpg image btw, also when this works I'll have to put an smaller image onto this one as well so ugh hope the library can do that too

EDIT: guys use ImageIO, i'm leaving the working code for the basic

public void prova(String nome, String profilo, MultipartFile foto) {
        try {
            BufferedImage image = ImageIO.read(new File(path));
            Font font = new Font("Arial", Font.BOLD, 18);
            Graphics g = image.getGraphics();
            g.setFont(font);
            g.setColor(Color.GREEN);
            g.drawString(nome, 0, 20);
            ImageIO.write(image, "jpg", new File(path.substring(0, path.lastIndexOf("\\")+1)+"processedImage.png"));
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

Answer 1

I do not know imagej, but in with ImageIO the pattern would be similar:

• load the image
• process it (draw the string on top)
• save the image

In your example I cannot see that you try to save the image back to disk. As I do not use ImageJ myself I can only suggest to check the documentation. See https://albert.rierol.net/imagej_programming_tutorials.html#How%20to%20integrate%20a%20new%20file%20format%20reader%20and%20writer, especially the part regarding the writer. For those who prefer no link-only answers I copied the example code mentioned there:

static public void saveCustom(ImagePlus imp, String path) {  
    File file = new File(path);  
    DataOutputStream dos = null;  
    try {  
        dos = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file)));  

        // read data:  
        FileInfo fi = imp.getFileInfo();  
        // HEADER: ... read all header tags and metadata  
          
        dos.write( ... );  

        // BODY: ... read all stack slices (or single slice)  
        for (int i=1; i<imp.getNSlices(); i++) {  
            dos.write( ... );  
        }  
        dos.flush();  

    } catch (Exception e) {  
        e.printStackTrace();  
    } finally {  
        dos.close();  
    }  
}