img2pdf

One picture to pdf

import com.itextpdf.text.Document;
import com.itextpdf.text.Image;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.PdfContentByte;

import com.itextpdf.text.pdf.PdfWriter;

import java.io.FileOutputStream;

public class ImgToPdf {
    
    public static void main(String[] args) {
    
        try {
    
            String outPath = "pdf.pdf";
            Image instance = Image.getInstance("C:\\Users\\Administrator\\Desktop\\QQ Screenshot 20220624140018.png");
            float pageWidth = instance.getWidth();
            float pageHeight = instance.getHeight();
            Document document = new Document(new Rectangle(pageWidth, pageHeight));// Create a new document and set the page size 
            FileOutputStream outputStream = new FileOutputStream(outPath);// Create a new one pdf file ;
            PdfWriter writer = PdfWriter.getInstance(document, outputStream);// Put the new pdf  Assign a value to  document
            writer.setPdfVersion(PdfWriter.VERSION_1_5);
            document.open();// open  document file 
            PdfContentByte cb = writer.getDirectContent();
            cb.addImage(instance,pageWidth,0,0,pageHeight,0,0);
            outputStream.flush();// Close file 
            document.close();// Close file 
            outputStream.close();// Close file 
        } catch (Exception e) {
    
            e.printStackTrace();
        }
    }
}

Multiple pictures to pdf

import com.itextpdf.text.Document;
import com.itextpdf.text.Image;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.PdfContentByte;

import com.itextpdf.text.pdf.PdfWriter;

import java.io.FileOutputStream;
import java.util.ArrayList;
import java.util.List;

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

        List<String> listImg = new ArrayList<String>();
        listImg.add("C:\\Users\\Administrator\\Desktop\\QQ Screenshot 20220624140018.png");
        listImg.add("C:\\Users\\Administrator\\Desktop\\QQ Screenshot 20220624140844.png");
        try {
    

            String outPath = "pdf.pdf";
            Image instance = Image.getInstance(listImg.get(0));
            float pageWidth = instance.getWidth();
            float pageHeight = instance.getHeight();
            Document document = new Document(new Rectangle(pageWidth, pageHeight));// Create a new document and set the page size 
            FileOutputStream outputStream = new FileOutputStream(outPath);// Create a new one pdf file ;
            PdfWriter writer = PdfWriter.getInstance(document, outputStream);// Put the new pdf  Assign a value to  document
            writer.setPdfVersion(PdfWriter.VERSION_1_5);
            document.open();// open  document file 
            PdfContentByte cb = writer.getDirectContent();
            cb.addImage(instance,pageWidth,0,0,pageHeight,0,0);
            for(int i=1;i<listImg.size();i++){
    
                Image instance2 = Image.getInstance(listImg.get(i));
                float pageWidth2= instance2.getWidth();
                float pageHeight2 = instance2.getHeight();
                document.setPageSize(new Rectangle(pageWidth2,pageHeight2));
                document.newPage();
                cb.addImage(instance2,pageWidth2,0,0,pageHeight2,0,0);
            }
            outputStream.flush();// Close file 
            document.close();// Close file 
            outputStream.close();// Close file 
        } catch (Exception e) {
    
            e.printStackTrace();
        }
    }
}