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Java Program to Convert PNG Images to JPEG

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PNG and JPG formats are used for image illustrations. Both the formats are used to provide good compatibilities with certain types of images like PNG works better with line drawings and icon graphics whereas JPG works well with photographs. However, both are interconvertible with respect to each other for usage and storage of media and pictures.

In Java, write() method is used to convert an image from gif type of format to jpg, use the static method write() provided by the class ImageIO under javax.imageio package. Following utility class implements a static method known as converImg(), which takes input and output image path as parameters and format output image.


boolean write(RenderedImage image, String formatName, OutputStream output)

Parameters: write() method accepts 3 parameters namely image, formatName and output.

  1. Image: The input image as a subclass of the RenderedImage interface, such as BufferedImage.To obtain a BufferedImage object from the input image file, we can use the read(InputStream) which is also provided by the ImageIO class.
  2. formatName: specifies format type of the output image.
  3. output specifies an OutputStream to which the output image will be written.

Return Type: Boolean value where returning true if it can find an ImageWriter and perform conversion successfully else it will return false.

Exceptions: It will throw IOException if an error occurs during execution. It is shown later on in the implementation part.


Note: For input and output images path, Input and input images been passed are present on the desktop of the machine

  • Input image with name “demoImage.png”
  • Output Image with name “demoImage.jpeg”

Code is present at the directory mentioned below

  • /Users/mayanksolanki/Desktop/Job/Coding/GFG/Folder/



// Java Program to Convert PNG Image to JPEG Image
// Importing BufferedImage class from java.awt package
// to describe an image with accessible buffer of image
import java.awt.image.BufferedImage;
// Importing all input output classes
// Importing an interface
// to determine the setting of IIOParam object
import javax.imageio.ImageIO;
// Class 1
// helper class
class HelperClass {
    // Method
    // To convert image format
    public static boolean convertImg(String inputImgPath,
                                     String outputImgPath,
                                     String formatType)
        throws IOException
        // Creating an object  of FileInputStream to read
        FileInputStream inputStream
            = new FileInputStream(inputImgPath);
        // Creating an object  of FileOutputStream to write
        FileOutputStream outputStream
            = new FileOutputStream(outputImgPath);
        // Reading the  input image from file
        BufferedImage inputImage
        // Writing to the output image in specified format
        boolean result = ImageIO.write(
            inputImage, formatType, outputStream);
        // Closing the streams in order to avoid read write
        // operations
        return result;
// Class 2
// Main class
public class GFG {
    // Main class
    public static void main(String[] args)
        // Here, the local directories from machine
        //  is passed as in strings
        // Creating a string to store the path of image
        // to be converted
        String inputImage
            = "/Users/mayanksolanki/Desktop/demoImage.png";
        // Creating a string to
        // store path of converted image
        String outputImage
            = "/Users/mayanksolanki/Desktop/demoImage.jpeg";
        // Creating another string that will be
        // store format of converted image
        // Simply creating  creating just to hold the format
        // type
        String formatType = "JPEG";
        // Try block to check for exceptions
        try {
            // result will store boolean value whether image
            // is converted successfully or not
            boolean result = HelperClass.convertImg(
                inputImage, outputImage, formatType);
            if (result) {
                // Display message when image is converted
                // successfully
                    "Image converted to jpeg successfully.");
            else {
                // Display message when image is not
                // converted successfully
                    "Could not convert image.");
        // Catch block to handle the exceptions
        catch (IOException ex) {
            // Display message when exception is thrown
                "Error during converting image.");
            // Print the line number
            // where the exception occurred


Case 1: When an error is thrown 

Case 2: Successful compilation but exception is thrown at runtime(failed to run properly)  

Case 3: Successful compilation and successfully run 

Image converted to jpeg successfully.

When executed it will show Image converted to jpeg successfully, we can find that on console and a new jpeg image created in the file


Last Updated : 13 Jun, 2022
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