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POInvert image after streaming from url is not working in servlet java
 

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  1. POInvert image after streaming from url is not working in servlet java
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    <p>I want to invert image after image get streamed from given url in servlet, but its not working. But it giving me same image as it is when i send parameter invert=true in url to this servlet and giving me exception <strong>NullPointerException</strong> at below line. </p> <p><code>for (int y = 0; y &lt; bImageFromConvert.getHeight(); y++) {</code></p> <p>Let me know where I am doing mistake. Please point me below is correct way to do invert thing, if not please show me way to make it work.</p> <p>Here is code of servlet:</p> <pre><code>import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.URL; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.imageio.ImageIO; import java.awt.*; import java.awt.image.BufferedImage; import org.apache.log4j.Logger; import java.io.ByteArrayInputStream; public class TestImage extends HttpServlet{ /* *Initialize the Logger. */ private static Logger log = Logger.getLogger(TestImage.class); @Override public void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{ String imageURL="http://&lt;host_name&gt;/getimage"; //removed actual url String invert = request.getParameter("invert"); InputStream resultInStream = null; //Gets the response's outputStream instance to write a image in the response. OutputStream resultOutStream = response.getOutputStream(); try{ //Initialize the URL for the requested image. URL imageUrl = new URL(imageURL); //opens the inputStream of the URL. resultInStream = imageUrl.openStream(); //Initialize the byte array object to read and hold the bytes form the image URL stream. byte[] buffer = new byte[4096]; int bytes_read; //writes the image bytes into the response's output stream. while((bytes_read=resultInStream.read(buffer)) != -1){ resultOutStream.write(buffer, 0, bytes_read); } InputStream in = new ByteArrayInputStream(buffer); BufferedImage bImageFromConvert = ImageIO.read(in); /** * Code to invert image fetched from url */ if(invert != "true"){ for (int x = 0; x &lt; bImageFromConvert.getWidth(); x++) { for (int y = 0; y &lt; bImageFromConvert.getHeight(); y++) { int rgba = bImageFromConvert.getRGB(x, y); Color col = new Color(rgba, true); col = new Color(255 - col.getRed(), 255 - col.getGreen(), 255 - col.getBlue()); bImageFromConvert.setRGB(x, y, col.getRGB()); } } } //Closing all the input and output streams. bImageFromConvert.flush(); in.close(); resultOutStream.close(); resultInStream.close(); } catch (Exception e) { log.error("Unable to read and write the image",e); } } } </code></pre> <p>[Solved] Fixed code:</p> <pre><code>import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.URL; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.imageio.ImageIO; import java.awt.*; import java.awt.image.BufferedImage; import org.apache.log4j.Logger; import java.io.ByteArrayInputStream; public class TestImage extends HttpServlet { /** * */ private static final long serialVersionUID = 1L; /* * Initialize the Logger. */ private static Logger log = Logger.getLogger(TestImage.class); @Override public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String imageURL="http://&lt;host_name&gt;/getimage"; //removed actual url // Sets the response content type to jpg image. String invert = request.getParameter("invert"); InputStream resultInStream = null; // Gets the response's outputStream instance to write a image in the // response. OutputStream resultOutStream = response.getOutputStream(); BufferedImage bImageFromConvert = null; try { // Initialize the URL for the requested image. URL imageUrl = new URL(imageURL); // opens the inputStream of the URL. if (object!=null &amp;&amp; !object.equalsIgnoreCase("")) { resultInStream = imageUrl.openStream(); if("true".equals(invert)){ /** * Code to invert image fetched from url */ bImageFromConvert = ImageIO.read(resultInStream); for (int x = 0; x &lt; bImageFromConvert.getWidth(); x++) { for (int y = 0; y &lt; bImageFromConvert.getHeight(); y++) { int rgba = bImageFromConvert.getRGB(x, y); Color col = new Color(rgba, true); col = new Color(255 - col.getRed(), 255 - col.getGreen(), 255 - col.getBlue()); bImageFromConvert.setRGB(x, y, col.getRGB()); } } ImageIO.write(bImageFromConvert, "JPG", resultOutStream); }else{ // Initialize the byte array object to read and hold the bytes form // the image URL stream. byte[] buffer = new byte[4096]; int bytes_read; // writes the image bytes into the response's output stream. while ((bytes_read = resultInStream.read(buffer)) != -1) { resultOutStream.write(buffer, 0, bytes_read); } } // Closing all the input and output streams. } resultOutStream.flush(); } catch (Exception e) { log.error("Unable to read and write the image", e); } finally { if (resultOutStream != null) { try { resultOutStream.close(); } catch (Exception ignore) { } } if (resultInStream != null) { try { resultInStream.close(); } catch (Exception ignore) { } } } } } </code></pre>
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