diff --git a/src/main/java/lc/captchas/FontFunCaptcha.java b/src/main/java/lc/captchas/FontFunCaptcha.java
index be09485..8dbea52 100644
--- a/src/main/java/lc/captchas/FontFunCaptcha.java
+++ b/src/main/java/lc/captchas/FontFunCaptcha.java
@@ -9,7 +9,7 @@ import java.util.Map;
 import java.util.List;
 import lc.captchas.interfaces.Challenge;
 import lc.captchas.interfaces.ChallengeProvider;
-import lc.misc.DPISetter;
+import lc.misc.PngImageWriter;
 import lc.misc.HelperFunctions;
 
 public class FontFunCaptcha implements ChallengeProvider {
@@ -74,8 +74,7 @@ public class FontFunCaptcha implements ChallengeProvider {
     graphics2D.dispose();
     ByteArrayOutputStream baos = new ByteArrayOutputStream();
     try {
-      DPISetter dpi = new DPISetter();
-      dpi.setDPI(baos, img);
+      PngImageWriter.write(baos, img);
     } catch (Exception e) {
       e.printStackTrace();
     }
diff --git a/src/main/java/lc/captchas/ShadowTextCaptcha.java b/src/main/java/lc/captchas/ShadowTextCaptcha.java
index 16f2b54..a797c50 100644
--- a/src/main/java/lc/captchas/ShadowTextCaptcha.java
+++ b/src/main/java/lc/captchas/ShadowTextCaptcha.java
@@ -13,7 +13,7 @@ import java.util.Map;
 import java.util.List;
 
 import lc.misc.HelperFunctions;
-import lc.misc.DPISetter;
+import lc.misc.PngImageWriter;
 import lc.captchas.interfaces.Challenge;
 import lc.captchas.interfaces.ChallengeProvider;
 
@@ -67,8 +67,7 @@ public class ShadowTextCaptcha implements ChallengeProvider {
     g2d.dispose();
     ByteArrayOutputStream baos = new ByteArrayOutputStream();
     try {
-      DPISetter dpi = new DPISetter();
-      dpi.setDPI(baos, img2);
+      PngImageWriter.write(baos, img2);
     } catch (Exception e) {
       e.printStackTrace();
     }
diff --git a/src/main/java/lc/misc/DPISetter.java b/src/main/java/lc/misc/PngImageWriter.java
similarity index 87%
rename from src/main/java/lc/misc/DPISetter.java
rename to src/main/java/lc/misc/PngImageWriter.java
index 38b8c07..21b5034 100644
--- a/src/main/java/lc/misc/DPISetter.java
+++ b/src/main/java/lc/misc/PngImageWriter.java
@@ -15,12 +15,12 @@ import javax.imageio.metadata.IIOMetadataNode;
 import javax.imageio.stream.ImageOutputStream;
 import java.awt.image.BufferedImage;
 
-public class DPISetter {
+public class PngImageWriter {
 
-  final int DPI = 245;
-  final double INCH_2_CM = 2.54;
+  static final int DPI = 245;
+  static final double INCH_2_CM = 2.54;
 
-  public void setDPI(ByteArrayOutputStream boas, BufferedImage gridImage) throws IOException {
+  public static void write(ByteArrayOutputStream boas, BufferedImage gridImage) throws IOException {
     final String formatName = "png";
     for (Iterator<ImageWriter> iw = ImageIO.getImageWritersByFormatName(formatName);
         iw.hasNext(); ) {
@@ -45,7 +45,7 @@ public class DPISetter {
     }
   }
 
-  public void setDPIMeta(IIOMetadata metadata) throws IIOInvalidTreeException {
+  private static void setDPIMeta(IIOMetadata metadata) throws IIOInvalidTreeException {
 
     // for PNG, it's dots per millimeter
     double dotsPerMilli = 1.0 * DPI / 10 / INCH_2_CM;
diff --git a/src/main/scala/lc/captchas/DebugCaptcha.scala b/src/main/scala/lc/captchas/DebugCaptcha.scala
index 5a0f0f1..f0add52 100644
--- a/src/main/scala/lc/captchas/DebugCaptcha.scala
+++ b/src/main/scala/lc/captchas/DebugCaptcha.scala
@@ -11,7 +11,7 @@ import java.util.List
 import lc.misc.HelperFunctions
 import lc.captchas.interfaces.Challenge
 import lc.captchas.interfaces.ChallengeProvider
-import lc.misc.DPISetter
+import lc.misc.PngImageWriter
 
 /** This captcha is only for debugging purposes. It creates very simple captchas that are deliberately easy to solve with OCR engines */
 class DebugCaptcha extends ChallengeProvider {
@@ -53,8 +53,7 @@ class DebugCaptcha extends ChallengeProvider {
     graphics2D.dispose()
     val baos = new ByteArrayOutputStream()
     try {
-      val dpi = new DPISetter();
-      dpi.setDPI(baos, img);
+      PngImageWriter.write(baos, img);
     } catch {
       case e: Exception =>
         e.printStackTrace()
diff --git a/src/main/scala/lc/captchas/LabelCaptcha.scala b/src/main/scala/lc/captchas/LabelCaptcha.scala
index 7b85e06..18048f8 100644
--- a/src/main/scala/lc/captchas/LabelCaptcha.scala
+++ b/src/main/scala/lc/captchas/LabelCaptcha.scala
@@ -10,7 +10,7 @@ import java.awt.Color
 import lc.captchas.interfaces.ChallengeProvider
 import lc.captchas.interfaces.Challenge
 import java.util.{List => JavaList, Map => JavaMap}
-import lc.misc.DPISetter
+import lc.misc.PngImageWriter
 
 class LabelCaptcha extends ChallengeProvider {
   private var knownFiles = new File("known").list.toList
@@ -50,8 +50,7 @@ class LabelCaptcha extends ChallengeProvider {
 
       val token = encrypt(knownImageFile + "," + unknownImageFile)
       val baos = new ByteArrayOutputStream()
-      val dpi = new DPISetter();
-      dpi.setDPI(baos, mergedImage);
+      PngImageWriter.write(baos, mergedImage);
 
       new Challenge(baos.toByteArray(), "image/png", token)
     }