diff --git a/src/core/pnm.cpp b/src/core/pnm.cpp
index 5b1f138..7c3f724 100644
--- a/src/core/pnm.cpp
+++ b/src/core/pnm.cpp
@@ -44,7 +44,7 @@ PNM::PNM(int width, int height, QImage::Format format) :
     {
     case QImage::Format_Mono:
         break;
-    case QImage::Format_Indexed8:
+    case QImage::Format_Grayscale8:
         this->setColorCount(256);
 
         for (int i = 0; i < 256; i++)
diff --git a/src/core/tools.cpp b/src/core/tools.cpp
index b45d5bb..82d624e 100644
--- a/src/core/tools.cpp
+++ b/src/core/tools.cpp
@@ -21,7 +21,7 @@ void Tools::negativeImage()
     ImageViewer* iv = getViewer(); // Get the ImageViewer which holds the image.
 
     if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Mono
-                                                          << QImage::Format_Indexed8
+                                                          << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -45,7 +45,7 @@ void Tools::correctBrightnessContrastGamma()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -75,7 +75,7 @@ void Tools::histogramEqualize()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -87,7 +87,7 @@ void Tools::histogramStretch()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -113,7 +113,7 @@ void Tools::blurGauss()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -132,7 +132,7 @@ void Tools::blurLinear()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -152,7 +152,7 @@ void Tools::blurUniform()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -170,7 +170,7 @@ void Tools::binGradient()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -182,7 +182,7 @@ void Tools::binIterBimodal()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -194,7 +194,7 @@ void Tools::binManual()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -216,7 +216,7 @@ void Tools::binNiblack()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -234,7 +234,7 @@ void Tools::binOtsu()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -252,7 +252,7 @@ void Tools::noiseMedian()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -269,7 +269,7 @@ void Tools::noiseBilateral()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -294,7 +294,7 @@ void Tools::morphDilate()
     ImageViewer* iv = getViewer();
 
     if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Mono
-                                                          << QImage::Format_Indexed8
+                                                          << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -316,7 +316,7 @@ void Tools::morphErode()
     ImageViewer* iv = getViewer();
 
     if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Mono
-                                                          << QImage::Format_Indexed8
+                                                          << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -338,7 +338,7 @@ void Tools::morphOpen()
     ImageViewer* iv = getViewer();
 
     if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Mono
-                                                          << QImage::Format_Indexed8
+                                                          << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -360,7 +360,7 @@ void Tools::morphClose()
     ImageViewer* iv = getViewer();
 
     if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Mono
-                                                          << QImage::Format_Indexed8
+                                                          << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -387,7 +387,7 @@ void Tools::edgeSobel()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -399,7 +399,7 @@ void Tools::edgePrewitt()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -411,7 +411,7 @@ void Tools::edgeRoberts()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -424,7 +424,7 @@ void Tools::edgeLaplacian()
     ImageViewer* iv = getViewer();
 
     if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Mono
-                                                          << QImage::Format_Indexed8
+                                                          << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -444,7 +444,7 @@ void Tools::edgeZero()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -470,7 +470,7 @@ void Tools::mapHeight()
     ImageViewer* iv = getViewer();
 
     if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Mono
-                                                          << QImage::Format_Indexed8
+                                                          << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -483,7 +483,7 @@ void Tools::mapHorizon()
     ImageViewer* iv = getViewer();
 
     if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Mono
-                                                          << QImage::Format_Indexed8
+                                                          << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -524,7 +524,7 @@ void Tools::edgeCanny()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -549,7 +549,7 @@ void Tools::houghTransform()
     ImageViewer* iv = getViewer();
 
     if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Mono
-                                                          << QImage::Format_Indexed8
+                                                          << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -590,7 +590,7 @@ void Tools::cornerHarris()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
@@ -633,7 +633,7 @@ void Tools::segmentation()
 {
     ImageViewer* iv = getViewer();
 
-    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Indexed8
+    if (!SupportedImageFormat(iv, QList<QImage::Format>() << QImage::Format_Grayscale8
                                                           << QImage::Format_RGB32))
         return;
 
diff --git a/src/core/transformations/conversion_grayscale.cpp b/src/core/transformations/conversion_grayscale.cpp
index 34dc613..7cc66cb 100644
--- a/src/core/transformations/conversion_grayscale.cpp
+++ b/src/core/transformations/conversion_grayscale.cpp
@@ -17,7 +17,7 @@ PNM* ConversionGrayscale::transform()
     int width = image->width();
     int height = image->height();
 
-    PNM* newImage = new PNM(width, height, QImage::Format_Indexed8);
+    PNM* newImage = new PNM(width, height, QImage::Format_Grayscale8);
 
     if (image->format() == QImage::Format_Mono)
     {
diff --git a/src/core/transformations/edge_canny.cpp b/src/core/transformations/edge_canny.cpp
index 2c9695a..b52129f 100644
--- a/src/core/transformations/edge_canny.cpp
+++ b/src/core/transformations/edge_canny.cpp
@@ -22,7 +22,7 @@ PNM* EdgeCanny::transform()
     int upper_thresh = getParameter("upper_threshold").toInt(),
         lower_thresh = getParameter("lower_threshold").toInt();
 
-    PNM* newImage = new PNM(width, height, QImage::Format_Indexed8);
+    PNM* newImage = new PNM(width, height, QImage::Format_Grayscale8);
 
     qDebug() << Q_FUNC_INFO << "Not implemented yet!";
 
diff --git a/src/core/transformations/edge_zero.cpp b/src/core/transformations/edge_zero.cpp
index f74d68f..541943f 100644
--- a/src/core/transformations/edge_zero.cpp
+++ b/src/core/transformations/edge_zero.cpp
@@ -21,7 +21,7 @@ PNM* EdgeZeroCrossing::transform()
     double sigma = getParameter("sigma").toDouble();
     int    t     = getParameter("threshold").toInt();
 
-    PNM* newImage = new PNM(width, height, QImage::Format_Indexed8);
+    PNM* newImage = new PNM(width, height, QImage::Format_Grayscale8);
 
     qDebug() << Q_FUNC_INFO << "Not implemented yet!";
 
diff --git a/src/core/transformations/map_height.cpp b/src/core/transformations/map_height.cpp
index f8b1413..71687d3 100644
--- a/src/core/transformations/map_height.cpp
+++ b/src/core/transformations/map_height.cpp
@@ -15,7 +15,7 @@ PNM* MapHeight::transform()
     int width  = image->width(),
         height = image->height();
 
-    PNM* newImage = new PNM(width, height, QImage::Format_Indexed8);
+    PNM* newImage = new PNM(width, height, QImage::Format_Grayscale8);
 
     qDebug() << Q_FUNC_INFO << "Not implemented yet!";
 
diff --git a/src/core/transformations/map_horizon.cpp b/src/core/transformations/map_horizon.cpp
index 80b2cb3..ebcef32 100644
--- a/src/core/transformations/map_horizon.cpp
+++ b/src/core/transformations/map_horizon.cpp
@@ -33,7 +33,7 @@ PNM* MapHorizon::transform()
         dy = -1;
     }
 
-    PNM* newImage = new PNM(width, height, QImage::Format_Indexed8);
+    PNM* newImage = new PNM(width, height, QImage::Format_Grayscale8);
 
     qDebug() << Q_FUNC_INFO << "Not implemented yet!";
 
diff --git a/src/core/transformations/negative_image.cpp b/src/core/transformations/negative_image.cpp
index 01c4e53..bc948df 100644
--- a/src/core/transformations/negative_image.cpp
+++ b/src/core/transformations/negative_image.cpp
@@ -33,9 +33,8 @@ PNM* NegativeImage::transform()
                 newImage->setPixel(x,y, color == Qt::white ? Qt::color0 : Qt::color1);
             }
     }
-    else if (image->format() == QImage::Format_Indexed8)
+    else if (image->format() == QImage::Format_Grayscale8) // Iterate over image space
     {
-        // Iterate over image space
         for (int x=0; x<width; x++)
             for (int y=0; y<height; y++)
             {
@@ -44,7 +43,7 @@ PNM* NegativeImage::transform()
                 int v = qGray(pixel);    // Get the 0-255 value of the L channel
                 v = PIXEL_VAL_MAX - v;
 
-                newImage->setPixel(x,y, v);
+                newImage->setPixel(x,y, QColor(v,v,v).rgb());
             }
     }
     else //if (image->format() == QImage::Format_RGB32)
diff --git a/src/gui/mainwindow.cpp b/src/gui/mainwindow.cpp
index 2cd4a18..9ad3244 100644
--- a/src/gui/mainwindow.cpp
+++ b/src/gui/mainwindow.cpp
@@ -135,7 +135,7 @@ QString MainWindow::textFormat(QImage::Format format)
 {
     if (format == QImage::Format_RGB32)
         return "Color RGB 32-bit";
-    else if (format == QImage::Format_Indexed8)
+    else if (format == QImage::Format_Grayscale8)
         return "Grayscale 8-bit";
     else if (format == QImage::Format_Mono)
         return "Black & white 1-bit";
diff --git a/src/gui/mainwindow.h b/src/gui/mainwindow.h
index 9d93d59..b11ee7c 100644
--- a/src/gui/mainwindow.h
+++ b/src/gui/mainwindow.h
@@ -2,7 +2,7 @@
 #define MAINWINDOW_H
 
 #define PROGRAM_NAME "PTO"
-#define PROGRAM_VER "3.1.3.37"
+#define PROGRAM_VER "3.1.3.38"
 #define DEFAULT_IMG "lenna_512x512.pnm"
 
 #include <QMainWindow>