From Farshid Lashkari, "I've updated the dds, png, and jpeg plugins to support writing images with the GL_DEPTH_COMPONENT pixel format. They will simply treat it the same as the GL_LUMINANCE pixel format."

src/osgPlugins/dds/ReaderWriterDDS.cpp

@@ -1147,6 +1147,7 @@ bool WriteDDSFile(const osg::Image *img, std::ostream& fout, bool autoFlipDDSWri
         }
         break;
     case GL_LUMINANCE:
+    case GL_DEPTH_COMPONENT:
         {
             ddpf.dwRBitMask         = 0x000000ff;
             PF_flags |= DDPF_LUMINANCE;

src/osgPlugins/jpeg/ReaderWriterJPEG.cpp

@@ -665,6 +665,7 @@ class ReaderWriterJPEG : public osgDB::ReaderWriter
             int image_components = 3;
             // Only cater for gray, alpha and RGB for now
             switch(img.getPixelFormat()) {
+              case(GL_DEPTH_COMPONENT):
               case(GL_LUMINANCE):
               case(GL_ALPHA): {
                   image_color_space = JCS_GRAYSCALE;

src/osgPlugins/png/ReaderWriterPNG.cpp

@@ -114,6 +114,7 @@ class ReaderWriterPNG : public osgDB::ReaderWriter
 
             int bit_depth = img.getPixelSizeInBits();
             switch(img.getPixelFormat()) {
+                case(GL_DEPTH_COMPONENT): color = PNG_COLOR_TYPE_GRAY; break;
                 case(GL_LUMINANCE): color = PNG_COLOR_TYPE_GRAY; break;
                 case(GL_ALPHA): color = PNG_COLOR_TYPE_GRAY; break; //Couldn't find a color type for pure alpha, using gray instead
                 case(GL_LUMINANCE_ALPHA): color = PNG_COLOR_TYPE_GRAY_ALPHA ; bit_depth /= 2; break;