0025544: Visualization, TKOpenGl - support grayscale textures

Image_PixMap::ImgFormat - extend enumeration by ImgAlpha and ImgAlphaF.
OpenGl_Workspace::setTextureParams() - specify GL_REPLACE for 1-component textures with disabled modulation.
OpenGl_Texture::GetDataFormat() - return GL_LUMINANCE format for ImgGray format and GL_ALPHA for ImgAlpha.

vmarkerstest - override pixel format for grayscale images to ImgAlpha.

Add test case bugs/vis/bug25544_graytexture.

src/Image/Image_AlienPixMap.cxx

@@ -78,6 +78,7 @@ namespace
     switch (theFormat)
     {
       case Image_PixMap::ImgGrayF:
+      case Image_PixMap::ImgAlphaF:
         return FIT_FLOAT;
       case Image_PixMap::ImgRGBAF:
         return FIT_RGBAF;
@@ -90,6 +91,7 @@ namespace
       case Image_PixMap::ImgRGB:
       case Image_PixMap::ImgBGR:
       case Image_PixMap::ImgGray:
+      case Image_PixMap::ImgAlpha:
         return FIT_BITMAP;
       default:
         return FIT_UNKNOWN;
@@ -448,7 +450,8 @@ bool Image_AlienPixMap::Save (const TCollection_AsciiString& theFileName)
     }
     case FIF_EXR:
     {
-      if (Format() == Image_PixMap::ImgGray)
+      if (Format() == Image_PixMap::ImgGray
+       || Format() == Image_PixMap::ImgAlpha)
       {
         anImageToDump = FreeImage_ConvertToType (myLibImage, FIT_FLOAT);
       }

src/Image/Image_PixMap.cxx

@@ -15,6 +15,7 @@
 
 #include <Image_PixMap.hxx>
 #include <NCollection_AlignedAllocator.hxx>
+#include <Standard_ProgramError.hxx>
 
 #include <algorithm>
 
@@ -48,6 +49,7 @@ Standard_Size Image_PixMap::SizePixelBytes (const Image_PixMap::ImgFormat thePix
   switch (thePixelFormat)
   {
     case ImgGrayF:
+    case ImgAlphaF:
       return sizeof(float);
     case ImgRGBAF:
     case ImgBGRAF:
@@ -65,17 +67,32 @@ Standard_Size Image_PixMap::SizePixelBytes (const Image_PixMap::ImgFormat thePix
     case ImgBGR:
       return 3;
     case ImgGray:
-    default:
+    case ImgAlpha:
+      return 1;
+    case ImgUNKNOWN:
       return 1;
   }
+  return 1;
 }
 
 // =======================================================================
-// function : setFormat
+// function : SetFormat
 // purpose  :
 // =======================================================================
-void Image_PixMap::setFormat (Image_PixMap::ImgFormat thePixelFormat)
+void Image_PixMap::SetFormat (Image_PixMap::ImgFormat thePixelFormat)
 {
+  if (myImgFormat == thePixelFormat)
+  {
+    return;
+  }
+
+  if (!IsEmpty()
+    && SizePixelBytes (myImgFormat) != SizePixelBytes (thePixelFormat))
+  {
+    Standard_ProgramError::Raise ("Image_PixMap::SetFormat() - incompatible pixel format");
+    return;
+  }
+
   myImgFormat = thePixelFormat;
 }
 
@@ -201,6 +218,12 @@ Quantity_Color Image_PixMap::PixelColor (const Standard_Integer theX,
                              Quantity_Parameter (Standard_Real (aPixel)),
                              Quantity_TOC_RGB);
     }
+    case ImgAlphaF:
+    {
+      const Standard_ShortReal& aPixel = Value<Standard_ShortReal> (theY, theX);
+      theAlpha = aPixel;
+      return Quantity_Color (1.0, 1.0, 1.0, Quantity_TOC_RGB);
+    }
     case ImgRGBAF:
     {
       const Image_ColorRGBAF& aPixel = Value<Image_ColorRGBAF> (theY, theX);
@@ -300,11 +323,19 @@ Quantity_Color Image_PixMap::PixelColor (const Standard_Integer theX,
                              Quantity_Parameter (Standard_Real (aPixel) / 255.0),
                              Quantity_TOC_RGB);
     }
-    default:
+    case ImgAlpha:
     {
-      // not supported image type
-      theAlpha = 0.0; // transparent
-      return Quantity_Color (0.0, 0.0, 0.0, Quantity_TOC_RGB);
+      const Standard_Byte& aPixel = Value<Standard_Byte> (theY, theX);
+      theAlpha = Standard_Real (aPixel) / 255.0;
+      return Quantity_Color (1.0, 1.0, 1.0, Quantity_TOC_RGB);
+    }
+    case ImgUNKNOWN:
+    {
+      break;
     }
   }
+
+  // unsupported image type
+  theAlpha = 0.0; // transparent
+  return Quantity_Color (0.0, 0.0, 0.0, Quantity_TOC_RGB);
 }

src/Image/Image_PixMap.hxx

@@ -30,14 +30,16 @@ public:
   //! This enumeration define packed image plane formats
   typedef enum tagFormat {
       ImgUNKNOWN = 0, //!< unsupported or unknown format
-      ImgGray    = 1, //!< 1 byte per pixel
+      ImgGray    = 1, //!< 1 byte per pixel, intensity of the color
+      ImgAlpha,       //!< 1 byte per pixel, transparency
       ImgRGB,         //!< 3 bytes packed RGB image plane
       ImgBGR,         //!< same as RGB but with different components order
       ImgRGB32,       //!< 4 bytes packed RGB image plane (1 extra byte for alignment, may have undefined value)
       ImgBGR32,       //!< same as RGB but with different components order
       ImgRGBA,        //!< 4 bytes packed RGBA image plane
       ImgBGRA,        //!< same as RGBA but with different components order
-      ImgGrayF,       //!< 1 float  (4-bytes) per pixel (1-component plane)
+      ImgGrayF,       //!< 1 float  (4-bytes) per pixel (1-component plane), intensity of the color
+      ImgAlphaF,      //!< 1 float  (4-bytes) per pixel (1-component plane), transparency
       ImgRGBF,        //!< 3 floats (12-bytes) RGB image plane
       ImgBGRF,        //!< same as RGBF but with different components order
       ImgRGBAF,       //!< 4 floats (16-bytes) RGBA image plane
@@ -59,6 +61,12 @@ public: // high-level API
     return myImgFormat;
   }
 
+  //! Override pixel format specified by InitXXX() methods.
+  //! Will throw exception if pixel size of new format is not equal to currently initialized format.
+  //! Intended to switch formats indicating different interpretation of the same data
+  //! (e.g. ImgGray and ImgAlpha).
+  Standard_EXPORT void SetFormat (const ImgFormat thePixelFormat);
+
   //! @return image width in pixels
   inline Standard_Size Width() const
   {
@@ -258,11 +266,6 @@ public: //! @name low-level API for batch-processing (pixels reading / compariso
     return *reinterpret_cast<ColorType_t* >(myData.ChangeValue (theRow, theCol));
   }
 
-protected:
-
-  //! Setup pixel format
-  Standard_EXPORT void setFormat (ImgFormat thePixelFormat);
-
 protected:
 
   Image_PixMapData myData;      //!< data buffer