[ft] Stroker and glyph border

[Fred408]

Hello,

I'm using freetype to render subtitles to display in video. All the glyphs
look
really great with the anti-aliasing and everything seems to work fine. 

However, I am now trying to add a black border (contour) to the glyph shapes
so that
they remain visible in most background video. I use the stroker to create
the
contour but I can't manage to adjust the contour position so that it fits
perfectly
the edge of the shape. 
  
Once I have rendered the contour to a bitmap, how can I position it so that
it fits
perfectly with the white glyph shapes edges ?

My code is just below.

Thanks alot for the help,

Fred


Here is my code : (in bold are passages I'm unsure about)
_____________________________________________________________


   // Init freeType
error = FT_Init_FreeType(&library);
   // Create Face
error = FT_New_Face(library, "arial.ttf", 0, &face);
   // Set Pixel size
error = FT_Set_Pixel_Sizes(face, 256, 0);
   // Shortcut to glyph slot
pSlot = (face->glyph);


   // for each character in the string
for(i=0 ; i<strlen(text) ; i++){

       // load the glyph in the glyphSlot
   error = FT_Load_Char(face, text[i], FT_LOAD_RENDER);
      // compute the upper left corner of the glyph
   nPosX = penx + pSlot->metrics.horiBearingX/64+1;
   nPosY = peny - pSlot->metrics.horiBearingY/64+1;
      // draw the glyph to the bitmap
   for(j=0 ; j<pSlot->bitmap.rows ; j++){
      for(k=0 ; k<pSlot->bitmap.width ; k++){
         bitmap[nPosY+j][nPosX+k] =
pSlot->bitmap.buffer[(j*(pSlot->bitmap.width))+k];
      }
   }


      // Up to here everything looks great.
      // Now lets add some nice black contour to the glyph shapes.


      // load the glyph once again but without rendering it
   error = FT_Load_Char(face, text[i], FT_LOAD_DEFAULT);
      // copy from glyphSlot to glyph
   error = FT_Get_Glyph( pSlot, &glyph );
      // create stroker
   FT_Stroker_New(library, &stroker);


      // Configure stroker (how to choose radius ?)
   FT_Stroker_Set(stroker, 
     16, // ?? 
     FT_STROKER_LINECAP_ROUND,
     FT_STROKER_LINEJOIN_ROUND,
     0 
   );


      // Apply stroke to the glyph to create the contour
   error = FT_Glyph_Stroke( &glyph, stroker, 0 );
      // Render the contour glyph to the bitmap
   error = FT_Glyph_To_Bitmap( &glyph, FT_RENDER_MODE_NORMAL, &origin, 0 );

      // cast the contour glyph to a bitmapGlyph
   glyphBitmap = (FT_BitmapGlyph)glyph;

      // Compute contour glyph upper left corner
   nPosX = penx + pSlot->metrics.horiBearingX/64;//+?
   nPosY = peny - pSlot->metrics.horiBearingY/64;//+?

      // Draw the contour to another bitmap
   for(j=0 ; j<glyphBitmap->bitmap.rows ; j++){
      for(k=0 ; k<glyphBitmap->bitmap.width ; k++){
          bitmap2[nPosY+j][nPosX+k] =
      glyphBitmap->bitmap.buffer[(j*(glyphBitmap->bitmap.width))+k];
      }
   }
 

      // update the penX coordinate with the glyph or with the contour
      // glyph horiAdvance ? (if the contour is very thick we have to take
      // it into account in the pen update)
   penx += pSlot->metrics.horiAdvance/64; // ?
}

_________________________________________________________

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