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# OpenGL FreeType2 with OpenGL

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Hi!!11111 I'm trying to use glBitmap fonts with freetype. This is actually part of the code (from freetype tutorial)


FT_GlyphSlot  slot = face->glyph;  // a small shortcut

FT_UInt       glyph_index;
int           pen_x, pen_y, n;

.. initialise library ..
.. create face object ..
.. set character size ..

pen_x = 300;
pen_y = 200;

for ( n = 0; n < num_chars; n++ )
{
// load glyph image into the slot (erase previous one)

if (error) continue;  // ignore errors

// now, draw to our target surface

my_draw_bitmap( &slot->bitmap,
pen_x + slot->bitmap_left,
pen_y - slot->bitmap_top );

// increment pen position

}


I'v modified it to go throught each character from 32 to 127 and create opengl displaylist in place if my_draw_bitmap. The problem is that I get only some extraordinary pixel-figures where can not be seen any characters. The problem is that I can't get correct conversion for the data from FT_Bitmap to glBitmap. I'w googled and searched all tutorials but can't get it working. There's not any example for the my_draw_bitmap procedure. Can anyone help? Edited by - stefu on March 21, 2002 3:21:03 PM

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Hmm, I did something similar a while ago. But I used standard alpha textures instead of GL bitmaps, so that I could get antialiased fonts. The conversion from the FT_Bitmap was straight forward:

  FT_Bitmap *bitmap = ...  // source bitmapchar *texture_data = ...  // destination alpha texture (512*128)for( y=0; y<bitmap->rows; y++ ) for( x=0; x<bitmap->width; x++ ) texture_data[y*512+x] = bitmap->buffer[y*bitmap->pitch+x];

The destination texture has a fixed width of 512, so be careful if you want to modify it, don''t forget to adapt the loop. And this thing is not fast, so use it only in a preprocess, not in realtime (or optimize it).

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Thanks.
The problem was that I didn''t know the bitmap format.
It seems each row must be k*32 bits (dword alignment).
I used k*8 bits, that was wrong.

Also all characters were upside-down.

Here''s the conversion that works now for me
if someone want''s to use Freetype in OpenGL

  	base = 0;	pixel_height = 18;	int error = FT_Init_FreeType( &library );	if ( error ) return;	error = FT_New_Face( library, "/usr/share/fonts/truetype/commercial/arial.ttf",0, &face );        if ( error ) return;	error = FT_Set_Pixel_Sizes(              face,   /* handle to face object            */              0,      /* pixel_width                      */              16 );   /* pixel_height                     */ 	   FT_GlyphSlot  slot = face->glyph;  // a small shortcut	   base = glGenLists(96);								// Storage For 96 Characters       for ( int n = 0; n < 96; n++ )	   {	     int ch = n+32;         // load glyph image into the slot (erase previous one)         error = FT_Load_Char( face, ch, FT_LOAD_RENDER|FT_LOAD_MONOCHROME);         if (error) continue;  // ignore errors		char bmp[64*64]; // be carrefull!!!                		memset(bmp,0,sizeof(bmp));		for(int y=0; y<slot->bitmap.rows; y++)		{			int dst_pitch = 4;			while(slot->bitmap.pitch>dst_pitch) dst_pitch+=4;			GLubyte *src_row = slot->bitmap.buffer + y*slot->bitmap.pitch;			GLubyte *dst_row = bmp + (slot->bitmap.rows-y-1)*dst_pitch;			int src_pitch = slot->bitmap.pitch;			for(int x=0; x<src_pitch; x++ )			{				dst_row[x] = src_row[x];			}		}	     glNewList(base+n,GL_COMPILE);		 // bitmap is a binary image		 glBitmap(slot->bitmap.width,   				slot->bitmap.rows,				-slot->bitmap_left,				slot->bitmap.rows-slot->bitmap_top,				(slot->advance.x>>6),				(slot->advance.y>>6),                bmp ); 	     glEndList();       }

ps. Can I share fon''t with my app? Is there free font''s to do that? (Just to ake sure font is always available in the same location.)

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