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stefu

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)

         error = FT_Load_Char( face, text[n], FT_LOAD_RENDER | FT_LOAD_MONOCHROME );
         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 

         pen_x += slot->advance.x >> 6;
       }

    
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 bitmap

char *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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