Re: [ft] FT_Set_Char_Size vs. FT_Set_Pixel_Sizes

[Olumide]

On 17/11/2016 18:25, Werner LEMBERG wrote:
> > I have used FT_Set_Pixel_Sizes( face , 32 , 32 ) -- because 32 by 32
> > is the maximum font dimension of a font in my application. Upon
> > inspection of the resulting face->glyph I get a bitmap that's only
> > about 25% of the size specified in FT_Set_Pixel_Sizes (Bitmap
> > details: rows = top = 22, width = 13, left = 1).  Of course I may
> > have completely misunderstood what FT_Set_Pixel_Sizes does.  Please
> > do correct me where my thinking or understanding is incorrect.
>
> Your thinking *is* incorrect :-) FT_Set_Pixel_Sizes sets the *nominal*
> size for the whole font, this is, the size the font designer thinks
> the font looks best for a given pixel size.  In many cases, the
> largest glyphs in the font (e.g., `|', `(', or `)') have this height,
> but usually the actual glyph heights are lower.
>
> You might try the `FT_Request_Size' function using
> `FT_SIZE_REQUEST_TYPE_REAL_DIM' or `FT_SIZE_REQUEST_TYPE_BBOX' to
> better approximate your desired height.  Note, however, that with
> activated hinting the only possibility to exactly make a glyph fit
> into a given height is trial and error: You start with an
> approximation value, then look at the delta relative to the wanted
> height, then decrease or increase the size as needed and try again.
> If you are unfortunate, the glyph height jumps by two pixels, not
> fitting your desired height at all...

I've just tried the following

FT_Size_RequestRec req = { FT_SIZE_REQUEST_TYPE_BBOX , 0 , 3450 , 0 , 0 };
FT_Request_Size( face , &req );

Where 3450 is experimentally obtained such that the bitmap has 32 rows 
for the tallest (pipe character). Then I loaded the character 
'f'(shorter than the pipe symbol) expecting to get a bitmap with fewer 
rows, instead I got a bitmap with a larger number of rows.

So I returned to the previous approach and set

FT_Set_Pixel_Sizes( face , 55 , 55 );

Where the value 55 is experimentally obtained such that the resulting 
bitmap has 32 rows for the tallest (pipe character). Again Then I loaded 
the character 'f' expecting to get a bitmap with fewer rows, instead I 
got a bitmap with a larger number of rows.

Any advise will be much appreciated.

Regards,

- Olumide