Re: [ft] Fw: freetype cache and glyph metrics

[Michael Plitkins]

The bitmap stuff is working great. Case closed!

Michael

On Wed, Sep 29, 2010 at 12:14 PM, Brady Duga <address@hidden> wrote:
> Ah, I see. Yeah, I am pretty sure (though mainly from memory) that you can 
> get the descender that way. I think you can recreate all the per-glyph 
> metrics available from normal font loading using some combination of 
> advances, top/left, and the bitmap data *except* for lsb/rsb deltas, which 
> you can't really get using the cache.
>
> --Brady
>
> On Sep 29, 2010, at 11:28 AM, Michael Plitkins wrote:
>
>> Trust me, this is a very special case of character at a time rendering
>> with some character tops or baselines aligned to neighboring glyph top
>> edges, etc. as opposed to a run of text. If the bitmap height - top
>> will get me a descender, then I am all done.
>>
>> Michael
>>
>> On Wed, Sep 29, 2010 at 11:12 AM, Brady Duga <address@hidden> wrote:
>>> Again, I really don't think you want descenders per-glyph. So, say you want 
>>> to draw some text on a line. If we consider the upper-left of the screen to 
>>> be 0,0 with y increasing as we go down, and you want to draw a line whose 
>>> baseline is at y=100, then you:
>>>
>>> set x to 0
>>> set y to 100
>>> for every glyph:
>>>  get cached glyph info
>>>  draw bitmap at x+glyph.left, y - glyph.top
>>>  set x to x + glyph.advance.x
>>>
>>> This will place all your glyphs on the same baseline. If you really want to 
>>> know how much of the glyph extends below the line, then it is just the 
>>> bitmap height minus top.
>>>
>>> --Brady
>>>
>>> On Sep 29, 2010, at 11:04 AM, Michael Plitkins wrote:
>>>
>>>> Yes it does work, but there is still no way to get the descender. The
>>>> FT_GlyphRec already has some of the FT_Glyph_Metrics information in
>>>> the form of the advance. Why doesn't the FT_GlyphRec contain the
>>>> remaining information? Memory concerns? Performance?
>>>>
>>>> Thanks again for help and suggestions.
>>>>
>>>> Michael
>>>>
>>>> On Wed, Sep 29, 2010 at 9:50 AM, Michael Plitkins
>>>> <address@hidden> wrote:
>>>>> Thanks. This may well get me moving forward. I do indeed need to
>>>>> measure the horiBearingY because I am trying to line up type of
>>>>> different sizes to get the presentation that we need. Measuring a few
>>>>> sample characters will be adequate. Using the rendered bitmap still
>>>>> won't give me a way to calculate the descender though (all I will know
>>>>> is the actual full height of the rendered glyph).
>>>>>
>>>>> I knew that the FT_Load_Glyph(), was bogus, but it was my last ditch 
>>>>> attempt.
>>>>>
>>>>> Using FTC_CMapCache_Lookup() is on list my too.
>>>>>
>>>>> Many thanks and I will report how this turns out.
>>>>>
>>>>> Michael
>>>>>
>>>>> On Wed, Sep 29, 2010 at 8:34 AM, Brady Duga <address@hidden> wrote:
>>>>>> Well, I am not entirely sure what you want to do. Using horiBearingY as 
>>>>>> the
>>>>>> ascender seems weird - do you really want to use glyph metrics for line
>>>>>> metrics? Or do you really need the ascender/descender info for every 
>>>>>> glyph?
>>>>>> In any case, you shouldn't be calling FT_Load_Glyph when using the cache
>>>>>> system. Instead, you let the cache subsytem make that call using the load
>>>>>> flags you supply to FTC_ImageCache_LookupScaler(). That gives you an
>>>>>> FT_Glyph which you can use for basic glyph metrics. Specifically the
>>>>>> "advance" vector of that struct tells you how far to move to account for
>>>>>> this glyph. In a more interesting case, you would pass FT_LOAD_RENDER to 
>>>>>> the
>>>>>> cache subsystem, which should make the returned glyph be an 
>>>>>> FT_BitmapGlyph.
>>>>>> That in turn gives you the left/top coordinates for the actual bitmap, 
>>>>>> plus
>>>>>> an FT_Bitmap struct you can use for more information. Once you have the 
>>>>>> top
>>>>>> and left values, you can essentially calculate the horibearingX/Y, though
>>>>>> you may not need to bother. The nice thing about using the cache is, in 
>>>>>> most
>>>>>> cases rendering is fast (already cached). It's only a problem if you 
>>>>>> plan to
>>>>>> measure a *lot* of glyphs that you don't plan to render. Of course, in 
>>>>>> that
>>>>>> case there isn't much point in using the cache at all.
>>>>>> You might also want to consider caching the char map
>>>>>> using FTC_CMapCache_Lookup instead of FT_Get_Char_Index.
>>>>>> --Brady
>>>>>>
>>>>>>
>>>>>> On Sep 28, 2010, at 11:30 PM, Werner LEMBERG wrote:
>>>>>>
>>>>>> Please help this guy.
>>>>>>
>>>>>>
>>>>>>    Werner
>>>>>>
>>>>>> From: Michael Plitkins <address@hidden>
>>>>>> Date: September 28, 2010 9:50:48 PM PDT
>>>>>> To: address@hidden
>>>>>> Subject: freetype cache and glyph metrics
>>>>>>
>>>>>>
>>>>>> Hello Werner,
>>>>>>
>>>>>> I have been using freetype for some time and have come to my first
>>>>>> stumbling block: When using the image and font face caches, how can I
>>>>>> get the the full metrics of a glyph (metrics.horiBearingY, etc.)? It
>>>>>> seems that information is only available from the FT_GlyphSlotRec in
>>>>>> the face itself. When using the cache APIs all of my attempts to get
>>>>>> at the FT_Glyph_Metrics have yielded inconsistent results. Here is one
>>>>>> of my latest attempts:
>>>>>>
>>>>>> void nlGfxContext :: GetGlyphMetrics(nlULONG aHeight, char aGlyph,
>>>>>> nlFontMetrics *aOutMetrics)
>>>>>> {
>>>>>>    if ((mFont != NULL) && (aOutMetrics != NULL))
>>>>>>    {
>>>>>>        FT_Face         font;
>>>>>>        FTC_ScalerRec   scaler;
>>>>>>
>>>>>>        scaler.face_id = mFont;
>>>>>>        scaler.width = 0;
>>>>>>        scaler.height = aHeight;
>>>>>>        scaler.pixel = 1;
>>>>>>        scaler.x_res = 0;
>>>>>>        scaler.y_res = 0;
>>>>>>
>>>>>>        font = mGlobals->LookupFontID(mFont);
>>>>>>
>>>>>>        if (font != NULL)
>>>>>>        {
>>>>>>            FTC_ImageCache  icache = mGlobals->GetFontImageCache();
>>>>>>            FT_Glyph        glyph;
>>>>>>            FTC_Node        node;
>>>>>>            FT_UInt         charidx = FT_Get_Char_Index(font, aGlyph);
>>>>>>            FT_Error        err;
>>>>>>
>>>>>>            err = FTC_ImageCache_LookupScaler(icache, &scaler,
>>>>>> FT_LOAD_DEFAULT, charidx, &glyph, &node);
>>>>>>
>>>>>>            FT_Load_Glyph(font, charidx, FT_LOAD_DEFAULT);
>>>>>>
>>>>>>            if (err == FT_Err_Ok)
>>>>>>            {
>>>>>>                aOutMetrics->mHeight = font->glyph->metrics.height >> 6;
>>>>>>                aOutMetrics->mAscender = 
>>>>>> font->glyph->metrics.horiBearingY >>
>>>>>> 6;
>>>>>>                aOutMetrics->mDescender = -(aOutMetrics->mHeight -
>>>>>> aOutMetrics->mAscender);
>>>>>>                aOutMetrics->mMaxAdvance =
>>>>>> font->glyph->metrics.horiAdvance >> 6;
>>>>>>
>>>>>>                FTC_Node_Unref(node, mGlobals->GetFontCacheManager());
>>>>>>            }
>>>>>>        }
>>>>>>    }
>>>>>> }
>>>>>>
>>>>>> This is my horrible attempt to use the image cache scaler to get the
>>>>>> glyph that i want at the size that i want and somehow get the glyph
>>>>>> metrics to be set as i want as part of the FT_Load_Glyph(). It seems
>>>>>> like it shouldn't work and it doesn't.
>>>>>>
>>>>>> How does one get the metrics for an individual glyph and use the
>>>>>> caching subsystems at the same time?
>>>>>>
>>>>>> I apologize in advance if this has been answered somewhere out on the
>>>>>> internet, but I was unable to find it.
>>>>>>
>>>>>> Many thanks.
>>>>>>
>>>>>> Michael Plitkins
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Freetype mailing list
>>>>>> address@hidden
>>>>>> http://lists.nongnu.org/mailman/listinfo/freetype
>>>>>>
>>>>>>
>>>>>
>>>
>>>
>
>