Typography's Trimmable Feature

[prepare]

see verybadcat/CSharpMath#107

I copy this image from that link.

pic 1

[prepare]

Plan:

1. List<Type2Instruction> could be unload after you create a glyph outline from it.
2. Unload many openfont tables that are not need by user
3. Optimize List<Type2Instruction>

---

[prepare]

Before I add unload features Trimmable features.
Today I push an optimization on CFF Instructions. (3)

(see : 8bcde3c)

and

I think the new compact form of CFF instructions will

1. reduce memory usage.
2. not affect the performance.
3. still compat with CFF standard

---

in this version,
Instruction in compact form use space about 44% of original one

[prepare]

Typography's Trimmable Feature

pic 2: from pic1, the objects in red rect are the targets of the Trimmable feature

see Trimmable feature on latest master

This can be used with ttf, otf (cff) , svg, bitmap font.

After TrimDown(), the Typeface removes 'glyph-building instructions' of all kinds.
=>It can't be used for generating glyph outline output.

BUT It preserves the 'TextLayout information' (eg. GSUB, GPOS) =>.
the trimmed typeface can be used for text-layout process.

you can 'restore' the information again with RestoreUp()

Hope this will reduce memory usuage :)

using Typography.OpenFont;
using Typography.OpenFont.Trimmable;
 

//....
//...

    static void TestLoadAndReload(string filename)
        {

            //Trimmable feature tests:           
            //[A] read the font file as usual => get full information about the font 
            Typeface typeface = null;
            using (FileStream fs = new FileStream(filename, FileMode.Open))
            {
                //read in full mode
                OpenFontReader openFontReader = new OpenFontReader();
                typeface = openFontReader.Read(fs);
            }

            //before
            bool hasColor1 = typeface.HasColorTable();
            bool hasSvg1 = typeface.HasSvgTable();
            bool hasCff1 = typeface.IsCffFont;
            TrimMode glyphMode1 = typeface.GetTrimMode();
            Glyph g1_1 = typeface.GetGlyph(1);

            //---------------------------------------------------------
            //[B] if you create paths from glyphs, or atlas from glyph 
            //   and you don't want any glyph-building-detail (eg. to reduce memory usuage)
            //   but you still want to use the typeface for text-layout
            //   you can trim it down
            RestoreTicket ticket = typeface.TrimDown();//***

            //[C] you can GetGlyph() but this is ANOTHER NEW GLYPH
            //without building instruction( eg. no cff,ttf,svg data,bitmap)
            //

            Glyph g1_2 = typeface.GetGlyph(1);

            //** if you cache the the old version of 'full-info' glyph**
            // the info is still cache on the old glyph and it can be used as 'full-info' glyph
            // TrimDown() DOES NOT go to delete that glyph.

            bool hasColor2 = typeface.HasColorTable();
            bool hasSvg2 = typeface.HasSvgTable();
            bool hasCff2 = typeface.IsCffFont;

            TrimMode glyphMode2 = typeface.GetTrimMode();
            //---------------------------------------------------------

            //[D] can we load glyph detail again?
            //yes=> this need 'ticket' from latest TrimDown()
            //if you don't have it, you can't restore it.           

            using (FileStream fs = new FileStream(filename, FileMode.Open))
            {
                typeface.RestoreUp(ticket, fs);
            }
        }

Trimmable test, FormTestTrimmableFeature