[Devel] FreeType performance issue.

[강 재민]

After changing FreeType library source code a little, I tested it on ARM7 platform and got this result.

 

Test String : "The coalition, called the United Iraqi Alliance, is backed by Grand A"

Font Size : (20 << 6) X (20 << 6), 72DPI

Render Mode : Antialiased.

 

It took 1550 milisecond to Load_Glyph and Render_Glyph above test string(except physical lcd access routine).

This performance result doesn't meet my goal so I'm looking for some parts to be optimized, something like below.

 

 

 

In 'ftgrays.c ' file, the 'gray_convert_glyph' function calls 'gray_compute_cbox' function first to get an glyph boundary.

 

*gray_compute_cbox function costs O(n) - n is the number of points

 

But in this time, I think FreeType can use (raster->target).width, (raster->target).height.

I think the code can be changed like this

 

  static int

  gray_convert_glyph( RAS_ARG )

  {
    TBand            bands[40];
    TBand* volatile  band;
    int volatile     n, num_bands;
    TPos volatile    min, max, max_y;
    FT_BBox*         clip;

 

    /* Set up state in the raster object */
    /*gray_compute_cbox( RAS_VAR );*/                // Don't need

    raster->min_ex = 0;                              // Added

    raster->max_ex = (raster->target).width;         // Added

    raster->min_ey = 0;                              // Added

    raster->max_ey = (raster->target).height;        // Added

    ...

 

 

Would you tell me if there is any reason that I can't do like this?

 

I'm going to inspect all glyph points iteration code to optimize.

 

And any opinions about performance would be helpful... thank you.