[truetype] Always use interpreter v35 for B/W rendering (#51051).
* src/truetype/ttgload.c (tt_loader_init) [TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL]: Adjust `subpixel_hinting_lean', `grayscale_cleartype', and `vertical_lcd_lean' accordingly. * src/truetype/ttinterp.c (Ins_GETINFO): Updated. (TT_RunIns): Update `backward_compatibility' flag.
This commit is contained in:
Nikolaus Waxweiler
Werner Lemberg
parent
ab2599ea3f
commit
a0455468fd
12
ChangeLog
12
ChangeLog
|
|
@ -1,3 +1,15 @@
|
|||
2017-05-20 Nikolaus Waxweiler <madigens@gmail.com>
|
||||
|
||||
[truetype] Always use interpreter v35 for B/W rendering (#51051).
|
||||
|
||||
* src/truetype/ttgload.c (tt_loader_init)
|
||||
[TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL]: Adjust
|
||||
`subpixel_hinting_lean', `grayscale_cleartype', and
|
||||
`vertical_lcd_lean' accordingly.
|
||||
|
||||
* src/truetype/ttinterp.c (Ins_GETINFO): Updated.
|
||||
(TT_RunIns): Update `backward_compatibility' flag.
|
||||
|
||||
2017-05-20 Alexei Podtelezhnikov <apodtele@gmail.com>
|
||||
|
||||
[smooth] Implement minimal dynamic padding for LCD filtering.
|
||||
|
|
|
|||
|
|
@ -2339,13 +2339,19 @@
|
|||
#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
|
||||
if ( driver->interpreter_version == TT_INTERPRETER_VERSION_40 )
|
||||
{
|
||||
subpixel_hinting_lean = TRUE;
|
||||
grayscale_cleartype = !FT_BOOL( load_flags &
|
||||
FT_LOAD_TARGET_LCD ||
|
||||
load_flags &
|
||||
FT_LOAD_TARGET_LCD_V );
|
||||
exec->vertical_lcd_lean = FT_BOOL( load_flags &
|
||||
FT_LOAD_TARGET_LCD_V );
|
||||
subpixel_hinting_lean =
|
||||
FT_BOOL( FT_LOAD_TARGET_MODE( load_flags ) !=
|
||||
FT_RENDER_MODE_MONO );
|
||||
grayscale_cleartype =
|
||||
FT_BOOL( subpixel_hinting_lean &&
|
||||
!( ( load_flags &
|
||||
FT_LOAD_TARGET_LCD ) ||
|
||||
( load_flags &
|
||||
FT_LOAD_TARGET_LCD_V ) ) );
|
||||
exec->vertical_lcd_lean =
|
||||
FT_BOOL( subpixel_hinting_lean &&
|
||||
( load_flags &
|
||||
FT_LOAD_TARGET_LCD_V ) );
|
||||
}
|
||||
else
|
||||
{
|
||||
|
|
|
|||
|
|
@ -7345,7 +7345,7 @@
|
|||
/* */
|
||||
/* The only smoothing method FreeType supports unless someone sets */
|
||||
/* FT_LOAD_TARGET_MONO. */
|
||||
if ( ( args[0] & 2048 ) != 0 )
|
||||
if ( ( args[0] & 2048 ) != 0 && exc->subpixel_hinting_lean )
|
||||
K |= 1 << 18;
|
||||
|
||||
/********************************/
|
||||
|
|
@ -7589,11 +7589,21 @@
|
|||
#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
|
||||
|
||||
#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
|
||||
/* Toggle backward compatibility according to what font says, except */
|
||||
/* when it's a `tricky' font that heavily relies on the interpreter to */
|
||||
/* render glyphs correctly, e.g. DFKai-SB. Backward compatibility */
|
||||
/* hacks may break it. */
|
||||
/*
|
||||
* Toggle backward compatibility according to what font wants, except
|
||||
* when
|
||||
*
|
||||
* 1) we have a `tricky' font that heavily relies on the interpreter to
|
||||
* render glyphs correctly, for example DFKai-SB, or
|
||||
* 2) FT_RENDER_MODE_MONO (i.e, monochome rendering) is requested.
|
||||
*
|
||||
* In those cases, backward compatibility needs to be turned off to get
|
||||
* correct rendering. The rendering is then completely up to the
|
||||
* font's programming.
|
||||
*
|
||||
*/
|
||||
if ( SUBPIXEL_HINTING_MINIMAL &&
|
||||
exc->subpixel_hinting_lean &&
|
||||
!FT_IS_TRICKY( &exc->face->root ) )
|
||||
exc->backward_compatibility = !( exc->GS.instruct_control & 4 );
|
||||
else
|
||||
|
|
|
|||
|
|
@ -253,23 +253,38 @@ FT_BEGIN_HEADER
|
|||
|
||||
#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
|
||||
/*
|
||||
* Modern TrueType fonts are usually rendered through Microsoft's
|
||||
* collection of rendering techniques called ClearType (e.g., subpixel
|
||||
* rendering and subpixel hinting). When ClearType was introduced, most
|
||||
* fonts were not ready. Microsoft decided to implement a backward
|
||||
* compatibility mode that employed several simple to complicated
|
||||
* assumptions and tricks that modified the interpretation of the
|
||||
* bytecode contained in these fonts to make them look ClearType-y
|
||||
* somehow. Most (web)fonts that were released since then have come to
|
||||
* rely on these hacks to render correctly, even some of Microsoft's
|
||||
* flagship ClearType fonts (Calibri, Cambria, Segoe UI).
|
||||
* FreeType supports ClearType-like hinting of TrueType fonts through
|
||||
* the version 40 interpreter. This is achieved through several hacks
|
||||
* in the base (v35) interpreter, as detailed below.
|
||||
*
|
||||
* The minimal subpixel hinting code (interpreter version 40) employs a
|
||||
* small list of font-agnostic hacks to bludgeon non-native-ClearType
|
||||
* fonts (except tricky ones[1]) into submission. It will not try to
|
||||
* toggle hacks for specific fonts for performance and complexity
|
||||
* reasons. The focus is on modern (web)fonts rather than legacy fonts
|
||||
* that were made for black-and-white rendering.
|
||||
* ClearType is an umbrella term for several rendering techniques
|
||||
* employed by Microsoft's various GUI and rendering toolkit
|
||||
* implementations, most importantly: subpixel rendering for using the
|
||||
* RGB subpixels of LCDs to approximately triple the perceived
|
||||
* resolution on the x-axis and subpixel hinting for positioning stems
|
||||
* on subpixel borders. TrueType programming is explicit, i.e., fonts
|
||||
* must be programmed to take advantage of ClearType's possibilities.
|
||||
*
|
||||
* When ClearType was introduced, it seemed unlikely that all fonts
|
||||
* would be reprogrammed, so Microsoft decided to implement a backward
|
||||
* compatibility mode. It employs several simple to complicated
|
||||
* assumptions and tricks, many of them font-dependent, that modify the
|
||||
* interpretation of the bytecode contained in these fonts to retrofit
|
||||
* them into a ClearType-y look. The quality of the results varies.
|
||||
* Most (web)fonts that were released since then have come to rely on
|
||||
* these hacks to render correctly, even some of Microsoft's flagship
|
||||
* fonts (e.g., Calibri, Cambria, Segoe UI).
|
||||
*
|
||||
* FreeType's minimal subpixel hinting code (interpreter version 40)
|
||||
* employs a small list of font-agnostic hacks loosely based on the
|
||||
* public information available on Microsoft's compatibility mode[2].
|
||||
* The focus is on modern (web)fonts rather than legacy fonts that were
|
||||
* made for monochrome rendering. It will not match ClearType rendering
|
||||
* exactly. Unlike the `Infinality' code (interpreter version 38) that
|
||||
* came before, it will not try to toggle hacks for specific fonts for
|
||||
* performance and complexity reasons. It will fall back to version 35
|
||||
* behavior for tricky fonts[1] or when monochrome rendering is
|
||||
* requested.
|
||||
*
|
||||
* Major hacks
|
||||
*
|
||||
|
|
@ -347,7 +362,8 @@ FT_BEGIN_HEADER
|
|||
*
|
||||
*/
|
||||
|
||||
/* Using v40 implies subpixel hinting. Used to detect interpreter */
|
||||
/* Using v40 implies subpixel hinting, unless FT_RENDER_MODE_MONO has been
|
||||
* requested. Used to detect interpreter */
|
||||
/* version switches. `_lean' to differentiate from the Infinality */
|
||||
/* `subpixel_hinting', which is managed differently. */
|
||||
FT_Bool subpixel_hinting_lean;
|
||||
|
|
|
|||
Loading…
Reference in New Issue