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[truetype] Identify the tricky fonts by cvt/fpgm/prep checksums.

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Some Latin TrueType fonts are still expected to be unhinted.
Fix Savannah bug #31645.

* src/truetype/ttobjs.c (tt_check_trickyness): Divided to...
(tt_check_trickyness_family): this checking family name, and
(tt_check_trickyness_sfnt_ids): this checking cvt/fpgm/prep.
(tt_get_sfnt_checksum): Function to retrieve the sfnt checksum
for specified subtable even if cleared by lazy PDF generators.
(tt_synth_sfnt_checksum): Function to calculate the checksum.
This commit is contained in:
suzuki toshiya 2010-11-23 02:47:10 +09:00
parent ec4372f565
commit 9f5dd61bf3
2 changed files with 171 additions and 9 deletions
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13
ChangeLog
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@ -1,3 +1,16 @@
2010-11-22 suzuki toshiya <mpsuzuki@hiroshima-u.ac.jp>
[truetype] Identify the tricky fonts by cvt/fpgm/prep checksums.
Some Latin TrueType fonts are still expected to be unhinted.
Fix Savannah bug #31645.
* src/truetype/ttobjs.c (tt_check_trickyness): Divided to...
(tt_check_trickyness_family): this checking family name, and
(tt_check_trickyness_sfnt_ids): this checking cvt/fpgm/prep.
(tt_get_sfnt_checksum): Function to retrieve the sfnt checksum
for specified subtable even if cleared by lazy PDF generators.
(tt_synth_sfnt_checksum): Function to calculate the checksum.
2010-11-18 Werner Lemberg <wl@gnu.org>
[truetype] Fix `loca' handling for inconsistent number of glyphs.

167
src/truetype/ttobjs.c
View File

@ -147,7 +147,7 @@
/* This list shall be expanded as we find more of them. */
static FT_Bool
tt_check_trickyness( FT_String* name )
tt_check_trickyness_family( FT_String* name )
{
#define TRICK_NAMES_MAX_CHARACTERS 16
#define TRICK_NAMES_COUNT 8
@ -163,13 +163,6 @@
"MingLi43", /* mingli.ttf */
};
int nn;
if ( !name )
return TRUE;
/* Note that we only check the face name at the moment; it might */
/* be worth to do more checks for a few special cases. */
for ( nn = 0; nn < TRICK_NAMES_COUNT; nn++ )
if ( ft_strstr( name, trick_names[nn] ) )
return TRUE;
@ -178,6 +171,162 @@
}
/* XXX: this function should be in sfnt module */
/* some PDF generators clear the checksum in TrueType header */
/* (Quartz ContextPDF clears all, Bullzip PDF Printer clears */
/* for the subsetted subtables), we have to recalculate when */
/* it is cleared. */
static FT_UInt32
tt_synth_sfnt_checksum( FT_Stream stream,
FT_ULong length )
{
FT_Error error;
FT_UInt32 checksum = 0;
int i;
if ( FT_FRAME_ENTER( length ) )
return 0;
for ( ; length > 3; length -= 4 )
checksum += (FT_UInt32)FT_GET_ULONG();
for ( i = 3; length > 0; length --, i-- )
checksum += (FT_UInt32)( FT_GET_BYTE() << ( i * 8 ) );
FT_FRAME_EXIT();
return checksum;
}
/* XXX: this function should be in sfnt module */
static FT_ULong
tt_get_sfnt_checksum( TT_Face face,
FT_UShort i )
{
if ( face->dir_tables[i].CheckSum )
return face->dir_tables[i].CheckSum;
else if ( !face->goto_table )
return 0;
else if ( !face->goto_table( face,
face->dir_tables[i].Tag,
face->root.stream,
NULL ) )
return 0;
return (FT_ULong)tt_synth_sfnt_checksum( face->root.stream,
face->dir_tables[i].Length );
}
typedef struct tt_sfnt_id_rec_
{
FT_ULong CheckSum;
FT_ULong Length;
} tt_sfnt_id_rec;
static FT_Bool
tt_check_trickyness_sfnt_ids( TT_Face face )
{
#define TRICK_SFNT_IDS_PER_FACE 3
#define TRICK_SFNT_IDS_NUM_FACES 5
static const tt_sfnt_id_rec sfnt_id[TRICK_SFNT_IDS_NUM_FACES]
[TRICK_SFNT_IDS_PER_FACE] = {
#define TRICK_SFNT_ID_cvt 0
#define TRICK_SFNT_ID_fpgm 1
#define TRICK_SFNT_ID_prep 2
{ /* MingLiU 1995 */
{ 0x05bcf058, 0x000002e4 }, /* cvt */
{ 0x28233bf1, 0x000087c4 }, /* fpgm */
{ 0xa344a1ea, 0x000001e1 } /* prep */
},
{ /* MingLiU 1996- */
{ 0x05bcf058, 0x000002e4 }, /* cvt */
{ 0x28233bf1, 0x000087c4 }, /* fpgm */
{ 0xa344a1eb, 0x000001e1 } /* prep */
},
{ /* DFKaiShu */
{ 0x11e5ead4, 0x00000350 }, /* cvt */
{ 0x5a30ca3b, 0x00009063 }, /* fpgm */
{ 0x13a42602, 0x0000007e } /* prep */
},
{ /* HuaTianKaiTi */
{ 0xfffbfffc, 0x00000008 }, /* cvt */
{ 0x9c9e48b8, 0x0000bea2 }, /* fpgm */
{ 0x70020112, 0x00000008 } /* prep */
},
{ /* HuaTianSongTi */
{ 0xfffbfffc, 0x00000008 }, /* cvt */
{ 0x0a5a0483, 0x00017c39 }, /* fpgm */
{ 0x70020112, 0x00000008 } /* prep */
}
};
FT_ULong checksum;
int num_matched_ids[TRICK_SFNT_IDS_NUM_FACES];
int i, j, k;
FT_MEM_SET( num_matched_ids, 0, sizeof( int ) * TRICK_SFNT_IDS_NUM_FACES );
for ( i = 0; i < face->num_tables; i++ )
{
checksum = 0;
switch( face->dir_tables[i].Tag )
{
case TTAG_cvt:
k = TRICK_SFNT_ID_cvt;
break;
case TTAG_fpgm:
k = TRICK_SFNT_ID_fpgm;
break;
case TTAG_prep:
k = TRICK_SFNT_ID_prep;
break;
default:
continue;
}
for ( j = 0; j < TRICK_SFNT_IDS_NUM_FACES; j++ )
if ( face->dir_tables[i].Length == sfnt_id[j][k].Length )
{
if ( !checksum )
checksum = tt_get_sfnt_checksum( face, i );
if ( sfnt_id[j][k].CheckSum == checksum )
num_matched_ids[j] ++;
if ( num_matched_ids[j] == TRICK_SFNT_IDS_PER_FACE )
return TRUE;
}
}
return FALSE;
}
static FT_Bool
tt_check_trickyness( FT_Face face )
{
if ( !face )
return FALSE;
/* Note that we only check the face name at the moment; it might */
/* be worth to do more checks for a few special cases. */
if ( face->family_name )
{
if ( tt_check_trickyness_family( face->family_name ) )
return TRUE;
else
return FALSE;
}
/* Type42 may lack `name' tables, try to identfiy tricky fonts by */
/* the checksums of Type42-persistent sfnt tables; cvt, fpgm, prep */
if ( tt_check_trickyness_sfnt_ids( ( TT_Face )face ) )
return TRUE;
return FALSE;
}
/*************************************************************************/
/* */
/* <Function> */
@ -252,7 +401,7 @@
if ( error )
goto Exit;
if ( tt_check_trickyness( ttface->family_name ) )
if ( tt_check_trickyness( ttface ) )
ttface->face_flags |= FT_FACE_FLAG_TRICKY;
error = tt_face_load_hdmx( face, stream );