Reading a TrueType File
Posted: Fri Oct 16, 2015 10:30 pm
Here is a little program to obtain some of the metrics from a truetype file. It reads the .ttf file directly, not relying on functions specific to any operating system. This program finds the ascender, descender and line gap (external leading) of a font. In this demo both times and arial are available.
Code: Select all
;Font metrics
;Updated on 10/18/2015 by chris319
OpenConsole()
pointSize = 72
;internal leading ;accents
Procedure.q EndianQ(val.q)
Protected addr.l = @val
EnableASM
MOV edx, addr
MOV eax, [edx + 4]
MOV edx, [edx]
BSWAP eax
BSWAP edx
DisableASM
ProcedureReturn
EndProcedure
Procedure.l EndianL(val.l);change endian of 32-bit variable
!MOV Eax,dword[p.v_val]
!BSWAP Eax
!MOV dword[p.v_val],Eax
ProcedureReturn val.l
EndProcedure
Structure fontHeader
tableVersionNumber.l
fontRevision.l
checkSumAdjustment.l
magicNumber.l
flags.u
unitsPerEm.u
created.q
modified.q
xMin.w
yMin.w
xMax.w
yMax.w
; USHORT macStyle
; USHORT lowestRecPPEM
; SHORT fontDirectionHint
; SHORT indexToLocFormat
; SHORT glyphDataFormat
EndStructure
fontHeader.fontHeader
;Structure Size_Metrics
; x_ppem.u; /* horizontal pixels per EM */
; y_ppem.u; /* vertical pixels per EM */
; FT_Fixed x_scale; /* scaling values used to convert font */
; FT_Fixed y_scale; /* units to 26.6 fractional pixels */
; FT_Pos ascender; /* ascender in 26.6 frac. pixels */
; FT_Pos descender; /* descender in 26.6 frac. pixels */
; FT_Pos height; /* text height in 26.6 frac. pixels */
; FT_Pos max_advance; /* max horizontal advance, in 26.6 pixels */
;EndStructure
;sizeMetrics.Size_Metrics
Structure TT_HoriHeader
Version.l
; Version.u
Ascender.w
Descender.w
lineGap.w
EndStructure
hh.TT_HoriHeader
Structure tagTT_OFFSET_TABLE
MajorVersion.u
uMinorVersion.u
numTables.u
uSearchRange.u
uEntrySelector.u
uRangeShift.u
EndStructure
offsetTable.tagTT_OFFSET_TABLE
Structure tagTT_TABLE_DIRECTORY
szTag.a[4] ;table name
CheckSum.l ;Checksum
Offset.l ;Offset from beginning of file
Length.l ;length of the table in bytes
EndStructure
tableDirectory.tagTT_TABLE_DIRECTORY
szTag.s
Structure _tagTT_NAME_TABLE_HEADER ;Header of names table
uFSelector.u ;format selector. Always 0
uNRCount.u ;Name Records count
uStorageOffset.u ;Offset for strings storage from start of the table
EndStructure
Structure tagTT_NAME_RECORD ;Record in names table
uPlatformID.u
uEncodingID.u
uLanguageID.u
uNameID.u
uStringLength.u
uStringOffset.u ;from start of storage area
EndStructure
;fontName$ = "arial.ttf"
fontName$ = "times.ttf"
;fontName$ = "verdana.ttf"
result = ReadFile(1,fontName$)
If result = 0:Debug "Error opening font file":EndIf
PrintN(fontName$)
LoadFont(1,"times new roman",72)
ReadData(1,@offsetTable,SizeOf(offsetTable))
;FileSeek(1,SizeOf(offsetTable))
test$ = ""
While test$ <> "hhea"
ReadData(1,@tableDirectory,SizeOf(tableDirectory))
test$ = PeekS(@tableDirectory\szTag[0], 4, #PB_Ascii)
Wend
tableDirectory\Offset = EndianL(tableDirectory\Offset)
;EnableASM:ROL tableDirectory\Offset,8:DisableASM ;swap bytes
FileSeek(1,tableDirectory\Offset.l)
ReadData(1,@hh,SizeOf(TT_HoriHeader))
EnableASM:ROL hh\Ascender,8:DisableASM ;swap bytes
;Debug hh\ascender
floatAscender.f = hh\Ascender
EnableASM:ROL hh\Descender,8:DisableASM ;swap bytes
;Debug hh\Descender
floatDescender.f = hh\Descender
EnableASM:ROL hh\lineGap,8:DisableASM ;swap bytes
;Debug hh\lineGap
floatLineGap.f = hh\lineGap
;EnableASM:ROL hh\Version,16:DisableASM ;swap bytes
;hh\Version = EndianL(hh\Version)
FileSeek(1,0)
ReadData(1,@offsetTable,SizeOf(offsetTable))
FileSeek(1,SizeOf(offsetTable))
test$ = ""
Repeat
ReadData(1,@tableDirectory,SizeOf(tableDirectory))
test$ = PeekS(@tableDirectory\szTag[0], 4, #PB_Ascii)
Until test$ = "head"
tableDirectory\Offset = EndianL(tableDirectory\Offset);CONVERT TO LITTLE ENDIAN
FileSeek(1,tableDirectory\Offset)
ReadData(1,@fontHeader,SizeOf(fontHeader))
;Debug Bin(fontHeader\tableVersionNumber)
;EnableASM:ROL fontHeader\magicNumber,16:DisableASM ;swap bytes
;Debug Hex(fontHeader\magicNumber,#PB_Long)
EnableASM:ROL fontHeader\unitsPerEm,8:DisableASM ;swap bytes
PrintN("Units per em: "+Str(fontHeader\unitsPerEm))
scale.f = pointSize/fontHeader\unitsPerEm
;Debug floatAscender *scale
;Debug floatDescender *scale
;Debug floatLineGap *scale
;Debug floatLineGap *scale
floatAscender * scale
floatDescender * scale
floatLineGap * scale
PrintN("Ascender "+StrF(floatAscender,0) + "")
PrintN("Descender "+StrF(floatDescender,0) + "")
PrintN("Line gap (external leading) "+StrF(floatLineGap,0) + "")
emHeight = fontHeader\unitsPerEm/pointSize
PrintN("em Height: "+Str(emHeight))
internalLeading = (floatAscender) - (floatDescender) - emHeight
PrintN("Internal leading: "+Str(internalLeading))
CloseFile(1)
OpenWindow(1,500,150,600,400,"",#PB_Window_BorderLess)
StartDrawing(WindowOutput(1))
DrawingFont(FontID(1))
DrawText(50,0,"ghi"+Chr(202),#White,#Red)
;LineXY(0,72-floatAscender*scale,600,72-floatAscender*scale,#White)
;LineXY(0,floatDescender*scale,600,floatDescender*scale,#White)
;LineXY(0,pointSize,600,pointSize,#White)
;LineXY(0,emHeight,600,emHeight,#White);emHeight
;Debug (floatAscender - floatDescender)+internalLeading;emHeight
baseLine=(floatAscender - floatDescender)+emHeight
LineXY(0,baseLine,600,baseLine,#Black);base line
;LineXY(0,(baseLine + emHeight)- floatlineGap,600,(baseLine + emHeight)- floatlineGap,#Green)
LineXY(0,(baseLine + emHeight),600,(baseLine + emHeight),#Yellow)
lineSpace=baseLine + emHeight
DrawText(50,lineSpace,Chr(202)+"ight",#White,#Red)
LineXY(0,emHeight+floatDescender+floatLineGap,600,emHeight+floatDescender+floatLineGap,#Blue)
;LineXY(0,baseLine-internalLeading,600,baseLine-internalLeading,#Blue)
StopDrawing()
PrintN(Chr(10)+"Press any key to exit")
While Inkey() = ""
Delay(100)
Wend
End