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Add opentype ascender, descender and units-per-em to font properties

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Prefer font ascender, descender when creating OS/2 table
scale PDF ascender and descender in OS/2 table by font units per em if it exists
Fix the truetype font header to prevent Windows rejecting a Mac truetype font
This commit is contained in:
Adil Allawi 2011-09-16 13:50:11 +01:00
parent cac74d7cb3
commit 870de2f7f3
1 changed files with 37 additions and 11 deletions
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48
fonts.js
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@ -12,6 +12,9 @@ var kMaxWaitForFontFace = 1000;
// Unicode Private Use Area
var kCmapGlyphOffset = 0xE000;
// PDF Glyph Space Units are one Thousandth of a TextSpace Unit except for Type 3 fonts
var kPDFGlyphSpaceUnits = 1000;
// Until hinting is fully supported this constant can be used
var kHintingEnabled = false;
@ -534,6 +537,10 @@ var Font = (function Font() {
};
function createOpenTypeHeader(sfnt, file, numTables) {
// Windows hates the Mac TrueType sfnt version number
if (sfnt == 'true')
sfnt = string32(0x00010000);
// sfnt version (4 bytes)
var header = sfnt;
@ -694,6 +701,24 @@ var Font = (function Font() {
}
}
var openTypeUnitsPerEm = (typeof (properties.openTypeUnitsPerEm) == 'undefined') ? kPDFGlyphSpaceUnits : properties.openTypeUnitsPerEm;
var typoAscent = properties.ascent;
var typoDescent = properties.descent;
var winAscent = typoAscent;
var winDescent = -typoDescent;
// if the font already has ascent and descent information then use these values
if (typeof (properties.openTypeAscent) != 'undefined') {
typoAscent = properties.openTypeAscent;
typoDescent = properties.openTypeDescent;
winAscent = properties.openTypeYMax;
winDescent = -properties.openTypeYMin;
} else if (openTypeUnitsPerEm != kPDFGlyphSpaceUnits) {
// if the font units differ to the PDF glyph space units then scale up the values
typoAscent = Math.round(typoAscent * openTypeUnitsPerEm / kPDFGlyphSpaceUnits);
typoDescent = Math.round(typoDescent * openTypeUnitsPerEm / kPDFGlyphSpaceUnits);
}
return '\x00\x03' + // version
'\x02\x24' + // xAvgCharWidth
'\x01\xF4' + // usWeightClass
@ -722,11 +747,11 @@ var Font = (function Font() {
string16(firstCharIndex ||
properties.firstChar) + // usFirstCharIndex
string16(lastCharIndex || properties.lastChar) + // usLastCharIndex
string16(properties.ascent) + // sTypoAscender
string16(properties.descent) + // sTypoDescender
string16(typoAscent) + // sTypoAscender
string16(typoDescent) + // sTypoDescender
'\x00\x64' + // sTypoLineGap (7%-10% of the unitsPerEM value)
string16(properties.ascent) + // usWinAscent
string16(-properties.descent) + // usWinDescent
string16(winAscent) + // usWinAscent
string16(winDescent) + // usWinDescent
'\x00\x00\x00\x00' + // ulCodePageRange1 (Bits 0-31)
'\x00\x00\x00\x00' + // ulCodePageRange2 (Bits 32-63)
string16(properties.xHeight) + // sxHeight
@ -1047,18 +1072,19 @@ var Font = (function Font() {
virtualOffset: numTables * (4 * 4)
};
//extract some more font properties from the OpenType head and hhea tables
properties.openTypeUnitsPerEm = int16([head.data[18], head.data[19]]);
properties.openTypeYMax = int16([head.data[42], head.data[43]]);
properties.openTypeYMin = int16([head.data[38], head.data[39]]) - 0x10000; //always negative
properties.openTypeAscent = int16([hhea.data[4], hhea.data[5]]);
properties.openTypeDescent = int16([hhea.data[6], hhea.data[7]]) - 0x10000; //always negative
// The new numbers of tables will be the last one plus the num
// of missing tables
createOpenTypeHeader(header.version, ttf, numTables);
if (requiredTables.indexOf('OS/2') != -1) {
if (typeof(head) != 'undefined') {
var ymax = int16([head.data[42],head.data[43]]);
var ymin = int16([head.data[38],head.data[39]]) - 0x10000; //always negative
properties.ascent = ymax;
properties.descent = ymin;
}
tables.push({
tag: 'OS/2',
data: stringToArray(createOS2Table(properties))