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'use strict';
// See documentation here: http://www.microsoft.com/typography/otspec/glyf.htm
var _ = require('lodash');
var ByteBuffer = require('microbuffer');
function getFlags(glyph) {
var result = [];
_.forEach(glyph.ttfContours, function (contour) {
_.forEach(contour, function (point) {
var flag = point.onCurve ? 1 : 0;
if (point.x === 0) {
flag += 16;
} else {
if (-0xFF <= point.x && point.x <= 0xFF) {
flag += 2; // the corresponding x-coordinate is 1 byte long
}
if (point.x > 0 && point.x <= 0xFF) {
flag += 16; // If x-Short Vector is set, this bit describes the sign of the value, with 1 equalling positive and 0 negative
}
}
if (point.y === 0) {
flag += 32;
} else {
if (-0xFF <= point.y && point.y <= 0xFF) {
flag += 4; // the corresponding y-coordinate is 1 byte long
}
if (point.y > 0 && point.y <= 0xFF) {
flag += 32; // If y-Short Vector is set, this bit describes the sign of the value, with 1 equalling positive and 0 negative.
}
}
result.push(flag);
});
});
return result;
}
//repeating flags can be packed
function compactFlags(flags) {
var result = [];
var prevFlag = -1;
var firstRepeat = false;
_.forEach(flags, function (flag) {
if (prevFlag === flag) {
if (firstRepeat) {
result[result.length - 1] += 8; //current flag repeats previous one, need to set 3rd bit of previous flag and set 1 to the current one
result.push(1);
firstRepeat = false;
} else {
result[result.length - 1]++; //when flag is repeating second or more times, we need to increase the last flag value
}
} else {
firstRepeat = true;
prevFlag = flag;
result.push(flag);
}
});
return result;
}
function getCoords(glyph, coordName) {
var result = [];
_.forEach(glyph.ttfContours, function (contour) {
result.push.apply(result, _.map(contour, coordName));
});
return result;
}
function compactCoords(coords) {
return _.filter(coords, function (coord) {
return coord !== 0;
});
}
//calculates length of glyph data in GLYF table
function glyphDataSize(glyph) {
// Ignore glyphs without outlines. These will get a length of zero in the “loca” table
if (!glyph.contours.length) {
return 0;
}
var result = 12; //glyph fixed properties
result += glyph.contours.length * 2; //add contours
_.forEach(glyph.ttf_x, function (x) {
//add 1 or 2 bytes for each coordinate depending of its size
result += ((-0xFF <= x && x <= 0xFF)) ? 1 : 2;
});
_.forEach(glyph.ttf_y, function (y) {
//add 1 or 2 bytes for each coordinate depending of its size
result += ((-0xFF <= y && y <= 0xFF)) ? 1 : 2;
});
// Add flags length to glyph size.
result += glyph.ttf_flags.length;
if (result % 4 !== 0) { // glyph size must be divisible by 4.
result += 4 - result % 4;
}
return result;
}
function tableSize(font) {
var result = 0;
_.forEach(font.glyphs, function (glyph) {
glyph.ttf_size = glyphDataSize(glyph);
result += glyph.ttf_size;
});
font.ttf_glyph_size = result; //sum of all glyph lengths
return result;
}
function createGlyfTable(font) {
_.forEach(font.glyphs, function (glyph) {
glyph.ttf_flags = getFlags(glyph);
glyph.ttf_flags = compactFlags(glyph.ttf_flags);
glyph.ttf_x = getCoords(glyph, 'x');
glyph.ttf_x = compactCoords(glyph.ttf_x);
glyph.ttf_y = getCoords(glyph, 'y');
glyph.ttf_y = compactCoords(glyph.ttf_y);
});
var buf = new ByteBuffer(tableSize(font));
_.forEach(font.glyphs, function (glyph) {
// Ignore glyphs without outlines. These will get a length of zero in the “loca” table
if (!glyph.contours.length) {
return;
}
var offset = buf.tell();
buf.writeInt16(glyph.contours.length); // numberOfContours
buf.writeInt16(glyph.xMin); // xMin
buf.writeInt16(glyph.yMin); // yMin
buf.writeInt16(glyph.xMax); // xMax
buf.writeInt16(glyph.yMax); // yMax
// Array of end points
var endPtsOfContours = -1;
var ttfContours = glyph.ttfContours;
_.forEach(ttfContours, function (contour) {
endPtsOfContours += contour.length;
buf.writeInt16(endPtsOfContours);
});
buf.writeInt16(0); // instructionLength, is not used here
// Array of flags
_.forEach(glyph.ttf_flags, function (flag) {
buf.writeInt8(flag);
});
// Array of X relative coordinates
_.forEach(glyph.ttf_x, function (x) {
if (-0xFF <= x && x <= 0xFF) {
buf.writeUint8(Math.abs(x));
} else {
buf.writeInt16(x);
}
});
// Array of Y relative coordinates
_.forEach(glyph.ttf_y, function (y) {
if (-0xFF <= y && y <= 0xFF) {
buf.writeUint8(Math.abs(y));
} else {
buf.writeInt16(y);
}
});
var tail = (buf.tell() - offset) % 4;
if (tail !== 0) { // glyph size must be divisible by 4.
for (; tail < 4; tail++) {
buf.writeUint8(0);
}
}
});
return buf;
}
module.exports = createGlyfTable;