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import r from 'restructure';
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// Flags for simple glyphs
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const ON_CURVE = 1 << 0;
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const X_SHORT_VECTOR = 1 << 1;
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const Y_SHORT_VECTOR = 1 << 2;
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const REPEAT = 1 << 3;
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const SAME_X = 1 << 4;
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const SAME_Y = 1 << 5;
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class Point {
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static size(val) {
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return val >= 0 && val <= 255 ? 1 : 2;
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}
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static encode(stream, value) {
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if (value >= 0 && value <= 255) {
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stream.writeUInt8(value);
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} else {
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stream.writeInt16BE(value);
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}
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}
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}
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let Glyf = new r.Struct({
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numberOfContours: r.int16, // if negative, this is a composite glyph
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xMin: r.int16,
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yMin: r.int16,
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xMax: r.int16,
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yMax: r.int16,
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endPtsOfContours: new r.Array(r.uint16, 'numberOfContours'),
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instructions: new r.Array(r.uint8, r.uint16),
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flags: new r.Array(r.uint8, 0),
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xPoints: new r.Array(Point, 0),
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yPoints: new r.Array(Point, 0)
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});
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/**
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* Encodes TrueType glyph outlines
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*/
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export default class TTFGlyphEncoder {
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encodeSimple(path, instructions = []) {
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let endPtsOfContours = [];
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let xPoints = [];
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let yPoints = [];
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let flags = [];
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let same = 0;
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let lastX = 0, lastY = 0, lastFlag = 0;
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let pointCount = 0;
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for (let i = 0; i < path.commands.length; i++) {
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let c = path.commands[i];
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for (let j = 0; j < c.args.length; j += 2) {
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let x = c.args[j];
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let y = c.args[j + 1];
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let flag = 0;
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// If the ending point of a quadratic curve is the midpoint
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// between the control point and the control point of the next
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// quadratic curve, we can omit the ending point.
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if (c.command === 'quadraticCurveTo' && j === 2) {
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let next = path.commands[i + 1];
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if (next && next.command === 'quadraticCurveTo') {
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let midX = (lastX + next.args[0]) / 2;
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let midY = (lastY + next.args[1]) / 2;
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if (x === midX && y === midY) {
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continue;
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}
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}
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}
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// All points except control points are on curve.
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if (!(c.command === 'quadraticCurveTo' && j === 0)) {
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flag |= ON_CURVE;
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}
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flag = this._encodePoint(x, lastX, xPoints, flag, X_SHORT_VECTOR, SAME_X);
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flag = this._encodePoint(y, lastY, yPoints, flag, Y_SHORT_VECTOR, SAME_Y);
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if (flag === lastFlag && same < 255) {
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flags[flags.length - 1] |= REPEAT;
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same++;
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} else {
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if (same > 0) {
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flags.push(same);
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same = 0;
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}
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flags.push(flag);
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lastFlag = flag;
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}
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lastX = x;
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lastY = y;
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pointCount++;
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}
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if (c.command === 'closePath') {
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endPtsOfContours.push(pointCount - 1);
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}
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}
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// Close the path if the last command didn't already
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if (path.commands.length > 1 && path.commands[path.commands.length - 1].command !== 'closePath') {
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endPtsOfContours.push(pointCount - 1);
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}
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let bbox = path.bbox;
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let glyf = {
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numberOfContours: endPtsOfContours.length,
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xMin: bbox.minX,
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yMin: bbox.minY,
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xMax: bbox.maxX,
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yMax: bbox.maxY,
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endPtsOfContours: endPtsOfContours,
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instructions: instructions,
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flags: flags,
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xPoints: xPoints,
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yPoints: yPoints
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};
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let size = Glyf.size(glyf);
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let tail = 4 - (size % 4);
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let stream = new r.EncodeStream(size + tail);
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Glyf.encode(stream, glyf);
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// Align to 4-byte length
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if (tail !== 0) {
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stream.fill(0, tail);
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}
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return stream.buffer;
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}
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_encodePoint(value, last, points, flag, shortFlag, sameFlag) {
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let diff = value - last;
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if (value === last) {
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flag |= sameFlag;
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} else {
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if (-255 <= diff && diff <= 255) {
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flag |= shortFlag;
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if (diff < 0) {
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diff = -diff;
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} else {
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flag |= sameFlag;
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}
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}
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points.push(diff);
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}
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return flag;
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}
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}
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