+/* string-lerp - progressively turn one string into another
+ Copyright 2014 Joe Wreschnig
+ Licensed under the terms of the GNU GPL v2 or later
+ @license http://www.gnu.org/licenses/gpl-2.0.html
+ @source: http://yukkurigames.com/string-lerp/
+*//*
+ This program is free software; you can redistribute it and/or
+ modify it under the terms of the GNU General Public License as
+ published by the Free Software Foundation; either version 2 of the
+ License, or (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ General Public License for more details.
+
+ As additional permission, you may distribute the program or works
+ based on it without the copy of the GNU GPL normally required,
+ provided you include this license notice and a URL through which
+ recipients can access the corresponding source code.
+*/
+
+/*globals exports, Uint32Array */
+
(function (exports) {
"use strict";
var MAX_MATRIX_SIZE = 256 * 256;
- function createMatrix(i, j) {
- return new Uint32Array(i * j);
- }
+ function costMatrix(source, target, ins, del, sub) {
+ /** Calculate the Levenshtein cost matrix for source and target
+
+ If source and target are strings, they cannot contain any
+ astral or combining codepoints. Such data must be passed
+ as arrays of strings with one element per glyph.
+
+ ins, del, and sub are the costs for insertion, deletion,
+ and substition respectively. Their default value is 1. If
+ only ins is passed, del and sub are set to the same cost.
+ If ins and del are passed, sub is set to the more
+ expensive of the two.
- function levenshteinMatrix(s, t) {
- /** Calculate the Levenshtein edit distance matrix for two strings
+ The matrix is returned as a flat typed array.
- The matrix is returned as a flat unsigned typed array.
-
Following http://en.wikipedia.org/wiki/Levenshtein_distance
*/
- var m = s.length + 1;
- var n = t.length + 1;
- var d = createMatrix(m, n);
+ ins = ins === undefined ? 1 : (ins | 0);
+ del = (del | 0) || ins;
+ sub = (sub | 0) || Math.max(ins, del);
+ var m = source.length + 1;
+ var n = target.length + 1;
+ var d = new Uint32Array(m * n);
var i, j;
for (i = 1; i < m; ++i)
d[n * i] = i;
d[j] = j;
for (j = 1; j < n; ++j)
for (i = 1; i < m; ++i)
- if (s[i - 1] === t[j - 1])
+ if (source[i - 1] === target[j - 1])
d[n * i + j] = d[n * (i - 1) + j - 1];
else
- d[n * i + j] = 1 + Math.min(d[n * (i - 1) + j ],
- d[n * i + j - 1],
- d[n * (i - 1) + j - 1]);
+ d[n * i + j] = Math.min(del + d[n * (i - 1) + j ],
+ ins + d[n * i + j - 1],
+ sub + d[n * (i - 1) + j - 1]);
return d;
}
- function editPath(d, s, t) {
- /** Given a Levenshtein result matrix, trace the shortest edit */
- var path = []
- var i = s.length;
- var j = t.length;
+ // First, note that deletion is just substition with nothing, so
+ // any DEL operation can be replaced by a SUB. Second, the
+ // operation code *is* the necessary slice offset for applying the
+ // diff.
+ var INS = 0, SUB = 1;
+
+ function editPath(costs, target) {
+ /** Given a cost matrix and a target, create an edit list */
+ var path = [];
+ var j = target.length;
var n = j + 1;
+ var i = costs.length / n - 1;
while (i || j) {
- var sub = (i && j) ? d[n * (i - 1) + j - 1] : Infinity;
- var del = i ? d[n * (i - 1) + j] : Infinity;
- var ins = j ? d[n * i + j - 1] : Infinity;
+ var sub = (i && j) ? costs[n * (i - 1) + j - 1] : Infinity;
+ var del = i ? costs[n * (i - 1) + j] : Infinity;
+ var ins = j ? costs[n * i + j - 1] : Infinity;
if (sub <= ins && sub <= del) {
- if (d[n * i + j] !== d[n * (i - 1) + j - 1])
- path.push(["sub", i - 1, t[j - 1]]);
+ if (costs[n * i + j] !== costs[n * (i - 1) + j - 1])
+ path.push([SUB, i - 1, target[j - 1]]);
--i; --j;
} else if (ins <= del) {
- path.push(["ins", i, t[j - 1]]);
+ path.push([INS, i, target[j - 1]]);
--j;
} else {
- path.push(["del", i - 1]);
+ path.push([SUB, i - 1, ""]);
--i;
}
}
return path;
}
- function applyEdits(edits, s) {
- /** Apply the list of edits to s */
- var i;
- for (i = 0; i < edits.length; ++i) {
- var edit = edits[i];
- switch (edit[0]) {
- case "sub":
- s = s.slice(0, edit[1]) + edit[2] + s.slice(edit[1] + 1);
- break;
- case "ins":
- s = s.slice(0, edit[1]) + edit[2] + s.slice(edit[1]);
- break;
- case "del":
- s = s.slice(0, edit[1]) + s.slice(edit[1] + 1);
- break;
- }
+ function diff(source, target, ins, del, sub) {
+ /** Create a list of edits to turn source into target
+
+ ins, del, and sub are as passed to costMatrix.
+ */
+ return editPath(costMatrix(source, target, ins, del, sub), target);
+ }
+
+ function patchArray(diff, source) {
+ for (var i = 0; i < diff.length; ++i) {
+ var edit = diff[i];
+ source.splice(edit[1], edit[0], edit[2]);
}
- return s;
+ return source;
}
- function slowLerp(a, b, p) {
- /** Interpolate between two strings slowly
+ function patchString(diff, source) {
+ for (var i = 0; i < diff.length; ++i) {
+ var edit = diff[i];
+ var head = source.slice(0, edit[1]);
+ var tail = source.slice(edit[1] + edit[0]);
+ source = head + edit[2] + tail;
+ }
+ return source;
+ }
+
+ function patch(diff, source) {
+ /** Apply a list of edits to source */
+ var patcher = Array.isArray(source) ? patchArray : patchString;
+ return patcher(diff, source);
+ }
+
+ // Matches if a string contains combining characters or astral
+ // codepoints (technically, the first half surrogate of an astral
+ // codepoint).
+ var MULTI = /[\u0300-\u036F\u1DC0-\u1DFF\u20D0-\u20FF\uD800-\uDBFF\uFE20-\uFE2F]/;
+
+ // Match an entire (potentially astral) codepoint and any
+ // combining characters following it.
+ var GLYPH = /[\0-\u02FF\u0370-\u1DBF\u1E00-\u20CF\u2100-\uD7FF\uD800-\uFE1F\uFE30-\uFFFF][\u0300-\u036F\u1DC0-\u1DFF\u20D0-\u20FF\uDC00-\uDFFF\uFE20-\uFE2F]*/g;
+
+ function diffLerpAstral(source, target, amount) {
+ // This split is not perfect for all languages, but at least
+ // it won't create invalid surrogate pairs or orphaned
+ // combining characters.
+ var sourceGlyphs = source.match(GLYPH) || [];
+ var targetGlyphs = target.match(GLYPH) || [];
+ var edits = diff(targetGlyphs, sourceGlyphs, 2, 2, 3);
+ // The edit path works from the string end, forwards, because
+ // that's how Levenshtein edits work. To match LTR reading
+ // direction (and the behavior of fastLerp), swap the strings
+ // and invert the parameter when editing.
+ var partial = edits.slice(0, Math.round((1 - amount) * edits.length));
+ return patchArray(partial, targetGlyphs).join("");
+ }
+
+ function diffLerpBasic(source, target, amount) {
+ var edits = diff(target, source, 2, 2, 3);
+ // The edit path works from the string end, forwards, because
+ // that's how Levenshtein edits work. To match LTR reading
+ // direction (and the behavior of fastLerp), swap the strings
+ // and invert the parameter when editing.
+ var partial = edits.slice(0, Math.round((1 - amount) * edits.length));
+ return patchString(partial, target);
+ }
+
+ function diffLerp(source, target, amount) {
+ /** Interpolate between two strings using edit operations
This interpolation algorithm applys a partial edit of one
string into the other. This produces nice looking results,
but can take a significant amount of time and memory to
compute the edits. It is not recommended for strings
longer than a few hundred characters.
- */
- var edits = editPath(levenshteinMatrix(a, b), a, b);
- var partial = edits.slice(0, Math.round(p * edits.length));
- return applyEdits(partial, a);
+ */
+
+ if (source.match(MULTI) || target.match(MULTI))
+ return diffLerpAstral(source, target, amount);
+ else
+ return diffLerpBasic(source, target, amount);
}
- function fastLerp(a, b, p) {
- /** Interpolate between two strings very quickly
+ var NUMBERS = /(-?\d{1,20}(?:\.\d{1,20})?)/g;
+
+ function areNumericTwins(source, target) {
+ /** Check if a and b differ only in numerals */
+ return source.replace(NUMBERS, "0") === target.replace(NUMBERS, "0");
+ }
+
+ function nlerp(source, target, amount) {
+ return source + (target - source) * amount;
+ }
+
+ function numericLerp(source, target, amount) {
+ /** Interpolate numerically between strings containing numbers
+
+ Numbers may have a leading "-" and a single "." to mark
+ the decimal point, but something must be after the ".".
+ No other floating point syntax (e.g. 1e6) is supported.
+ They are treated as fixed-point values, with the point's
+ position itself interpolating.
+
+ For example, numericLerp("0.0", "100".0, 0.123) === "12.3"
+ because the "." in "0.0" is interpreted as a decimal
+ point. But numericLerp("0.", "100.", 0.123) === "12."
+ because the strings are interpreted as integers followed
+ by a full stop.
+
+ Calling this functions on strings that differ in more than
+ numerals gives undefined results.
+ */
+
+ var targetParts = target.split(NUMBERS);
+ var match;
+ var i = 1;
+ while ((match = NUMBERS.exec(source))) {
+ var sourcePart = match[0];
+ var targetPart = targetParts[i];
+ var part = nlerp(+sourcePart, +targetPart, amount);
+ var sourcePoint = sourcePart.indexOf(".");
+ var targetPoint = targetPart.indexOf(".");
+ var point = Math.round(nlerp(
+ sourcePoint >= 0 ? (sourcePart.length - 1) - sourcePoint : 0,
+ targetPoint >= 0 ? (targetPart.length - 1) - targetPoint : 0,
+ amount));
+ targetParts[i] = part.toFixed(point);
+ i += 2;
+ }
+ return targetParts.join("");
+ }
+
+ function fastLerpAstral(source, target, amount) {
+ var sourceGlyphs = source.match(GLYPH) || [];
+ var targetGlyphs = target.match(GLYPH) || [];
+ var sourceLength = Math.round(sourceGlyphs.length * amount);
+ var targetLength = Math.round(targetGlyphs.length * amount);
+ var head = targetGlyphs.slice(0, targetLength);
+ var tail = sourceGlyphs.slice(sourceLength, sourceGlyphs.length);
+ head.push.apply(head, tail);
+ return head.join("");
+ }
+
+ function fastLerpBasic(source, target, amount) {
+ var sourceLength = Math.round(source.length * amount);
+ var targetLength = Math.round(target.length * amount);
+ var head = target.substring(0, targetLength);
+ var tail = source.substring(sourceLength, source.length);
+ return head + tail;
+ }
+
+ function fastLerp(source, target, amount) {
+ /** Interpolate between two strings based on length
This interpolation algorithm progressively replaces the
front of one string with another. This approach is fast
but does not look good when the strings are similar.
- */
- var alen = Math.round(a.length * p);
- var blen = Math.round(b.length * p);
- return b.substring(0, blen) + a.substring(alen, a.length);
+ */
+
+ // TODO: Consider fast-pathing this even more for very large
+ // strings, e.g. in the megabyte range. These are large enough
+ // that it should be fine to just pick a codepoint and search
+ // for the nearest glyph start.
+ if (source.match(MULTI) || target.match(MULTI))
+ return fastLerpAstral(source, target, amount);
+ else
+ return fastLerpBasic(source, target, amount);
}
- function lerp(a, b, p) {
- a = a.toString();
- b = b.toString();
- var n = a.length * b.length;
- // TODO: if both strings are integers, do an integer lerp.
- // TODO: if both strings are numbers, do a numeric lerp.
- return (n && n < MAX_MATRIX_SIZE)
- ? slowLerp(a, b, p)
- : fastLerp(a, b, p);
+ function lerp(source, target, amount) {
+ /** Interpolate between two strings as best as possible
+
+ If the strings are identical aside from numbers in them,
+ they are passed through numericLerp.
+
+ If the strings are not numbers and short, they are passed
+ through diffLerp.
+
+ Otherwise, they are passed through fastLerp.
+ */
+ source = source.toString();
+ target = target.toString();
+
+ // Fast path for boundary cases.
+ if (amount === 0) return source;
+ if (amount === 1) return target;
+
+ if (areNumericTwins(source, target))
+ return numericLerp(source, target, amount);
+
+ // Numeric lerps should over- and under-shoot when fed numbers
+ // outside 0 to 1, but other types cannot.
+ if (amount < 0) return source;
+ if (amount > 1) return target;
+
+ var n = source.length * target.length;
+ var appropriate = (n && n < MAX_MATRIX_SIZE) ? diffLerp : fastLerp;
+ return appropriate(source, target, amount);
}
- exports.levenshteinMatrix = levenshteinMatrix;
- exports.editPath = editPath;
+ exports.costMatrix = costMatrix;
+ exports.patch = patch;
+ exports.diff = diff;
exports.fastLerp = fastLerp;
- exports.slowLerp = slowLerp;
- exports.applyEdits = applyEdits;
+ exports.diffLerp = diffLerp;
+ exports.numericLerp = numericLerp;
exports.lerp = lerp;
})(typeof exports === "undefined" ? (this.stringLerp = {}) : exports);
projects / string-lerp.git / blobdiff