Fantasy-Map-Generator/libs/rgbquant.js
2020-05-16 00:52:45 +03:00

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JavaScript

/*
* Copyright (c) 2015, Leon Sorokin
* All rights reserved. (MIT Licensed)
*
* RgbQuant.js - an image quantization lib
*/
(function(){
function RgbQuant(opts) {
opts = opts || {};
// 1 = by global population, 2 = subregion population threshold
this.method = opts.method || 2;
// desired final palette size
this.colors = opts.colors || 256;
// # of highest-frequency colors to start with for palette reduction
this.initColors = opts.initColors || 4096;
// color-distance threshold for initial reduction pass
this.initDist = opts.initDist || 0.01;
// subsequent passes threshold
this.distIncr = opts.distIncr || 0.005;
// palette grouping
this.hueGroups = opts.hueGroups || 10;
this.satGroups = opts.satGroups || 10;
this.lumGroups = opts.lumGroups || 10;
// if > 0, enables hues stats and min-color retention per group
this.minHueCols = opts.minHueCols || 0;
// HueStats instance
this.hueStats = this.minHueCols ? new HueStats(this.hueGroups, this.minHueCols) : null;
// subregion partitioning box size
this.boxSize = opts.boxSize || [64,64];
// number of same pixels required within box for histogram inclusion
this.boxPxls = opts.boxPxls || 2;
// palette locked indicator
this.palLocked = false;
// palette sort order
// this.sortPal = ['hue-','lum-','sat-'];
// dithering/error diffusion kernel name
this.dithKern = opts.dithKern || null;
// dither serpentine pattern
this.dithSerp = opts.dithSerp || false;
// minimum color difference (0-1) needed to dither
this.dithDelta = opts.dithDelta || 0;
// accumulated histogram
this.histogram = {};
// palette - rgb triplets
this.idxrgb = opts.palette ? opts.palette.slice(0) : [];
// palette - int32 vals
this.idxi32 = [];
// reverse lookup {i32:idx}
this.i32idx = {};
// {i32:rgb}
this.i32rgb = {};
// enable color caching (also incurs overhead of cache misses and cache building)
this.useCache = opts.useCache !== false;
// min color occurance count needed to qualify for caching
this.cacheFreq = opts.cacheFreq || 10;
// allows pre-defined palettes to be re-indexed (enabling palette compacting and sorting)
this.reIndex = opts.reIndex || this.idxrgb.length == 0;
// selection of color-distance equation
this.colorDist = opts.colorDist == "manhattan" ? distManhattan : distEuclidean;
// if pre-defined palette, build lookups
if (this.idxrgb.length > 0) {
var self = this;
this.idxrgb.forEach(function(rgb, i) {
var i32 = (
(255 << 24) | // alpha
(rgb[2] << 16) | // blue
(rgb[1] << 8) | // green
rgb[0] // red
) >>> 0;
self.idxi32[i] = i32;
self.i32idx[i32] = i;
self.i32rgb[i32] = rgb;
});
}
}
// gathers histogram info
RgbQuant.prototype.sample = function sample(img, width) {
if (this.palLocked)
throw "Cannot sample additional images, palette already assembled.";
var data = getImageData(img, width);
switch (this.method) {
case 1: this.colorStats1D(data.buf32); break;
case 2: this.colorStats2D(data.buf32, data.width); break;
}
};
// image quantizer
// todo: memoize colors here also
// @retType: 1 - Uint8Array (default), 2 - Indexed array, 3 - Match @img type (unimplemented, todo)
RgbQuant.prototype.reduce = function reduce(img, retType, dithKern, dithSerp) {
if (!this.palLocked)
this.buildPal();
dithKern = dithKern || this.dithKern;
dithSerp = typeof dithSerp != "undefined" ? dithSerp : this.dithSerp;
retType = retType || 1;
// reduce w/dither
if (dithKern)
var out32 = this.dither(img, dithKern, dithSerp);
else {
var data = getImageData(img),
buf32 = data.buf32,
len = buf32.length,
out32 = new Uint32Array(len);
for (var i = 0; i < len; i++) {
var i32 = buf32[i];
out32[i] = this.nearestColor(i32);
}
}
if (retType == 1)
return new Uint8Array(out32.buffer);
if (retType == 2) {
var out = [],
len = out32.length;
for (var i = 0; i < len; i++) {
var i32 = out32[i];
out[i] = this.i32idx[i32];
}
return out;
}
};
// adapted from http://jsbin.com/iXofIji/2/edit by PAEz
RgbQuant.prototype.dither = function(img, kernel, serpentine) {
// http://www.tannerhelland.com/4660/dithering-eleven-algorithms-source-code/
var kernels = {
FloydSteinberg: [
[7 / 16, 1, 0],
[3 / 16, -1, 1],
[5 / 16, 0, 1],
[1 / 16, 1, 1]
],
FalseFloydSteinberg: [
[3 / 8, 1, 0],
[3 / 8, 0, 1],
[2 / 8, 1, 1]
],
Stucki: [
[8 / 42, 1, 0],
[4 / 42, 2, 0],
[2 / 42, -2, 1],
[4 / 42, -1, 1],
[8 / 42, 0, 1],
[4 / 42, 1, 1],
[2 / 42, 2, 1],
[1 / 42, -2, 2],
[2 / 42, -1, 2],
[4 / 42, 0, 2],
[2 / 42, 1, 2],
[1 / 42, 2, 2]
],
Atkinson: [
[1 / 8, 1, 0],
[1 / 8, 2, 0],
[1 / 8, -1, 1],
[1 / 8, 0, 1],
[1 / 8, 1, 1],
[1 / 8, 0, 2]
],
Jarvis: [ // Jarvis, Judice, and Ninke / JJN?
[7 / 48, 1, 0],
[5 / 48, 2, 0],
[3 / 48, -2, 1],
[5 / 48, -1, 1],
[7 / 48, 0, 1],
[5 / 48, 1, 1],
[3 / 48, 2, 1],
[1 / 48, -2, 2],
[3 / 48, -1, 2],
[5 / 48, 0, 2],
[3 / 48, 1, 2],
[1 / 48, 2, 2]
],
Burkes: [
[8 / 32, 1, 0],
[4 / 32, 2, 0],
[2 / 32, -2, 1],
[4 / 32, -1, 1],
[8 / 32, 0, 1],
[4 / 32, 1, 1],
[2 / 32, 2, 1],
],
Sierra: [
[5 / 32, 1, 0],
[3 / 32, 2, 0],
[2 / 32, -2, 1],
[4 / 32, -1, 1],
[5 / 32, 0, 1],
[4 / 32, 1, 1],
[2 / 32, 2, 1],
[2 / 32, -1, 2],
[3 / 32, 0, 2],
[2 / 32, 1, 2],
],
TwoSierra: [
[4 / 16, 1, 0],
[3 / 16, 2, 0],
[1 / 16, -2, 1],
[2 / 16, -1, 1],
[3 / 16, 0, 1],
[2 / 16, 1, 1],
[1 / 16, 2, 1],
],
SierraLite: [
[2 / 4, 1, 0],
[1 / 4, -1, 1],
[1 / 4, 0, 1],
],
};
if (!kernel || !kernels[kernel]) {
throw 'Unknown dithering kernel: ' + kernel;
}
var ds = kernels[kernel];
var data = getImageData(img),
// buf8 = data.buf8,
buf32 = data.buf32,
width = data.width,
height = data.height,
len = buf32.length;
var dir = serpentine ? -1 : 1;
for (var y = 0; y < height; y++) {
if (serpentine)
dir = dir * -1;
var lni = y * width;
for (var x = (dir == 1 ? 0 : width - 1), xend = (dir == 1 ? width : 0); x !== xend; x += dir) {
// Image pixel
var idx = lni + x,
i32 = buf32[idx],
r1 = (i32 & 0xff),
g1 = (i32 & 0xff00) >> 8,
b1 = (i32 & 0xff0000) >> 16;
// Reduced pixel
var i32x = this.nearestColor(i32),
r2 = (i32x & 0xff),
g2 = (i32x & 0xff00) >> 8,
b2 = (i32x & 0xff0000) >> 16;
buf32[idx] =
(255 << 24) | // alpha
(b2 << 16) | // blue
(g2 << 8) | // green
r2;
// dithering strength
if (this.dithDelta) {
var dist = this.colorDist([r1, g1, b1], [r2, g2, b2]);
if (dist < this.dithDelta)
continue;
}
// Component distance
var er = r1 - r2,
eg = g1 - g2,
eb = b1 - b2;
for (var i = (dir == 1 ? 0 : ds.length - 1), end = (dir == 1 ? ds.length : 0); i !== end; i += dir) {
var x1 = ds[i][1] * dir,
y1 = ds[i][2];
var lni2 = y1 * width;
if (x1 + x >= 0 && x1 + x < width && y1 + y >= 0 && y1 + y < height) {
var d = ds[i][0];
var idx2 = idx + (lni2 + x1);
var r3 = (buf32[idx2] & 0xff),
g3 = (buf32[idx2] & 0xff00) >> 8,
b3 = (buf32[idx2] & 0xff0000) >> 16;
var r4 = Math.max(0, Math.min(255, r3 + er * d)),
g4 = Math.max(0, Math.min(255, g3 + eg * d)),
b4 = Math.max(0, Math.min(255, b3 + eb * d));
buf32[idx2] =
(255 << 24) | // alpha
(b4 << 16) | // blue
(g4 << 8) | // green
r4; // red
}
}
}
}
return buf32;
};
// reduces histogram to palette, remaps & memoizes reduced colors
RgbQuant.prototype.buildPal = function buildPal(noSort) {
if (this.palLocked || this.idxrgb.length > 0 && this.idxrgb.length <= this.colors) return;
var histG = this.histogram,
sorted = sortedHashKeys(histG, true);
if (sorted.length == 0)
throw "Nothing has been sampled, palette cannot be built.";
switch (this.method) {
case 1:
var cols = this.initColors,
last = sorted[cols - 1],
freq = histG[last];
var idxi32 = sorted.slice(0, cols);
// add any cut off colors with same freq as last
var pos = cols, len = sorted.length;
while (pos < len && histG[sorted[pos]] == freq)
idxi32.push(sorted[pos++]);
// inject min huegroup colors
if (this.hueStats)
this.hueStats.inject(idxi32);
break;
case 2:
var idxi32 = sorted;
break;
}
// int32-ify values
idxi32 = idxi32.map(function(v){return +v;});
this.reducePal(idxi32);
if (!noSort && this.reIndex)
this.sortPal();
// build cache of top histogram colors
if (this.useCache)
this.cacheHistogram(idxi32);
this.palLocked = true;
};
RgbQuant.prototype.palette = function palette(tuples, noSort) {
this.buildPal(noSort);
return tuples ? this.idxrgb : new Uint8Array((new Uint32Array(this.idxi32)).buffer);
};
RgbQuant.prototype.prunePal = function prunePal(keep) {
var i32;
for (var j = 0; j < this.idxrgb.length; j++) {
if (!keep[j]) {
i32 = this.idxi32[j];
this.idxrgb[j] = null;
this.idxi32[j] = null;
delete this.i32idx[i32];
}
}
// compact
if (this.reIndex) {
var idxrgb = [],
idxi32 = [],
i32idx = {};
for (var j = 0, i = 0; j < this.idxrgb.length; j++) {
if (this.idxrgb[j]) {
i32 = this.idxi32[j];
idxrgb[i] = this.idxrgb[j];
i32idx[i32] = i;
idxi32[i] = i32;
i++;
}
}
this.idxrgb = idxrgb;
this.idxi32 = idxi32;
this.i32idx = i32idx;
}
};
// reduces similar colors from an importance-sorted Uint32 rgba array
RgbQuant.prototype.reducePal = function reducePal(idxi32) {
// if pre-defined palette's length exceeds target
if (this.idxrgb.length > this.colors) {
// quantize histogram to existing palette
var len = idxi32.length, keep = {}, uniques = 0, idx, pruned = false;
for (var i = 0; i < len; i++) {
// palette length reached, unset all remaining colors (sparse palette)
if (uniques == this.colors && !pruned) {
this.prunePal(keep);
pruned = true;
}
idx = this.nearestIndex(idxi32[i]);
if (uniques < this.colors && !keep[idx]) {
keep[idx] = true;
uniques++;
}
}
if (!pruned) {
this.prunePal(keep);
pruned = true;
}
}
// reduce histogram to create initial palette
else {
// build full rgb palette
var idxrgb = idxi32.map(function(i32) {
return [
(i32 & 0xff),
(i32 & 0xff00) >> 8,
(i32 & 0xff0000) >> 16,
];
});
var len = idxrgb.length,
palLen = len,
thold = this.initDist;
// palette already at or below desired length
if (palLen > this.colors) {
while (palLen > this.colors) {
var memDist = [];
// iterate palette
for (var i = 0; i < len; i++) {
var pxi = idxrgb[i], i32i = idxi32[i];
if (!pxi) continue;
for (var j = i + 1; j < len; j++) {
var pxj = idxrgb[j], i32j = idxi32[j];
if (!pxj) continue;
var dist = this.colorDist(pxi, pxj);
if (dist < thold) {
// store index,rgb,dist
memDist.push([j, pxj, i32j, dist]);
// kill squashed value
delete(idxrgb[j]);
palLen--;
}
}
}
// palette reduction pass
// console.log("palette length: " + palLen);
// if palette is still much larger than target, increment by larger initDist
thold += (palLen > this.colors * 3) ? this.initDist : this.distIncr;
}
// if palette is over-reduced, re-add removed colors with largest distances from last round
if (palLen < this.colors) {
// sort descending
sort.call(memDist, function(a,b) {
return b[3] - a[3];
});
var k = 0;
while (palLen < this.colors) {
// re-inject rgb into final palette
idxrgb[memDist[k][0]] = memDist[k][1];
palLen++;
k++;
}
}
}
var len = idxrgb.length;
for (var i = 0; i < len; i++) {
if (!idxrgb[i]) continue;
this.idxrgb.push(idxrgb[i]);
this.idxi32.push(idxi32[i]);
this.i32idx[idxi32[i]] = this.idxi32.length - 1;
this.i32rgb[idxi32[i]] = idxrgb[i];
}
}
};
// global top-population
RgbQuant.prototype.colorStats1D = function colorStats1D(buf32) {
var histG = this.histogram,
num = 0, col,
len = buf32.length;
for (var i = 0; i < len; i++) {
col = buf32[i];
// skip transparent
if ((col & 0xff000000) >> 24 == 0) continue;
// collect hue stats
if (this.hueStats)
this.hueStats.check(col);
if (col in histG)
histG[col]++;
else
histG[col] = 1;
}
};
// population threshold within subregions
// FIXME: this can over-reduce (few/no colors same?), need a way to keep
// important colors that dont ever reach local thresholds (gradients?)
RgbQuant.prototype.colorStats2D = function colorStats2D(buf32, width) {
var boxW = this.boxSize[0],
boxH = this.boxSize[1],
area = boxW * boxH,
boxes = makeBoxes(width, buf32.length / width, boxW, boxH),
histG = this.histogram,
self = this;
boxes.forEach(function(box) {
var effc = Math.max(Math.round((box.w * box.h) / area) * self.boxPxls, 2),
histL = {}, col;
iterBox(box, width, function(i) {
col = buf32[i];
// skip transparent
if ((col & 0xff000000) >> 24 == 0) return;
// collect hue stats
if (self.hueStats)
self.hueStats.check(col);
if (col in histG)
histG[col]++;
else if (col in histL) {
if (++histL[col] >= effc)
histG[col] = histL[col];
}
else
histL[col] = 1;
});
});
if (this.hueStats)
this.hueStats.inject(histG);
};
// TODO: group very low lum and very high lum colors
// TODO: pass custom sort order
RgbQuant.prototype.sortPal = function sortPal() {
var self = this;
this.idxi32.sort(function(a,b) {
var idxA = self.i32idx[a],
idxB = self.i32idx[b],
rgbA = self.idxrgb[idxA],
rgbB = self.idxrgb[idxB];
var hslA = rgb2hsl(rgbA[0],rgbA[1],rgbA[2]),
hslB = rgb2hsl(rgbB[0],rgbB[1],rgbB[2]);
// sort all grays + whites together
var hueA = (rgbA[0] == rgbA[1] && rgbA[1] == rgbA[2]) ? -1 : hueGroup(hslA.h, self.hueGroups);
var hueB = (rgbB[0] == rgbB[1] && rgbB[1] == rgbB[2]) ? -1 : hueGroup(hslB.h, self.hueGroups);
var hueDiff = hueB - hueA;
if (hueDiff) return -hueDiff;
var lumDiff = lumGroup(+hslB.l.toFixed(2)) - lumGroup(+hslA.l.toFixed(2));
if (lumDiff) return -lumDiff;
var satDiff = satGroup(+hslB.s.toFixed(2)) - satGroup(+hslA.s.toFixed(2));
if (satDiff) return -satDiff;
});
// sync idxrgb & i32idx
this.idxi32.forEach(function(i32, i) {
self.idxrgb[i] = self.i32rgb[i32];
self.i32idx[i32] = i;
});
};
// TOTRY: use HUSL - http://boronine.com/husl/
RgbQuant.prototype.nearestColor = function nearestColor(i32) {
var idx = this.nearestIndex(i32);
return idx === null ? 0 : this.idxi32[idx];
};
// TOTRY: use HUSL - http://boronine.com/husl/
RgbQuant.prototype.nearestIndex = function nearestIndex(i32) {
// alpha 0 returns null index
if ((i32 & 0xff000000) >> 24 == 0)
return null;
if (this.useCache && (""+i32) in this.i32idx)
return this.i32idx[i32];
var min = 1000,
idx,
rgb = [
(i32 & 0xff),
(i32 & 0xff00) >> 8,
(i32 & 0xff0000) >> 16,
],
len = this.idxrgb.length;
for (var i = 0; i < len; i++) {
if (!this.idxrgb[i]) continue; // sparse palettes
var dist = this.colorDist(rgb, this.idxrgb[i]);
if (dist < min) {
min = dist;
idx = i;
}
}
return idx;
};
RgbQuant.prototype.cacheHistogram = function cacheHistogram(idxi32) {
for (var i = 0, i32 = idxi32[i]; i < idxi32.length && this.histogram[i32] >= this.cacheFreq; i32 = idxi32[i++])
this.i32idx[i32] = this.nearestIndex(i32);
};
function HueStats(numGroups, minCols) {
this.numGroups = numGroups;
this.minCols = minCols;
this.stats = {};
for (var i = -1; i < numGroups; i++)
this.stats[i] = {num: 0, cols: []};
this.groupsFull = 0;
}
HueStats.prototype.check = function checkHue(i32) {
if (this.groupsFull == this.numGroups + 1)
this.check = function() {return;};
var r = (i32 & 0xff),
g = (i32 & 0xff00) >> 8,
b = (i32 & 0xff0000) >> 16,
hg = (r == g && g == b) ? -1 : hueGroup(rgb2hsl(r,g,b).h, this.numGroups),
gr = this.stats[hg],
min = this.minCols;
gr.num++;
if (gr.num > min)
return;
if (gr.num == min)
this.groupsFull++;
if (gr.num <= min)
this.stats[hg].cols.push(i32);
};
HueStats.prototype.inject = function injectHues(histG) {
for (var i = -1; i < this.numGroups; i++) {
if (this.stats[i].num <= this.minCols) {
switch (typeOf(histG)) {
case "Array":
this.stats[i].cols.forEach(function(col){
if (histG.indexOf(col) == -1)
histG.push(col);
});
break;
case "Object":
this.stats[i].cols.forEach(function(col){
if (!histG[col])
histG[col] = 1;
else
histG[col]++;
});
break;
}
}
}
};
// Rec. 709 (sRGB) luma coef
var Pr = .2126,
Pg = .7152,
Pb = .0722;
// http://alienryderflex.com/hsp.html
function rgb2lum(r,g,b) {
return Math.sqrt(
Pr * r*r +
Pg * g*g +
Pb * b*b
);
}
var rd = 255,
gd = 255,
bd = 255;
var euclMax = Math.sqrt(Pr*rd*rd + Pg*gd*gd + Pb*bd*bd);
// perceptual Euclidean color distance
function distEuclidean(rgb0, rgb1) {
var rd = rgb1[0]-rgb0[0],
gd = rgb1[1]-rgb0[1],
bd = rgb1[2]-rgb0[2];
return Math.sqrt(Pr*rd*rd + Pg*gd*gd + Pb*bd*bd) / euclMax;
}
var manhMax = Pr*rd + Pg*gd + Pb*bd;
// perceptual Manhattan color distance
function distManhattan(rgb0, rgb1) {
var rd = Math.abs(rgb1[0]-rgb0[0]),
gd = Math.abs(rgb1[1]-rgb0[1]),
bd = Math.abs(rgb1[2]-rgb0[2]);
return (Pr*rd + Pg*gd + Pb*bd) / manhMax;
}
// http://rgb2hsl.nichabi.com/javascript-function.php
function rgb2hsl(r, g, b) {
var max, min, h, s, l, d;
r /= 255;
g /= 255;
b /= 255;
max = Math.max(r, g, b);
min = Math.min(r, g, b);
l = (max + min) / 2;
if (max == min) {
h = s = 0;
} else {
d = max - min;
s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
switch (max) {
case r: h = (g - b) / d + (g < b ? 6 : 0); break;
case g: h = (b - r) / d + 2; break;
case b: h = (r - g) / d + 4; break
}
h /= 6;
}
// h = Math.floor(h * 360)
// s = Math.floor(s * 100)
// l = Math.floor(l * 100)
return {
h: h,
s: s,
l: rgb2lum(r,g,b),
};
}
function hueGroup(hue, segs) {
var seg = 1/segs,
haf = seg/2;
if (hue >= 1 - haf || hue <= haf)
return 0;
for (var i = 1; i < segs; i++) {
var mid = i*seg;
if (hue >= mid - haf && hue <= mid + haf)
return i;
}
}
function satGroup(sat) {
return sat;
}
function lumGroup(lum) {
return lum;
}
function typeOf(val) {
return Object.prototype.toString.call(val).slice(8,-1);
}
var sort = isArrSortStable() ? Array.prototype.sort : stableSort;
// must be used via stableSort.call(arr, fn)
function stableSort(fn) {
var type = typeOf(this[0]);
if (type == "Number" || type == "String") {
var ord = {}, len = this.length, val;
for (var i = 0; i < len; i++) {
val = this[i];
if (ord[val] || ord[val] === 0) continue;
ord[val] = i;
}
return this.sort(function(a,b) {
return fn(a,b) || ord[a] - ord[b];
});
}
else {
var ord = this.map(function(v){return v});
return this.sort(function(a,b) {
return fn(a,b) || ord.indexOf(a) - ord.indexOf(b);
});
}
}
// test if js engine's Array#sort implementation is stable
function isArrSortStable() {
var str = "abcdefghijklmnopqrstuvwxyz";
return "xyzvwtursopqmnklhijfgdeabc" == str.split("").sort(function(a,b) {
return ~~(str.indexOf(b)/2.3) - ~~(str.indexOf(a)/2.3);
}).join("");
}
// returns uniform pixel data from various img
// TODO?: if array is passed, createimagedata, createlement canvas? take a pxlen?
function getImageData(img, width) {
var can, ctx, imgd, buf8, buf32, height;
switch (typeOf(img)) {
case "HTMLImageElement":
can = document.createElement("canvas");
can.width = img.naturalWidth;
can.height = img.naturalHeight;
ctx = can.getContext("2d");
ctx.drawImage(img,0,0);
case "Canvas":
case "HTMLCanvasElement":
can = can || img;
ctx = ctx || can.getContext("2d");
case "CanvasRenderingContext2D":
ctx = ctx || img;
can = can || ctx.canvas;
imgd = ctx.getImageData(0, 0, can.width, can.height);
case "ImageData":
imgd = imgd || img;
width = imgd.width;
if (typeOf(imgd.data) == "CanvasPixelArray")
buf8 = new Uint8Array(imgd.data);
else
buf8 = imgd.data;
case "Array":
case "CanvasPixelArray":
buf8 = buf8 || new Uint8Array(img);
case "Uint8Array":
case "Uint8ClampedArray":
buf8 = buf8 || img;
buf32 = new Uint32Array(buf8.buffer);
case "Uint32Array":
buf32 = buf32 || img;
buf8 = buf8 || new Uint8Array(buf32.buffer);
width = width || buf32.length;
height = buf32.length / width;
}
return {
can: can,
ctx: ctx,
imgd: imgd,
buf8: buf8,
buf32: buf32,
width: width,
height: height,
};
}
// partitions a rect of wid x hgt into
// array of bboxes of w0 x h0 (or less)
function makeBoxes(wid, hgt, w0, h0) {
var wnum = ~~(wid/w0), wrem = wid%w0,
hnum = ~~(hgt/h0), hrem = hgt%h0,
xend = wid-wrem, yend = hgt-hrem;
var bxs = [];
for (var y = 0; y < hgt; y += h0)
for (var x = 0; x < wid; x += w0)
bxs.push({x:x, y:y, w:(x==xend?wrem:w0), h:(y==yend?hrem:h0)});
return bxs;
}
// iterates @bbox within a parent rect of width @wid; calls @fn, passing index within parent
function iterBox(bbox, wid, fn) {
var b = bbox,
i0 = b.y * wid + b.x,
i1 = (b.y + b.h - 1) * wid + (b.x + b.w - 1),
cnt = 0, incr = wid - b.w + 1, i = i0;
do {
fn.call(this, i);
i += (++cnt % b.w == 0) ? incr : 1;
} while (i <= i1);
}
// returns array of hash keys sorted by their values
function sortedHashKeys(obj, desc) {
var keys = [];
for (var key in obj)
keys.push(key);
return sort.call(keys, function(a,b) {
return desc ? obj[b] - obj[a] : obj[a] - obj[b];
});
}
// expose
this.RgbQuant = RgbQuant;
// expose to commonJS
if (typeof module !== 'undefined' && module.exports) {
module.exports = RgbQuant;
}
}).call(this);