algorithm changes to allow >10 tiles wide

sudoroom · Aug 26, 2013 · 72f886b · 72f886b
1 parent fafd44a
commit 72f886b
Show file tree

Hide file tree

Showing 8 changed files with 66 additions and 18 deletions.
diff --git a/README.md b/README.md
@@ -90,6 +90,13 @@ Faithful replica of Github's identicon style.
 
 ![github](https://raw.github.com/sehrgut/node-retricon/master/examples/images/github.png)
 
+### custom example
+Absurd settings, such as:
+`{ pixelSize: 8, pixelPadding: -2, tiles: 30, pixelColor: 0, bgColor: 1 }`
+can still yield quite serviceable results.
+
+![bat](https://raw.github.com/sehrgut/node-retricon/master/examples/images/bat.png)
+
 
 ## Algorithm
 
@@ -106,5 +113,8 @@ The array of booleans is taken to be a row-major array covering the left half
 of the final image. It is reflected about the central vertical axis (or column,
 for odd-order arrays) which is then rendered as the final visual hash.
 
+## Known Limitations
+* 30x30 tile images are the maximum which can be generated from SHA-512.
+
 [ghid]: https://github.com/blog/1586-identicons
 [gravatar]: https://en.gravatar.com/site/implement/images/
diff --git a/TODO.md b/TODO.md
@@ -15,4 +15,5 @@
   return a "colors" array. Useful for nudging colours away from low-contrast
   pairs, maybe desaturating, etc., to provide a more uniform look.
 * Allow null for foreground colour, to delete background and allow transparent
-* Allow pluggable hash functions
+* Allow pluggable hash functions
+* Change "pixel" references throughout source to "tile"
diff --git a/examples/example.js b/examples/example.js
@@ -1,6 +1,7 @@
 var retricon = require('../');
 var fmt = require('util').format;
 
+
 console.log('<html><head><title>retricons</title></head><body>');
 
 console.log('<div><h2>default</h2>');

diff --git a/examples/images/bat.png b/examples/images/bat.png
diff --git a/examples/large.js b/examples/large.js
@@ -0,0 +1,13 @@
+var retricon = require('../');
+var fmt = require('util').format;
+
+
+console.log('<html><head><title>retricons</title></head><body>');
+
+console.log('<h2>large</h2>');
+var custom = { pixelSize: 8, pixelPadding: -2, tiles: 30, pixelColor: 0, bgColor: 1 };
+for (var i=0; i<10; i++) {
+	console.log("<img src='" + retricon(i.toString(), custom).toDataURL() + "'>");
+}
+
+console.log('</body></html>');
diff --git a/lib/bright.js b/lib/bright.js
@@ -0,0 +1,18 @@
+function brightness(r, g, b) {
+	// http://www.nbdtech.com/Blog/archive/2008/04/27/Calculating-the-Perceived-Brightness-of-a-Color.aspx
+	return Math.sqrt( .241 * r * r + .691 * g * g + .068 * b * b )
+}
+
+function cmp_brightness(a, b) {
+	return brightness(a[0], a[1], a[2]) - brightness(b[0], b[1], b[2]);
+}
+
+function rcmp_brightness(a, b) {
+	return cmp_brightness(b, a);
+}
+
+module.exports = {
+	ness: brightness,
+	cmp: cmp_brightness,
+	rcmp: rcmp_brightness
+};
diff --git a/lib/index.js b/lib/index.js
@@ -3,38 +3,35 @@ var Canvas = require('canvas');
 var _ = require('lodash');
 var bu = require('./bufutil');
 var fmt = require('util').format;
+var unpack = require('./unpack');
+var bright = require('./bright');
 
 function fprint(buf, len) {
+	if (len > 64)
+		throw new Error(fmt("sha512 can only generate 64B of data: %dB requested", len));
+
 	return _(crypto.createHash('sha512').update(buf).digest())
 		.groupBy(function (x, k) { return Math.floor(k/len); })
 		.reduce(bu.xor);
 }
 
-function brightness(r, g, b) {
-	// http://www.nbdtech.com/Blog/archive/2008/04/27/Calculating-the-Perceived-Brightness-of-a-Color.aspx
-	return Math.sqrt( .241 * r * r + .691 * g * g + .068 * b * b )
-}
-
-function cmp_brightness(a, b) {
-	return brightness(a[0], a[1], a[2]) - brightness(b[0], b[1], b[2]);
-}
-
-function rcmp_brightness(a, b) {
-	return cmp_brightness(b, a);
-}
 
 function idhash(str, n, minFill, maxFill) {
 	var buf = new Buffer(str.length + 1);
 	buf.write(str);
 
 	for (var i=0; i<0x100; i++) {
 		buf[buf.length - 1] = i;
-		var f = fprint(buf, n+6);
-		var pixels = _(f.slice(6)).map(function (x) { return x > 0x7f; });
+		var f = fprint(buf, Math.ceil(n/8)+6);
+		var pixels = _(f.slice(6))
+			.map(function (x) { return unpack(x); })
+			.flatten().take(n);
+
 		var setPixels = pixels.filter().size();
 
 		var c = [ f.slice(0, 3), f.slice(3, 6)];
-		c.sort(cmp_brightness);
+		c.sort(bright.cmp);
+//		console.error(fmt("%d < %d < %d", minFill*n, setPixels, maxFill*n));
 		if (setPixels > (minFill * n) && setPixels < (maxFill * n))
 			return {
 				colors: c.map(function (x) { return x.toString('hex'); }),
@@ -60,9 +57,9 @@ function reflect(id, dimension) {
 				p = (row * mid) + mid - 1 - ad;
 			}
 			pic[row][col] = id.pixels[p];
+//			console.error(fmt("looking for %d, of %d for %d,%d", p, id.pixels.length, row, col))
 		}
 	}
-
 	return pic;
 }
 
@@ -107,7 +104,6 @@ function retricon(str, opts) {
 							(y*pixelSize) + border + opts.imagePadding,
 							pixelSize - (border * 2),
 							pixelSize - (border * 2));
-
 	return c;
 }
 

diff --git a/lib/unpack.js b/lib/unpack.js
@@ -0,0 +1,9 @@
+
+function unpack_byte(nMask) {
+	// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators
+	for (var i=0, nShifted = nMask, a = []; i<8; nShifted >>>= 1, i++)
+		a.push(Boolean(nShifted & 1));
+	return a;
+}
+
+module.exports = unpack_byte;