remove png functions, better versions in Ox.Image
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1 changed files with 1 additions and 96 deletions
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@ -322,101 +322,6 @@
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/*@
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Ox.encodePNG <f> Encodes a string into an image, returns a new image
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The string is compressed with deflate (by proxy of canvas), prefixed
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with its length (four bytes), and encoded bitwise into the red, green
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and blue bytes of all fully opaque pixels of the image, by flipping, if
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necessary, the least significant bit, so that for every byte, the total
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number of bits set to to 1, modulo 2, is the bit that we are encoding.
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(img, src) -> <e> An image into which the string has been encoded
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img <e> Any JavaScript PNG image object
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str <s> The string to be encoded
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@*/
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// fixme: remove, exists in image module
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Ox.encodePNG = function(img, str) {
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var c = Ox.canvas(img), i = 0;
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// Compress the string
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str = Ox.encodeDeflate(str);
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// Prefix the string with its length, as a four-byte value
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str = Ox.pad(Ox.encodeBase256(str.length), 4, Ox.char(0)) + str;
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// Create an array of bit values
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Ox.forEach(Ox.flatten(Ox.map(str, function(chr) {
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return Ox.map(Ox.range(8), function(i) {
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return chr.charCodeAt(0) >> 7 - i & 1;
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});
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})), function(bit) {
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// Skip all pixels that are not fully opaque
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while (i < c.data.length && i % 4 == 0 && c.data[i + 3] < 255) {
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i += 4;
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}
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if (i == c.data.length) {
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throw new RangeError('PNG codec can\'t encode data');
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}
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// If the number of bits set to one, modulo 2 is equal to the bit,
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// do nothing, otherwise, flip the least significant bit.
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c.data[i] += c.data[i].toString(2).replace(/0/g, '').length % 2
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== bit ? 0 : c.data[i] % 2 ? -1 : 1;
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i++;
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});
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c.context.putImageData(c.imageData, 0, 0);
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img = new Image();
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img.src = c.canvas.toDataURL();
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return img;
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/*
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wishlist:
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- only use deflate if it actually shortens the message
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- encode a decoy message into the least significant bit
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(and flip the second least significant bit, if at all)
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- write an extra png chunk containing some key
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*/
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};
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/*@
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Ox.decodePNG <f> Decodes an image, returns a string
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For every red, green and blue byte of every fully opaque pixel of the
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image, one bit, namely the number of bits of the byte set to one, modulo
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2, is being read, the result being the string, prefixed with its length
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(four bytes), which is decompressed with deflate (by proxy of canvas).
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(img, callback) -> <u> undefined
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img <e> The image into which the string has been encoded
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callback <f> Callback function
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str <s> The decoded string
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@*/
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Ox.decodePNG = function(img, callback) {
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var bits = '', data = Ox.canvas(img).data, flag = false, i = 0,
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len = 4, str = '';
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while (len) {
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// Skip all pixels that are not fully opaque
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while (i < data.length && i % 4 == 0 && data[i + 3] < 255) {
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i += 4;
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}
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if (i == data.length) {
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break;
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}
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// Read the number of bits set to one, modulo 2
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bits += data[i].toString(2).replace(/0/g, '').length % 2;
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if (++i % 8 == 0) {
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// Every 8 bits, add one byte
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str += Ox.char(parseInt(bits, 2));
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bits = '';
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// When length reaches 0 for the first time,
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// decode the string and treat it as the new length
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if (--len == 0 && !flag) {
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flag = true;
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len = Ox.decodeBase256(str);
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str = '';
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}
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}
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}
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try {
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Ox.decodeDeflate(str, callback);
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} catch (e) {
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throw new RangeError('PNG codec can\'t decode image');
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}
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};
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/*@
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/*@
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Ox.encodeUTF8 <f> Encodes a string as UTF-8
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Ox.encodeUTF8 <f> Encodes a string as UTF-8
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see http://en.wikipedia.org/wiki/UTF-8
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see http://en.wikipedia.org/wiki/UTF-8
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