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remove png functions, better versions in Ox.Image

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j 2012-05-22 19:49:29 +02:00
parent 3f35003ac9
commit 6fcca8f3a9
1 changed files with 1 additions and 96 deletions
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97
source/Ox/js/Encoding.js
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@ -322,101 +322,6 @@
);
};
/*@
Ox.encodePNG <f> Encodes a string into an image, returns a new image
The string is compressed with deflate (by proxy of canvas), prefixed
with its length (four bytes), and encoded bitwise into the red, green
and blue bytes of all fully opaque pixels of the image, by flipping, if
necessary, the least significant bit, so that for every byte, the total
number of bits set to to 1, modulo 2, is the bit that we are encoding.
(img, src) -> <e> An image into which the string has been encoded
img <e> Any JavaScript PNG image object
str <s> The string to be encoded
@*/
// fixme: remove, exists in image module
Ox.encodePNG = function(img, str) {
var c = Ox.canvas(img), i = 0;
// Compress the string
str = Ox.encodeDeflate(str);
// Prefix the string with its length, as a four-byte value
str = Ox.pad(Ox.encodeBase256(str.length), 4, Ox.char(0)) + str;
// Create an array of bit values
Ox.forEach(Ox.flatten(Ox.map(str, function(chr) {
return Ox.map(Ox.range(8), function(i) {
return chr.charCodeAt(0) >> 7 - i & 1;
});
})), function(bit) {
// Skip all pixels that are not fully opaque
while (i < c.data.length && i % 4 == 0 && c.data[i + 3] < 255) {
i += 4;
}
if (i == c.data.length) {
throw new RangeError('PNG codec can\'t encode data');
}
// If the number of bits set to one, modulo 2 is equal to the bit,
// do nothing, otherwise, flip the least significant bit.
c.data[i] += c.data[i].toString(2).replace(/0/g, '').length % 2
== bit ? 0 : c.data[i] % 2 ? -1 : 1;
i++;
});
c.context.putImageData(c.imageData, 0, 0);
img = new Image();
img.src = c.canvas.toDataURL();
return img;
/*
wishlist:
- only use deflate if it actually shortens the message
- encode a decoy message into the least significant bit
(and flip the second least significant bit, if at all)
- write an extra png chunk containing some key
*/
};
/*@
Ox.decodePNG <f> Decodes an image, returns a string
For every red, green and blue byte of every fully opaque pixel of the
image, one bit, namely the number of bits of the byte set to one, modulo
2, is being read, the result being the string, prefixed with its length
(four bytes), which is decompressed with deflate (by proxy of canvas).
(img, callback) -> <u> undefined
img <e> The image into which the string has been encoded
callback <f> Callback function
str <s> The decoded string
@*/
Ox.decodePNG = function(img, callback) {
var bits = '', data = Ox.canvas(img).data, flag = false, i = 0,
len = 4, str = '';
while (len) {
// Skip all pixels that are not fully opaque
while (i < data.length && i % 4 == 0 && data[i + 3] < 255) {
i += 4;
}
if (i == data.length) {
break;
}
// Read the number of bits set to one, modulo 2
bits += data[i].toString(2).replace(/0/g, '').length % 2;
if (++i % 8 == 0) {
// Every 8 bits, add one byte
str += Ox.char(parseInt(bits, 2));
bits = '';
// When length reaches 0 for the first time,
// decode the string and treat it as the new length
if (--len == 0 && !flag) {
flag = true;
len = Ox.decodeBase256(str);
str = '';
}
}
}
try {
Ox.decodeDeflate(str, callback);
} catch (e) {
throw new RangeError('PNG codec can\'t decode image');
}
};
/*@
Ox.encodeUTF8 <f> Encodes a string as UTF-8
see http://en.wikipedia.org/wiki/UTF-8
@ -496,4 +401,4 @@
return ret;
};
})();
})();