moriyoshi/declitimg.js

## declitimg.js
function declitimg(img) {
    var cv = document.createElement('canvas');
    cv.width = img.width;
    cv.height = img.height;
    var ctx = cv.getContext('2d');
    ctx.drawImage(img, 0, 0);
    var imd = ctx.getImageData(0, 0, img.width, img.height);
    var s = '';
    for (var i = 0; i < imd.data.length && imd.data[i] !== 0;) {
        var c1 = imd.data[i++];
        if (i % 4 == 3)
            i++;
        if (c1 < 0x80) {
            s += String.fromCharCode(c1);
        } else if (c1 < 0xc2) {
            throw "Invalid byte sequence";
        } else if (c1 < 0xe0) {
            if (i >= img.data.length)
                throw "Invalid byte sequence";
            var c2 = imd.data[i++];
            if (i % 4 == 3)
                i++;
            if (c2 < 0x80 || c2 >= 0xc0)
                throw "Invalid byte sequence";
            s += String.fromCharCode(((c1 & 0x1f) << 6) | (c2 & 0x3f));
        } else if (c1 < 0xf0) {
            if (i >= imd.data.length)
                throw "Invalid byte sequence";
            var c2 = imd.data[i++];
            if (i % 4 == 3)
                i++;
            if (c2 < 0x80 || c2 >= 0xc0)
                throw "Invalid byte sequence";
            if (i >= imd.data.length)
                throw "Invalid byte sequence";
            var c3 = imd.data[i++];
            if (i % 4 == 3)
                i++;
            if (c3 < 0x80 || c3 >= 0xc0)
                throw "Invalid byte sequence";
            s += String.fromCharCode(((c1 & 0x0f) << 12) | ((c2 & 0x3f) << 6) | (c3 & 0x3f));
        } else if (c1 < 0xf8) {
            if (i >= imd.data.length)
                throw "Invalid byte sequence";
            var c2 = imd.data[i++];
            if (i % 4 == 3)
                i++;
            if (c2 < 0x80 || c2 >= 0xc0)
                throw "Invalid byte sequence";
            if (i >= imd.data.length)
                throw "Invalid byte sequence";
            var c3 = imd.data[i++];
            if (i % 4 == 3)
                i++;
            if (c3 < 0x80 || c3 >= 0xc0)
                throw "Invalid byte sequence";
            if (++i >= imd.data.length)
                throw "Invalid byte sequence";
            var c4 = imd.data[i++];
            if (i % 4 == 3)
                i++;
            if (c4 < 0x80 || c4 >= 0xc0)
                throw "Invalid byte sequence";
            s += String.fromCharCode(((c1 & 0x07) << 18) | ((c2 & 0x3f) << 12) | ((c3 & 0x3f) << 6) | (c4 & 0x3f));
        } else {
            throw "Invalid byte sequence";
        }
    }
    return s;
}

## genlitimg.py
#!/usr/bin/env python
# encoding: utf-8

from PIL import Image
from cStringIO import StringIO
from base64 import b64encode

def encode(s):
    # convert str to octets if it's Unicode
    if isinstance(s, unicode):
        s = s.encode('UTF-8')
    # pad it
    s += "\x00" * (2 - (len(s) + 2) % 3)
    # create an Image object from the buffer
    im = Image.frombuffer('RGB', (len(s) / 4, 1), s, 'raw', 'RGB', 0, 1)
    out = StringIO()
    im.save(out, 'png', gamma=0.)
    return 'data:image/png;base64,' + b64encode(out.getvalue())

print encode(u'テスト')

## test.html
<html>
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
  <script type="text/javascript" src="declitimg.js"></script>
  <script type="text/javascript">
    var im = new Image();
    im.onload = function() {
      var out = document.getElementById('out');
      out.appendChild(document.createTextNode(declitimg(im)));
    };
    im.src = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAMAAAABCAIAAACUgoPjAAAAEklEQVR4nGN83NzG8N+YgfE8ABZpA/Cma4j9AAAAAElFTkSuQmCC';
  </script>
</head>
<body>
  <div id="out">
  </div>
</body>
</html>
	function declitimg(img) {
	var cv = document.createElement('canvas');
	cv.width = img.width;
	cv.height = img.height;
	var ctx = cv.getContext('2d');
	ctx.drawImage(img, 0, 0);
	var imd = ctx.getImageData(0, 0, img.width, img.height);
	var s = '';
	for (var i = 0; i < imd.data.length && imd.data[i] !== 0;) {
	var c1 = imd.data[i++];
	if (i % 4 == 3)
	i++;
	if (c1 < 0x80) {
	s += String.fromCharCode(c1);
	} else if (c1 < 0xc2) {
	throw "Invalid byte sequence";
	} else if (c1 < 0xe0) {
	if (i >= img.data.length)
	throw "Invalid byte sequence";
	var c2 = imd.data[i++];
	if (i % 4 == 3)
	i++;
	if (c2 < 0x80 \|\| c2 >= 0xc0)
	throw "Invalid byte sequence";
	s += String.fromCharCode(((c1 & 0x1f) << 6) \| (c2 & 0x3f));
	} else if (c1 < 0xf0) {
	if (i >= imd.data.length)
	throw "Invalid byte sequence";
	var c2 = imd.data[i++];
	if (i % 4 == 3)
	i++;
	if (c2 < 0x80 \|\| c2 >= 0xc0)
	throw "Invalid byte sequence";
	if (i >= imd.data.length)
	throw "Invalid byte sequence";
	var c3 = imd.data[i++];
	if (i % 4 == 3)
	i++;
	if (c3 < 0x80 \|\| c3 >= 0xc0)
	throw "Invalid byte sequence";
	s += String.fromCharCode(((c1 & 0x0f) << 12) \| ((c2 & 0x3f) << 6) \| (c3 & 0x3f));
	} else if (c1 < 0xf8) {
	if (i >= imd.data.length)
	throw "Invalid byte sequence";
	var c2 = imd.data[i++];
	if (i % 4 == 3)
	i++;
	if (c2 < 0x80 \|\| c2 >= 0xc0)
	throw "Invalid byte sequence";
	if (i >= imd.data.length)
	throw "Invalid byte sequence";
	var c3 = imd.data[i++];
	if (i % 4 == 3)
	i++;
	if (c3 < 0x80 \|\| c3 >= 0xc0)
	throw "Invalid byte sequence";
	if (++i >= imd.data.length)
	throw "Invalid byte sequence";
	var c4 = imd.data[i++];
	if (i % 4 == 3)
	i++;
	if (c4 < 0x80 \|\| c4 >= 0xc0)
	throw "Invalid byte sequence";
	s += String.fromCharCode(((c1 & 0x07) << 18) \| ((c2 & 0x3f) << 12) \| ((c3 & 0x3f) << 6) \| (c4 & 0x3f));
	} else {
	throw "Invalid byte sequence";
	}
	}
	return s;
	}
	#!/usr/bin/env python
	# encoding: utf-8

	from PIL import Image
	from cStringIO import StringIO
	from base64 import b64encode

	def encode(s):
	# convert str to octets if it's Unicode
	if isinstance(s, unicode):
	s = s.encode('UTF-8')
	# pad it
	s += "\x00" * (2 - (len(s) + 2) % 3)
	# create an Image object from the buffer
	im = Image.frombuffer('RGB', (len(s) / 4, 1), s, 'raw', 'RGB', 0, 1)
	out = StringIO()
	im.save(out, 'png', gamma=0.)
	return 'data:image/png;base64,' + b64encode(out.getvalue())

	print encode(u'テスト')
	<html>
	<head>
	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
	<script type="text/javascript" src="declitimg.js"></script>
	<script type="text/javascript">
	var im = new Image();
	im.onload = function() {
	var out = document.getElementById('out');
	out.appendChild(document.createTextNode(declitimg(im)));
	};
	im.src = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAMAAAABCAIAAACUgoPjAAAAEklEQVR4nGN83NzG8N+YgfE8ABZpA/Cma4j9AAAAAElFTkSuQmCC';
	</script>
	</head>
	<body>
	<div id="out">
	</div>
	</body>
	</html>