initial implementation of predictor

This commit is contained in:
sbarman 2011-06-16 17:03:15 -07:00
parent 72919470a9
commit 4959dcb6a9

176
pdf.js
View File

@ -230,7 +230,24 @@ var FlateStream = (function() {
0x50007, 0x50017, 0x5000f, 0x00000
]), 5];
function constructor(stream) {
function constructor(stream, params) {
if (IsDict(params)) {
var predType = params.get("Predictor");
if (predType && predType > 1) {
var colors = params.get("Colors");
if (!colors)
colors = 1;
var bpc = params.get("BitsPerComponent");
if (!bpc)
bpc = 8;
var cols = params.get("Columns");
if (!cols)
cols = 1;
this.pred = new FilterPredictor(this, predType, cols,
colors, bpc);
}
}
this.stream = stream;
this.dict = stream.dict;
var cmf = stream.getByte();
@ -506,6 +523,163 @@ var FlateStream = (function() {
return constructor;
})();
var FilterPredictor = (function() {
function constructor(str, type, width, colors, bits) {
this.str = str;
this.type = type;
this.width = width;
this.colors = colors;
this.bits = bits;
this.nVals = width * colors;
this.pixBytes = (colors * bits + 7) >> 3;
var rowBytes = (width * colors * bits + 7) >> 3;
this.rowBytes = rowBytes;
if (width < 0 || colors < 0 || bits < 0 ||bits > 16)
error("Invalid predictor");
var prevLine = [];
for (var i = 0; i < rowBytes; ++i)
prevLine.push(0);
this.prevLine = prevLine;
this.prevIdx = rowBytes;
}
constructor.prototype = {
getByte: function() {
if (this.prevIdx >= this.rowBytes) {
if(!this.getNextLine())
return;
}
return this.prevLine[this.prevIdx];
},
getNextLine: function() {
if (this.type >= 10) {
var curType = this.str.getRawByte();
if (!curType)
return;
curType += 10;
} else {
var curType = this.type;
}
var line = [];
for (var i = 0; i < this.rowBytes - this.pixBytes; i++)
line.push(this.str.getRawByte());
var pixBytes = this.pixBytes;
var rowBytes = this.rowBytes;
var prevLine = this.prevLine;
var upLeftBuf = [];
for (var i = 0, ii = pixBytes + 1; i < ii; ++i)
upLeftBuf.push(0);
for (var i = pixBytes, ii = rowBybtes; i < ii; ++i) {
for (var j = pixBytes; j > 0; --j) {
upLeftBuf[j] = upLeftBuf[j - 1];
upLeftBuf[0] = prevLine[i];
var c = line[i - pixBytes];
if (!c) {
if (i > pixBytes)
break;
return;
}
switch (curType) {
case 11:
prevLine[i] = prevLine[i - pixBytes] + c;
break;
case 12:
prevLine[i] = prevLine[i] + c;
break;
case 13:
prevLine[i] = ((prevLine[i - pixBytes]
+ prevLine[i]) >> 1) + c;
break;
case 14:
var left = prevLine[i - pixBytes];
var up = prevLine[i];
var upLeft = upLeftBuf[pixBytes];
var p = left + up - upLeft;
var pa = p - left;
if (pa < 0)
pa = -pa;
var pb = p - up;
if (pb < 0)
pb = -pb;
var pc = p - upLeft;
if (pc < 0)
pc = -pc;
if (pa <= pb && pa <= pc)
prevLine[i] = left + c;
else if (pb <= pc)
prevLine[i] = up + c;
else
prevLine[i] = upLeft + c;
break;
case 10:
default:
prevLine[i] = c;
break;
}
}
}
var bits = this.bits;
var colors = this.colors;
if (curPred === 2) {
if (bits === 1) {
var inbuf = prevLine[pixBytes - 1];
for (var i = pixBytes; i < rowBytes; i+= 8) {
inBuf = (inBuf << 8) | prevLine[i];
prevLine[i] ^= inBuf >> colors;
}
} else if (bits === 8) {
for (var i = pixBytes; i < rowBytes; ++i)
prevLine[i] += prevLine[i - colors];
} else {
for (var i = 0, ii = colors + 1; i < ii; ++i)
upLeftBuf[i] = 0;
var bitMask = (1 << bits) - 1;
var inbuf = 0, outbut = 0;
var inbits = 0, outbits = 0;
var j = pixBytes, k = pixBytes;
var width = this.width;
for (var i = 0; i < width; ++i) {
for (var kk = 0; kk < colors; ++kk) {
if (inbits < bits) {
inbuf = (inbuf << 8) | (prevLine[j++] & 255);
inbits += 8;
}
upLeftBuf[kk] = (upLeftBuf[kk] + (inbuf >>
(inbits - bits))) & bitMask;
inbits -= bits;
outbuf = (outbuf << bits) | upLeftBuf[kk];
outbits += bits;
if (outbits >= 8) {
prevLine[k++] = (outbuf >> (outbits - 8));
outbits -= 8;
}
}
}
if (outbits > 0) {
prevLine[k++] = (outbuf << (8 - outbits)) +
(inbuf & ((1 << (8 - outbits)) - 1))
}
}
}
prevIdx = pixBytes;
return true;
}
};
return constructor;
})();
var DecryptStream = (function() {
function constructor(str, fileKey, encAlgorithm, keyLength) {
// TODO