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working implementation of png and tiff predictors

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sbarman 2011-06-20 19:51:36 -07:00
parent 50bf57e353
commit 4635091c43
1 changed files with 91 additions and 14 deletions
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105
pdf.js
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@ -752,14 +752,66 @@ var PredictorStream = (function() {
this.rowBytes = rowBytes;
this.currentRow = new Uint8Array(rowBytes);
this.bufferLength = rowBytes;
this.pos = rowBytes;
}
constructor.prototype = {
readRowTiff : function() {
var currentRow = this.currentRow;
var rowBytes = this.rowBytes;
var pixBytes = this.pixBytes;
var bits = this.bits;
var colors = this.colors;
var rawBytes = this.stream.getBytes(rowBytes - pixBytes);
if (bits === 1) {
var inbuf = 0;
for (var i = pixBytes, j = 0; i < rowBytes; ++i, ++j) {
var c = rawBytes[j];
inBuf = (inBuf << 8) | c;
// bitwise addition is exclusive or
// first shift inBuf and then add
currentRow[i] = (c ^ (inBuf >> colors)) & 0xFF;
// truncate inBuf (assumes colors < 16)
inBuf &= 0xFFFF;
}
} else if (bits === 8) {
for (var i = pixBytes, j = 0; i < rowBytes; ++i, ++j)
currentRow[i] = currentRow[i - colors] + rawBytes[j];
} else {
var compArray = new Uint8Array(colors + 1);
var bitMask = (1 << bits) - 1;
var inbuf = 0, outbut = 0;
var inbits = 0, outbits = 0;
var j = 0, k = pixBytes;
var columns = this.columns;
for (var i = 0; i < columns; ++i) {
for (var kk = 0; kk < colors; ++kk) {
if (inbits < bits) {
inbuf = (inbuf << 8) | (rawBytes[j++] & 0xFF);
inbits += 8;
}
compArray[kk] = (compArray[kk] + (inbuf >>
(inbits - bits))) & bitMask;
inbits -= bits;
outbuf = (outbuf << bits) | compArray[kk];
outbits += bits;
if (outbits >= 8) {
currentRow[k++] = (outbuf >> (outbits - 8)) & 0xFF;
outbits -= 8;
}
}
}
if (outbits > 0) {
currentRow[k++] = (outbuf << (8 - outbits)) +
(inbuf & ((1 << (8 - outbits)) - 1))
}
}
this.pos = pixBytes;
},
readRowPng : function() {
// swap the buffers
var currentRow = this.currentRow;
var rowBytes = this.rowBytes;
@ -773,31 +825,56 @@ var PredictorStream = (function() {
case 0:
break;
case 1:
for (i = pixBytes; i < rowBytes; ++i)
currentRow[i] = (currentRow[i - pixBytes] + rawBytes[i]) & 0xFF;
// set the first pixel
for (var i = pixBytes, j = 0; i < rowBytes; ++i, ++j)
currentRow[i] = (currentRow[i - pixBytes] + rawBytes[j]) & 0xFF;
break;
case 2:
for (i = pixBytes; i < rowBytes; ++i)
currentRow[i] = (currentRow[i] + rawBytes[i]) & 0xFF;
for (var i = pixBytes, j = 0; i < rowBytes; ++i, ++j)
currentRow[i] = (currentRow[i] + rawBytes[j]) & 0xFF;
break;
case 3:
for (i = pixBytes; i < rowBytes; ++i)
currentRow[i] = (((currentRow[i] + currentRow[i - pixBytes])
>> 1) + rawBytes[i]) & 0xFF;
// set the first pixel
for (i = pixBytes, j = 0; i < rowBytes; ++i, ++j)
currentRow[i] = (((currentRow[i] + currentRow[i - pixBytes])
>> 1) + rawBytes[j]) & 0xFF;
break;
case 4:
for (i = pixBytes; i < rowBytes; ++i) {
// we need to save the up left pixels values. the simplest way
// is to create a new buffer
var lastRow = currentRow;
var currentRow = new Uint8Array(rowBytes);
for (var i = pixBytes, j = 0; i < rowBytes; ++i, ++j) {
var up = lastRow[i];
var upLeft = lastRow[i - pixBytes];
var left = currentRow[i - pixBytes];
var up = currentRow[i];
var upLeft =
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;
var c = rawBytes[j];
if (pa <= pb && pa <= pc)
currentRow[i] = left + c;
else if (pb <= pc)
currentRow[i] = up + c;
else
currentRow[i] = upLeft + c;
break;
this.currentRow = currentRow;
}
default:
error("Unsupported predictor");
break;
}
this.pos = 0;
this.bufferLength = currentRow.length;
this.currentRow = currentRow;
this.pos = pixBytes;
},
getByte : function() {
if (this.pos >= this.bufferLength) {