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Multi-color predictor; row predictor for sub and average

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notmasteryet 2011-06-19 23:23:21 -05:00
parent 8edc61bd2f
commit 8d4d0a6752
1 changed files with 18 additions and 4 deletions
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pdf.js
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@ -522,13 +522,13 @@ var PredictorStream = (function() {
this.colors = params.get("Colors") || 1;
this.bitsPerComponent = params.get("BitsPerComponent") || 8;
this.columns = params.get("Columns") || 1;
if (this.colors !== 1 || this.bitsPerComponent !== 8) {
error("Multi-color and multi-byte predictors are not supported");
if (this.bitsPerComponent !== 8) {
error("Multi-byte predictors are not supported");
}
if (this.predictor < 10 || this.predictor > 15) {
error("Unsupported predictor");
}
this.currentRow = new Uint8Array(this.columns);
this.currentRow = new Uint8Array(this.columns * this.colors);
this.pos = 0;
this.bufferLength = 0;
}
@ -536,19 +536,33 @@ var PredictorStream = (function() {
constructor.prototype = {
readRow : function() {
var lastRow = this.currentRow;
var colors = this.colors;
var predictor = this.stream.getByte();
var currentRow = this.stream.getBytes(this.columns), i;
var currentRow = this.stream.getBytes(this.columns * colors), i;
switch (predictor) {
default:
error("Unsupported predictor");
break;
case 0:
break;
case 1:
for (i = colors; i < currentRow.length; ++i) {
currentRow[i] = (currentRow[i - colors] + currentRow[i]) & 0xFF;
}
break;
case 2:
for (i = 0; i < currentRow.length; ++i) {
currentRow[i] = (lastRow[i] + currentRow[i]) & 0xFF;
}
break;
case 3:
for (i = 0; i < color; ++i) {
currentRow[i] = ((lastRow[i] >> 1) + currentRow[i]) & 0xFF;
}
for (; i < currentRow.length; ++i) {
currentRow[i] = (((lastRow[i] + currentRow[i]) >> 1) + currentRow[i]) & 0xFF;
}
break;
}
this.pos = 0;
this.bufferLength = currentRow.length;