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v0.4.0-alpha

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This commit is contained in:
Kuba Niegowski 2012-11-29 00:39:43 +01:00
parent a6406c85f2
commit a527d93d7b
2 changed files with 24 additions and 27 deletions
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7
README.md
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@ -59,7 +59,8 @@ As input any color type is accepted (grayscale, rgb, palette, grayscale with alp
- `checkCRC` - whether parser should be strict about checksums in source stream (default: `true`)
- `deflateChunkSize` - chunk size used for deflating data chunks, this should be power of 2 and must not be less than 256 and more than 32*1024 (default: 32 kB)
- `deflateLevel` - compression level for delate (default: 9)
- `filterType` - png filtering method for scanlines (default: -1 => auto)
- `deflateStrategy` - compression strategy for delate (default: 3)
- `filterType` - png filtering method for scanlines (default: -1 => auto, accepts array of numbers 0-4)
### Event "metadata"
@ -120,6 +121,10 @@ Gamma of image (0 if not specified)
Changelog
============
### 0.4.0-alpha - 29 Nov 2012
- added zlib deflateStrategy option, default to Z_RLE (by pdpotter)
- added possibility to use multiple filters (by pdpotter, modified by niegowski)
### 0.3.0-alpha - 23 Aug 2012
- Processing data as Streams, not complete Buffers of data

44
lib/filter.js
View file

@ -36,29 +36,20 @@ var Filter = module.exports = function(width, height, Bpp, data, options) {
this._line = 0;
options.filterTypes = options.filterTypes || [0,1,2,3,4];
this._filters = {};
for (var filterType in options.filterTypes) {
switch (filterType) {
case '0':
this._filters[filterType] = this._filterNone.bind(this);
break;
case '1':
this._filters[filterType] = this._filterSub.bind(this);
break;
case '2':
this._filters[filterType] = this._filterUp.bind(this);
break;
case '3':
this._filters[filterType] = this._filterAvg.bind(this);
break;
case '4':
this._filters[filterType] = this._filterPaeth.bind(this);
break;
default:
}
if (!('filterType' in options) || options.filterType == -1) {
options.filterType = [0, 1, 2, 3, 4];
} else if (typeof options.filterType == 'number') {
options.filterType = [options.filterType];
}
this._filters = {
0: this._filterNone.bind(this),
1: this._filterSub.bind(this),
2: this._filterUp.bind(this),
3: this._filterAvg.bind(this),
4: this._filterPaeth.bind(this)
};
this.read(this._width * Bpp + 1, this._reverseFilterLine.bind(this));
};
util.inherits(Filter, ChunkStream);
@ -98,7 +89,7 @@ Filter.prototype._reverseFilterLine = function(rawData) {
pxRowPos = this._line * pxLineLength,
filter = rawData[0];
if (filter === 0) {
if (filter == 0) {
for (var x = 0; x < this._width; x++) {
var pxPos = pxRowPos + (x << 2),
rawPos = 1 + x * this._Bpp;
@ -190,13 +181,14 @@ Filter.prototype.filter = function() {
for (var y = 0; y < this._height; y++) {
// find best filter for this line (with lowest sum of values)
var min = Infinity,
var filterTypes = this._options.filterType,
min = Infinity,
sel = 0;
for (var f in this._filters) {
var sum = this._filters[f](pxData, y, null);
for (var i = 0; i < filterTypes.length; i++) {
var sum = this._filters[filterTypes[i]](pxData, y, null);
if (sum < min) {
sel = f;
sel = filterTypes[i];
min = sum;
}
}