v0.4.0-alpha

README.md

@@ -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
 

lib/filter.js

@@ -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];
+    if (!('filterType' in options) || options.filterType == -1) {
-    this._filters = {};
+        options.filterType = [0, 1, 2, 3, 4];
-    for (var filterType in options.filterTypes) {
+    } else if (typeof options.filterType == 'number') {
-        switch (filterType) {
+        options.filterType = [options.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:
-        }
     }
 
+    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) {
+        for (var i = 0; i < filterTypes.length; i++) {
-            var sum = this._filters[f](pxData, y, null);
+            var sum = this._filters[filterTypes[i]](pxData, y, null);
             if (sum < min) {
-                sel = f;
+                sel = filterTypes[i];
                 min = sum;
             }
         }