jpeg-js
diff --git a/‎lib/decoder.js
Lines changed: 5 additions & 4 deletions b/‎lib/decoder.js
Lines changed: 5 additions & 4 deletions
diff --git a/‎test/fixtures/cmyk-grey.cmyk
Lines changed: 803 additions & 704 deletions b/‎test/fixtures/cmyk-grey.cmyk
Lines changed: 803 additions & 704 deletions
diff --git a/‎test/fixtures/skater-progressive.jpg
17.5 KB b/‎test/fixtures/skater-progressive.jpg
17.5 KB
diff --git a/‎test/fixtures/skater-progressive.rgba
Lines changed: 1203 additions & 0 deletions b/‎test/fixtures/skater-progressive.rgba
Lines changed: 1203 additions & 0 deletions
diff --git a/‎test/fixtures/skater.jpg
17.2 KB b/‎test/fixtures/skater.jpg
17.2 KB
diff --git a/‎test/index.js
Lines changed: 23 additions & 0 deletions b/‎test/index.js
Lines changed: 23 additions & 0 deletions
@@ -200,6 +200,7 @@ var JpegImage = (function jpegImage() {
       var k = spectralStart, e = spectralEnd, r = 0;
       while (k <= e) {
         var z = dctZigZag[k];
+        var direction = zz[z] < 0 ? -1 : 1;
         switch (successiveACState) {
         case 0: // initial state
           var rs = decodeHuffman(component.huffmanTableAC);
@@ -222,7 +223,7 @@ var JpegImage = (function jpegImage() {
         case 1: // skipping r zero items
         case 2:
           if (zz[z])
-            zz[z] += (readBit() << successive);
+            zz[z] += (readBit() << successive) * direction;
           else {
             r--;
             if (r === 0)
@@ -231,15 +232,15 @@ var JpegImage = (function jpegImage() {
           break;
         case 3: // set value for a zero item
           if (zz[z])
-            zz[z] += (readBit() << successive);
+            zz[z] += (readBit() << successive) * direction;
           else {
             zz[z] = successiveACNextValue << successive;
             successiveACState = 0;
           }
           break;
         case 4: // eob
           if (zz[z])
-            zz[z] += (readBit() << successive);
+            zz[z] += (readBit() << successive) * direction;
           break;
         }
         k++;
@@ -715,7 +716,7 @@ var JpegImage = (function jpegImage() {
                 huffmanValues[j] = data[offset];
               i += 17 + codeLengthSum;
 
-              ((huffmanTableSpec >> 4) === 0 ? 
+              ((huffmanTableSpec >> 4) === 0 ?
                 huffmanTablesDC : huffmanTablesAC)[huffmanTableSpec & 15] =
                 buildHuffmanTable(codeLengths, huffmanValues);
             }
 
@@ -104,6 +104,29 @@ it('should be able to decode a unconventional table JPEG', function (t) {
   t.end();
 });
 
+it('should be able to decode a progressive JPEG', function(t) {
+  var jpegData = fixture('skater-progressive.jpg');
+  var rawImageData = jpeg.decode(jpegData);
+  t.equal(rawImageData.width, 256);
+  t.equal(rawImageData.height, 256);
+  var expected = fixture('skater-progressive.rgba');
+  t.deepEqual(rawImageData.data, expected);
+  t.end();
+});
+
+it('should be able to decode a progressive JPEG the same as non-progressive', function(t) {
+  var jpegData = fixture('skater.jpg');
+  var rawImageData = jpeg.decode(jpegData);
+
+  var otherJpegData = fixture('skater-progressive.jpg');
+  var otherRawImageData = jpeg.decode(otherJpegData);
+
+  t.equal(rawImageData.width, otherRawImageData.width);
+  t.equal(rawImageData.height, otherRawImageData.height);
+  t.deepEqual(rawImageData.data, otherRawImageData.data);
+  t.end();
+});
+
 it('should be able to encode a JPEG', function (t) {
   var frameData = fixture('grumpycat.rgba');
   var rawImageData = {