Adds color components decoding to the JPEG

src/core/jpg.js

@@ -811,7 +811,7 @@ var JpegImage = (function jpegImage() {
       var scaleX = this.width / width, scaleY = this.height / height;
 
       var component, componentScaleX, componentScaleY, blocksPerScanline;
-      var x, y, i, j;
+      var x, y, i, j, k;
       var index;
       var offset = 0;
       var output;
@@ -843,6 +843,17 @@ var JpegImage = (function jpegImage() {
           }
         }
       }
+
+      // decodeTransform will contains pairs of multiplier (-256..256) and
+      // additive
+      var transform = this.decodeTransform;
+      if (transform) {
+        for (i = 0; i < dataLength;) {
+          for (j = 0, k = 0; j < numComponents; j++, i++, k += 2) {
+            data[i] = ((data[i] * transform[k]) >> 8) + transform[k + 1];
+          }
+        }
+      }
       return data;
     },
 
@@ -852,8 +863,6 @@ var JpegImage = (function jpegImage() {
         return true;
       } else if (this.numComponents == 3) {
         return true;
-      } else if (typeof this.colorTransform !== 'undefined') {
-        return !!this.colorTransform;
       } else {
         return false;
       }

src/core/stream.js

@@ -878,9 +878,27 @@ var JpegStream = (function JpegStreamClosure() {
     }
     try {
       var jpegImage = new JpegImage();
-      if (this.colorTransform != -1) {
-        jpegImage.colorTransform = this.colorTransform;
+
+      // checking if values needs to be transformed before conversion
+      if (this.dict && isArray(this.dict.get('Decode'))) {
+        var decodeArr = this.dict.get('Decode');
+        var bitsPerComponent = this.dict.get('BitsPerComponent') || 8;
+        var decodeArrLength = decodeArr.length;
+        var transform = new Int32Array(decodeArrLength);
+        var transformNeeded = false;
+        var maxValue = (1 << bitsPerComponent) - 1;
+        for (var i = 0; i < decodeArrLength; i += 2) {
+          transform[i] = ((decodeArr[i + 1] - decodeArr[i]) * 256) | 0;
+          transform[i + 1] = (decodeArr[i] * maxValue) | 0;
+          if (transform[i] !== 256 || transform[i + 1] !== 0) {
+            transformNeeded = true;
+          }
+        }
+        if (transformNeeded) {
+          jpegImage.decodeTransform = transform;
+        }
       }
+
       jpegImage.parse(this.bytes);
       var data = jpegImage.getData(this.drawWidth, this.drawHeight,
                                    /* forceRGBoutput = */true);

test/pdfs/issue4883.pdf.link

@@ -0,0 +1 @@
+http://web.archive.org/web/20140603135304/http://www.tipp2014.nl/TIPP2014_3rd_bulletin.pdf

test/test_manifest.json

@@ -1613,6 +1613,16 @@
        "lastPage": 2,
        "type": "eq"
     },
+    {  "id": "issue4883",
+      "file": "pdfs/issue4883.pdf",
+      "md5": "2fac0d9a189ca5fcef8626153d050be8",
+      "rounds": 1,
+      "link": true,
+      "firstPage": 1,
+      "lastPage": 1,
+      "type": "eq",
+      "about": "CMYK JPEG with Decode"
+    },
     {  "id": "bug903856",
        "file": "pdfs/bug903856.pdf",
        "md5": "286eaa9d06a5809f4f08f2093cef8f3f",