[Pkg-javascript-commits] [pdf.js] 16/207: Adds color components decoding to the JPEG

[David Prévot]

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taffit pushed a commit to branch master
in repository pdf.js.

commit 6235e3a61cd3fd91cda5b9fecf3ac2581a82bc86
Author: Yury Delendik <ydelendik at mozilla.com>
Date:   Tue Jun 3 08:51:57 2014 -0500

    Adds color components decoding to the JPEG
---
 src/core/jpg.js    | 15 ++++++++++++---
 src/core/stream.js | 22 ++++++++++++++++++++--
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/src/core/jpg.js b/src/core/jpg.js
index cb61a23..1b043a0 100644
--- a/src/core/jpg.js
+++ b/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;
       }
diff --git a/src/core/stream.js b/src/core/stream.js
index f2996a6..669cab1 100644
--- a/src/core/stream.js
+++ b/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);

-- 
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