Merge pull request #8783 from Snuffleupagus/image-decoders-Uint8ClampedArray

Use `Uint8ClampedArray` when returning image data in `src/core/jbig2.js` and `src/core/jpg.js`

src/core/image.js

@@ -253,7 +253,7 @@ var PDFImage = (function PDFImageClosure() {
     // in this thread can be relying on its contents.
     if (inverseDecode) {
       for (i = 0; i < actualLength; i++) {
-        data[i] = ~data[i];
+        data[i] ^= 0xFF;
       }
     }
 

src/core/jbig2.js

@@ -955,7 +955,7 @@ var Jbig2Image = (function Jbig2ImageClosure() {
     onPageInformation: function SimpleSegmentVisitor_onPageInformation(info) {
       this.currentPageInfo = info;
       var rowSize = (info.width + 7) >> 3;
-      var buffer = new Uint8Array(rowSize * info.height);
+      var buffer = new Uint8ClampedArray(rowSize * info.height);
       // The contents of ArrayBuffers are initialized to 0.
       // Fill the buffer with 0xFF only if info.defaultPixelValue is set
       if (info.defaultPixelValue) {

src/core/jpx.js

@@ -1386,7 +1386,7 @@ var JpxImage = (function JpxImageClosure() {
         transformedTiles[c] = transformTile(context, tile, c);
       }
       var tile0 = transformedTiles[0];
-      var out = new Uint8Array(tile0.items.length * componentsCount);
+      var out = new Uint8ClampedArray(tile0.items.length * componentsCount);
       var result = {
         left: tile0.left,
         top: tile0.top,
@@ -1396,8 +1396,8 @@ var JpxImage = (function JpxImageClosure() {
       };
 
       // Section G.2.2 Inverse multi component transform
-      var shift, offset, max, min, maxK;
+      var shift, offset;
-      var pos = 0, j, jj, y0, y1, y2, r, g, b, k, val;
+      var pos = 0, j, jj, y0, y1, y2;
       if (tile.codingStyleDefaultParameters.multipleComponentTransform) {
         var fourComponents = componentsCount === 4;
         var y0items = transformedTiles[0].items;
@@ -1410,9 +1410,6 @@ var JpxImage = (function JpxImageClosure() {
         // compute shift and offset only once.
         shift = components[0].precision - 8;
         offset = (128 << shift) + 0.5;
-        max = 255 * (1 << shift);
-        maxK = max * 0.5;
-        min = -maxK;
 
         var component0 = tile.components[0];
         var alpha01 = componentsCount - 3;
@@ -1423,12 +1420,9 @@ var JpxImage = (function JpxImageClosure() {
             y0 = y0items[j] + offset;
             y1 = y1items[j];
             y2 = y2items[j];
-            r = y0 + 1.402 * y2;
+            out[pos++] = (y0 + 1.402 * y2) >> shift;
-            g = y0 - 0.34413 * y1 - 0.71414 * y2;
+            out[pos++] = (y0 - 0.34413 * y1 - 0.71414 * y2) >> shift;
-            b = y0 + 1.772 * y1;
+            out[pos++] = (y0 + 1.772 * y1) >> shift;
-            out[pos++] = r <= 0 ? 0 : r >= max ? 255 : r >> shift;
-            out[pos++] = g <= 0 ? 0 : g >= max ? 255 : g >> shift;
-            out[pos++] = b <= 0 ? 0 : b >= max ? 255 : b >> shift;
           }
         } else {
           // inverse reversible multiple component transform
@@ -1436,18 +1430,16 @@ var JpxImage = (function JpxImageClosure() {
             y0 = y0items[j] + offset;
             y1 = y1items[j];
             y2 = y2items[j];
-            g = y0 - ((y2 + y1) >> 2);
+            let g = y0 - ((y2 + y1) >> 2);
-            r = g + y2;
+
-            b = g + y1;
+            out[pos++] = (g + y2) >> shift;
-            out[pos++] = r <= 0 ? 0 : r >= max ? 255 : r >> shift;
+            out[pos++] = g >> shift;
-            out[pos++] = g <= 0 ? 0 : g >= max ? 255 : g >> shift;
+            out[pos++] = (g + y1) >> shift;
-            out[pos++] = b <= 0 ? 0 : b >= max ? 255 : b >> shift;
           }
         }
         if (fourComponents) {
           for (j = 0, pos = 3; j < jj; j++, pos += 4) {
-            k = y3items[j];
+            out[pos] = (y3items[j] + offset) >> shift;
-            out[pos] = k <= min ? 0 : k >= maxK ? 255 : (k + offset) >> shift;
           }
         }
       } else { // no multi-component transform
@@ -1455,12 +1447,8 @@ var JpxImage = (function JpxImageClosure() {
           var items = transformedTiles[c].items;
           shift = components[c].precision - 8;
           offset = (128 << shift) + 0.5;
-          max = (127.5 * (1 << shift));
-          min = -max;
           for (pos = c, j = 0, jj = items.length; j < jj; j++) {
-            val = items[j];
+            out[pos] = (items[j] + offset) >> shift;
-            out[pos] = val <= min ? 0 :
-                       val >= max ? 255 : (val + offset) >> shift;
             pos += componentsCount;
           }
         }

src/core/stream.js

@@ -991,7 +991,7 @@ var JpxStream = (function JpxStreamClosure() {
     if (tileCount === 1) {
       this.buffer = jpxImage.tiles[0].items;
     } else {
-      var data = new Uint8Array(width * height * componentsCount);
+      var data = new Uint8ClampedArray(width * height * componentsCount);
 
       for (var k = 0; k < tileCount; k++) {
         var tileComponents = jpxImage.tiles[k];