Merge pull request #9325 from Snuffleupagus/decodeACSuccessive-less-blur

Adjust `decodeACSuccessive` in src/core/jpg.js to improve the rendering quality of (progressive) JPEG images

src/core/jpg.js

@@ -235,53 +235,54 @@ var JpegImage = (function JpegImageClosure() {
       var s;
       var rs;
       while (k <= e) {
-        var z = dctZigZag[k];
+        let offsetZ = offset + dctZigZag[k];
+        let sign = component.blockData[offsetZ] < 0 ? -1 : 1;
         switch (successiveACState) {
-        case 0: // initial state
-          rs = decodeHuffman(component.huffmanTableAC);
-          s = rs & 15;
-          r = rs >> 4;
-          if (s === 0) {
-            if (r < 15) {
-              eobrun = receive(r) + (1 << r);
-              successiveACState = 4;
+          case 0: // initial state
+            rs = decodeHuffman(component.huffmanTableAC);
+            s = rs & 15;
+            r = rs >> 4;
+            if (s === 0) {
+              if (r < 15) {
+                eobrun = receive(r) + (1 << r);
+                successiveACState = 4;
+              } else {
+                r = 16;
+                successiveACState = 1;
+              }
             } else {
-              r = 16;
-              successiveACState = 1;
+              if (s !== 1) {
+                throw new JpegError('invalid ACn encoding');
+              }
+              successiveACNextValue = receiveAndExtend(s);
+              successiveACState = r ? 2 : 3;
             }
-          } else {
-            if (s !== 1) {
-              throw new JpegError('invalid ACn encoding');
+            continue;
+          case 1: // skipping r zero items
+          case 2:
+            if (component.blockData[offsetZ]) {
+              component.blockData[offsetZ] += sign * (readBit() << successive);
+            } else {
+              r--;
+              if (r === 0) {
+                successiveACState = successiveACState === 2 ? 3 : 0;
+              }
             }
-            successiveACNextValue = receiveAndExtend(s);
-            successiveACState = r ? 2 : 3;
-          }
-          continue;
-        case 1: // skipping r zero items
-        case 2:
-          if (component.blockData[offset + z]) {
-            component.blockData[offset + z] += (readBit() << successive);
-          } else {
-            r--;
-            if (r === 0) {
-              successiveACState = successiveACState === 2 ? 3 : 0;
+            break;
+          case 3: // set value for a zero item
+            if (component.blockData[offsetZ]) {
+              component.blockData[offsetZ] += sign * (readBit() << successive);
+            } else {
+              component.blockData[offsetZ] =
+                successiveACNextValue << successive;
+              successiveACState = 0;
             }
-          }
-          break;
-        case 3: // set value for a zero item
-          if (component.blockData[offset + z]) {
-            component.blockData[offset + z] += (readBit() << successive);
-          } else {
-            component.blockData[offset + z] =
-              successiveACNextValue << successive;
-            successiveACState = 0;
-          }
-          break;
-        case 4: // eob
-          if (component.blockData[offset + z]) {
-            component.blockData[offset + z] += (readBit() << successive);
-          }
-          break;
+            break;
+          case 4: // eob
+            if (component.blockData[offsetZ]) {
+              component.blockData[offsetZ] += sign * (readBit() << successive);
+            }
+            break;
         }
         k++;
       }

test/pdfs/.gitignore

@@ -67,6 +67,7 @@
 !issue9105_reduced.pdf
 !issue9291.pdf
 !bad-PageLabels.pdf
+!decodeACSuccessive.pdf
 !filled-background.pdf
 !ArabicCIDTrueType.pdf
 !ThuluthFeatures.pdf

test/test_manifest.json

@@ -3589,6 +3589,14 @@
        "type": "eq",
        "nativeImageDecoderSupport": "none"
     },
+    {  "id": "decodeACSuccessive",
+       "file": "pdfs/decodeACSuccessive.pdf",
+       "md5": "7749c032624fe27ab8e8d7d5e9a4a93f",
+       "rounds": 1,
+       "link": false,
+       "type": "eq",
+       "nativeImageDecoderSupport": "none"
+    },
     {  "id": "issue5592",
        "file": "pdfs/issue5592.pdf",
        "md5": "a0750f95afa80c880f7966df7062616c",