From f554d0c9c89b8e4bb837f2193c767f63ea8869a0 Mon Sep 17 00:00:00 2001
From: Calixte Denizet <calixte.denizet@gmail.com>
Date: Thu, 16 Jul 2026 21:04:45 +0200
Subject: [PATCH] Implement SmaskInData == 2 for JPX images

---
 src/core/image.js             |  70 +++++++++++++++++++++++++---------
 test/pdfs/.gitignore          |   1 +
 test/pdfs/jpx_smaskindata.pdf | Bin 0 -> 2515 bytes
 test/test_manifest.json       |   7 ++++
 4 files changed, 61 insertions(+), 17 deletions(-)
 create mode 100644 test/pdfs/jpx_smaskindata.pdf

diff --git a/src/core/image.js b/src/core/image.js
index 8861461d2..fe3883a2f 100644
--- a/src/core/image.js
+++ b/src/core/image.js
@@ -119,7 +119,7 @@ class PDFImage {
         this.jpxDecoderOptions = {
           numComponents: 0,
           isIndexedColormap: false,
-          smaskInData: dict.has("SMaskInData"),
+          smaskInData: dict.get("SMaskInData") >= 1,
           reducePower,
         };
         if (reducePower) {
@@ -196,6 +196,25 @@ class PDFImage {
     if (!this.imageMask) {
       let colorSpace = dict.getRaw("CS") || dict.getRaw("ColorSpace");
       const hasColorSpace = !!colorSpace;
+
+      if (
+        this.jpxDecoderOptions?.smaskInData &&
+        dict.get("SMaskInData") === 2
+      ) {
+        this.jpxPremultiplied = true;
+        if (this.matte) {
+          const matteColorSpace = ColorSpaceUtils.parse({
+            cs: hasColorSpace ? colorSpace : Name.get("DeviceRGB"),
+            xref,
+            resources: isInline ? res : null,
+            pdfFunctionFactory,
+            globalColorSpaceCache,
+            localColorSpaceCache,
+          });
+          this.preblendMatte = matteColorSpace.getRgb(this.matte, 0);
+        }
+      }
+
       if (!hasColorSpace) {
         if (this.jpxDecoderOptions) {
           colorSpace = Name.get("DeviceRGBA");
@@ -654,22 +673,7 @@ class PDFImage {
     });
   }
 
-  undoPreblend(buffer, width, height) {
-    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
-      assert(
-        buffer instanceof Uint8ClampedArray,
-        'PDFImage.undoPreblend: Unsupported "buffer" type.'
-      );
-    }
-    const matte = this.smask?.matte;
-    if (!matte) {
-      return;
-    }
-    const matteRgb = this.colorSpace.getRgb(matte, 0);
-    const matteR = matteRgb[0];
-    const matteG = matteRgb[1];
-    const matteB = matteRgb[2];
-    const length = width * height * 4;
+  static #undoPreblend(buffer, length, matteR, matteG, matteB) {
     for (let i = 0; i < length; i += 4) {
       const alpha = buffer[i + 3];
       if (alpha === 0) {
@@ -687,6 +691,27 @@ class PDFImage {
     }
   }
 
+  undoPreblend(buffer, width, height) {
+    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
+      assert(
+        buffer instanceof Uint8ClampedArray,
+        'PDFImage.undoPreblend: Unsupported "buffer" type.'
+      );
+    }
+    const matte = this.smask?.matte;
+    if (!matte) {
+      return;
+    }
+    const matteRgb = this.colorSpace.getRgb(matte, 0);
+    PDFImage.#undoPreblend(
+      buffer,
+      width * height * 4,
+      matteRgb[0],
+      matteRgb[1],
+      matteRgb[2]
+    );
+  }
+
   async createImageData(forceRGBA = false, isOffscreenCanvasSupported = false) {
     const drawWidth = this.drawWidth;
     const drawHeight = this.drawHeight;
@@ -717,6 +742,17 @@ class PDFImage {
         { internal: isOffscreenCanvasSupported && mustBeResized }
       ));
 
+      if (this.jpxPremultiplied) {
+        const matteRgb = this.preblendMatte;
+        PDFImage.#undoPreblend(
+          imgArray,
+          imgArray.length,
+          matteRgb?.[0] ?? 0,
+          matteRgb?.[1] ?? 0,
+          matteRgb?.[2] ?? 0
+        );
+      }
+
       if (isOffscreenCanvasSupported) {
         if (!mustBeResized) {
           return this.createBitmap(
diff --git a/test/pdfs/.gitignore b/test/pdfs/.gitignore
index 19c9ff2ad..e25516a81 100644
--- a/test/pdfs/.gitignore
+++ b/test/pdfs/.gitignore
@@ -945,3 +945,4 @@
 !issue20504_skia.pdf
 !issue21579.pdf
 !saslprep-r6.pdf
+!jpx_smaskindata.pdf
diff --git a/test/pdfs/jpx_smaskindata.pdf b/test/pdfs/jpx_smaskindata.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..26d47af90272df6ff4589bdcbeffeaa8881f2eb4
GIT binary patch
literal 2515
zcmeHJPj3=I6dx2*-PYKHQI9Vgj<SDXVM!Wn3T>s@K*7W&wK2=?0E@7LyVIui(%wuw
znRwP1zkt#BJ$mru!8Fkif^T+NN})}>G<a}fci!K5Z{{~|W)hX+%6&DdONn2<kG@MP
zD8TA%X<-56C;L4La>3+ghc!X2m`&<~h6Yv0=Oyae!cg$19YQ;~z;;{?D#(u<+lQ@`
z@Y^176oN@d5yqqF7{<X~T#l>{=^(DWPHo3rVtcTqpg>J4kXE)qu2P@vcoya-65lM>
z+tlI#UFzzfhrXq51~L(ug=|C`U<717kLitMC_+XVKBjJyw=ke441DfUvnwe{9hztq
zB?2CWhV&9rLZpaB#J0L1i!6!^Hclxq`AD0Y)Mih7vy)m?J#jWdwLoN$*Z><b?q~oZ
zn9<D0wVgT-;4O6#R*;t*?pLT+VBH>b#rzu}uQ(k}J&@Nbn?-6d8_k|NHqL?u@<Zx0
zTLHWU)?r?)XIiK((p|@*)zu}CYwM=}qU08F^$7cQlXEIS!v%(T4W?7e7$eh32$^eF
z0Io}~C8TdQFvE6F1Ek5IEo0k4_LkGKJ#1t6ULx_C8Egr;VX=-UM1;)ad)KmQgTw<q
zHZZ+}+-3ZQR`0Ppt6%PK5G}A0+E5d)*!3tMpNYkW|9+Lsh1z(W#QM)jd~vaFlLUzs
zaBXmELwz60J?gGimRDhydcMP4(2{yG-G58O_%K0qe0O{}Kll9T+tt|TfC@hSACq8;
zmHUr?IYcivRrEeg7rlE!^boUa4~`G-T={Z<K+fJi3qG;iTsVB^6&;q{|Du~Hy0OYT
z3pH^tTsUffv4i3<8Wmkuoodm2oNm$K{wlUinEm?ZKvdkPpF#1RTXuUMZAc2_BxU$O
zM%Pn1G+-!G@t_nBxF@m<p8jJpRl~z;Or{xlj~SDtv$$7}$#N;&08Y!)lra%QH8i~V
rM0VUWoeuSa%UI2MMInbb9md45JGg}T-1K-bMor7AQX;WjUXlI)K>|+j

literal 0
HcmV?d00001

diff --git a/test/test_manifest.json b/test/test_manifest.json
index b2607f01d..c60a97fdf 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -14479,5 +14479,12 @@
     "rounds": 1,
     "type": "eq",
     "password": "S\u00AASL\u00ADprep"
+  },
+  {
+    "id": "jpx_smaskindata",
+    "file": "pdfs/jpx_smaskindata.pdf",
+    "md5": "f7a8628b14ca176700247f106c16812a",
+    "rounds": 1,
+    "type": "eq"
   }
 ]