From a41792981e6b90f048855870f600adef538b4dbe Mon Sep 17 00:00:00 2001
From: douglasmatheus <douglasmatheusmeirelles@gmail.com>
Date: Fri, 22 May 2026 17:02:57 -0300
Subject: [PATCH] Fix putImage mutating the global filters array
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The internal getFilters() returns the live reference to the document's
filters array. putImage was calling splice() on that reference to strip
"FlateEncode" before writing image data — but this side-effect persists
between save()/output() calls.

After the first putImage during a save, the document's filters array
becomes empty, so all subsequent page content streams are emitted
uncompressed. Result: the 1st PDF output is normal size, but every
subsequent output() balloons (e.g. 5 KB compressed page stream becomes
95 KB raw, only on documents that contain images).

Fix: copy the array via .slice() before mutating, so putImage's local
view is independent of the document state.

Repro:
  const doc = new jsPDF({ compress: true });
  doc.addImage(jpg, "JPEG", 10, 10, 100, 75);
  const a = doc.output();
  const b = doc.output();
  console.assert(a.length === b.length); // failed before this fix

Regression covered by new test in test/specs/addimage.spec.js.
---
 src/modules/addimage.js     |  6 +++++-
 test/specs/addimage.spec.js | 18 +++++++++++++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/modules/addimage.js b/src/modules/addimage.js
index abaf2fb43..aee148fd6 100644
--- a/src/modules/addimage.js
+++ b/src/modules/addimage.js
@@ -203,7 +203,11 @@ import { atob } from "../libs/AtobBtoa.js";
     var putStream = this.internal.putStream;
     var getFilters = this.internal.getFilters;
 
-    var filter = getFilters();
+    // getFilters() returns the live reference to the document-wide filters
+    // array. Copy it before mutating so we don't strip FlateEncode from
+    // subsequent output() calls (which would emit page content streams
+    // uncompressed after the first call to putImage).
+    var filter = getFilters().slice();
     while (filter.indexOf("FlateEncode") !== -1) {
       filter.splice(filter.indexOf("FlateEncode"), 1);
     }
diff --git a/test/specs/addimage.spec.js b/test/specs/addimage.spec.js
index 94eac858c..956eb073f 100644
--- a/test/specs/addimage.spec.js
+++ b/test/specs/addimage.spec.js
@@ -64,7 +64,9 @@ describe("Module: addimage", () => {
       canvas.width = 0;
       canvas.height = 100;
 
-      var expectedError = new Error("Given canvas must have data. Canvas width: 0, height: 100");
+      var expectedError = new Error(
+        "Given canvas must have data. Canvas width: 0, height: 100"
+      );
 
       expect(function() {
         doc.addImage(canvas, 10, 10);
@@ -92,4 +94,18 @@ describe("Module: addimage", () => {
       }).not.toThrow();
     });
   }
+
+  it("repeated output() after addImage produces identical PDFs (regression: putImage was mutating the global filters array)", () => {
+    const doc = new jsPDF({ compress: true });
+    doc.addImage(jpg, "JPEG", 10, 10, 100, 75);
+
+    const out1 = doc.output();
+    const out2 = doc.output();
+    const out3 = doc.output();
+
+    expect(out2.length).toEqual(out1.length);
+    expect(out3.length).toEqual(out1.length);
+    expect(out2).toEqual(out1);
+    expect(out3).toEqual(out1);
+  });
 });