diff --git a/core/fxcodec/BUILD.gn b/core/fxcodec/BUILD.gn
index cab5d9e..c964be9 100644
--- a/core/fxcodec/BUILD.gn
+++ b/core/fxcodec/BUILD.gn
@@ -12,7 +12,6 @@
     "basic/basicmodule.h",
     "codec/cfx_codec_memory.cpp",
     "codec/cfx_codec_memory.h",
-    "codec/codec_int.h",
     "codec/codec_module_iface.h",
     "codec/scanlinedecoder.cpp",
     "codec/scanlinedecoder.h",
@@ -67,6 +66,8 @@
     "jpeg/jpegmodule.h",
     "jpx/cjpx_decoder.cpp",
     "jpx/cjpx_decoder.h",
+    "jpx/jpx_decode_utils.cpp",
+    "jpx/jpx_decode_utils.h",
     "jpx/jpxmodule.cpp",
     "jpx/jpxmodule.h",
   ]
diff --git a/core/fxcodec/bmp/bmpmodule.cpp b/core/fxcodec/bmp/bmpmodule.cpp
index 21b9390..5cdb681 100644
--- a/core/fxcodec/bmp/bmpmodule.cpp
+++ b/core/fxcodec/bmp/bmpmodule.cpp
@@ -10,7 +10,6 @@
 
 #include "core/fxcodec/bmp/cfx_bmpcontext.h"
 #include "core/fxcodec/codec/cfx_codec_memory.h"
-#include "core/fxcodec/codec/codec_int.h"
 #include "core/fxcodec/fx_codec.h"
 #include "core/fxge/fx_dib.h"
 #include "third_party/base/ptr_util.h"
diff --git a/core/fxcodec/codec/fx_codec_jpx_unittest.cpp b/core/fxcodec/codec/fx_codec_jpx_unittest.cpp
index 4acd4e0..def5065 100644
--- a/core/fxcodec/codec/fx_codec_jpx_unittest.cpp
+++ b/core/fxcodec/codec/fx_codec_jpx_unittest.cpp
@@ -6,10 +6,14 @@
 
 #include <limits>
 
-#include "core/fxcodec/codec/codec_int.h"
+#include "core/fxcodec/jpx/cjpx_decoder.h"
+#include "core/fxcodec/jpx/jpx_decode_utils.h"
+#include "core/fxcrt/fx_memory.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/libopenjpeg20/opj_malloc.h"
 
+namespace fxcodec {
+
 static const OPJ_OFF_T kSkipError = static_cast<OPJ_OFF_T>(-1);
 static const OPJ_SIZE_T kReadError = static_cast<OPJ_SIZE_T>(-1);
 
@@ -425,7 +429,7 @@
     img.comps[0] = y;
     img.comps[1] = u;
     img.comps[2] = v;
-    sycc420_to_rgb(&img);
+    CJPX_Decoder::Sycc420ToRgbForTesting(&img);
     if (testcase.expected) {
       EXPECT_EQ(img.comps[0].w, img.comps[1].w);
       EXPECT_EQ(img.comps[0].h, img.comps[1].h);
@@ -443,3 +447,5 @@
   }
   FX_Free(img.comps);
 }
+
+}  // namespace fxcodec
diff --git a/core/fxcodec/fax/faxmodule.cpp b/core/fxcodec/fax/faxmodule.cpp
index 75e79a2c..60bec6a 100644
--- a/core/fxcodec/fax/faxmodule.cpp
+++ b/core/fxcodec/fax/faxmodule.cpp
@@ -12,7 +12,6 @@
 #include <vector>
 
 #include "build/build_config.h"
-#include "core/fxcodec/codec/codec_int.h"
 #include "core/fxcodec/codec/scanlinedecoder.h"
 #include "core/fxcodec/fx_codec.h"
 #include "core/fxcrt/cfx_binarybuf.h"
diff --git a/core/fxcodec/fx_codec.cpp b/core/fxcodec/fx_codec.cpp
index 18c745e..5625534 100644
--- a/core/fxcodec/fx_codec.cpp
+++ b/core/fxcodec/fx_codec.cpp
@@ -11,7 +11,6 @@
 #include <memory>
 #include <utility>
 
-#include "core/fxcodec/codec/codec_int.h"
 #include "core/fxcodec/jbig2/jbig2module.h"
 #include "core/fxcodec/jpeg/jpegmodule.h"
 #include "core/fxcrt/fx_extension.h"
diff --git a/core/fxcodec/gif/gifmodule.cpp b/core/fxcodec/gif/gifmodule.cpp
index 1c3cdb5..cc82e38 100644
--- a/core/fxcodec/gif/gifmodule.cpp
+++ b/core/fxcodec/gif/gifmodule.cpp
@@ -7,7 +7,6 @@
 #include "core/fxcodec/gif/gifmodule.h"
 
 #include "core/fxcodec/codec/cfx_codec_memory.h"
-#include "core/fxcodec/codec/codec_int.h"
 #include "core/fxcodec/fx_codec.h"
 #include "core/fxcodec/gif/cfx_gif.h"
 #include "core/fxcodec/gif/cfx_gifcontext.h"
diff --git a/core/fxcodec/icc/iccmodule.cpp b/core/fxcodec/icc/iccmodule.cpp
index 6927749..e9a8cd6 100644
--- a/core/fxcodec/icc/iccmodule.cpp
+++ b/core/fxcodec/icc/iccmodule.cpp
@@ -10,7 +10,6 @@
 #include <memory>
 #include <vector>
 
-#include "core/fxcodec/codec/codec_int.h"
 #include "third_party/base/ptr_util.h"
 #include "third_party/base/stl_util.h"
 
diff --git a/core/fxcodec/jpx/cjpx_decoder.cpp b/core/fxcodec/jpx/cjpx_decoder.cpp
index 118aaf2..6e8ba7a 100644
--- a/core/fxcodec/jpx/cjpx_decoder.cpp
+++ b/core/fxcodec/jpx/cjpx_decoder.cpp
@@ -8,21 +8,20 @@
 
 #include <algorithm>
 #include <limits>
-#include <memory>
-#include <type_traits>
 #include <utility>
-#include <vector>
 
+#include "core/fxcodec/jpx/jpx_decode_utils.h"
 #include "core/fxcrt/fx_safe_types.h"
 #include "third_party/base/optional.h"
 #include "third_party/base/ptr_util.h"
 #include "third_party/base/stl_util.h"
 
-#ifndef USE_SYSTEM_LIBOPENJPEG2
-#include "third_party/libopenjpeg20/openjpeg.h"
+#if !defined(USE_SYSTEM_LIBOPENJPEG2)
 #include "third_party/libopenjpeg20/opj_malloc.h"
 #endif
 
+namespace fxcodec {
+
 namespace {
 
 // Used with std::unique_ptr to call opj_image_data_free on raw memory.
@@ -144,184 +143,10 @@
          (img->comps[0].h + 1) / 2 == img->comps[1].h;
 }
 
-bool sycc422_size_is_valid(opj_image_t* img) {
-  return sycc420_422_size_is_valid(img) && img->comps[0].h == img->comps[1].h;
-}
-
-void sycc422_to_rgb(opj_image_t* img) {
-  if (!sycc422_size_is_valid(img))
-    return;
-
-  int prec = img->comps[0].prec;
-  if (prec <= 0 || prec >= 32)
-    return;
-
-  int offset = 1 << (prec - 1);
-  int upb = (1 << prec) - 1;
-  OPJ_UINT32 maxw = img->comps[0].w;
-  OPJ_UINT32 maxh = img->comps[0].h;
-  FX_SAFE_SIZE_T max_size = maxw;
-  max_size *= maxh;
-  max_size *= sizeof(int);
-  if (!max_size.IsValid())
-    return;
-
-  const int* y = img->comps[0].data;
-  const int* cb = img->comps[1].data;
-  const int* cr = img->comps[2].data;
-  if (!y || !cb || !cr)
-    return;
-
-  Optional<OpjImageRgbData> data = alloc_rgb(max_size.ValueOrDie());
-  if (!data.has_value())
-    return;
-
-  int* r = data.value().r.get();
-  int* g = data.value().g.get();
-  int* b = data.value().b.get();
-  for (uint32_t i = 0; i < maxh; ++i) {
-    OPJ_UINT32 j;
-    for (j = 0; j < (maxw & ~static_cast<OPJ_UINT32>(1)); j += 2) {
-      sycc_to_rgb(offset, upb, *y++, *cb, *cr, r++, g++, b++);
-      sycc_to_rgb(offset, upb, *y++, *cb++, *cr++, r++, g++, b++);
-    }
-    if (j < maxw) {
-      sycc_to_rgb(offset, upb, *y++, *cb++, *cr++, r++, g++, b++);
-    }
-  }
-
-  opj_image_data_free(img->comps[0].data);
-  opj_image_data_free(img->comps[1].data);
-  opj_image_data_free(img->comps[2].data);
-  img->comps[0].data = data.value().r.release();
-  img->comps[1].data = data.value().g.release();
-  img->comps[2].data = data.value().b.release();
-  img->comps[1].w = maxw;
-  img->comps[1].h = maxh;
-  img->comps[2].w = maxw;
-  img->comps[2].h = maxh;
-  img->comps[1].dx = img->comps[0].dx;
-  img->comps[2].dx = img->comps[0].dx;
-  img->comps[1].dy = img->comps[0].dy;
-  img->comps[2].dy = img->comps[0].dy;
-}
-
 bool sycc420_must_extend_cbcr(OPJ_UINT32 y, OPJ_UINT32 cbcr) {
   return (y & 1) && (cbcr == y / 2);
 }
 
-bool is_sycc420(const opj_image_t* img) {
-  return img->comps[0].dx == 1 && img->comps[0].dy == 1 &&
-         img->comps[1].dx == 2 && img->comps[1].dy == 2 &&
-         img->comps[2].dx == 2 && img->comps[2].dy == 2;
-}
-
-bool is_sycc422(const opj_image_t* img) {
-  return img->comps[0].dx == 1 && img->comps[0].dy == 1 &&
-         img->comps[1].dx == 2 && img->comps[1].dy == 1 &&
-         img->comps[2].dx == 2 && img->comps[2].dy == 1;
-}
-
-bool is_sycc444(const opj_image_t* img) {
-  return img->comps[0].dx == 1 && img->comps[0].dy == 1 &&
-         img->comps[1].dx == 1 && img->comps[1].dy == 1 &&
-         img->comps[2].dx == 1 && img->comps[2].dy == 1;
-}
-
-void color_sycc_to_rgb(opj_image_t* img) {
-  if (img->numcomps < 3) {
-    img->color_space = OPJ_CLRSPC_GRAY;
-    return;
-  }
-  if (is_sycc420(img))
-    sycc420_to_rgb(img);
-  else if (is_sycc422(img))
-    sycc422_to_rgb(img);
-  else if (is_sycc444(img))
-    sycc444_to_rgb(img);
-  else
-    return;
-
-  img->color_space = OPJ_CLRSPC_SRGB;
-}
-
-}  // namespace
-
-OPJ_SIZE_T opj_read_from_memory(void* p_buffer,
-                                OPJ_SIZE_T nb_bytes,
-                                void* p_user_data) {
-  DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
-  if (!srcData || !srcData->src_data || srcData->src_size == 0)
-    return static_cast<OPJ_SIZE_T>(-1);
-
-  // Reads at EOF return an error code.
-  if (srcData->offset >= srcData->src_size)
-    return static_cast<OPJ_SIZE_T>(-1);
-
-  OPJ_SIZE_T bufferLength = srcData->src_size - srcData->offset;
-  OPJ_SIZE_T readlength = nb_bytes < bufferLength ? nb_bytes : bufferLength;
-  memcpy(p_buffer, &srcData->src_data[srcData->offset], readlength);
-  srcData->offset += readlength;
-  return readlength;
-}
-
-OPJ_OFF_T opj_skip_from_memory(OPJ_OFF_T nb_bytes, void* p_user_data) {
-  DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
-  if (!srcData || !srcData->src_data || srcData->src_size == 0)
-    return static_cast<OPJ_OFF_T>(-1);
-
-  // Offsets are signed and may indicate a negative skip. Do not support this
-  // because of the strange return convention where either bytes skipped or
-  // -1 is returned. Following that convention, a successful relative seek of
-  // -1 bytes would be required to to give the same result as the error case.
-  if (nb_bytes < 0)
-    return static_cast<OPJ_OFF_T>(-1);
-
-  auto unsigned_nb_bytes =
-      static_cast<std::make_unsigned<OPJ_OFF_T>::type>(nb_bytes);
-  // Additionally, the offset may take us beyond the range of a size_t (e.g.
-  // 32-bit platforms). If so, just clamp at EOF.
-  if (unsigned_nb_bytes >
-      std::numeric_limits<OPJ_SIZE_T>::max() - srcData->offset) {
-    srcData->offset = srcData->src_size;
-  } else {
-    OPJ_SIZE_T checked_nb_bytes = static_cast<OPJ_SIZE_T>(unsigned_nb_bytes);
-    // Otherwise, mimic fseek() semantics to always succeed, even past EOF,
-    // clamping at EOF.  We can get away with this since we don't actually
-    // provide negative relative skips from beyond EOF back to inside the
-    // data, which would be the only reason to need to know exactly how far
-    // beyond EOF we are.
-    srcData->offset =
-        std::min(srcData->offset + checked_nb_bytes, srcData->src_size);
-  }
-  return nb_bytes;
-}
-
-OPJ_BOOL opj_seek_from_memory(OPJ_OFF_T nb_bytes, void* p_user_data) {
-  DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
-  if (!srcData || !srcData->src_data || srcData->src_size == 0)
-    return OPJ_FALSE;
-
-  // Offsets are signed and may indicate a negative position, which would
-  // be before the start of the file. Do not support this.
-  if (nb_bytes < 0)
-    return OPJ_FALSE;
-
-  auto unsigned_nb_bytes =
-      static_cast<std::make_unsigned<OPJ_OFF_T>::type>(nb_bytes);
-  // Additionally, the offset may take us beyond the range of a size_t (e.g.
-  // 32-bit platforms). If so, just clamp at EOF.
-  if (unsigned_nb_bytes > std::numeric_limits<OPJ_SIZE_T>::max()) {
-    srcData->offset = srcData->src_size;
-  } else {
-    OPJ_SIZE_T checked_nb_bytes = static_cast<OPJ_SIZE_T>(nb_bytes);
-    // Otherwise, mimic fseek() semantics to always succeed, even past EOF,
-    // again clamping at EOF.
-    srcData->offset = std::min(checked_nb_bytes, srcData->src_size);
-  }
-  return OPJ_TRUE;
-}
-
 void sycc420_to_rgb(opj_image_t* img) {
   if (!sycc420_size_is_valid(img))
     return;
@@ -460,6 +285,110 @@
   img->comps[2].dy = img->comps[0].dy;
 }
 
+bool sycc422_size_is_valid(opj_image_t* img) {
+  return sycc420_422_size_is_valid(img) && img->comps[0].h == img->comps[1].h;
+}
+
+void sycc422_to_rgb(opj_image_t* img) {
+  if (!sycc422_size_is_valid(img))
+    return;
+
+  int prec = img->comps[0].prec;
+  if (prec <= 0 || prec >= 32)
+    return;
+
+  int offset = 1 << (prec - 1);
+  int upb = (1 << prec) - 1;
+  OPJ_UINT32 maxw = img->comps[0].w;
+  OPJ_UINT32 maxh = img->comps[0].h;
+  FX_SAFE_SIZE_T max_size = maxw;
+  max_size *= maxh;
+  max_size *= sizeof(int);
+  if (!max_size.IsValid())
+    return;
+
+  const int* y = img->comps[0].data;
+  const int* cb = img->comps[1].data;
+  const int* cr = img->comps[2].data;
+  if (!y || !cb || !cr)
+    return;
+
+  Optional<OpjImageRgbData> data = alloc_rgb(max_size.ValueOrDie());
+  if (!data.has_value())
+    return;
+
+  int* r = data.value().r.get();
+  int* g = data.value().g.get();
+  int* b = data.value().b.get();
+  for (uint32_t i = 0; i < maxh; ++i) {
+    OPJ_UINT32 j;
+    for (j = 0; j < (maxw & ~static_cast<OPJ_UINT32>(1)); j += 2) {
+      sycc_to_rgb(offset, upb, *y++, *cb, *cr, r++, g++, b++);
+      sycc_to_rgb(offset, upb, *y++, *cb++, *cr++, r++, g++, b++);
+    }
+    if (j < maxw) {
+      sycc_to_rgb(offset, upb, *y++, *cb++, *cr++, r++, g++, b++);
+    }
+  }
+
+  opj_image_data_free(img->comps[0].data);
+  opj_image_data_free(img->comps[1].data);
+  opj_image_data_free(img->comps[2].data);
+  img->comps[0].data = data.value().r.release();
+  img->comps[1].data = data.value().g.release();
+  img->comps[2].data = data.value().b.release();
+  img->comps[1].w = maxw;
+  img->comps[1].h = maxh;
+  img->comps[2].w = maxw;
+  img->comps[2].h = maxh;
+  img->comps[1].dx = img->comps[0].dx;
+  img->comps[2].dx = img->comps[0].dx;
+  img->comps[1].dy = img->comps[0].dy;
+  img->comps[2].dy = img->comps[0].dy;
+}
+
+bool is_sycc420(const opj_image_t* img) {
+  return img->comps[0].dx == 1 && img->comps[0].dy == 1 &&
+         img->comps[1].dx == 2 && img->comps[1].dy == 2 &&
+         img->comps[2].dx == 2 && img->comps[2].dy == 2;
+}
+
+bool is_sycc422(const opj_image_t* img) {
+  return img->comps[0].dx == 1 && img->comps[0].dy == 1 &&
+         img->comps[1].dx == 2 && img->comps[1].dy == 1 &&
+         img->comps[2].dx == 2 && img->comps[2].dy == 1;
+}
+
+bool is_sycc444(const opj_image_t* img) {
+  return img->comps[0].dx == 1 && img->comps[0].dy == 1 &&
+         img->comps[1].dx == 1 && img->comps[1].dy == 1 &&
+         img->comps[2].dx == 1 && img->comps[2].dy == 1;
+}
+
+void color_sycc_to_rgb(opj_image_t* img) {
+  if (img->numcomps < 3) {
+    img->color_space = OPJ_CLRSPC_GRAY;
+    return;
+  }
+  if (is_sycc420(img))
+    sycc420_to_rgb(img);
+  else if (is_sycc422(img))
+    sycc422_to_rgb(img);
+  else if (is_sycc444(img))
+    sycc444_to_rgb(img);
+  else
+    return;
+
+  img->color_space = OPJ_CLRSPC_SRGB;
+}
+
+}  // namespace
+
+// static
+void CJPX_Decoder::Sycc420ToRgbForTesting(opj_image_t* img) {
+  sycc420_to_rgb(img);
+}
+
 CJPX_Decoder::CJPX_Decoder(ColorSpaceOption option)
     : m_ColorSpaceOption(option) {}
 
@@ -512,7 +441,7 @@
     return false;
 
   m_Image = pTempImage;
-#ifndef USE_SYSTEM_LIBOPENJPEG2
+#if !defined(USE_SYSTEM_LIBOPENJPEG2)
   m_Image->pdfium_use_colorspace = (m_ColorSpaceOption != kNoColorSpace);
 #endif
   return true;
@@ -551,7 +480,7 @@
     // TODO(palmer): Using |opj_free| here resolves the crash described in
     // https://crbug.com/737033, but ultimately we need to harmonize the
     // memory allocation strategy across OpenJPEG and its PDFium callers.
-#ifndef USE_SYSTEM_LIBOPENJPEG2
+#if !defined(USE_SYSTEM_LIBOPENJPEG2)
     opj_free(m_Image->icc_profile_buf);
 #else
     free(m_Image->icc_profile_buf);
@@ -643,3 +572,5 @@
   }
   return true;
 }
+
+}  // namespace fxcodec
diff --git a/core/fxcodec/jpx/cjpx_decoder.h b/core/fxcodec/jpx/cjpx_decoder.h
index 8c607e2..11d94c1 100644
--- a/core/fxcodec/jpx/cjpx_decoder.h
+++ b/core/fxcodec/jpx/cjpx_decoder.h
@@ -10,16 +10,19 @@
 #include <memory>
 #include <vector>
 
-#include "core/fxcodec/codec/codec_int.h"
 #include "core/fxcrt/unowned_ptr.h"
 #include "third_party/base/span.h"
 
-#ifdef USE_SYSTEM_LIBOPENJPEG2
+#if defined(USE_SYSTEM_LIBOPENJPEG2)
 #include <openjpeg.h>
 #else
 #include "third_party/libopenjpeg20/openjpeg.h"
 #endif
 
+namespace fxcodec {
+
+struct DecodeData;
+
 class CJPX_Decoder {
  public:
   enum ColorSpaceOption {
@@ -28,6 +31,8 @@
     kIndexedColorSpace
   };
 
+  static void Sycc420ToRgbForTesting(opj_image_t* img);
+
   explicit CJPX_Decoder(ColorSpaceOption option);
   ~CJPX_Decoder();
 
@@ -48,4 +53,8 @@
   opj_dparameters_t m_Parameters;
 };
 
+}  // namespace fxcodec
+
+using fxcodec::CJPX_Decoder;
+
 #endif  // CORE_FXCODEC_JPX_CJPX_DECODER_H_
diff --git a/core/fxcodec/jpx/jpx_decode_utils.cpp b/core/fxcodec/jpx/jpx_decode_utils.cpp
new file mode 100644
index 0000000..d3842d7
--- /dev/null
+++ b/core/fxcodec/jpx/jpx_decode_utils.cpp
@@ -0,0 +1,91 @@
+// Copyright 2019 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#include "core/fxcodec/jpx/jpx_decode_utils.h"
+
+#include <string.h>
+
+#include <algorithm>
+#include <limits>
+
+namespace fxcodec {
+
+OPJ_SIZE_T opj_read_from_memory(void* p_buffer,
+                                OPJ_SIZE_T nb_bytes,
+                                void* p_user_data) {
+  DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
+  if (!srcData || !srcData->src_data || srcData->src_size == 0)
+    return static_cast<OPJ_SIZE_T>(-1);
+
+  // Reads at EOF return an error code.
+  if (srcData->offset >= srcData->src_size)
+    return static_cast<OPJ_SIZE_T>(-1);
+
+  OPJ_SIZE_T bufferLength = srcData->src_size - srcData->offset;
+  OPJ_SIZE_T readlength = nb_bytes < bufferLength ? nb_bytes : bufferLength;
+  memcpy(p_buffer, &srcData->src_data[srcData->offset], readlength);
+  srcData->offset += readlength;
+  return readlength;
+}
+
+OPJ_OFF_T opj_skip_from_memory(OPJ_OFF_T nb_bytes, void* p_user_data) {
+  DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
+  if (!srcData || !srcData->src_data || srcData->src_size == 0)
+    return static_cast<OPJ_OFF_T>(-1);
+
+  // Offsets are signed and may indicate a negative skip. Do not support this
+  // because of the strange return convention where either bytes skipped or
+  // -1 is returned. Following that convention, a successful relative seek of
+  // -1 bytes would be required to to give the same result as the error case.
+  if (nb_bytes < 0)
+    return static_cast<OPJ_OFF_T>(-1);
+
+  auto unsigned_nb_bytes =
+      static_cast<std::make_unsigned<OPJ_OFF_T>::type>(nb_bytes);
+  // Additionally, the offset may take us beyond the range of a size_t (e.g.
+  // 32-bit platforms). If so, just clamp at EOF.
+  if (unsigned_nb_bytes >
+      std::numeric_limits<OPJ_SIZE_T>::max() - srcData->offset) {
+    srcData->offset = srcData->src_size;
+  } else {
+    OPJ_SIZE_T checked_nb_bytes = static_cast<OPJ_SIZE_T>(unsigned_nb_bytes);
+    // Otherwise, mimic fseek() semantics to always succeed, even past EOF,
+    // clamping at EOF.  We can get away with this since we don't actually
+    // provide negative relative skips from beyond EOF back to inside the
+    // data, which would be the only reason to need to know exactly how far
+    // beyond EOF we are.
+    srcData->offset =
+        std::min(srcData->offset + checked_nb_bytes, srcData->src_size);
+  }
+  return nb_bytes;
+}
+
+OPJ_BOOL opj_seek_from_memory(OPJ_OFF_T nb_bytes, void* p_user_data) {
+  DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
+  if (!srcData || !srcData->src_data || srcData->src_size == 0)
+    return OPJ_FALSE;
+
+  // Offsets are signed and may indicate a negative position, which would
+  // be before the start of the file. Do not support this.
+  if (nb_bytes < 0)
+    return OPJ_FALSE;
+
+  auto unsigned_nb_bytes =
+      static_cast<std::make_unsigned<OPJ_OFF_T>::type>(nb_bytes);
+  // Additionally, the offset may take us beyond the range of a size_t (e.g.
+  // 32-bit platforms). If so, just clamp at EOF.
+  if (unsigned_nb_bytes > std::numeric_limits<OPJ_SIZE_T>::max()) {
+    srcData->offset = srcData->src_size;
+  } else {
+    OPJ_SIZE_T checked_nb_bytes = static_cast<OPJ_SIZE_T>(nb_bytes);
+    // Otherwise, mimic fseek() semantics to always succeed, even past EOF,
+    // again clamping at EOF.
+    srcData->offset = std::min(checked_nb_bytes, srcData->src_size);
+  }
+  return OPJ_TRUE;
+}
+
+}  // namespace fxcodec
diff --git a/core/fxcodec/codec/codec_int.h b/core/fxcodec/jpx/jpx_decode_utils.h
similarity index 76%
rename from core/fxcodec/codec/codec_int.h
rename to core/fxcodec/jpx/jpx_decode_utils.h
index e5f75d5..4403cb8 100644
--- a/core/fxcodec/codec/codec_int.h
+++ b/core/fxcodec/jpx/jpx_decode_utils.h
@@ -4,19 +4,19 @@
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
-#ifndef CORE_FXCODEC_CODEC_CODEC_INT_H_
-#define CORE_FXCODEC_CODEC_CODEC_INT_H_
+#ifndef CORE_FXCODEC_JPX_JPX_DECODE_UTILS_H_
+#define CORE_FXCODEC_JPX_JPX_DECODE_UTILS_H_
 
-#include <limits.h>
+#include <stdint.h>
 
-#include "core/fxcodec/jbig2/JBig2_Context.h"
-
-#ifdef USE_SYSTEM_LIBOPENJPEG2
+#if defined(USE_SYSTEM_LIBOPENJPEG2)
 #include <openjpeg.h>
 #else
 #include "third_party/libopenjpeg20/openjpeg.h"
 #endif
 
+namespace fxcodec {
+
 struct DecodeData {
   DecodeData(const uint8_t* data, OPJ_SIZE_T size)
       : src_data(data), src_size(size), offset(0) {}
@@ -26,8 +26,6 @@
   OPJ_SIZE_T offset;
 };
 
-void sycc420_to_rgb(opj_image_t* img);
-
 /* Wrappers for C-style callbacks. */
 OPJ_SIZE_T opj_read_from_memory(void* p_buffer,
                                 OPJ_SIZE_T nb_bytes,
@@ -35,4 +33,6 @@
 OPJ_OFF_T opj_skip_from_memory(OPJ_OFF_T nb_bytes, void* p_user_data);
 OPJ_BOOL opj_seek_from_memory(OPJ_OFF_T nb_bytes, void* p_user_data);
 
-#endif  // CORE_FXCODEC_CODEC_CODEC_INT_H_
+}  // namespace fxcodec
+
+#endif  // CORE_FXCODEC_JPX_JPX_DECODE_UTILS_H_
diff --git a/core/fxcodec/png/pngmodule.cpp b/core/fxcodec/png/pngmodule.cpp
index f74fc50..9742bc6 100644
--- a/core/fxcodec/png/pngmodule.cpp
+++ b/core/fxcodec/png/pngmodule.cpp
@@ -9,7 +9,6 @@
 #include <algorithm>
 
 #include "core/fxcodec/codec/cfx_codec_memory.h"
-#include "core/fxcodec/codec/codec_int.h"
 #include "core/fxcodec/fx_codec.h"
 #include "core/fxcrt/unowned_ptr.h"
 #include "core/fxge/fx_dib.h"
diff --git a/core/fxcodec/tiff/tiffmodule.cpp b/core/fxcodec/tiff/tiffmodule.cpp
index 5633e95..c02b55b 100644
--- a/core/fxcodec/tiff/tiffmodule.cpp
+++ b/core/fxcodec/tiff/tiffmodule.cpp
@@ -10,7 +10,6 @@
 #include <memory>
 
 #include "core/fxcodec/codec/cfx_codec_memory.h"
-#include "core/fxcodec/codec/codec_int.h"
 #include "core/fxcodec/fx_codec.h"
 #include "core/fxcrt/fx_safe_types.h"
 #include "core/fxcrt/fx_stream.h"