diff --git a/BUILD.gn b/BUILD.gn
index 4b6e658..60d656f 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1550,6 +1550,7 @@
     "core/fpdfdoc/cpdf_filespec_unittest.cpp",
     "core/fpdftext/fpdf_text_int_unittest.cpp",
     "core/fxcodec/codec/fx_codec_jpx_unittest.cpp",
+    "core/fxcodec/jbig2/JBig2_Image_unittest.cpp",
     "core/fxcrt/cfx_retain_ptr_unittest.cpp",
     "core/fxcrt/fx_basic_bstring_unittest.cpp",
     "core/fxcrt/fx_basic_gcc_unittest.cpp",
diff --git a/core/fxcodec/jbig2/JBig2_Context.cpp b/core/fxcodec/jbig2/JBig2_Context.cpp
index 256ce39..911eb0b 100644
--- a/core/fxcodec/jbig2/JBig2_Context.cpp
+++ b/core/fxcodec/jbig2/JBig2_Context.cpp
@@ -924,7 +924,7 @@
     if (!m_bBufSpecified) {
       JBig2PageInfo* pPageInfo = m_PageInfoList.back();
       if ((pPageInfo->m_bIsStriped == 1) &&
-          (ri.y + ri.height > m_pPage->m_nHeight)) {
+          (ri.y + ri.height > m_pPage->height())) {
         m_pPage->expand(ri.y + ri.height, (pPageInfo->m_cFlags & 4) ? 1 : 0);
       }
     }
@@ -1015,8 +1015,8 @@
 
   pHRD->HNUMPATS = pPatternDict->NUMPATS;
   pHRD->HPATS = pPatternDict->HDPATS;
-  pHRD->HPW = pPatternDict->HDPATS[0]->m_nWidth;
-  pHRD->HPH = pPatternDict->HDPATS[0]->m_nHeight;
+  pHRD->HPW = pPatternDict->HDPATS[0]->width();
+  pHRD->HPH = pPatternDict->HDPATS[0]->height();
   pSegment->m_nResultType = JBIG2_IMAGE_POINTER;
   if (pHRD->HMMR == 0) {
     const size_t size = GetHuffContextSize(pHRD->HTEMPLATE);
@@ -1042,7 +1042,7 @@
     if (!m_bBufSpecified) {
       JBig2PageInfo* pPageInfo = m_PageInfoList.back();
       if (pPageInfo->m_bIsStriped == 1 &&
-          ri.y + ri.height > m_pPage->m_nHeight) {
+          ri.y + ri.height > m_pPage->height()) {
         m_pPage->expand(ri.y + ri.height, (pPageInfo->m_cFlags & 4) ? 1 : 0);
       }
     }
@@ -1108,7 +1108,7 @@
         if (!m_bBufSpecified) {
           JBig2PageInfo* pPageInfo = m_PageInfoList.back();
           if ((pPageInfo->m_bIsStriped == 1) &&
-              (m_ri.y + m_ri.height > m_pPage->m_nHeight)) {
+              (m_ri.y + m_ri.height > m_pPage->height())) {
             m_pPage->expand(m_ri.y + m_ri.height,
                             (pPageInfo->m_cFlags & 4) ? 1 : 0);
           }
@@ -1142,7 +1142,7 @@
     if (!m_bBufSpecified) {
       JBig2PageInfo* pPageInfo = m_PageInfoList.back();
       if ((pPageInfo->m_bIsStriped == 1) &&
-          (m_ri.y + m_ri.height > m_pPage->m_nHeight)) {
+          (m_ri.y + m_ri.height > m_pPage->height())) {
         m_pPage->expand(m_ri.y + m_ri.height,
                         (pPageInfo->m_cFlags & 4) ? 1 : 0);
       }
@@ -1215,7 +1215,7 @@
     if (!m_bBufSpecified) {
       JBig2PageInfo* pPageInfo = m_PageInfoList.back();
       if ((pPageInfo->m_bIsStriped == 1) &&
-          (ri.y + ri.height > m_pPage->m_nHeight)) {
+          (ri.y + ri.height > m_pPage->height())) {
         m_pPage->expand(ri.y + ri.height, (pPageInfo->m_cFlags & 4) ? 1 : 0);
       }
     }
diff --git a/core/fxcodec/jbig2/JBig2_GrdProc.cpp b/core/fxcodec/jbig2/JBig2_GrdProc.cpp
index 9527c1e..b692909 100644
--- a/core/fxcodec/jbig2/JBig2_GrdProc.cpp
+++ b/core/fxcodec/jbig2/JBig2_GrdProc.cpp
@@ -71,7 +71,7 @@
 
   FX_BOOL LTP = FALSE;
   uint8_t* pLine = GBREG->m_pData;
-  int32_t nStride = GBREG->m_nStride;
+  int32_t nStride = GBREG->stride();
   int32_t nStride2 = nStride << 1;
   int32_t nLineBytes = ((GBW + 7) >> 3) - 1;
   int32_t nBitsLeft = GBW - (nLineBytes << 3);
@@ -197,7 +197,7 @@
 
   FX_BOOL LTP = FALSE;
   uint8_t* pLine = GBREG->m_pData;
-  int32_t nStride = GBREG->m_nStride;
+  int32_t nStride = GBREG->stride();
   int32_t nStride2 = nStride << 1;
   int32_t nLineBytes = ((GBW + 7) >> 3) - 1;
   int32_t nBitsLeft = GBW - (nLineBytes << 3);
@@ -320,7 +320,7 @@
 
   FX_BOOL LTP = FALSE;
   uint8_t* pLine = GBREG->m_pData;
-  int32_t nStride = GBREG->m_nStride;
+  int32_t nStride = GBREG->stride();
   int32_t nStride2 = nStride << 1;
   int32_t nLineBytes = ((GBW + 7) >> 3) - 1;
   int32_t nBitsLeft = GBW - (nLineBytes << 3);
@@ -441,7 +441,7 @@
 
   FX_BOOL LTP = FALSE;
   uint8_t* pLine = GBREG->m_pData;
-  int32_t nStride = GBREG->m_nStride;
+  int32_t nStride = GBREG->stride();
   int32_t nLineBytes = ((GBW + 7) >> 3) - 1;
   int32_t nBitsLeft = GBW - (nLineBytes << 3);
   for (uint32_t h = 0; h < GBH; h++) {
@@ -602,7 +602,7 @@
     }
   }
   m_ReplaceRect.left = 0;
-  m_ReplaceRect.right = pImage->m_nWidth;
+  m_ReplaceRect.right = pImage->width();
   m_ReplaceRect.top = iline;
   m_ReplaceRect.bottom = m_loopIndex;
   if (m_ProssiveStatus == FXCODEC_STATUS_DECODE_FINISH) {
@@ -624,9 +624,9 @@
   }
   bitpos = (int)pStream->getBitPos();
   FaxG4Decode(pStream->getBuf(), pStream->getLength(), &bitpos,
-              (*pImage)->m_pData, GBW, GBH, (*pImage)->m_nStride);
+              (*pImage)->m_pData, GBW, GBH, (*pImage)->stride());
   pStream->setBitPos(bitpos);
-  for (i = 0; (uint32_t)i < (*pImage)->m_nStride * GBH; i++) {
+  for (i = 0; (uint32_t)i < (*pImage)->stride() * GBH; i++) {
     (*pImage)->m_pData[i] = ~(*pImage)->m_pData[i];
   }
   m_ProssiveStatus = FXCODEC_STATUS_DECODE_FINISH;
@@ -653,7 +653,7 @@
   if (!m_pLine) {
     m_pLine = pImage->m_pData;
   }
-  int32_t nStride = pImage->m_nStride;
+  int32_t nStride = pImage->stride();
   int32_t nStride2 = nStride << 1;
   int32_t nLineBytes = ((GBW + 7) >> 3) - 1;
   int32_t nBitsLeft = GBW - (nLineBytes << 3);
@@ -791,7 +791,7 @@
   if (!m_pLine) {
     m_pLine = pImage->m_pData;
   }
-  int32_t nStride = pImage->m_nStride;
+  int32_t nStride = pImage->stride();
   int32_t nStride2 = nStride << 1;
   int32_t nLineBytes = ((GBW + 7) >> 3) - 1;
   int32_t nBitsLeft = GBW - (nLineBytes << 3);
@@ -924,7 +924,7 @@
   if (!m_pLine) {
     m_pLine = pImage->m_pData;
   }
-  int32_t nStride = pImage->m_nStride;
+  int32_t nStride = pImage->stride();
   int32_t nStride2 = nStride << 1;
   int32_t nLineBytes = ((GBW + 7) >> 3) - 1;
   int32_t nBitsLeft = GBW - (nLineBytes << 3);
@@ -1057,7 +1057,7 @@
   if (!m_pLine)
     m_pLine = pImage->m_pData;
 
-  int32_t nStride = pImage->m_nStride;
+  int32_t nStride = pImage->stride();
   int32_t nLineBytes = ((GBW + 7) >> 3) - 1;
   int32_t nBitsLeft = GBW - (nLineBytes << 3);
   for (; m_loopIndex < GBH; m_loopIndex++) {
diff --git a/core/fxcodec/jbig2/JBig2_GrrdProc.cpp b/core/fxcodec/jbig2/JBig2_GrrdProc.cpp
index 25c9ea2..672692d 100644
--- a/core/fxcodec/jbig2/JBig2_GrrdProc.cpp
+++ b/core/fxcodec/jbig2/JBig2_GrrdProc.cpp
@@ -20,13 +20,13 @@
   if (GRTEMPLATE == 0) {
     if ((GRAT[0] == -1) && (GRAT[1] == -1) && (GRAT[2] == -1) &&
         (GRAT[3] == -1) && (GRREFERENCEDX == 0) &&
-        (GRW == (uint32_t)GRREFERENCE->m_nWidth)) {
+        (GRW == (uint32_t)GRREFERENCE->width())) {
       return decode_Template0_opt(pArithDecoder, grContext);
     }
     return decode_Template0_unopt(pArithDecoder, grContext);
   }
 
-  if ((GRREFERENCEDX == 0) && (GRW == (uint32_t)GRREFERENCE->m_nWidth))
+  if ((GRREFERENCEDX == 0) && (GRW == (uint32_t)GRREFERENCE->width()))
     return decode_Template1_opt(pArithDecoder, grContext);
   return decode_Template1_unopt(pArithDecoder, grContext);
 }
@@ -162,10 +162,10 @@
   FX_BOOL LTP = FALSE;
   uint8_t* pLine = GRREG->m_pData;
   uint8_t* pLineR = GRREFERENCE->m_pData;
-  intptr_t nStride = GRREG->m_nStride;
-  intptr_t nStrideR = GRREFERENCE->m_nStride;
-  int32_t GRWR = GRREFERENCE->m_nWidth;
-  int32_t GRHR = GRREFERENCE->m_nHeight;
+  intptr_t nStride = GRREG->stride();
+  intptr_t nStrideR = GRREFERENCE->stride();
+  int32_t GRWR = GRREFERENCE->width();
+  int32_t GRHR = GRREFERENCE->height();
   if (GRREFERENCEDY < -GRHR + 1 || GRREFERENCEDY > GRHR - 1)
     GRREFERENCEDY = 0;
   intptr_t nOffset = -GRREFERENCEDY * nStrideR;
@@ -396,10 +396,10 @@
   FX_BOOL LTP = FALSE;
   uint8_t* pLine = GRREG->m_pData;
   uint8_t* pLineR = GRREFERENCE->m_pData;
-  intptr_t nStride = GRREG->m_nStride;
-  intptr_t nStrideR = GRREFERENCE->m_nStride;
-  int32_t GRWR = GRREFERENCE->m_nWidth;
-  int32_t GRHR = GRREFERENCE->m_nHeight;
+  intptr_t nStride = GRREG->stride();
+  intptr_t nStrideR = GRREFERENCE->stride();
+  int32_t GRWR = GRREFERENCE->width();
+  int32_t GRHR = GRREFERENCE->height();
   if (GRREFERENCEDY < -GRHR + 1 || GRREFERENCEDY > GRHR - 1) {
     GRREFERENCEDY = 0;
   }
diff --git a/core/fxcodec/jbig2/JBig2_Image.cpp b/core/fxcodec/jbig2/JBig2_Image.cpp
index cf0ee3b..b8cb211 100644
--- a/core/fxcodec/jbig2/JBig2_Image.cpp
+++ b/core/fxcodec/jbig2/JBig2_Image.cpp
@@ -10,46 +10,65 @@
 #include "core/fxcrt/include/fx_coordinates.h"
 #include "core/fxcrt/include/fx_safe_types.h"
 
-CJBig2_Image::CJBig2_Image(int32_t w, int32_t h) {
+namespace {
+
+const int kMaxImagePixels = INT_MAX - 31;
+const int kMaxImageBytes = kMaxImagePixels / 8;
+
+}  // namespace
+
+CJBig2_Image::CJBig2_Image(int32_t w, int32_t h)
+    : m_pData(nullptr),
+      m_nWidth(0),
+      m_nHeight(0),
+      m_nStride(0),
+      m_bOwnsBuffer(true) {
+  if (w < 0 || h < 0 || w > kMaxImagePixels)
+    return;
+
+  int32_t stride_pixels = (w + 31) & ~31;
+  if (h > kMaxImagePixels / stride_pixels)
+    return;
+
   m_nWidth = w;
   m_nHeight = h;
-  if (m_nWidth <= 0 || m_nHeight <= 0 || m_nWidth > INT_MAX - 31) {
-    m_pData = nullptr;
-    m_bNeedFree = FALSE;
-    return;
-  }
-  m_nStride = ((w + 31) >> 5) << 2;
-  if (m_nStride * m_nHeight > 0 && 104857600 / (int)m_nStride > m_nHeight) {
-    m_pData = FX_Alloc2D(uint8_t, m_nStride, m_nHeight);
-  } else {
-    m_pData = nullptr;
-  }
-  m_bNeedFree = TRUE;
+  m_nStride = stride_pixels / 8;
+  m_pData = FX_Alloc2D(uint8_t, m_nStride, m_nHeight);
 }
-CJBig2_Image::CJBig2_Image(int32_t w,
-                           int32_t h,
-                           int32_t stride,
-                           uint8_t* pBuf) {
+
+CJBig2_Image::CJBig2_Image(int32_t w, int32_t h, int32_t stride, uint8_t* pBuf)
+    : m_pData(nullptr),
+      m_nWidth(0),
+      m_nHeight(0),
+      m_nStride(0),
+      m_bOwnsBuffer(false) {
+  if (w < 0 || h < 0 || stride < 0 || stride > kMaxImageBytes)
+    return;
+
+  int32_t stride_pixels = 8 * stride;
+  if (stride_pixels < w || h > kMaxImagePixels / stride_pixels)
+    return;
+
   m_nWidth = w;
   m_nHeight = h;
   m_nStride = stride;
   m_pData = pBuf;
-  m_bNeedFree = FALSE;
 }
-CJBig2_Image::CJBig2_Image(const CJBig2_Image& im) {
-  m_nWidth = im.m_nWidth;
-  m_nHeight = im.m_nHeight;
-  m_nStride = im.m_nStride;
-  if (im.m_pData) {
+
+CJBig2_Image::CJBig2_Image(const CJBig2_Image& other)
+    : m_pData(nullptr),
+      m_nWidth(other.m_nWidth),
+      m_nHeight(other.m_nHeight),
+      m_nStride(other.m_nStride),
+      m_bOwnsBuffer(true) {
+  if (other.m_pData) {
     m_pData = FX_Alloc2D(uint8_t, m_nStride, m_nHeight);
-    JBIG2_memcpy(m_pData, im.m_pData, m_nStride * m_nHeight);
-  } else {
-    m_pData = nullptr;
+    JBIG2_memcpy(m_pData, other.m_pData, m_nStride * m_nHeight);
   }
-  m_bNeedFree = TRUE;
 }
+
 CJBig2_Image::~CJBig2_Image() {
-  if (m_bNeedFree) {
+  if (m_bOwnsBuffer) {
     FX_Free(m_pData);
   }
 }
@@ -209,30 +228,24 @@
   }
   return pImage;
 }
-void CJBig2_Image::expand(int32_t h, FX_BOOL v) {
-  if (!m_pData || h <= m_nHeight) {
-    return;
-  }
-  uint32_t dwH = pdfium::base::checked_cast<uint32_t>(h);
-  uint32_t dwStride = pdfium::base::checked_cast<uint32_t>(m_nStride);
-  uint32_t dwHeight = pdfium::base::checked_cast<uint32_t>(m_nHeight);
-  FX_SAFE_UINT32 safeMemSize = dwH;
-  safeMemSize *= dwStride;
-  if (!safeMemSize.IsValid()) {
-    return;
-  }
-  // The guaranteed reallocated memory is to be < 4GB (unsigned int).
-  m_pData = FX_Realloc(uint8_t, m_pData, safeMemSize.ValueOrDie());
 
-  // The result of dwHeight * dwStride doesn't overflow after the
-  // checking of safeMemSize.
-  // The same as the result of (dwH - dwHeight) * dwStride) because
-  // dwH - dwHeight is always less than dwH(h) which is checked in
-  // the calculation of dwH * dwStride.
-  JBIG2_memset(m_pData + dwHeight * dwStride, v ? 0xff : 0,
-               (dwH - dwHeight) * dwStride);
+void CJBig2_Image::expand(int32_t h, FX_BOOL v) {
+  if (!m_pData || h <= m_nHeight || h > kMaxImageBytes / m_nStride)
+    return;
+
+  if (m_bOwnsBuffer) {
+    m_pData = FX_Realloc(uint8_t, m_pData, h * m_nStride);
+  } else {
+    uint8_t* pExternalBuffer = m_pData;
+    m_pData = FX_Alloc(uint8_t, h * m_nStride);
+    JBIG2_memcpy(m_pData, pExternalBuffer, m_nHeight * m_nStride);
+    m_bOwnsBuffer = true;
+  }
+  JBIG2_memset(m_pData + m_nHeight * m_nStride, v ? 0xff : 0,
+               (h - m_nHeight) * m_nStride);
   m_nHeight = h;
 }
+
 FX_BOOL CJBig2_Image::composeTo_opt2(CJBig2_Image* pDst,
                                      int32_t x,
                                      int32_t y,
diff --git a/core/fxcodec/jbig2/JBig2_Image.h b/core/fxcodec/jbig2/JBig2_Image.h
index a18a95d..f27b86e 100644
--- a/core/fxcodec/jbig2/JBig2_Image.h
+++ b/core/fxcodec/jbig2/JBig2_Image.h
@@ -9,6 +9,8 @@
 
 #include "core/fxcodec/jbig2/JBig2_Define.h"
 
+struct FX_RECT;
+
 enum JBig2ComposeOp {
   JBIG2_COMPOSE_OR = 0,
   JBIG2_COMPOSE_AND = 1,
@@ -17,23 +19,21 @@
   JBIG2_COMPOSE_REPLACE = 4
 };
 
-struct FX_RECT;
 class CJBig2_Image {
  public:
   CJBig2_Image(int32_t w, int32_t h);
-
   CJBig2_Image(int32_t w, int32_t h, int32_t stride, uint8_t* pBuf);
-
   CJBig2_Image(const CJBig2_Image& im);
-
   ~CJBig2_Image();
 
-  FX_BOOL getPixel(int32_t x, int32_t y);
+  int32_t width() const { return m_nWidth; }
+  int32_t height() const { return m_nHeight; }
+  int32_t stride() const { return m_nStride; }
 
+  FX_BOOL getPixel(int32_t x, int32_t y);
   int32_t setPixel(int32_t x, int32_t y, FX_BOOL v);
 
   void copyLine(int32_t hTo, int32_t hFrom);
-
   void fill(FX_BOOL v);
 
   FX_BOOL composeTo(CJBig2_Image* pDst,
@@ -67,19 +67,15 @@
                       const FX_RECT* pSrcRect);
 
   CJBig2_Image* subImage(int32_t x, int32_t y, int32_t w, int32_t h);
-
   void expand(int32_t h, FX_BOOL v);
 
- public:
-  int32_t m_nWidth;
-
-  int32_t m_nHeight;
-
-  int32_t m_nStride;
-
   uint8_t* m_pData;
 
-  FX_BOOL m_bNeedFree;
+ private:
+  int32_t m_nWidth;   // 1-bit pixels
+  int32_t m_nHeight;  // lines
+  int32_t m_nStride;  // bytes
+  bool m_bOwnsBuffer;
 };
 
 #endif  // CORE_FXCODEC_JBIG2_JBIG2_IMAGE_H_
diff --git a/core/fxcodec/jbig2/JBig2_Image_unittest.cpp b/core/fxcodec/jbig2/JBig2_Image_unittest.cpp
new file mode 100644
index 0000000..788f922
--- /dev/null
+++ b/core/fxcodec/jbig2/JBig2_Image_unittest.cpp
@@ -0,0 +1,105 @@
+// Copyright 2016 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.
+
+// TODO(tsepez) this requires a lot more testing.
+
+#include <stdint.h>
+
+#include "core/fxcodec/jbig2/JBig2_Image.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+const int32_t kWidthPixels = 80;
+const int32_t kWidthBytes = 10;
+const int32_t kStrideBytes = kWidthBytes + 1;  // For testing stride != width.
+const int32_t kHeightLines = 20;
+const int32_t kLargerHeightLines = 100;
+const int32_t kTooLargeHeightLines = 40000000;
+
+}  // namespace
+
+TEST(fxcodec, JBig2ImageCreate) {
+  CJBig2_Image img(kWidthPixels, kHeightLines);
+  img.setPixel(0, 0, true);
+  img.setPixel(kWidthPixels - 1, kHeightLines - 1, false);
+  EXPECT_EQ(kWidthPixels, img.width());
+  EXPECT_EQ(kHeightLines, img.height());
+  EXPECT_TRUE(img.getPixel(0, 0));
+  EXPECT_FALSE(img.getPixel(kWidthPixels - 1, kHeightLines - 1));
+}
+
+TEST(fxcodec, JBig2ImageCreateTooBig) {
+  CJBig2_Image img(kWidthPixels, kTooLargeHeightLines);
+  EXPECT_EQ(0, img.width());
+  EXPECT_EQ(0, img.height());
+  EXPECT_EQ(nullptr, img.m_pData);
+}
+
+TEST(fxcodec, JBig2ImageCreateExternal) {
+  uint8_t buf[kHeightLines * kStrideBytes];
+  CJBig2_Image img(kWidthPixels, kHeightLines, kStrideBytes, buf);
+  img.setPixel(0, 0, true);
+  img.setPixel(kWidthPixels - 1, kHeightLines - 1, false);
+  EXPECT_EQ(kWidthPixels, img.width());
+  EXPECT_EQ(kHeightLines, img.height());
+  EXPECT_TRUE(img.getPixel(0, 0));
+  EXPECT_FALSE(img.getPixel(kWidthPixels - 1, kHeightLines - 1));
+}
+
+TEST(fxcodec, JBig2ImageCreateExternalTooBig) {
+  uint8_t buf[kHeightLines * kStrideBytes];
+  CJBig2_Image img(kWidthPixels, kTooLargeHeightLines, kStrideBytes, buf);
+  EXPECT_EQ(0, img.width());
+  EXPECT_EQ(0, img.height());
+  EXPECT_EQ(nullptr, img.m_pData);
+}
+
+TEST(fxcodec, JBig2ImageExpand) {
+  CJBig2_Image img(kWidthPixels, kHeightLines);
+  img.setPixel(0, 0, true);
+  img.setPixel(kWidthPixels - 1, kHeightLines - 1, false);
+  img.expand(kLargerHeightLines, true);
+  EXPECT_EQ(kWidthPixels, img.width());
+  EXPECT_EQ(kLargerHeightLines, img.height());
+  EXPECT_TRUE(img.getPixel(0, 0));
+  EXPECT_FALSE(img.getPixel(kWidthPixels - 1, kHeightLines - 1));
+  EXPECT_TRUE(img.getPixel(kWidthPixels - 1, kLargerHeightLines - 1));
+}
+
+TEST(fxcodec, JBig2ImageExpandTooBig) {
+  CJBig2_Image img(kWidthPixels, kHeightLines);
+  img.setPixel(0, 0, true);
+  img.setPixel(kWidthPixels - 1, kHeightLines - 1, false);
+  img.expand(kTooLargeHeightLines, true);
+  EXPECT_EQ(kWidthPixels, img.width());
+  EXPECT_EQ(kHeightLines, img.height());
+  EXPECT_TRUE(img.getPixel(0, 0));
+  EXPECT_FALSE(img.getPixel(kWidthPixels - 1, kHeightLines - 1));
+}
+
+TEST(fxcodec, JBig2ImageExpandExternal) {
+  uint8_t buf[kHeightLines * kStrideBytes];
+  CJBig2_Image img(kWidthPixels, kHeightLines, kStrideBytes, buf);
+  img.setPixel(0, 0, true);
+  img.setPixel(kWidthPixels - 1, kHeightLines - 1, false);
+  img.expand(kLargerHeightLines, true);
+  EXPECT_EQ(kWidthPixels, img.width());
+  EXPECT_EQ(kLargerHeightLines, img.height());
+  EXPECT_TRUE(img.getPixel(0, 0));
+  EXPECT_FALSE(img.getPixel(kWidthPixels - 1, kHeightLines - 1));
+  EXPECT_TRUE(img.getPixel(kWidthPixels - 1, kLargerHeightLines - 1));
+}
+
+TEST(fxcodec, JBig2ImageExpandExternalTooBig) {
+  uint8_t buf[kHeightLines * kStrideBytes];
+  CJBig2_Image img(kWidthPixels, kHeightLines, kStrideBytes, buf);
+  img.setPixel(0, 0, true);
+  img.setPixel(kWidthPixels - 1, kHeightLines - 1, false);
+  img.expand(kTooLargeHeightLines, true);
+  EXPECT_EQ(kWidthPixels, img.width());
+  EXPECT_EQ(kHeightLines, img.height());
+  EXPECT_TRUE(img.getPixel(0, 0));
+  EXPECT_FALSE(img.getPixel(kWidthPixels - 1, kHeightLines - 1));
+}
diff --git a/core/fxcodec/jbig2/JBig2_SddProc.cpp b/core/fxcodec/jbig2/JBig2_SddProc.cpp
index 9ab6cb8..c6adfce 100644
--- a/core/fxcodec/jbig2/JBig2_SddProc.cpp
+++ b/core/fxcodec/jbig2/JBig2_SddProc.cpp
@@ -523,7 +523,7 @@
         if (pStream->getByteLeft() >= stride * HCHEIGHT) {
           BHC = new CJBig2_Image(TOTWIDTH, HCHEIGHT);
           for (I = 0; I < HCHEIGHT; I++) {
-            JBIG2_memcpy(BHC->m_pData + I * BHC->m_nStride,
+            JBIG2_memcpy(BHC->m_pData + I * BHC->stride(),
                          pStream->getPointer(), stride);
             pStream->offset(stride);
           }
diff --git a/core/fxcodec/jbig2/JBig2_TrdProc.cpp b/core/fxcodec/jbig2/JBig2_TrdProc.cpp
index 177db9d..f3dd6be 100644
--- a/core/fxcodec/jbig2/JBig2_TrdProc.cpp
+++ b/core/fxcodec/jbig2/JBig2_TrdProc.cpp
@@ -114,8 +114,8 @@
         if (!IBOI)
           return nullptr;
 
-        uint32_t WOI = IBOI->m_nWidth;
-        uint32_t HOI = IBOI->m_nHeight;
+        uint32_t WOI = IBOI->width();
+        uint32_t HOI = IBOI->height();
         if ((int)(WOI + RDWI) < 0 || (int)(HOI + RDHI) < 0)
           return nullptr;
 
@@ -150,8 +150,8 @@
       if (!IBI) {
         continue;
       }
-      uint32_t WI = IBI->m_nWidth;
-      uint32_t HI = IBI->m_nHeight;
+      uint32_t WI = IBI->width();
+      uint32_t HI = IBI->height();
       if (TRANSPOSED == 0 && ((REFCORNER == JBIG2_CORNER_TOPRIGHT) ||
                               (REFCORNER == JBIG2_CORNER_BOTTOMRIGHT))) {
         CURS = CURS + WI - 1;
@@ -327,8 +327,8 @@
         if (!IBOI)
           return nullptr;
 
-        uint32_t WOI = IBOI->m_nWidth;
-        uint32_t HOI = IBOI->m_nHeight;
+        uint32_t WOI = IBOI->width();
+        uint32_t HOI = IBOI->height();
         if ((int)(WOI + RDWI) < 0 || (int)(HOI + RDHI) < 0)
           return nullptr;
 
@@ -350,8 +350,8 @@
       if (!pIBI)
         return nullptr;
 
-      uint32_t WI = pIBI->m_nWidth;
-      uint32_t HI = pIBI->m_nHeight;
+      uint32_t WI = pIBI->width();
+      uint32_t HI = pIBI->height();
       if (TRANSPOSED == 0 && ((REFCORNER == JBIG2_CORNER_TOPRIGHT) ||
                               (REFCORNER == JBIG2_CORNER_BOTTOMRIGHT))) {
         CURS += WI - 1;