Revert "Reland "Remove ContrastAdjust().""

This reverts commit d5ec7ab0cd0663184d6056bc6fc87c86ec345342.

Reason for revert: Did not mean to reland, just create the reland CL.

Original change's description:
> Reland "Remove ContrastAdjust()."
> 
> Original change's description:
> > Revert "Remove ContrastAdjust()."
> > 
> > This reverts commit 53d443f042b590ae2d920def16bc9daf66f8427d.
> > 
> > Reason for revert: Breaks PDFToPWGRasterBrowserTest
> > 
> > Original change's description:
> > > Remove ContrastAdjust().
> > > 
> > > This post-processing increased the contrast of scaled-down features -
> > > mainly lines and fonts, relative to the background. The effect does not
> > > improved readability and in some cases makes the scaled-down version
> > > look like a different document at a glance. Text that is normal
> > > weight appears bold when scaled down in these cases.
> > > 
> > > Change-Id: I2544d45e2bcec25d6742d2a60c1316d8df08cce1
> > > Reviewed-on: https://pdfium-review.googlesource.com/15471
> > > Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
> > > Reviewed-by: dsinclair <dsinclair@chromium.org>
> > 
> > TBR=bungeman@chromium.org,dsinclair@chromium.org,hnakashima@chromium.org
> > 
> > # Not skipping CQ checks because original CL landed > 1 day ago.
> > 
> > Change-Id: I7f61650bc6d917b3c6640da60f3f740ef4498de0
> > Reviewed-on: https://pdfium-review.googlesource.com/16970
> > Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
> > Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
> 
> TBR=bungeman@chromium.org,dsinclair@chromium.org,hnakashima@chromium.org
> 
> Change-Id: I77d4377d30908d1e2d4dc842300a761072a5fbd4
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://pdfium-review.googlesource.com/16990
> Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
> Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>

TBR=bungeman@chromium.org,dsinclair@chromium.org,hnakashima@chromium.org

Change-Id: Ie2e91662a1e82c0a793952aab47c2acbde1596d4
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://pdfium-review.googlesource.com/16991
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>

3 files changed, 56 insertions, 7 deletions

diff --git a/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp b/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp
index 91e625ab26..3770e98d86 100644
--- a/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp
+++ b/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp
@@ -43,11 +43,11 @@ TEST_F(CPDFSecurityHandlerEmbeddertest, OwnerPassword) {
 
 TEST_F(CPDFSecurityHandlerEmbeddertest, PasswordAfterGenerateSave) {
 #if _FX_PLATFORM_ == _FX_PLATFORM_LINUX_
-  const char md5[] = "7048dca58e2ed8f93339008b91e4eb4e";
+  const char md5[] = "e4a3701ca5b2a759e06455aa8d97d46e";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
   const char md5[] = "6951b6c9891dfe0332a5b1983e484400";
 #else
-  const char md5[] = "a5dde3c6c37b8716b9b369a03752a728";
+  const char md5[] = "50985f3440d3f66c3b599ab138214015";
 #endif  // _FX_PLATFORM_ == _FX_PLATFORM_LINUX_
   {
     ASSERT_TRUE(OpenDocument("encrypted.pdf", "5678", true));
diff --git a/core/fpdfapi/parser/fpdf_parser_decode_embeddertest.cpp b/core/fpdfapi/parser/fpdf_parser_decode_embeddertest.cpp
index bf2fd6d10f..bb186924b6 100644
--- a/core/fpdfapi/parser/fpdf_parser_decode_embeddertest.cpp
+++ b/core/fpdfapi/parser/fpdf_parser_decode_embeddertest.cpp
@@ -115,9 +115,9 @@ TEST_F(FPDFParserDecodeEmbeddertest, Bug_455199) {
 #if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
   const char kExpectedMd5sum[] = "b90475ca64d1348c3bf5e2b77ad9187a";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
-  const char kExpectedMd5sum[] = "e5a6fa28298db07484cd922f3e210c88";
+  const char kExpectedMd5sum[] = "9a2637b73fd5265309bfddd9c69476cd";
 #else
-  const char kExpectedMd5sum[] = "2baa4c0e1758deba1b9c908e1fbd04ed";
+  const char kExpectedMd5sum[] = "f7e129d97c58e91adeace32a4327b925";
 #endif
   CompareBitmap(bitmap, 200, 200, kExpectedMd5sum);
   FPDFBitmap_Destroy(bitmap);
diff --git a/core/fxge/cfx_facecache.cpp b/core/fxge/cfx_facecache.cpp
index 3f037ac65a..a3e58ff29c 100644
--- a/core/fxge/cfx_facecache.cpp
+++ b/core/fxge/cfx_facecache.cpp
@@ -35,8 +35,48 @@ namespace {
 
 constexpr uint32_t kInvalidGlyphIndex = static_cast<uint32_t>(-1);
 
+constexpr int kMinPixel = 0;
+constexpr int kMaxPixel = 255;
+
 constexpr int kMaxGlyphDimension = 2048;
 
+void ContrastAdjust(uint8_t* pDataIn,
+                    uint8_t* pDataOut,
+                    int nWidth,
+                    int nHeight,
+                    int nSrcRowBytes,
+                    int nDstRowBytes) {
+  int max = kMinPixel;
+  int min = kMaxPixel;
+  for (int row = 0; row < nHeight; row++) {
+    uint8_t* pRow = pDataIn + row * nSrcRowBytes;
+    for (int col = 0; col < nWidth; col++) {
+      int val = pRow[col];
+      max = std::max(val, max);
+      min = std::min(val, min);
+    }
+  }
+  int diff = max - min;
+  if (diff == kMinPixel || diff == kMaxPixel) {
+    int rowbytes = std::min(abs(nSrcRowBytes), nDstRowBytes);
+    for (int row = 0; row < nHeight; row++) {
+      memcpy(pDataOut + row * nDstRowBytes, pDataIn + row * nSrcRowBytes,
+             rowbytes);
+    }
+    return;
+  }
+  float rate = 255.f / diff;
+  for (int row = 0; row < nHeight; row++) {
+    uint8_t* pSrcRow = pDataIn + row * nSrcRowBytes;
+    uint8_t* pDstRow = pDataOut + row * nDstRowBytes;
+    for (int col = 0; col < nWidth; col++) {
+      int val = static_cast<int>((pSrcRow[col] - min) * rate + 0.5);
+      pDstRow[col] =
+          static_cast<uint8_t>(pdfium::clamp(val, kMinPixel, kMaxPixel));
+    }
+  }
+}
+
 struct UniqueKeyGen {
   void Generate(int count, ...);
 
@@ -184,9 +224,18 @@ std::unique_ptr<CFX_GlyphBitmap> CFX_FaceCache::RenderGlyph(
     }
   } else {
     memset(pDestBuf, 0, dest_pitch * bmheight);
-    int rowbytes = std::min(abs(src_pitch), dest_pitch);
-    for (int row = 0; row < bmheight; row++)
-      memcpy(pDestBuf + row * dest_pitch, pSrcBuf + row * src_pitch, rowbytes);
+    if (anti_alias == FXFT_RENDER_MODE_MONO &&
+        FXFT_Get_Bitmap_PixelMode(FXFT_Get_Glyph_Bitmap(m_Face)) ==
+            FXFT_PIXEL_MODE_MONO) {
+      int rowbytes = abs(src_pitch) > dest_pitch ? dest_pitch : abs(src_pitch);
+      for (int row = 0; row < bmheight; row++) {
+        memcpy(pDestBuf + row * dest_pitch, pSrcBuf + row * src_pitch,
+               rowbytes);
+      }
+    } else {
+      ContrastAdjust(pSrcBuf, pDestBuf, bmwidth, bmheight, src_pitch,
+                     dest_pitch);
+    }
   }
   return pGlyphBitmap;
 }