Avoid multiplying by 0x010101 for RGB value computation

Replaces CL at https://pdfium-review.googlesource.com/c/pdfium/+/75770

It is clearer to use the pre-existing ArgbEncode() function rather
than realizing that this multiplication results in an RGB value
where all the components are equal.

-- use unsigned shifts in ArgbEncode() to avoid undefined behavior.

Change-Id: Icd5003d0c85b78ef5d0020a74d73a3926fe22cd8
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/75811
Reviewed-by: Daniel Hosseinian <dhoss@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

core/fxge/dib/cfx_dibbase.cpp

diff --git a/core/fxge/dib/cfx_dibbase.cpp b/core/fxge/dib/cfx_dibbase.cpp
index a58b84f..cff1d79 100644
--- a/core/fxge/dib/cfx_dibbase.cpp
+++ b/core/fxge/dib/cfx_dibbase.cpp
@@ -650,7 +650,7 @@
   } else if (GetBPP() == 8) {
     m_palette.resize(256);
     for (int i = 0; i < 256; ++i)
-      m_palette[i] = 0xff000000 | (i * 0x10101);
+      m_palette[i] = ArgbEncode(0xff, i, i, i);
   }
 }
 
@@ -690,7 +690,7 @@
   if (GetBPP() == 1)
     return index ? 0xffffffff : 0xff000000;
 
-  return index * 0x10101 | 0xff000000;
+  return ArgbEncode(0xff, index, index, index);
 }
 
 void CFX_DIBBase::SetPaletteArgb(int index, uint32_t color) {
@@ -840,7 +840,7 @@
       pal[i] = (palette[i] & 0x00ffffff) | (alpha << 24);
   } else {
     for (int i = 0; i < 256; ++i)
-      pal[i] = (i * 0x10101) | (alpha << 24);
+      pal[i] = ArgbEncode(alpha, i, i, i);
   }
 }
 

core/fxge/dib/cfx_dibitmap.cpp

diff --git a/core/fxge/dib/cfx_dibitmap.cpp b/core/fxge/dib/cfx_dibitmap.cpp
index 4c85633..1052b35 100644
--- a/core/fxge/dib/cfx_dibitmap.cpp
+++ b/core/fxge/dib/cfx_dibitmap.cpp
@@ -515,7 +515,7 @@
       return (*pos) << 24;
     case FXDIB_Format::k8bppRgb:
       return HasPalette() ? GetPaletteSpan()[*pos]
-                          : (0xff000000 | ((*pos) * 0x10101));
+                          : ArgbEncode(0xff, *pos, *pos, *pos);
     case FXDIB_Format::kRgb:
     case FXDIB_Format::kRgb32:
       return FXARGB_GETDIB(pos) | 0xff000000;

core/fxge/dib/cfx_imagetransformer.cpp

diff --git a/core/fxge/dib/cfx_imagetransformer.cpp b/core/fxge/dib/cfx_imagetransformer.cpp
index ffcc7d9..c5e1576 100644
--- a/core/fxge/dib/cfx_imagetransformer.cpp
+++ b/core/fxge/dib/cfx_imagetransformer.cpp
@@ -309,7 +309,7 @@
       argb[i] = palette[i];
   } else {
     for (size_t i = 0; i < pdfium::size(argb); i++)
-      argb[i] = 0xff000000 | (i * 0x010101);
+      argb[i] = ArgbEncode(0xff, i, i, i);
   }
   int destBpp = calc_data.bitmap->GetBPP() / 8;
   auto func = [&calc_data, &argb](const BilinearData& data, uint8_t* dest) {

core/fxge/dib/cfx_scanlinecompositor.cpp

diff --git a/core/fxge/dib/cfx_scanlinecompositor.cpp b/core/fxge/dib/cfx_scanlinecompositor.cpp
index 47c8880..e8362d7 100644
--- a/core/fxge/dib/cfx_scanlinecompositor.cpp
+++ b/core/fxge/dib/cfx_scanlinecompositor.cpp
@@ -2253,7 +2253,8 @@
                                                    int DestBpp,
                                                    const uint8_t* clip_scan) {
   for (int col = 0; col < pixel_count; col++) {
-    FX_ARGB argb = pPalette ? pPalette[*src_scan] : (*src_scan) * 0x010101;
+    FX_ARGB argb = pPalette ? pPalette[*src_scan]
+                            : ArgbEncode(0, *src_scan, *src_scan, *src_scan);
     int src_r = FXARGB_R(argb);
     int src_g = FXARGB_G(argb);
     int src_b = FXARGB_B(argb);
@@ -2764,7 +2765,7 @@
     pPalette[1] = 0xffffffff;
   } else {
     for (size_t i = 0; i < pal_count; ++i)
-      pPalette[i] = i * 0x10101;
+      pPalette[i] = ArgbEncode(0, i, i, i);
   }
 }
 

core/fxge/dib/fx_dib.h

diff --git a/core/fxge/dib/fx_dib.h b/core/fxge/dib/fx_dib.h
index 2cfdd49..a167214 100644
--- a/core/fxge/dib/fx_dib.h
+++ b/core/fxge/dib/fx_dib.h
@@ -122,7 +122,7 @@
 // Returns FX_COLORREF.
 FX_COLORREF ArgbToColorRef(FX_ARGB argb);
 
-constexpr FX_ARGB ArgbEncode(int a, int r, int g, int b) {
+constexpr FX_ARGB ArgbEncode(uint32_t a, uint32_t r, uint32_t g, uint32_t b) {
   return (a << 24) | (r << 16) | (g << 8) | b;
 }
 

core/fxge/win32/cgdi_device_driver.cpp

diff --git a/core/fxge/win32/cgdi_device_driver.cpp b/core/fxge/win32/cgdi_device_driver.cpp
index 5648c2d..57c127a 100644
--- a/core/fxge/win32/cgdi_device_driver.cpp
+++ b/core/fxge/win32/cgdi_device_driver.cpp
@@ -172,13 +172,11 @@
       uint32_t* pPalette = (uint32_t*)(pbmih + 1);
       if (pBitmap->HasPalette()) {
         pdfium::span<const uint32_t> palette = pBitmap->GetPaletteSpan();
-        for (int i = 0; i < 256; i++) {
+        for (int i = 0; i < 256; i++)
           pPalette[i] = palette[i];
-        }
       } else {
-        for (int i = 0; i < 256; i++) {
-          pPalette[i] = i * 0x010101;
-        }
+        for (int i = 0; i < 256; i++)
+          pPalette[i] = ArgbEncode(0, i, i, i);
       }
     }
     if (pBitmap->GetBPP() == 1) {