From 4bbd80aab2043c3a9162448ae6cae572412417de Mon Sep 17 00:00:00 2001
From: Pavel Krajcevski <pavel@cs.unc.edu>
Date: Mon, 2 Sep 2013 19:14:31 -0400
Subject: [PATCH] Make sure to preserve bit depth when bilinearly upscaling

---
 PVRTCEncoder/src/Image.cpp      | 28 ++++++++++++++++++++++++++++
 PVRTCEncoder/test/ImageTest.cpp | 17 +++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/PVRTCEncoder/src/Image.cpp b/PVRTCEncoder/src/Image.cpp
index 60beac4..96b992a 100644
--- a/PVRTCEncoder/src/Image.cpp
+++ b/PVRTCEncoder/src/Image.cpp
@@ -96,6 +96,17 @@ Image::~Image() {
   delete [] m_Pixels;
 }
 
+#ifndef NDEBUG
+static bool CompareBitDepths(const uint8 (&depth1)[4],
+                             const uint8 (&depth2)[4]) {
+  bool ok = true;
+  for(uint32 i = 0; i < 4; i++) {
+    ok = ok && depth1[i] == depth2[i];
+  }
+  return ok;
+}
+#endif
+
 void Image::BilinearUpscale(uint32 times, EWrapMode wrapMode) {
   const uint32 newWidth = m_Width << times;
   const uint32 newHeight = m_Height << times;
@@ -125,6 +136,23 @@ void Image::BilinearUpscale(uint32 times, EWrapMode wrapMode) {
       const Pixel &bottomLeft = GetPixel(lowXIdx, highYIdx, wrapMode);
       const Pixel &bottomRight = GetPixel(highXIdx, highYIdx, wrapMode);
 
+      // Make sure the bit depth matches the original...
+      uint8 bitDepth[4];
+      topLeft.GetBitDepth(bitDepth);
+      p.ChangeBitDepth(bitDepth);
+#ifndef NDEBUG
+      uint8 debugDepth[4];
+
+      topRight.GetBitDepth(debugDepth);
+      assert(CompareBitDepths(bitDepth, debugDepth));
+
+      bottomLeft.GetBitDepth(debugDepth);
+      assert(CompareBitDepths(bitDepth, debugDepth));
+
+      bottomRight.GetBitDepth(debugDepth);
+      assert(CompareBitDepths(bitDepth, debugDepth));
+#endif //NDEBUG
+
       // bilerp each channel....
       for(uint32 c = 0; c < 4; c++) {
         const uint16 left =
diff --git a/PVRTCEncoder/test/ImageTest.cpp b/PVRTCEncoder/test/ImageTest.cpp
index cf5984f..86d3095 100644
--- a/PVRTCEncoder/test/ImageTest.cpp
+++ b/PVRTCEncoder/test/ImageTest.cpp
@@ -151,6 +151,13 @@ TEST(Image, BilinearUpscale) {
 
 TEST(Image, BilinearUpscaleWrapped) {
   PVRTCC::Pixel pxs[16];
+
+  // Make sure that our bit depth is less than full...
+  for(int i = 0; i < 16; i++) {
+    const uint8 newBitDepth[4] = { 6, 5, 6, 5 };
+    pxs[i].ChangeBitDepth(newBitDepth);
+  }
+
   for(int i = 0; i < 4; i++) {
     for(int j = 0; j < 4; j++) {
       pxs[j*4 + i].R() = i*4;
@@ -166,6 +173,16 @@ TEST(Image, BilinearUpscaleWrapped) {
   for(uint32 i = 0; i < img.GetWidth(); i++) {
     for(uint32 j = 0; j < img.GetHeight(); j++) {
       const PVRTCC::Pixel &p = img(i, j);
+
+      // First make sure that the bit depth didn't change
+      uint8 depth[4];
+      p.GetBitDepth(depth);
+      EXPECT_EQ(depth[0], 6);
+      EXPECT_EQ(depth[1], 5);
+      EXPECT_EQ(depth[2], 6);
+      EXPECT_EQ(depth[3], 5);
+
+      // Now make sure that the values are correct.
       if(i == 0) {
         EXPECT_EQ(p.R(), 6);
       } else if(i == 1) {