Add PVRTC Pixel class

This class accepts a pixels with up to 8-bit components. With the way PVRTC is laid out, there are many different bit modes that we could run into. This lets us change between any that we'd like to deal with.
2025-01-08 06:15:31 +00:00 · 2013-08-28 17:49:53 -04:00 · 2013-08-28 17:49:53 -04:00 · 53e7879742
parent 5c80b4f373
commit 53e7879742
3 changed files with 246 additions and 0 deletions
--- a/PVRTCEncoder/CMakeLists.txt
+++ b/PVRTCEncoder/CMakeLists.txt
@ -56,10 +56,12 @@ INCLUDE_DIRECTORIES(${FasTC_BINARY_DIR}/PVRTCEncoder/include)

 SET( HEADERS
  include/PVRTCCompressor.h
+  src/Pixel.h
 )

 SET( SOURCES
  src/Decompressor.cpp
+  src/Pixel.cpp
 )

 ADD_LIBRARY( PVRTCEncoder
--- a/PVRTCEncoder/src/Pixel.cpp
+++ b/PVRTCEncoder/src/Pixel.cpp
@ -0,0 +1,138 @@
+/* FasTC
+ * Copyright (c) 2013 University of North Carolina at Chapel Hill.
+ * All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for educational, research, and non-profit purposes, without
+ * fee, and without a written agreement is hereby granted, provided that the
+ * above copyright notice, this paragraph, and the following four paragraphs
+ * appear in all copies.
+ *
+ * Permission to incorporate this software into commercial products may be
+ * obtained by contacting the authors or the Office of Technology Development
+ * at the University of North Carolina at Chapel Hill <otd@unc.edu>.
+ *
+ * This software program and documentation are copyrighted by the University of
+ * North Carolina at Chapel Hill. The software program and documentation are
+ * supplied "as is," without any accompanying services from the University of
+ * North Carolina at Chapel Hill or the authors. The University of North
+ * Carolina at Chapel Hill and the authors do not warrant that the operation of
+ * the program will be uninterrupted or error-free. The end-user understands
+ * that the program was developed for research purposes and is advised not to
+ * rely exclusively on the program for any reason.
+ *
+ * IN NO EVENT SHALL THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL OR THE
+ * AUTHORS BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL,
+ * OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF
+ * THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF NORTH CAROLINA
+ * AT CHAPEL HILL OR THE AUTHORS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL AND THE AUTHORS SPECIFICALLY
+ * DISCLAIM ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE AND ANY 
+ * STATUTORY WARRANTY OF NON-INFRINGEMENT. THE SOFTWARE PROVIDED HEREUNDER IS ON
+ * AN "AS IS" BASIS, AND THE UNIVERSITY  OF NORTH CAROLINA AT CHAPEL HILL AND
+ * THE AUTHORS HAVE NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, 
+ * ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Please send all BUG REPORTS to <pavel@cs.unc.edu>.
+ *
+ * The authors may be contacted via:
+ *
+ * Pavel Krajcevski
+ * Dept of Computer Science
+ * 201 S Columbia St
+ * Frederick P. Brooks, Jr. Computer Science Bldg
+ * Chapel Hill, NC 27599-3175
+ * USA
+ * 
+ * <http://gamma.cs.unc.edu/FasTC/>
+ */
+
+#include "Pixel.h"
+
+#include <cstring>
+#include <cassert>
+
+namespace PVRTCC {
+
+  void Pixel::FromBits(uint8 *bits, uint8 channelDepth[4], uint8 bitOffset) {
+    memcpy(m_BitDepth, channelDepth, sizeof(m_BitDepth));
+
+    uint32 nBits = bitOffset;
+    for(uint32 i = 0; i < 4; i++) {
+      nBits += channelDepth[i];
+    }
+
+    const uint32 nBytes = (nBits >> 3) + ((nBits & 0x7) > 0);
+    assert(nBytes > 0);
+
+    int32 byteIdx = nBytes - 1;
+    uint32 bitIdx = bitOffset;
+    while(bitIdx >= 8) {
+      bitIdx -= 8;
+      byteIdx--;
+      assert(byteIdx >= 0);
+    }
+
+    for(int32 i = 3; i >= 0; i--) {
+      uint8 &channel = m_Component[i];
+      uint32 depth = channelDepth[i];
+
+      assert(depth <= 8);
+
+      channel = 0;
+      if(depth + bitIdx < 8) {
+        channel = bits[byteIdx] & ((1 << depth) - 1);
+        bitIdx += depth;
+      } else {
+        const uint32 numLowBits = 8 - bitIdx;
+        uint32 bitsLeft = depth - numLowBits;
+        channel |= (bits[byteIdx] >> bitIdx) & ((1 << numLowBits) - 1);
+        byteIdx--;
+        assert(byteIdx >= 0 || (i == 0 && bitsLeft == 0));
+
+        uint8 highBits = bits[byteIdx] & ((1 << bitsLeft) - 1);
+        channel |= highBits << numLowBits;
+        bitIdx = bitsLeft;
+      }
+    }
+  }
+
+  uint8 Pixel::ChangeBitDepth(uint8 val, uint8 oldDepth, uint8 newDepth) {
+    assert(newDepth <= 8);
+    assert(oldDepth <= 8);
+
+    if(oldDepth == newDepth) {
+      // Do nothing
+      return val;
+    } else if(newDepth > oldDepth) {
+      uint8 bitsLeft = newDepth;
+      uint8 ret = 0;
+      while(bitsLeft > oldDepth) {
+        ret |= val;
+        ret <<= oldDepth;
+        bitsLeft -= oldDepth;
+      }
+
+      return ret | (val >> (oldDepth - bitsLeft));
+
+    } else {
+      // oldDepth > newDepth
+      uint8 bitsWasted = oldDepth - newDepth;
+      return val >> bitsWasted;
+    }
+
+    assert(!"We shouldn't get here.");
+    return 0;
+  }
+
+  void Pixel::ChangeBitDepth(uint8 (&depth)[4]) {
+    for(uint32 i = 0; i < 4; i++) {
+      m_Component[i] = ChangeBitDepth(m_Component[i], m_BitDepth[i], depth[i]);
+      m_BitDepth[i] = depth[i];
+    }
+  }
+
+}  // namespace PVRTCC
--- a/PVRTCEncoder/src/Pixel.h
+++ b/PVRTCEncoder/src/Pixel.h
@ -0,0 +1,106 @@
+/* FasTC
+ * Copyright (c) 2013 University of North Carolina at Chapel Hill.
+ * All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for educational, research, and non-profit purposes, without
+ * fee, and without a written agreement is hereby granted, provided that the
+ * above copyright notice, this paragraph, and the following four paragraphs
+ * appear in all copies.
+ *
+ * Permission to incorporate this software into commercial products may be
+ * obtained by contacting the authors or the Office of Technology Development
+ * at the University of North Carolina at Chapel Hill <otd@unc.edu>.
+ *
+ * This software program and documentation are copyrighted by the University of
+ * North Carolina at Chapel Hill. The software program and documentation are
+ * supplied "as is," without any accompanying services from the University of
+ * North Carolina at Chapel Hill or the authors. The University of North
+ * Carolina at Chapel Hill and the authors do not warrant that the operation of
+ * the program will be uninterrupted or error-free. The end-user understands
+ * that the program was developed for research purposes and is advised not to
+ * rely exclusively on the program for any reason.
+ *
+ * IN NO EVENT SHALL THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL OR THE
+ * AUTHORS BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL,
+ * OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF
+ * THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF NORTH CAROLINA
+ * AT CHAPEL HILL OR THE AUTHORS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL AND THE AUTHORS SPECIFICALLY
+ * DISCLAIM ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE AND ANY 
+ * STATUTORY WARRANTY OF NON-INFRINGEMENT. THE SOFTWARE PROVIDED HEREUNDER IS ON
+ * AN "AS IS" BASIS, AND THE UNIVERSITY  OF NORTH CAROLINA AT CHAPEL HILL AND
+ * THE AUTHORS HAVE NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, 
+ * ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Please send all BUG REPORTS to <pavel@cs.unc.edu>.
+ *
+ * The authors may be contacted via:
+ *
+ * Pavel Krajcevski
+ * Dept of Computer Science
+ * 201 S Columbia St
+ * Frederick P. Brooks, Jr. Computer Science Bldg
+ * Chapel Hill, NC 27599-3175
+ * USA
+ * 
+ * <http://gamma.cs.unc.edu/FasTC/>
+ */
+
+#ifndef PVRTCENCODER_SRC_PIXEL_H_
+#define PVRTCENCODER_SRC_PIXEL_H_
+
+#include "TexCompTypes.h"
+
+namespace PVRTCC {
+
+class Pixel {
+ public:
+  Pixel(): m_R(0), m_G(0), m_B(0), m_A(0) { }
+
+  explicit Pixel(uint8 *bits,
+                 uint8 channelDepth[4] = static_cast<uint8 *>(0),
+                 uint8 bitOffset = 0) {
+    FromBits(bits, channelDepth);
+  }
+
+  // Reads a pixel from memory given the bit depth. If NULL then
+  // it is assumed to be 8 bit RGBA. The bit offset is the offset
+  // from the least significant bit from which we start reading
+  // the pixel values.
+  void FromBits(uint8 *bits,
+                uint8 channelDepth[4] = static_cast<uint8 *>(0),
+                uint8 bitOffset = 0);
+
+  // Changes the depth of each pixel. This scales the values to
+  // the appropriate bit depth by either truncating the least
+  // significant bits when going from larger to smaller bit depth
+  // or by repeating the most significant bits when going from
+  // smaller to larger bit depths.
+  void ChangeBitDepth(uint8 (&newDepth)[4]);
+
+  // Changes the bit depth of a single component. See the comment
+  // above for how we do this.
+  static uint8 ChangeBitDepth(uint8 val, uint8 oldDepth, uint8 newDepth);
+
+ private:
+  union {
+    struct {
+      uint8 m_R;
+      uint8 m_G;
+      uint8 m_B;
+      uint8 m_A;
+    };
+    uint8 m_Component[4];
+  };
+
+  // This contains the number of bits that each pixel has.
+  uint8 m_BitDepth[4];
+};
+
+}  // namespace PVRTCC
+
+#endif  // PVRTCENCODER_SRC_PIXEL_H_