text: ﻿//------------------------------------------------------------------------------
  // File: AMVideo.cpp
  //
  // Desc: DirectShow base classes - implements helper functions for
  //       bitmap formats.
  //
  // Copyright (c) 1992-2001 Microsoft Corporation.  All rights reserved.
  //------------------------------------------------------------------------------
  
  
  #include <streams.h>
  #include <limits.h>
  
  // These are bit field masks for true colour devices
  
  const DWORD bits555[] = {0x007C00,0x0003E0,0x00001F};
  const DWORD bits565[] = {0x00F800,0x0007E0,0x00001F};
  const DWORD bits888[] = {0xFF0000,0x00FF00,0x0000FF};
  
  // This maps bitmap subtypes into a bits per pixel value and also a
  // name. unicode and ansi versions are stored because we have to
  // return a pointer to a static string.
  const struct {
      const GUID *pSubtype;
      WORD BitCount;
      CHAR *pName;
      WCHAR *wszName;
  } BitCountMap[] =  { &MEDIASUBTYPE_RGB1,        1,   "RGB Monochrome",     L"RGB Monochrome",   
                       &MEDIASUBTYPE_RGB4,        4,   "RGB VGA",            L"RGB VGA",          
                       &MEDIASUBTYPE_RGB8,        8,   "RGB 8",              L"RGB 8",            
                       &MEDIASUBTYPE_RGB565,      16,  "RGB 565 (16 bit)",   L"RGB 565 (16 bit)", 
                       &MEDIASUBTYPE_RGB555,      16,  "RGB 555 (16 bit)",   L"RGB 555 (16 bit)", 
                       &MEDIASUBTYPE_RGB24,       24,  "RGB 24",             L"RGB 24",           
                       &MEDIASUBTYPE_RGB32,       32,  "RGB 32",             L"RGB 32",
                       &MEDIASUBTYPE_ARGB32,    32,  "ARGB 32",             L"ARGB 32",
                       &MEDIASUBTYPE_Overlay,     0,   "Overlay",            L"Overlay",          
                       &GUID_NULL,                0,   "UNKNOWN",            L"UNKNOWN"           
  };
  
  // Return the size of the bitmap as defined by this header
  
  STDAPI_(DWORD) GetBitmapSize(const BITMAPINFOHEADER *pHeader)
  {
      return DIBSIZE(*pHeader);
  }
  
  
  // This is called if the header has a 16 bit colour depth and needs to work
  // out the detailed type from the bit fields (either RGB 565 or RGB 555)
  
  STDAPI_(const GUID) GetTrueColorType(const BITMAPINFOHEADER *pbmiHeader)
  {
      BITMAPINFO *pbmInfo = (BITMAPINFO *) pbmiHeader;
      ASSERT(pbmiHeader->biBitCount == 16);
  
      // If its BI_RGB then it's RGB 555 by default
  
      if (pbmiHeader->biCompression == BI_RGB) {
          return MEDIASUBTYPE_RGB555;
      }
  
      // Compare the bit fields with RGB 555
  
      DWORD *pMask = (DWORD *) pbmInfo->bmiColors;
      if (pMask[0] == bits555[0]) {
          if (pMask[1] == bits555[1]) {
              if (pMask[2] == bits555[2]) {
                  return MEDIASUBTYPE_RGB555;
              }
          }
      }
  
      // Compare the bit fields with RGB 565
  
      pMask = (DWORD *) pbmInfo->bmiColors;
      if (pMask[0] == bits565[0]) {
          if (pMask[1] == bits565[1]) {
              if (pMask[2] == bits565[2]) {
                  return MEDIASUBTYPE_RGB565;
              }
          }
      }
      return GUID_NULL;
  }
  
  
  // Given a BITMAPINFOHEADER structure this returns the GUID sub type that is
  // used to describe it in format negotiations. For example a video codec fills
  // in the format block with a VIDEOINFO structure, it also fills in the major
  // type with MEDIATYPE_VIDEO and the subtype with a GUID that matches the bit
  // count, for example if it is an eight bit image then MEDIASUBTYPE_RGB8
  
  STDAPI_(const GUID) GetBitmapSubtype(const BITMAPINFOHEADER *pbmiHeader)
  {
      ASSERT(pbmiHeader);
  
      // If it's not RGB then create a GUID from the compression type
  
      if (pbmiHeader->biCompression != BI_RGB) {
          if (pbmiHeader->biCompression != BI_BITFIELDS) {
              FOURCCMap FourCCMap(pbmiHeader->biCompression);
              return (const GUID) FourCCMap;
          }
      }
  
      // Map the RGB DIB bit depth to a image GUID
  
      switch(pbmiHeader->biBitCount) {
          case 1    :   return MEDIASUBTYPE_RGB1;
          case 4    :   return MEDIASUBTYPE_RGB4;
          case 8    :   return MEDIASUBTYPE_RGB8;
          case 16   :   return GetTrueColorType(pbmiHeader);
          case 24   :   return MEDIASUBTYPE_RGB24;
          case 32   :   return MEDIASUBTYPE_RGB32;
      }
      return GUID_NULL;
  }
  
  
  // Given a video bitmap subtype we return the number of bits per pixel it uses
  // We return a WORD bit count as thats what the BITMAPINFOHEADER uses. If the
  // GUID subtype is not found in the table we return an invalid USHRT_MAX
  
  STDAPI_(WORD) GetBitCount(const GUID *pSubtype)
  {
      ASSERT(pSubtype);
      const GUID *pMediaSubtype;
      INT iPosition = 0;
  
      // Scan the mapping list seeing if the source GUID matches any known
      // bitmap subtypes, the list is terminated by a GUID_NULL entry
  
      while (TRUE) {
          pMediaSubtype = BitCountMap[iPosition].pSubtype;
          if (IsEqualGUID(*pMediaSubtype,GUID_NULL)) {
              return USHRT_MAX;
          }
          if (IsEqualGUID(*pMediaSubtype,*pSubtype)) {
              return BitCountMap[iPosition].BitCount;
          }
          iPosition++;
      }
  }
  
  
  // Given a bitmap subtype we return a description name that can be used for
  // debug purposes. In a retail build this function still returns the names
  // If the subtype isn't found in the lookup table we return string UNKNOWN
  
  int LocateSubtype(const GUID *pSubtype)
  {
      ASSERT(pSubtype);
      const GUID *pMediaSubtype;
      INT iPosition = 0;
  
      // Scan the mapping list seeing if the source GUID matches any known
      // bitmap subtypes, the list is terminated by a GUID_NULL entry
  
      while (TRUE) {
          pMediaSubtype = BitCountMap[iPosition].pSubtype;
          if (IsEqualGUID(*pMediaSubtype,*pSubtype) ||
              IsEqualGUID(*pMediaSubtype,GUID_NULL)
              )
          {
              break;
          }
          
          iPosition++;
      }
  
      return iPosition;
  }
  
  
  
  STDAPI_(WCHAR *) GetSubtypeNameW(const GUID *pSubtype)
  {
      return BitCountMap[LocateSubtype(pSubtype)].wszName;
  }
  
  STDAPI_(CHAR *) GetSubtypeNameA(const GUID *pSubtype)
  {
      return BitCountMap[LocateSubtype(pSubtype)].pName;
  }
  
  #ifndef GetSubtypeName
  #error wxutil.h should have defined GetSubtypeName
  #endif
  #undef GetSubtypeName
  
  // this is here for people that linked to it directly; most people
  // would use the header file that picks the A or W version.
  STDAPI_(CHAR *) GetSubtypeName(const GUID *pSubtype)
  {
      return GetSubtypeNameA(pSubtype);
  }
  
  
  // The mechanism for describing a bitmap format is with the BITMAPINFOHEADER
  // This is really messy to deal with because it invariably has fields that
  // follow it holding bit fields, palettes and the rest. This function gives
  // the number of bytes required to hold a VIDEOINFO that represents it. This
  // count includes the prefix information (like the rcSource rectangle) the
  // BITMAPINFOHEADER field, and any other colour information on the end.
  //
  // WARNING If you want to copy a BITMAPINFOHEADER into a VIDEOINFO always make
  // sure that you use the HEADER macro because the BITMAPINFOHEADER field isn't
  // right at the start of the VIDEOINFO (there are a number of other fields),
  //
  //     CopyMemory(HEADER(pVideoInfo),pbmi,sizeof(BITMAPINFOHEADER));
  //
  
  STDAPI_(LONG) GetBitmapFormatSize(const BITMAPINFOHEADER *pHeader)
  {
      // Everyone has this to start with this  
      LONG Size = SIZE_PREHEADER + pHeader->biSize;
  
      ASSERT(pHeader->biSize >= sizeof(BITMAPINFOHEADER));
      
      // Does this format use a palette, if the number of colours actually used
      // is zero then it is set to the maximum that are allowed for that colour
      // depth (an example is 256 for eight bits). Truecolour formats may also
      // pass a palette with them in which case the used count is non zero
  
      // This would scare me.
      ASSERT(pHeader->biBitCount <= iPALETTE || pHeader->biClrUsed == 0);
  
      if (pHeader->biBitCount <= iPALETTE || pHeader->biClrUsed) {
          LONG Entries = (DWORD) 1 << pHeader->biBitCount;
          if (pHeader->biClrUsed) {
              Entries = pHeader->biClrUsed;
          }
          Size += Entries * sizeof(RGBQUAD);
      }
  
      // Truecolour formats may have a BI_BITFIELDS specifier for compression
      // type which means that room for three DWORDs should be allocated that
      // specify where in each pixel the RGB colour components may be found
  
      if (pHeader->biCompression == BI_BITFIELDS) {
          Size += SIZE_MASKS;
      }
  
      // A BITMAPINFO for a palettised image may also contain a palette map that
      // provides the information to map from a source palette to a destination
      // palette during a BitBlt for example, because this information is only
      // ever processed during drawing you don't normally store the palette map
      // nor have any way of knowing if it is present in the data structure
  
      return Size;
  }
  
  
  // Returns TRUE if the VIDEOINFO contains a palette
  
  STDAPI_(BOOL) ContainsPalette(const VIDEOINFOHEADER *pVideoInfo)
  {
      if (PALETTISED(pVideoInfo) == FALSE) {
          if (pVideoInfo->bmiHeader.biClrUsed == 0) {
              return FALSE;
          }
      }
      return TRUE;
  }
  
  
  // Return a pointer to the first entry in a palette
  
  STDAPI_(const RGBQUAD *) GetBitmapPalette(const VIDEOINFOHEADER *pVideoInfo)
  {
      if (pVideoInfo->bmiHeader.biCompression == BI_BITFIELDS) {
          return TRUECOLOR(pVideoInfo)->bmiColors;
      }
      return COLORS(pVideoInfo);
  }
  