alphablend.c

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/*
 * PROJECT:         Win32 subsystem
 * LICENSE:         See COPYING in the top level directory
 * FILE:            subsystems/win32/win32k/dib/stretchblt.c
 * PURPOSE:         AlphaBlend implementation suitable for all bit depths
 * PROGRAMMERS:     Jérôme Gardou
 */

#include <win32k.h>

#define NDEBUG
#include <debug.h>

typedef union
{
  ULONG ul;
  struct
  {
    UCHAR red;
    UCHAR green;
    UCHAR blue;
    UCHAR alpha;
  } col;
} NICEPIXEL32;

static __inline UCHAR
Clamp8(ULONG val)
{
  return (val > 255) ? 255 : (UCHAR)val;
}

BOOLEAN
DIB_XXBPP_AlphaBlend(SURFOBJ* Dest, SURFOBJ* Source, RECTL* DestRect,
                     RECTL* SourceRect, CLIPOBJ* ClipRegion,
                     XLATEOBJ* ColorTranslation, BLENDOBJ* BlendObj)
{
  INT DstX, DstY, SrcX, SrcY;
  BLENDFUNCTION BlendFunc;
  register NICEPIXEL32 DstPixel32;
  register NICEPIXEL32 SrcPixel32;
  UCHAR Alpha, SrcBpp = BitsPerFormat(Source->iBitmapFormat);
  EXLATEOBJ* pexlo;
  EXLATEOBJ exloSrcRGB, exloDstRGB, exloRGBSrc;
  PFN_DIB_PutPixel pfnDibPutPixel = DibFunctionsForBitmapFormat[Dest->iBitmapFormat].DIB_PutPixel;

  DPRINT("DIB_16BPP_AlphaBlend: srcRect: (%d,%d)-(%d,%d), dstRect: (%d,%d)-(%d,%d)\n",
    SourceRect->left, SourceRect->top, SourceRect->right, SourceRect->bottom,
    DestRect->left, DestRect->top, DestRect->right, DestRect->bottom);

  BlendFunc = BlendObj->BlendFunction;
  if (BlendFunc.BlendOp != AC_SRC_OVER)
  {
    DPRINT1("BlendOp != AC_SRC_OVER\n");
    return FALSE;
  }
  if (BlendFunc.BlendFlags != 0)
  {
    DPRINT1("BlendFlags != 0\n");
    return FALSE;
  }
  if ((BlendFunc.AlphaFormat & ~AC_SRC_ALPHA) != 0)
  {
    DPRINT1("Unsupported AlphaFormat (0x%x)\n", BlendFunc.AlphaFormat);
    return FALSE;
  }
  if ((BlendFunc.AlphaFormat & AC_SRC_ALPHA) != 0 &&
    SrcBpp != 32)
  {
    DPRINT1("Source bitmap must be 32bpp when AC_SRC_ALPHA is set\n");
    return FALSE;
  }

  if (!ColorTranslation)
  {
    DPRINT1("ColorTranslation must not be NULL!\n");
    return FALSE;
  }

  pexlo = CONTAINING_RECORD(ColorTranslation, EXLATEOBJ, xlo);
  EXLATEOBJ_vInitialize(&exloSrcRGB, pexlo->ppalSrc, &gpalRGB, 0, 0, 0);
  EXLATEOBJ_vInitialize(&exloDstRGB, pexlo->ppalDst, &gpalRGB, 0, 0, 0);
  EXLATEOBJ_vInitialize(&exloRGBSrc, &gpalRGB, pexlo->ppalSrc, 0, 0, 0);

  SrcY = SourceRect->top;
  DstY = DestRect->top;
  while ( DstY < DestRect->bottom )
  {
    SrcX = SourceRect->left;
    DstX = DestRect->left;
    while(DstX < DestRect->right)
    {
      SrcPixel32.ul = DIB_GetSource(Source, SrcX, SrcY, &exloSrcRGB.xlo);
      SrcPixel32.col.red = (SrcPixel32.col.red * BlendFunc.SourceConstantAlpha) / 255;
      SrcPixel32.col.green = (SrcPixel32.col.green * BlendFunc.SourceConstantAlpha) / 255;
      SrcPixel32.col.blue = (SrcPixel32.col.blue * BlendFunc.SourceConstantAlpha) / 255;

      Alpha = ((BlendFunc.AlphaFormat & AC_SRC_ALPHA) != 0) ?
           (SrcPixel32.col.alpha * BlendFunc.SourceConstantAlpha) / 255 :
           BlendFunc.SourceConstantAlpha ;

      DstPixel32.ul = DIB_GetSource(Dest, DstX, DstY, &exloDstRGB.xlo);
      DstPixel32.col.red = Clamp8((DstPixel32.col.red * (255 - Alpha)) / 255 + SrcPixel32.col.red) ;
      DstPixel32.col.green = Clamp8((DstPixel32.col.green * (255 - Alpha)) / 255 + SrcPixel32.col.green) ;
      DstPixel32.col.blue = Clamp8((DstPixel32.col.blue * (255 - Alpha)) / 255 + SrcPixel32.col.blue) ;
      DstPixel32.ul = XLATEOBJ_iXlate(&exloRGBSrc.xlo, DstPixel32.ul);
      pfnDibPutPixel(Dest, DstX, DstY, XLATEOBJ_iXlate(ColorTranslation, DstPixel32.ul));

      DstX++;
      SrcX = SourceRect->left + ((DstX-DestRect->left)*(SourceRect->right - SourceRect->left))
                                            /(DestRect->right-DestRect->left);
    }
    DstY++;
    SrcY = SourceRect->top + ((DstY-DestRect->top)*(SourceRect->bottom - SourceRect->top))
                                            /(DestRect->bottom-DestRect->top);
  }

  EXLATEOBJ_vCleanup(&exloDstRGB);
  EXLATEOBJ_vCleanup(&exloRGBSrc);
  EXLATEOBJ_vCleanup(&exloSrcRGB);

  return TRUE;
}