/* FreeRDP: A Remote Desktop Protocol Client

 * Alpha blending routines.

 * vi:ts=4 sw=4:

 *

 * (c) Copyright 2012 Hewlett-Packard Development Company, L.P.

 * Licensed under the Apache License, Version 2.0 (the "License"); you may

 * not use this file except in compliance with the License. You may obtain

 * a copy of the License at http://www.apache.org/licenses/LICENSE-2.0.

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express

 * or implied. See the License for the specific language governing

 * permissions and limitations under the License.

 *

 * Note: this code assumes the second operand is fully opaque,

 * e.g.

 *   newval = alpha1*val1 + (1-alpha1)*val2

 * rather than

 *   newval = alpha1*val1 + (1-alpha1)*alpha2*val2

 */

#include <freerdp/config.h>

#include <freerdp/types.h>

#include <freerdp/primitives.h>

#include "prim_internal.h"

#define ALPHA(_k_) (((_k_)&0xFF000000U) >> 24)

#define RED(_k_) (((_k_)&0x00FF0000U) >> 16)

#define GRN(_k_) (((_k_)&0x0000FF00U) >> 8)

#define BLU(_k_) (((_k_)&0x000000FFU))

/* ------------------------------------------------------------------------- */

static pstatus_t general_alphaComp_argb(const BYTE* pSrc1, UINT32 src1Step, const BYTE* pSrc2,

                                        UINT32 src2Step, BYTE* pDst, UINT32 dstStep, UINT32 width,

                                        UINT32 height)

{

  for (UINT32 y = 0; y < height; y++)

  {

    const UINT32* sptr1 = (const UINT32*)(pSrc1 + y * src1Step);

    const UINT32* sptr2 = (const UINT32*)(pSrc2 + y * src2Step);

    UINT32* dptr = (UINT32*)(pDst + y * dstStep);

    for (UINT32 x = 0; x < width; x++)

    {

      const UINT32 src1 = *sptr1++;

      const UINT32 src2 = *sptr2++;

      UINT32 alpha = ALPHA(src1) + 1;

      if (alpha == 256)

      {

        /* If alpha is 255+1, just copy src1. */

        *dptr++ = src1;

      }

      else if (alpha <= 1)

      {

        /* If alpha is 0+1, just copy src2. */

        *dptr++ = src2;

      }

      else

      {

        /* A perfectly accurate blend would do (a*src + (255-a)*dst)/255

         * rather than adding one to alpha and dividing by 256, but this

         * is much faster and only differs by one 16% of the time.

         * I'm not sure who first designed the double-ops trick

         * (Red Blue and Alpha Green).

         */

        UINT32 rb = 0;

        UINT32 ag = 0;

        UINT32 s2rb = src2 & 0x00FF00FFU;

        UINT32 s2ag = (src2 >> 8) & 0x00FF00FFU;

        UINT32 s1rb = src1 & 0x00FF00FFU;

        UINT32 s1ag = (src1 >> 8) & 0x00FF00FFU;

        UINT32 drb = s1rb - s2rb;

        UINT32 dag = s1ag - s2ag;

        drb *= alpha;

        dag *= alpha;

        rb = ((drb >> 8) + s2rb) & 0x00FF00FFU;

        ag = (((dag >> 8) + s2ag) << 8) & 0xFF00FF00U;

        *dptr++ = rb | ag;

      }

    }

  }

  return PRIMITIVES_SUCCESS;

}

/* ------------------------------------------------------------------------- */

void primitives_init_alphaComp(primitives_t* prims)

{

  prims->alphaComp_argb = general_alphaComp_argb;

}