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/* 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;
}
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