s_blend.c

Mesa is an open-source implementation of the OpenGL specification - a system for rendering interacti

/*
 * Mesa 3-D graphics library
 * Version:  7.1
 *
 * Copyright (C) 1999-2008  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */


/**
 * \file swrast/s_blend.c
 * \brief software blending.
 * \author Brian Paul
 *
 * Only a few blend modes have been optimized (min, max, transparency, add)
 * more optimized cases can easily be added if needed.
 * Celestia uses glBlendFunc(GL_SRC_ALPHA, GL_ONE), for example.
 */



#include "glheader.h"
#include "context.h"
#include "colormac.h"
#include "macros.h"

#include "s_blend.h"
#include "s_context.h"
#include "s_span.h"


#if defined(USE_MMX_ASM)
#include "x86/mmx.h"
#include "x86/common_x86_asm.h"
#define _BLENDAPI _ASMAPI
#else
#define _BLENDAPI
#endif


/**
 * Integer divide by 255
 * Declare "int divtemp" before using.
 * This satisfies Glean and should be reasonably fast.
 * Contributed by Nathan Hand.
 */
#define DIV255(X)  (divtemp = (X), ((divtemp << 8) + divtemp + 256) >> 16)



/**
 * Special case for glBlendFunc(GL_ZERO, GL_ONE).
 * No-op means the framebuffer values remain unchanged.
 * Any chanType ok.
 */
static void _BLENDAPI
blend_noop(GLcontext *ctx, GLuint n, const GLubyte mask[],
           GLvoid *src, const GLvoid *dst, GLenum chanType)
{
   GLint bytes;

   ASSERT(ctx->Color.BlendEquationRGB == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendEquationA == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendSrcRGB == GL_ZERO);
   ASSERT(ctx->Color.BlendDstRGB == GL_ONE);
   (void) ctx;

   /* just memcpy */
   if (chanType == GL_UNSIGNED_BYTE)
      bytes = 4 * n * sizeof(GLubyte);
   else if (chanType == GL_UNSIGNED_SHORT)
      bytes = 4 * n * sizeof(GLushort);
   else
      bytes = 4 * n * sizeof(GLfloat);

   _mesa_memcpy(src, dst, bytes);
}


/**
 * Special case for glBlendFunc(GL_ONE, GL_ZERO)
 * Any chanType ok.
 */
static void _BLENDAPI
blend_replace(GLcontext *ctx, GLuint n, const GLubyte mask[],
              GLvoid *src, const GLvoid *dst, GLenum chanType)
{
   ASSERT(ctx->Color.BlendEquationRGB == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendEquationA == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendSrcRGB == GL_ONE);
   ASSERT(ctx->Color.BlendDstRGB == GL_ZERO);
   (void) ctx;
   (void) n;
   (void) mask;
   (void) src;
   (void) dst;
}


/**
 * Common transparency blending mode:
 * glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA).
 */
static void _BLENDAPI
blend_transparency_ubyte(GLcontext *ctx, GLuint n, const GLubyte mask[],
                         GLvoid *src, const GLvoid *dst, GLenum chanType)
{
   GLubyte (*rgba)[4] = (GLubyte (*)[4]) src;
   const GLubyte (*dest)[4] = (const GLubyte (*)[4]) dst;
   GLuint i;

   ASSERT(ctx->Color.BlendEquationRGB == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendEquationA == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendSrcRGB == GL_SRC_ALPHA);
   ASSERT(ctx->Color.BlendSrcA == GL_SRC_ALPHA);
   ASSERT(ctx->Color.BlendDstRGB == GL_ONE_MINUS_SRC_ALPHA);
   ASSERT(ctx->Color.BlendDstA == GL_ONE_MINUS_SRC_ALPHA);
   ASSERT(chanType == GL_UNSIGNED_BYTE);

   (void) ctx;

   for (i = 0; i < n; i++) {
      if (mask[i]) {
         const GLint t = rgba[i][ACOMP];  /* t is in [0, 255] */
         if (t == 0) {
            /* 0% alpha */
            COPY_4UBV(rgba[i], dest[i]);
         }
         else if (t != 255) {
	    GLint divtemp;
            const GLint r = DIV255((rgba[i][RCOMP] - dest[i][RCOMP]) * t) + dest[i][RCOMP];
            const GLint g = DIV255((rgba[i][GCOMP] - dest[i][GCOMP]) * t) + dest[i][GCOMP];
            const GLint b = DIV255((rgba[i][BCOMP] - dest[i][BCOMP]) * t) + dest[i][BCOMP];
            const GLint a = DIV255((rgba[i][ACOMP] - dest[i][ACOMP]) * t) + dest[i][ACOMP]; 
            ASSERT(r <= 255);
            ASSERT(g <= 255);
            ASSERT(b <= 255);
            ASSERT(a <= 255);
            rgba[i][RCOMP] = (GLubyte) r;
            rgba[i][GCOMP] = (GLubyte) g;
            rgba[i][BCOMP] = (GLubyte) b;
            rgba[i][ACOMP] = (GLubyte) a;
         }
      }
   }
}


static void _BLENDAPI
blend_transparency_ushort(GLcontext *ctx, GLuint n, const GLubyte mask[],
                          GLvoid *src, const GLvoid *dst, GLenum chanType)
{
   GLushort (*rgba)[4] = (GLushort (*)[4]) src;
   const GLushort (*dest)[4] = (const GLushort (*)[4]) dst;
   GLuint i;

   ASSERT(ctx->Color.BlendEquationRGB == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendEquationA == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendSrcRGB == GL_SRC_ALPHA);
   ASSERT(ctx->Color.BlendSrcA == GL_SRC_ALPHA);
   ASSERT(ctx->Color.BlendDstRGB == GL_ONE_MINUS_SRC_ALPHA);
   ASSERT(ctx->Color.BlendDstA == GL_ONE_MINUS_SRC_ALPHA);
   ASSERT(chanType == GL_UNSIGNED_SHORT);

   (void) ctx;

   for (i = 0; i < n; i++) {
      if (mask[i]) {
         const GLint t = rgba[i][ACOMP];
         if (t == 0) {
            /* 0% alpha */
            COPY_4V(rgba[i], dest[i]);
         }
         else if (t != 65535) {
            const GLfloat tt = (GLfloat) t / 65535.0F;
            GLushort r = (GLushort) ((rgba[i][RCOMP] - dest[i][RCOMP]) * tt + dest[i][RCOMP]);
            GLushort g = (GLushort) ((rgba[i][GCOMP] - dest[i][GCOMP]) * tt + dest[i][GCOMP]);
            GLushort b = (GLushort) ((rgba[i][BCOMP] - dest[i][BCOMP]) * tt + dest[i][BCOMP]);
            GLushort a = (GLushort) ((rgba[i][ACOMP] - dest[i][ACOMP]) * tt + dest[i][ACOMP]);
            ASSIGN_4V(rgba[i], r, g, b, a);
         }
      }
   }
}


static void _BLENDAPI
blend_transparency_float(GLcontext *ctx, GLuint n, const GLubyte mask[],
                         GLvoid *src, const GLvoid *dst, GLenum chanType)
{
   GLfloat (*rgba)[4] = (GLfloat (*)[4]) src;
   const GLfloat (*dest)[4] = (const GLfloat (*)[4]) dst;
   GLuint i;

   ASSERT(ctx->Color.BlendEquationRGB == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendEquationA == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendSrcRGB == GL_SRC_ALPHA);
   ASSERT(ctx->Color.BlendSrcA == GL_SRC_ALPHA);
   ASSERT(ctx->Color.BlendDstRGB == GL_ONE_MINUS_SRC_ALPHA);
   ASSERT(ctx->Color.BlendDstA == GL_ONE_MINUS_SRC_ALPHA);
   ASSERT(chanType == GL_FLOAT);

   (void) ctx;

   for (i = 0; i < n; i++) {
      if (mask[i]) {
         const GLfloat t = rgba[i][ACOMP];  /* t in [0, 1] */
         if (t == 0.0F) {
            /* 0% alpha */
            COPY_4V(rgba[i], dest[i]);
         }
         else if (t != 1.0F) {
            GLfloat r = (rgba[i][RCOMP] - dest[i][RCOMP]) * t + dest[i][RCOMP];
            GLfloat g = (rgba[i][GCOMP] - dest[i][GCOMP]) * t + dest[i][GCOMP];
            GLfloat b = (rgba[i][BCOMP] - dest[i][BCOMP]) * t + dest[i][BCOMP];
            GLfloat a = (rgba[i][ACOMP] - dest[i][ACOMP]) * t + dest[i][ACOMP];
            ASSIGN_4V(rgba[i], r, g, b, a);
         }
      }
   }
}



/**
 * Add src and dest: glBlendFunc(GL_ONE, GL_ONE).
 * Any chanType ok.
 */
static void _BLENDAPI
blend_add(GLcontext *ctx, GLuint n, const GLubyte mask[],
          GLvoid *src, const GLvoid *dst, GLenum chanType)
{
   GLuint i;

   ASSERT(ctx->Color.BlendEquationRGB == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendEquationA == GL_FUNC_ADD);
   ASSERT(ctx->Color.BlendSrcRGB == GL_ONE);
   ASSERT(ctx->Color.BlendDstRGB == GL_ONE);
   (void) ctx;

   if (chanType == GL_UNSIGNED_BYTE) {
      GLubyte (*rgba)[4] = (GLubyte (*)[4]) src;
      const GLubyte (*dest)[4] = (const GLubyte (*)[4]) dst;
      for (i=0;i<n;i++) {
         if (mask[i]) {
            GLint r = rgba[i][RCOMP] + dest[i][RCOMP];
            GLint g = rgba[i][GCOMP] + dest[i][GCOMP];
            GLint b = rgba[i][BCOMP] + dest[i][BCOMP];
            GLint a = rgba[i][ACOMP] + dest[i][ACOMP];
            rgba[i][RCOMP] = (GLubyte) MIN2( r, 255 );
            rgba[i][GCOMP] = (GLubyte) MIN2( g, 255 );
            rgba[i][BCOMP] = (GLubyte) MIN2( b, 255 );
            rgba[i][ACOMP] = (GLubyte) MIN2( a, 255 );
         }
      }
   }
   else if (chanType == GL_UNSIGNED_SHORT) {
      GLushort (*rgba)[4] = (GLushort (*)[4]) src;
      const GLushort (*dest)[4] = (const GLushort (*)[4]) dst;
      for (i=0;i<n;i++) {
         if (mask[i]) {
            GLint r = rgba[i][RCOMP] + dest[i][RCOMP];
            GLint g = rgba[i][GCOMP] + dest[i][GCOMP];
            GLint b = rgba[i][BCOMP] + dest[i][BCOMP];
            GLint a = rgba[i][ACOMP] + dest[i][ACOMP];
            rgba[i][RCOMP] = (GLshort) MIN2( r, 255 );
            rgba[i][GCOMP] = (GLshort) MIN2( g, 255 );
            rgba[i][BCOMP] = (GLshort) MIN2( b, 255 );
            rgba[i][ACOMP] = (GLshort) MIN2( a, 255 );
         }
      }
   }
   else {
      GLfloat (*rgba)[4] = (GLfloat (*)[4]) src;
      const GLfloat (*dest)[4] = (const GLfloat (*)[4]) dst;
      ASSERT(chanType == GL_FLOAT);
      for (i=0;i<n;i++) {
         if (mask[i]) {
            /* don't RGB clamp to max */
            rgba[i][RCOMP] += dest[i][RCOMP];
            rgba[i][GCOMP] += dest[i][GCOMP];
            rgba[i][BCOMP] += dest[i][BCOMP];
            rgba[i][ACOMP] += dest[i][ACOMP];
         }
      }
   }
}



/**
 * Blend min function.
 * Any chanType ok.
 */
static void _BLENDAPI
blend_min(GLcontext *ctx, GLuint n, const GLubyte mask[],
          GLvoid *src, const GLvoid *dst, GLenum chanType)
{
   GLuint i;
   ASSERT(ctx->Color.BlendEquationRGB == GL_MIN);
   ASSERT(ctx->Color.BlendEquationA == GL_MIN);
   (void) ctx;

   if (chanType == GL_UNSIGNED_BYTE) {
      GLubyte (*rgba)[4] = (GLubyte (*)[4]) src;
      const GLubyte (*dest)[4] = (const GLubyte (*)[4]) dst;
      for (i=0;i<n;i++) {
         if (mask[i]) {
            rgba[i][RCOMP] = MIN2( rgba[i][RCOMP], dest[i][RCOMP] );
            rgba[i][GCOMP] = MIN2( rgba[i][GCOMP], dest[i][GCOMP] );
            rgba[i][BCOMP] = MIN2( rgba[i][BCOMP], dest[i][BCOMP] );
            rgba[i][ACOMP] = MIN2( rgba[i][ACOMP], dest[i][ACOMP] );
         }
      }
   }
   else if (chanType == GL_UNSIGNED_SHORT) {
      GLushort (*rgba)[4] = (GLushort (*)[4]) src;
      const GLushort (*dest)[4] = (const GLushort (*)[4]) dst;
      for (i=0;i<n;i++) {