blend.c

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/* $Id: blend.c,v 1.10 1998/01/27 03:42:40 brianp Exp $ */
 
/*
 * Mesa 3-D graphics library
 * Version:  2.6
 * Copyright (C) 1995-1997  Brian Paul
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
 
/*
 * $Log: blend.c,v $
 * Revision 1.10  1998/01/27 03:42:40  brianp
 * optimized more blending modes (Kai Schuetz)
 *
 * Revision 1.9  1997/07/24 01:24:45  brianp
 * changed precompiled header symbol from PCH to PC_HEADER
 *
 * Revision 1.8  1997/05/28 03:23:48  brianp
 * added precompiled header (PCH) support
 *
 * Revision 1.7  1997/04/20 19:51:57  brianp
 * replaced abort() with gl_problem()
 *
 * Revision 1.6  1997/02/15 18:27:56  brianp
 * fixed a few error messages
 *
 * Revision 1.5  1997/01/28 22:17:19  brianp
 * moved logic op blending into logic.c
 *
 * Revision 1.4  1997/01/04 00:13:11  brianp
 * was using ! instead of ~ to invert pixel bits (ugh!)
 *
 * Revision 1.3  1996/09/19 00:53:31  brianp
 * added missing returns after some gl_error() calls
 *
 * Revision 1.2  1996/09/15 14:18:10  brianp
 * now use GLframebuffer and GLvisual
 *
 * Revision 1.1  1996/09/13 01:38:16  brianp
 * Initial revision
 *
 */
 
 
#ifdef PC_HEADER
#include "all.h"
#else
#include <assert.h>
#include <stdlib.h>
#include "alphabuf.h"
#include "blend.h"
#include "context.h"
#include "dlist.h"
#include "macros.h"
#include "pb.h"
#include "span.h"
#include "types.h"
#endif
 
 
 
void gl_BlendFunc( GLcontext* ctx, GLenum sfactor, GLenum dfactor )
{
   if (INSIDE_BEGIN_END(ctx)) {
      gl_error( ctx, GL_INVALID_OPERATION, "glBlendFunc" );
      return;
   }
 
   switch (sfactor) {
      case GL_ZERO:
      case GL_ONE:
      case GL_DST_COLOR:
      case GL_ONE_MINUS_DST_COLOR:
      case GL_SRC_ALPHA:
      case GL_ONE_MINUS_SRC_ALPHA:
      case GL_DST_ALPHA:
      case GL_ONE_MINUS_DST_ALPHA:
      case GL_SRC_ALPHA_SATURATE:
         ctx->Color.BlendSrc = sfactor;
         break;
      default:
         gl_error( ctx, GL_INVALID_ENUM, "glBlendFunc(sfactor)" );
         return;
   }
 
   switch (dfactor) {
      case GL_ZERO:
      case GL_ONE:
      case GL_SRC_COLOR:
      case GL_ONE_MINUS_SRC_COLOR:
      case GL_SRC_ALPHA:
      case GL_ONE_MINUS_SRC_ALPHA:
      case GL_DST_ALPHA:
      case GL_ONE_MINUS_DST_ALPHA:
         ctx->Color.BlendDst = dfactor;
         break;
      default:
         gl_error( ctx, GL_INVALID_ENUM, "glBlendFunc(dfactor)" );
   }
 
   ctx->NewState |= NEW_RASTER_OPS;
}
 
 
 
/*
 * Do the real work of gl_blend_span() and gl_blend_pixels().
 * Input:  n - number of pixels
 *         mask - the usual write mask
 * In/Out:  red, green, blue, alpha - the incoming and modified pixels
 * Input:  rdest, gdest, bdest, adest - the pixels from the dest color buffer
 */
static void do_blend( GLcontext* ctx, GLuint n, const GLubyte mask[],
                      GLubyte red[], GLubyte green[],
                      GLubyte blue[], GLubyte alpha[],
                      const GLubyte rdest[], const GLubyte gdest[],
                      const GLubyte bdest[], const GLubyte adest[] )
{
   GLuint i;
 
   if (ctx->Color.BlendSrc==GL_SRC_ALPHA
       && ctx->Color.BlendDst==GL_ONE_MINUS_SRC_ALPHA) {
      /* Alpha blending */
      GLfloat ascale = 256.0f * ctx->Visual->InvAlphaScale;
      GLint rmax = (GLint) ctx->Visual->RedScale;
      GLint gmax = (GLint) ctx->Visual->GreenScale;
      GLint bmax = (GLint) ctx->Visual->BlueScale;
      GLint amax = (GLint) ctx->Visual->AlphaScale;
      for (i=0;i<n;i++) {
     if (mask[i]) {
        GLint r, g, b, a;
            GLint t = (GLint) ( alpha[i] * ascale );  /* t in [0,256] */
            GLint s = 256 - t;
        r = (red[i]   * t + rdest[i] * s) >> 8;
        g = (green[i] * t + gdest[i] * s) >> 8;
        b = (blue[i]  * t + bdest[i] * s) >> 8;
        a = (alpha[i] * t + adest[i] * s) >> 8;
 
        /* kai: I think the following clamping is not needed: */
 
        red[i]   = MIN2( r, rmax );
        green[i] = MIN2( g, gmax );
        blue[i]  = MIN2( b, bmax );
        alpha[i] = MIN2( a, amax );
     }
      }
   }
   else {
 
      /* clipped sum */
      if (ctx->Color.BlendSrc==GL_ONE
      && ctx->Color.BlendDst==GL_ONE) {
     GLint rmax = (GLint) ctx->Visual->RedScale;
     GLint gmax = (GLint) ctx->Visual->GreenScale;
     GLint bmax = (GLint) ctx->Visual->BlueScale;
     GLint amax = (GLint) ctx->Visual->AlphaScale;
     for (i=0; i < n; i++) {
        if (mask[i]) {
           red[i]   = MIN2(rmax, red[i]   + rdest[i]);
           green[i] = MIN2(gmax, green[i] + gdest[i]);
           blue[i]  = MIN2(bmax, blue[i]  + bdest[i]);
           alpha[i] = MIN2(amax, alpha[i] + adest[i]);
        }
     }
      }
 
      /* modulation */
      else if ((ctx->Color.BlendSrc==GL_ZERO &&
            ctx->Color.BlendDst==GL_SRC_COLOR)
           ||
           (ctx->Color.BlendSrc==GL_DST_COLOR &&
            ctx->Color.BlendDst==GL_ZERO)) {
     if (ctx->Visual->EightBitColor) {
        for (i=0; i < n; i++) {
           if (mask[i]) {
          red[i]   = (red[i]   * rdest[i]) / 255;
          green[i] = (green[i] * gdest[i]) / 255;
          blue[i]  = (blue[i]  * bdest[i]) / 255;
          alpha[i] = (alpha[i] * adest[i]) / 255;
           }
        }
     }
         else {
        GLint rmax = (GLint) ctx->Visual->RedScale;
        GLint gmax = (GLint) ctx->Visual->GreenScale;
        GLint bmax = (GLint) ctx->Visual->BlueScale;
        GLint amax = (GLint) ctx->Visual->AlphaScale;
        for (i=0; i < n; i++) {
           if (mask[i]) {
          red[i]   = (red[i]   * rdest[i]) / rmax;
          green[i] = (green[i] * gdest[i]) / gmax;
          blue[i]  = (blue[i]  * bdest[i]) / bmax;
          alpha[i] = (alpha[i] * adest[i]) / amax;
           }
        }
     }
      }else{
 
     /* General cases: */
 
     if (ctx->Visual->EightBitColor) {
        for (i=0;i<n;i++) {
           if (mask[i]) {
          GLint Rs, Gs, Bs, As;  /* Source colors */
          GLint Rd, Gd, Bd, Ad;  /* Dest colors */
          GLint Rss, Gss, Bss, Ass;  /* Source colors scaled */
          GLint Rds, Gds, Bds, Ads;  /* Dest colors scaled */
 
          /* Source Color */
          Rs = red[i];
          Gs = green[i];
          Bs = blue[i];
          As = alpha[i];
 
          /* Frame buffer color */
          Rd = rdest[i];
          Gd = gdest[i];
          Bd = bdest[i];
          Ad = adest[i];
 
          /* Source scaling */
          switch (ctx->Color.BlendSrc) {
             case GL_ZERO:
            Rss = Gss = Bss = Ass = 0;
            break;
             case GL_ONE:
            Rss = Rs * 255;
            Gss = Gs * 255;
            Bss = Bs * 255;
            Ass = As * 255;
            break;
             case GL_DST_COLOR:
            Rss = Rs * Rd;
            Gss = Gs * Gd;
            Bss = Bs * Bd;
            Ass = As * Ad;
            break;
             case GL_ONE_MINUS_DST_COLOR:
            Rss = Rs * (255 - Rd);
            Gss = Gs * (255 - Gd);
            Bss = Bs * (255 - Bd);
            Ass = As * (255 - Ad);
            break;
             case GL_SRC_ALPHA:
            Rss = Rs * As;
            Gss = Gs * As;
            Bss = Bs * As;
            Ass = As * As;
            break;
             case GL_ONE_MINUS_SRC_ALPHA:
            Rss = Rs * (255 - As);
            Gss = Gs * (255 - As);
            Bss = Bs * (255 - As);
            Ass = As * (255 - As);
            break;
             case GL_DST_ALPHA:
            Rss = Rs * Ad;
            Gss = Gs * Ad;
            Bss = Bs * Ad;
            Ass = As * Ad;
            break;
             case GL_ONE_MINUS_DST_ALPHA:
            Rss = Rs * (255 - Ad);
            Gss = Gs * (255 - Ad);
            Bss = Bs * (255 - Ad);
            Ass = As * (255 - Ad);
            break;
             case GL_SRC_ALPHA_SATURATE:
             {
                GLint sA = MIN2(As, 255 - Ad);
                Rss = Rs * sA;
                Gss = Gs * sA;
                Bss = Bs * sA;
                Ass = As * 255;
                break;
             }
             default:
            /* this should never happen */
            gl_problem(ctx, "Bad blend source factor in do_blend");
          }
 
          /* Dest scaling */
          switch (ctx->Color.BlendDst) {
             case GL_ZERO:
            Rds = Gds = Bds = Ads = 0;
            break;
             case GL_ONE:
            Rds = Rd * 255;
            Gds = Gd * 255;
            Bds = Bd * 255;
            Ads = Ad * 255;
            break;
             case GL_SRC_COLOR:
            Rds = Rd * Rs;
            Gds = Gd * Gs;
            Bds = Bd * Bs;
            Ads = Ad * As;
            break;
             case GL_ONE_MINUS_SRC_COLOR:
            Rds = Rs * (255 - Rs);
            Gds = Gs * (255 - Gs);
            Bds = Bs * (255 - Bs);
            Ads = As * (255 - As);
            break;
             case GL_SRC_ALPHA:
            Rds = Rd * As;
            Gds = Gd * As;
            Bds = Bd * As;
            Ads = Ad * As;
            break;
             case GL_ONE_MINUS_SRC_ALPHA:
            Rds = Rd * (255 - As);
            Gds = Gd * (255 - As);
            Bds = Bd * (255 - As);
            Ads = Ad * (255 - As);
            break;
             case GL_DST_ALPHA:
            Rds = Rd * Ad;
            Gds = Gd * Ad;
            Bds = Bd * Ad;
            Ads = Ad * Ad;
            break;
             case GL_ONE_MINUS_DST_ALPHA:
            Rds = Rd * (255 - Ad);
            Gds = Gd * (255 - Ad);
            Bds = Bd * (255 - Ad);
            Ads = Ad * (255 - Ad);
            break;
             default:
            /* this should never happen */
            gl_problem(ctx, "Bad blend dest factor in do_blend");
          }
 
          /* compute blended color */
            red[i]   = MIN2((Rss + Rds) / 255, 255);
            green[i] = MIN2((Gss + Gds) / 255, 255);
            blue[i]  = MIN2((Bss + Bds) / 255, 255);
            alpha[i] = MIN2((Ass + Ads) / 255, 255);
           }
        }
     }else{         /* !EightBitColor */
        GLfloat rmax = ctx->Visual->RedScale;
        GLfloat gmax = ctx->Visual->GreenScale;
        GLfloat bmax = ctx->Visual->BlueScale;
        GLfloat amax = ctx->Visual->AlphaScale;
        GLfloat rscale = 1.0f / rmax;
        GLfloat gscale = 1.0f / gmax;
        GLfloat bscale = 1.0f / bmax;
        GLfloat ascale = 1.0f / amax;
 
        for (i=0;i<n;i++) {
           if (mask[i]) {
          GLint Rs, Gs, Bs, As;  /* Source colors */
          GLint Rd, Gd, Bd, Ad;  /* Dest colors */
          GLfloat sR, sG, sB, sA;  /* Source scaling */
          GLfloat dR, dG, dB, dA;  /* Dest scaling */
          GLfloat r, g, b, a;
 
          /* Source Color */
          Rs = red[i];
          Gs = green[i];
          Bs = blue[i];
          As = alpha[i];
 
          /* Frame buffer color */
          Rd = rdest[i];
          Gd = gdest[i];
          Bd = bdest[i];
          Ad = adest[i];
 
          /* Source scaling */
          switch (ctx->Color.BlendSrc) {
             case GL_ZERO:
            sR = sG = sB = sA = 0.0F;
            break;
             case GL_ONE:
            sR = sG = sB = sA = 1.0F;
            break;
             case GL_DST_COLOR:
            sR = (GLfloat) Rd * rscale;
            sG = (GLfloat) Gd * gscale;
            sB = (GLfloat) Bd * bscale;
            sA = (GLfloat) Ad * ascale;
            break;
             case GL_ONE_MINUS_DST_COLOR:
            sR = 1.0F - (GLfloat) Rd * rscale;
            sG = 1.0F - (GLfloat) Gd * gscale;
            sB = 1.0F - (GLfloat) Bd * bscale;
            sA = 1.0F - (GLfloat) Ad * ascale;
            break;
             case GL_SRC_ALPHA:
            sR = sG = sB = sA = (GLfloat) As * ascale;
            break;
             case GL_ONE_MINUS_SRC_ALPHA:
            sR = sG = sB = sA = (GLfloat) 1.0F - (GLfloat) As * ascale;
            break;
             case GL_DST_ALPHA:
            sR = sG = sB = sA =(GLfloat) Ad * ascale;
            break;
             case GL_ONE_MINUS_DST_ALPHA:
            sR = sG = sB = sA = 1.0F - (GLfloat) Ad * ascale;
            break;
             case GL_SRC_ALPHA_SATURATE:
            if (As < 1.0F - (GLfloat) Ad * ascale) {
               sR = sG = sB = (GLfloat) As * ascale;
            }
            else {
               sR = sG = sB = 1.0F - (GLfloat) Ad * ascale;
            }
            sA = 1.0;
            break;
             default:
            /* this should never happen */
            gl_problem(ctx, "Bad blend source factor in do_blend");
          }
 
          /* Dest scaling */
          switch (ctx->Color.BlendDst) {
             case GL_ZERO:
            dR = dG = dB = dA = 0.0F;
            break;
             case GL_ONE:
            dR = dG = dB = dA = 1.0F;
            break;
             case GL_SRC_COLOR:
            dR = (GLfloat) Rs * rscale;
            dG = (GLfloat) Gs * gscale;
            dB = (GLfloat) Bs * bscale;
            dA = (GLfloat) As * ascale;
            break;
             case GL_ONE_MINUS_SRC_COLOR:
            dR = 1.0F - (GLfloat) Rs * rscale;
            dG = 1.0F - (GLfloat) Gs * gscale;
            dB = 1.0F - (GLfloat) Bs * bscale;
            dA = 1.0F - (GLfloat) As * ascale;
            break;
             case GL_SRC_ALPHA:
            dR = dG = dB = dA = (GLfloat) As * ascale;
            break;
             case GL_ONE_MINUS_SRC_ALPHA:
            dR = dG = dB = dA = (GLfloat) 1.0F - (GLfloat) As * ascale;
            break;
             case GL_DST_ALPHA:
            dR = dG = dB = dA = (GLfloat) Ad * ascale;
            break;
             case GL_ONE_MINUS_DST_ALPHA:
            dR = dG = dB = dA = 1.0F - (GLfloat) Ad * ascale;
            break;
             default:
            /* this should never happen */
            gl_problem(ctx, "Bad blend dest factor in do_blend");
          }
 
#ifdef DEBUG
          assert( sR>= 0.0 && sR<=1.0 );
          assert( sG>= 0.0 && sG<=1.0 );
          assert( sB>= 0.0 && sB<=1.0 );
          assert( sA>= 0.0 && sA<=1.0 );
          assert( dR>= 0.0 && dR<=1.0 );
          assert( dG>= 0.0 && dG<=1.0 );
          assert( dB>= 0.0 && dB<=1.0 );
          assert( dA>= 0.0 && dA<=1.0 );
#endif
 
          /* compute blended color */
          r = Rs * sR + Rd * dR;
          g = Gs * sG + Gd * dG;
          b = Bs * sB + Bd * dB;
          a = As * sA + Ad * dA;
          red[i]   = (GLint) CLAMP( r, 0.0F, rmax );
          green[i] = (GLint) CLAMP( g, 0.0F, gmax );
          blue[i]  = (GLint) CLAMP( b, 0.0F, bmax );
          alpha[i] = (GLint) CLAMP( a, 0.0F, amax );
           }
        }
     }
      }
   }
 
}
 
 
 
 
 
/*
 * Apply the blending operator to a span of pixels.
 * Input:  n - number of pixels in span
 *         x, y - location of leftmost pixel in span in window coords.
 *         mask - boolean mask indicating which pixels to blend.
 * In/Out:  red, green, blue, alpha - pixel values
 */
void gl_blend_span( GLcontext* ctx, GLuint n, GLint x, GLint y,
            GLubyte red[], GLubyte green[],
            GLubyte blue[], GLubyte alpha[],
            GLubyte mask[] )
{
   GLubyte rdest[MAX_WIDTH], gdest[MAX_WIDTH];
   GLubyte bdest[MAX_WIDTH], adest[MAX_WIDTH];
 
   /* Read span of current frame buffer pixels */
   gl_read_color_span( ctx, n, x, y, rdest, gdest, bdest, adest );
 
   do_blend( ctx, n, mask, red, green, blue, alpha, rdest, gdest, bdest, adest );
}
 
 
 
 
 
/*
 * Apply the blending operator to an array of pixels.
 * Input:  n - number of pixels in span
 *         x, y - array of pixel locations
 *         mask - boolean mask indicating which pixels to blend.
 * In/Out:  red, green, blue, alpha - array of pixel values
 */
void gl_blend_pixels( GLcontext* ctx,
                      GLuint n, const GLint x[], const GLint y[],
              GLubyte red[], GLubyte green[],
              GLubyte blue[], GLubyte alpha[],
              GLubyte mask[] )
{
   GLubyte rdest[PB_SIZE], gdest[PB_SIZE], bdest[PB_SIZE], adest[PB_SIZE];
 
   /* Read pixels from current color buffer */
   (*ctx->Driver.ReadColorPixels)( ctx, n, x, y, rdest, gdest, bdest, adest, mask );
   if (ctx->RasterMask & ALPHABUF_BIT) {
      gl_read_alpha_pixels( ctx, n, x, y, adest, mask );
   }
 
   do_blend( ctx, n, mask, red, green, blue, alpha, rdest, gdest, bdest, adest );
}