src/mesa/swrast/s_alpha.c

   1 /* $Id: s_alpha.c,v 1.1 2000/10/31 18:00:04 keithw Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  3.3
   6  *
   7  * Copyright (C) 1999-2000  Brian Paul   All Rights Reserved.
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a
  10  * copy of this software and associated documentation files (the "Software"),
  11  * to deal in the Software without restriction, including without limitation
  12  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  13  * and/or sell copies of the Software, and to permit persons to whom the
  14  * Software is furnished to do so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included
  17  * in all copies or substantial portions of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  20  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  22  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  23  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  24  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  */
  26
  27
  28 #include "glheader.h"
  29 #include "context.h"
  30 #include "colormac.h"
  31 #include "macros.h"
  32 #include "mmath.h"
  33
  34 #include "s_alpha.h"
  35
  36
  37
  38
  39
  40 /*
  41  * Apply the alpha test to a span of pixels.
  42  * In:  rgba - array of pixels
  43  * In/Out:  mask - current pixel mask.  Pixels which fail the alpha test
  44  *                 will set the corresponding mask flag to 0.
  45  * Return:  0 = all pixels in the span failed the alpha test.
  46  *          1 = one or more pixels passed the alpha test.
  47  */
  48 GLint
  49 _mesa_alpha_test( const GLcontext *ctx,
  50                   GLuint n, CONST GLchan rgba[][4], GLubyte mask[] )
  51 {
  52    GLuint i;
  53    GLchan ref = ctx->Color.AlphaRef;
  54
  55    /* switch cases ordered from most frequent to less frequent */
  56    switch (ctx->Color.AlphaFunc) {
  57       case GL_LESS:
  58          for (i=0;i<n;i++) {
  59             mask[i] &= (rgba[i][ACOMP] < ref);
  60          }
  61          return 1;
  62       case GL_LEQUAL:
  63          for (i=0;i<n;i++) {
  64             mask[i] &= (rgba[i][ACOMP] <= ref);
  65          }
  66          return 1;
  67       case GL_GEQUAL:
  68          for (i=0;i<n;i++) {
  69             mask[i] &= (rgba[i][ACOMP] >= ref);
  70          }
  71          return 1;
  72       case GL_GREATER:
  73          for (i=0;i<n;i++) {
  74             mask[i] &= (rgba[i][ACOMP] > ref);
  75          }
  76          return 1;
  77       case GL_NOTEQUAL:
  78          for (i=0;i<n;i++) {
  79             mask[i] &= (rgba[i][ACOMP] != ref);
  80          }
  81          return 1;
  82       case GL_EQUAL:
  83          for (i=0;i<n;i++) {
  84             mask[i] &= (rgba[i][ACOMP] == ref);
  85          }
  86          return 1;
  87       case GL_ALWAYS:
  88          /* do nothing */
  89          return 1;
  90       case GL_NEVER:
  91          /* caller should check for zero! */
  92          return 0;
  93       default:
  94          gl_problem( ctx, "Invalid alpha test in gl_alpha_test" );
  95          return 0;
  96    }
  97    /* Never get here */
  98    /*return 1;*/
  99 }