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alpha.c
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1 /* $Id: alpha.c,v 1.5 1997/07/24 01:24:28 brianp Exp $ */
2 
3 /*
4  * Mesa 3-D graphics library
5  * Version: 2.4
6  * Copyright (C) 1995-1997 Brian Paul
7  *
8  * This library is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Library General Public
10  * License as published by the Free Software Foundation; either
11  * version 2 of the License, or (at your option) any later version.
12  *
13  * This library is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Library General Public License for more details.
17  *
18  * You should have received a copy of the GNU Library General Public
19  * License along with this library; if not, write to the Free
20  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21  */
22 
23 
24 /*
25  * $Log: alpha.c,v $
26  * Revision 1.5 1997/07/24 01:24:28 brianp
27  * changed precompiled header symbol from PCH to PC_HEADER
28  *
29  * Revision 1.4 1997/05/28 03:23:09 brianp
30  * added precompiled header (PCH) support
31  *
32  * Revision 1.3 1997/03/13 03:07:53 brianp
33  * optimized gl_alpha_test() by removing conditional from inside loops
34  *
35  * Revision 1.2 1996/09/15 14:15:54 brianp
36  * now use GLframebuffer and GLvisual
37  *
38  * Revision 1.1 1996/09/13 01:38:16 brianp
39  * Initial revision
40  *
41  */
42 
43 
44 #ifdef PC_HEADER
45 #include "all.h"
46 #else
47 #include "alpha.h"
48 #include "context.h"
49 #include "types.h"
50 #include "dlist.h"
51 #include "macros.h"
52 #endif
53 
54 
55 
57 {
58  if (INSIDE_BEGIN_END(ctx)) {
59  gl_error( ctx, GL_INVALID_OPERATION, "glAlphaFunc" );
60  return;
61  }
62  switch (func) {
63  case GL_NEVER:
64  case GL_LESS:
65  case GL_EQUAL:
66  case GL_LEQUAL:
67  case GL_GREATER:
68  case GL_NOTEQUAL:
69  case GL_GEQUAL:
70  case GL_ALWAYS:
71  ctx->Color.AlphaFunc = func;
72  ctx->Color.AlphaRef = CLAMP( ref, 0.0F, 1.0F );
73  ctx->Color.AlphaRefUbyte = (GLubyte) (ctx->Color.AlphaRef
74  * ctx->Visual->AlphaScale);
75  break;
76  default:
77  gl_error( ctx, GL_INVALID_ENUM, "glAlphaFunc(func)" );
78  break;
79  }
80 }
81 
82 
83 
84 
85 /*
86  * Apply the alpha test to a span of pixels.
87  * In/Out: mask - current pixel mask. Pixels which fail the alpha test
88  * will set the corresponding mask flag to 0.
89  * Return: 0 = all pixels in the span failed the alpha test.
90  * 1 = one or more pixels passed the alpha test.
91  */
93  GLuint n, const GLubyte alpha[], GLubyte mask[] )
94 {
95  GLuint i;
96  GLubyte ref = ctx->Color.AlphaRefUbyte;
97 
98  /* switch cases ordered from most frequent to less frequent */
99  switch (ctx->Color.AlphaFunc) {
100  case GL_LESS:
101  for (i=0;i<n;i++) {
102  mask[i] &= (alpha[i] < ref);
103  }
104  return 1;
105  case GL_LEQUAL:
106  for (i=0;i<n;i++) {
107  mask[i] &= (alpha[i] <= ref);
108  }
109  return 1;
110  case GL_GEQUAL:
111  for (i=0;i<n;i++) {
112  mask[i] &= (alpha[i] >= ref);
113  }
114  return 1;
115  case GL_GREATER:
116  for (i=0;i<n;i++) {
117  mask[i] &= (alpha[i] > ref);
118  }
119  return 1;
120  case GL_NOTEQUAL:
121  for (i=0;i<n;i++) {
122  mask[i] &= (alpha[i] != ref);
123  }
124  return 1;
125  case GL_EQUAL:
126  for (i=0;i<n;i++) {
127  mask[i] &= (alpha[i] == ref);
128  }
129  return 1;
130  case GL_ALWAYS:
131  /* do nothing */
132  return 1;
133  case GL_NEVER:
134  /* caller should check for zero! */
135  return 0;
136  default:
137  gl_problem( ctx, "Invalid alpha test in gl_alpha_test" );
138  return 0;
139  }
140  /* Never get here */
141  return 1;
142 }
GLint gl_alpha_test(GLcontext *ctx, GLuint n, const GLubyte alpha[], GLubyte mask[])
Definition: alpha.c:92
GLenum func
Definition: glext.h:6028
#define GL_LEQUAL
Definition: gl.h:296
void gl_AlphaFunc(GLcontext *ctx, GLenum func, GLclampf ref)
Definition: alpha.c:56
unsigned char GLubyte
Definition: gl.h:157
GLdouble n
Definition: glext.h:7729
#define GL_GEQUAL
Definition: gl.h:299
GLvisual * Visual
Definition: types.h:1272
Definition: send.c:47
#define GL_LESS
Definition: gl.h:294
#define INSIDE_BEGIN_END(CTX)
Definition: macros.h:135
GLsizei GLenum const GLvoid GLsizei GLenum GLbyte GLbyte GLbyte GLdouble GLdouble GLdouble GLfloat GLfloat GLfloat GLint GLint GLint GLshort GLshort GLshort GLubyte GLubyte GLubyte GLuint GLuint GLuint GLushort GLushort GLushort GLbyte GLbyte GLbyte GLbyte GLdouble GLdouble GLdouble GLdouble GLfloat GLfloat GLfloat GLfloat GLint GLint GLint GLint GLshort GLshort GLshort GLshort GLubyte GLubyte GLubyte GLubyte GLuint GLuint GLuint GLuint GLushort GLushort GLushort GLushort GLboolean const GLdouble const GLfloat const GLint const GLshort const GLbyte const GLdouble const GLfloat const GLint const GLshort const GLdouble const GLfloat const GLint const GLshort const GLdouble const GLfloat const GLint const GLshort const GLdouble const GLfloat const GLint const GLshort const GLdouble const GLdouble const GLfloat const GLfloat const GLint const GLint const GLshort const GLshort const GLdouble const GLfloat const GLint const GLshort const GLdouble const GLfloat const GLint const GLshort const GLdouble const GLfloat const GLint const GLshort const GLdouble const GLfloat const GLint const GLshort const GLdouble const GLfloat const GLint const GLshort const GLdouble const GLfloat const GLint const GLshort const GLdouble const GLfloat const GLint const GLshort GLenum GLenum GLenum GLfloat GLenum GLint GLenum GLenum GLenum GLfloat GLenum GLenum GLint GLenum GLfloat GLenum GLint GLint GLushort GLenum GLenum GLfloat GLenum GLenum GLint GLfloat const GLubyte GLenum GLenum GLenum const GLfloat GLenum GLenum const GLint GLenum GLint GLint GLsizei GLsizei GLint GLenum GLenum const GLvoid GLenum GLenum const GLfloat GLenum GLenum const GLint GLenum GLenum const GLdouble GLenum GLenum const GLfloat GLenum GLenum const GLint GLsizei GLuint GLfloat GLuint GLbitfield GLfloat GLint GLuint GLboolean GLenum GLfloat GLenum GLbitfield GLenum GLfloat GLfloat GLint GLint const GLfloat GLenum GLfloat GLfloat GLint GLint GLfloat GLfloat GLint GLint const GLfloat GLint GLfloat GLfloat GLint GLfloat GLfloat GLint GLfloat GLfloat const GLdouble const GLfloat const GLdouble const GLfloat GLint i
Definition: glfuncs.h:248
GLenum GLint GLuint mask
Definition: glext.h:6028
#define CLAMP(f, min, max)
Definition: tif_color.c:177
GLenum GLint ref
Definition: glext.h:6028
GLfloat AlphaScale
Definition: types.h:1143
struct gl_colorbuffer_attrib Color
Definition: types.h:1319
#define GL_NOTEQUAL
Definition: gl.h:298
#define GL_ALWAYS
Definition: gl.h:300
#define GL_GREATER
Definition: gl.h:297
#define GL_NEVER
Definition: gl.h:293
#define GL_INVALID_OPERATION
Definition: gl.h:696
unsigned int GLenum
Definition: gl.h:150
void gl_problem(const GLcontext *ctx, const char *s)
Definition: context.c:1394
void gl_error(GLcontext *ctx, GLenum error, const char *s)
Definition: context.c:1421
unsigned int GLuint
Definition: gl.h:159
#define GL_INVALID_ENUM
Definition: gl.h:694
float GLclampf
Definition: gl.h:162
GLclampf GLclampf GLclampf alpha
Definition: gl.h:1740
int GLint
Definition: gl.h:156
#define F(x, y, z)
Definition: md5.c:51
#define GL_EQUAL
Definition: gl.h:295