progs/samples/blendeq.c

   1 /*
   2 ** blendeq.c - Demonstrates the use of the blend_minmax, blend_subtract,
   3 **    and blend_logic_op extensions using glBlendEquationEXT.
   4 **
   5 **    Over a two-color backround, draw rectangles using twelve blend
   6 **    options.  The values are read back as UNSIGNED_BYTE and printed
   7 **    in hex over each value.  These values are useful for logic
   8 **    op comparisons when channels are 8 bits deep.
   9 */
  10
  11 #include <string.h>
  12 #include <stdlib.h>
  13 #include <stdio.h>
  14 #ifdef _WIN32
  15 #include <windows.h>
  16 #endif
  17 #define GL_GLEXT_PROTOTYPES
  18 #include <GL/glut.h>
  19
  20 GLenum doubleBuffer;
  21 static int dithering = 0;
  22 int use11ops = 0;
  23 int supportlogops = 0;
  24 static int doPrint = 1;
  25 static int deltaY;
  26 GLint windW, windH;
  27
  28 static void DrawString(const char *string)
  29 {
  30     int i;
  31
  32     for (i = 0; string[i]; i++)
  33         glutBitmapCharacter(GLUT_BITMAP_9_BY_15, string[i]);
  34 }
  35
  36 static void Init(void)
  37 {
  38
  39     glDisable(GL_DITHER);
  40     glShadeModel(GL_FLAT);
  41 }
  42
  43 static void Reshape(int width, int height)
  44 {
  45
  46     windW = (GLint)width;
  47     windH = (GLint)height;
  48
  49     glViewport(0, 0, (GLint)width, (GLint)height);
  50     deltaY = windH /16;
  51
  52     glMatrixMode(GL_PROJECTION);
  53     glLoadIdentity();
  54     gluOrtho2D(0, windW, 0, windH);
  55     glMatrixMode(GL_MODELVIEW);
  56 }
  57
  58 static void Key(unsigned char key, int x, int y)
  59 {
  60
  61     switch (key) {
  62       case 27:
  63         exit(1);
  64       case 'd':
  65         dithering = !dithering;
  66         break;
  67       case 'l':
  68         if (supportlogops == 3)
  69            use11ops = (!use11ops);
  70         if (use11ops)
  71            printf("Using GL 1.1 color logic ops.\n");
  72         else printf("Using GL_EXT_blend_logic_op.\n");
  73         break;
  74       default:
  75         return;
  76     }
  77
  78     glutPostRedisplay();
  79 }
  80
  81 static void PrintColorStrings( void )
  82 {
  83     GLubyte ubbuf[3];
  84     int i, xleft, xright;
  85     char colorString[18];
  86
  87     xleft = 5 + windW/4;
  88     xright = 5 + windW/2;
  89
  90     for (i = windH - deltaY + 4; i > 0; i-=deltaY) {
  91         glReadPixels(xleft, i+10, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, ubbuf);
  92         sprintf(colorString, "(0x%x, 0x%x, 0x%x)",
  93                 ubbuf[0], ubbuf[1], ubbuf[2]);
  94         glRasterPos2f(xleft, i);
  95         DrawString(colorString);
  96         glReadPixels(xright, i+10, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, ubbuf);
  97         sprintf(colorString, "(0x%x, 0x%x, 0x%x)",
  98                 ubbuf[0], ubbuf[1], ubbuf[2]);
  99         glRasterPos2f(xright, i);
 100         DrawString(colorString);
 101     }
 102 }
 103
 104 static void Draw(void)
 105 {
 106     int stringOffset = 5, stringx = 8;
 107     int x1, x2, xleft, xright;
 108     int i;
 109
 110     (dithering) ? glEnable(GL_DITHER) : glDisable(GL_DITHER);
 111     glDisable(GL_BLEND);
 112     if (supportlogops & 2)
 113        glDisable(GL_COLOR_LOGIC_OP);
 114
 115     glClearColor(0.5, 0.6, 0.1, 1.0);
 116     glClear(GL_COLOR_BUFFER_BIT);
 117
 118     /* Draw background */
 119     glColor3f(0.1, 0.1, 1.0);
 120     glRectf(0.0, 0.0, windW/2, windH);
 121
 122     /* Draw labels */
 123     glColor3f(0.8, 0.8, 0.0);
 124     i = windH - deltaY + stringOffset;
 125     glRasterPos2f(stringx, i); i -= deltaY;
 126     DrawString("SOURCE");
 127     glRasterPos2f(stringx, i); i -= deltaY;
 128     DrawString("DEST");
 129     glRasterPos2f(stringx, i); i -= deltaY;
 130     DrawString("min");
 131     glRasterPos2f(stringx, i); i -= deltaY;
 132     DrawString("max");
 133     glRasterPos2f(stringx, i); i -= deltaY;
 134     DrawString("subtract");
 135     glRasterPos2f(stringx, i); i -= deltaY;
 136     DrawString("reverse_subtract");
 137     glRasterPos2f(stringx, i); i -= deltaY;
 138     DrawString("clear");
 139     glRasterPos2f(stringx, i); i -= deltaY;
 140     DrawString("set");
 141     glRasterPos2f(stringx, i); i -= deltaY;
 142     DrawString("copy");
 143     glRasterPos2f(stringx, i); i -= deltaY;
 144     DrawString("noop");
 145     glRasterPos2f(stringx, i); i -= deltaY;
 146     DrawString("and");
 147     glRasterPos2f(stringx, i); i -= deltaY;
 148     DrawString("invert");
 149     glRasterPos2f(stringx, i); i -= deltaY;
 150     DrawString("or");
 151     glRasterPos2f(stringx, i); i -= deltaY;
 152     DrawString("xor");
 153
 154
 155     i = windH - deltaY;
 156     x1 = windW/4;
 157     x2 = 3 * windW/4;
 158     xleft = 5 + windW/4;
 159     xright = 5 + windW/2;
 160
 161     /* Draw foreground color for comparison */
 162     glColor3f(0.9, 0.2, 0.8);
 163     glRectf(x1, i, x2, i+deltaY);
 164
 165     /* Leave one rectangle of background color */
 166
 167     /* Begin test cases */
 168     glEnable(GL_BLEND);
 169     glBlendFunc(GL_ONE, GL_ONE);
 170
 171     i -= 2*deltaY;
 172     glBlendEquationEXT(GL_MIN_EXT);
 173     glRectf(x1, i, x2, i+deltaY);
 174
 175     i -= deltaY;
 176     glBlendEquationEXT(GL_MAX_EXT);
 177     glRectf(x1, i, x2, i+deltaY);
 178
 179     i -= deltaY;
 180     glBlendEquationEXT(GL_FUNC_SUBTRACT_EXT);
 181     glRectf(x1, i, x2, i+deltaY);
 182
 183     i -= deltaY;
 184     glBlendEquationEXT(GL_FUNC_REVERSE_SUBTRACT_EXT);
 185     glRectf(x1, i, x2, i+deltaY);
 186
 187     glBlendFunc(GL_ONE, GL_ZERO);
 188     i -= deltaY;
 189     if (!use11ops)
 190        glBlendEquationEXT(GL_LOGIC_OP);
 191     else
 192        glEnable(GL_COLOR_LOGIC_OP);
 193     glLogicOp(GL_CLEAR);
 194     glRectf(x1, i, x2, i+deltaY);
 195
 196     i -= deltaY;
 197     glLogicOp(GL_SET);
 198     glRectf(x1, i, x2, i+deltaY);
 199
 200     i -= deltaY;
 201     glLogicOp(GL_COPY);
 202     glRectf(x1, i, x2, i+deltaY);
 203
 204     i -= deltaY;
 205     glLogicOp(GL_NOOP);
 206     glRectf(x1, i, x2, i+deltaY);
 207
 208     i -= deltaY;
 209     glLogicOp(GL_AND);
 210     glRectf(x1, i, x2, i+deltaY);
 211
 212     i -= deltaY;
 213     glLogicOp(GL_INVERT);
 214     glRectf(x1, i, x2, i+deltaY);
 215
 216     i -= deltaY;
 217     glLogicOp(GL_OR);
 218     glRectf(x1, i, x2, i+deltaY);
 219
 220     i -= deltaY;
 221     glLogicOp(GL_XOR);
 222     glRectf(x1, i, x2, i+deltaY);
 223     glRectf(x1, i+10, x2, i+5);
 224
 225   if (doPrint) {
 226       glDisable(GL_BLEND);
 227       if (supportlogops & 2)
 228           glDisable(GL_COLOR_LOGIC_OP);
 229       glColor3f(1.0, 1.0, 1.0);
 230       PrintColorStrings();
 231   }
 232   glFlush();
 233
 234     if (doubleBuffer) {
 235        glutSwapBuffers();
 236     }
 237
 238 }
 239
 240 static GLenum Args(int argc, char **argv)
 241 {
 242     GLint i;
 243
 244     doubleBuffer = GL_FALSE;
 245
 246     for (i = 1; i < argc; i++) {
 247         if (strcmp(argv[i], "-sb") == 0) {
 248             doubleBuffer = GL_FALSE;
 249         } else if (strcmp(argv[i], "-db") == 0) {
 250             doubleBuffer = GL_TRUE;
 251         } else {
 252             printf("%s (Bad option).\n", argv[i]);
 253             return GL_FALSE;
 254         }
 255     }
 256     return GL_TRUE;
 257 }
 258
 259 int main(int argc, char **argv)
 260 {
 261     GLenum type;
 262     char *s;
 263     char *extName1 = "GL_EXT_blend_logic_op";
 264     char *extName2 = "GL_EXT_blend_minmax";
 265     char *extName3 = "GL_EXT_blend_subtract";
 266     char *version;
 267
 268     glutInit(&argc, argv);
 269
 270     if (Args(argc, argv) == GL_FALSE) {
 271         exit(1);
 272     }
 273
 274     glutInitWindowPosition(0, 0); glutInitWindowSize( 800, 400);
 275
 276     type = GLUT_RGB;
 277     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 278     glutInitDisplayMode(type);
 279
 280     if (glutCreateWindow("Blend Equation") == GL_FALSE) {
 281         exit(1);
 282     }
 283
 284     /* Make sure blend_logic_op extension is there. */
 285     s = (char *) glGetString(GL_EXTENSIONS);
 286     version = (char*) glGetString(GL_VERSION);
 287     if (!s)
 288         exit(1);
 289     if (strstr(s,extName1)) {
 290         supportlogops = 1;
 291         use11ops = 0;
 292         printf("blend_logic_op extension available.\n");
 293     }
 294     if (strncmp(version,"1.1",3)>=0) {
 295         supportlogops += 2;
 296         use11ops = 1;
 297         printf("1.1 color logic ops available.\n");
 298     }
 299     if (supportlogops == 0) {
 300         printf("Blend_logic_op extension and GL 1.1 not present.\n");
 301         exit(1);
 302     }
 303     if (strstr(s,extName2) == 0) {
 304         printf("Blend_minmax extension is not present.\n");
 305         exit(1);
 306     }
 307     if (strstr(s,extName3) == 0) {
 308         printf("Blend_subtract extension is not present.\n");
 309         exit(1);
 310     }
 311
 312     Init();
 313
 314     glutReshapeFunc(Reshape);
 315     glutKeyboardFunc(Key);
 316     glutDisplayFunc(Draw);
 317     glutMainLoop();
 318     return 0;
 319 }