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