/* ** blendeq.c - Demonstrates the use of the blend_minmax, blend_subtract, ** and blend_logic_op extensions using glBlendEquationEXT. ** ** Over a two-color backround, draw rectangles using twelve blend ** options. The values are read back as UNSIGNED_BYTE and printed ** in hex over each value. These values are useful for logic ** op comparisons when channels are 8 bits deep. */ #include <string.h> #include <stdlib.h> #include <stdio.h> #ifdef _WIN32 #include <windows.h> #endif #define GL_GLEXT_PROTOTYPES #include <GL/glut.h> GLenum doubleBuffer; static int dithering = 0; int use11ops = 0; int supportlogops = 0; static int doPrint = 1; static int deltaY; GLint windW, windH; static void DrawString(const char *string) { int i; for (i = 0; string[i]; i++) glutBitmapCharacter(GLUT_BITMAP_9_BY_15, string[i]); } static void Init(void) { glDisable(GL_DITHER); glShadeModel(GL_FLAT); } static void Reshape(int width, int height) { windW = (GLint)width; windH = (GLint)height; glViewport(0, 0, (GLint)width, (GLint)height); deltaY = windH /16; glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(0, windW, 0, windH); glMatrixMode(GL_MODELVIEW); } static void Key(unsigned char key, int x, int y) { switch (key) { case 27: exit(1); case 'd': dithering = !dithering; break; case 'l': if (supportlogops == 3) use11ops = (!use11ops); if (use11ops) printf("Using GL 1.1 color logic ops.\n"); else printf("Using GL_EXT_blend_logic_op.\n"); break; default: return; } glutPostRedisplay(); } static void PrintColorStrings( void ) { GLubyte ubbuf[3]; int i, xleft, xright; char colorString[18]; xleft = 5 + windW/4; xright = 5 + windW/2; for (i = windH - deltaY + 4; i > 0; i-=deltaY) { glReadPixels(xleft, i+10, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, ubbuf); sprintf(colorString, "(0x%x, 0x%x, 0x%x)", ubbuf[0], ubbuf[1], ubbuf[2]); glRasterPos2f(xleft, i); DrawString(colorString); glReadPixels(xright, i+10, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, ubbuf); sprintf(colorString, "(0x%x, 0x%x, 0x%x)", ubbuf[0], ubbuf[1], ubbuf[2]); glRasterPos2f(xright, i); DrawString(colorString); } } static void Draw(void) { int stringOffset = 5, stringx = 8; int x1, x2, xleft, xright; int i; (dithering) ? glEnable(GL_DITHER) : glDisable(GL_DITHER); glDisable(GL_BLEND); if (supportlogops & 2) glDisable(GL_COLOR_LOGIC_OP); glClearColor(0.5, 0.6, 0.1, 1.0); glClear(GL_COLOR_BUFFER_BIT); /* Draw background */ glColor3f(0.1, 0.1, 1.0); glRectf(0.0, 0.0, windW/2, windH); /* Draw labels */ glColor3f(0.8, 0.8, 0.0); i = windH - deltaY + stringOffset; glRasterPos2f(stringx, i); i -= deltaY; DrawString("SOURCE"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("DEST"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("min"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("max"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("subtract"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("reverse_subtract"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("clear"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("set"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("copy"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("noop"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("and"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("invert"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("or"); glRasterPos2f(stringx, i); i -= deltaY; DrawString("xor"); i = windH - deltaY; x1 = windW/4; x2 = 3 * windW/4; xleft = 5 + windW/4; xright = 5 + windW/2; /* Draw foreground color for comparison */ glColor3f(0.9, 0.2, 0.8); glRectf(x1, i, x2, i+deltaY); /* Leave one rectangle of background color */ /* Begin test cases */ glEnable(GL_BLEND); glBlendFunc(GL_ONE, GL_ONE); i -= 2*deltaY; glBlendEquationEXT(GL_MIN_EXT); glRectf(x1, i, x2, i+deltaY); i -= deltaY; glBlendEquationEXT(GL_MAX_EXT); glRectf(x1, i, x2, i+deltaY); i -= deltaY; glBlendEquationEXT(GL_FUNC_SUBTRACT_EXT); glRectf(x1, i, x2, i+deltaY); i -= deltaY; glBlendEquationEXT(GL_FUNC_REVERSE_SUBTRACT_EXT); glRectf(x1, i, x2, i+deltaY); glBlendFunc(GL_ONE, GL_ZERO); i -= deltaY; if (!use11ops) glBlendEquationEXT(GL_LOGIC_OP); else glEnable(GL_COLOR_LOGIC_OP); glLogicOp(GL_CLEAR); glRectf(x1, i, x2, i+deltaY); i -= deltaY; glLogicOp(GL_SET); glRectf(x1, i, x2, i+deltaY); i -= deltaY; glLogicOp(GL_COPY); glRectf(x1, i, x2, i+deltaY); i -= deltaY; glLogicOp(GL_NOOP); glRectf(x1, i, x2, i+deltaY); i -= deltaY; glLogicOp(GL_AND); glRectf(x1, i, x2, i+deltaY); i -= deltaY; glLogicOp(GL_INVERT); glRectf(x1, i, x2, i+deltaY); i -= deltaY; glLogicOp(GL_OR); glRectf(x1, i, x2, i+deltaY); i -= deltaY; glLogicOp(GL_XOR); glRectf(x1, i, x2, i+deltaY); glRectf(x1, i+10, x2, i+5); if (doPrint) { glDisable(GL_BLEND); if (supportlogops & 2) glDisable(GL_COLOR_LOGIC_OP); glColor3f(1.0, 1.0, 1.0); PrintColorStrings(); } glFlush(); if (doubleBuffer) { glutSwapBuffers(); } } static GLenum Args(int argc, char **argv) { GLint i; doubleBuffer = GL_FALSE; for (i = 1; i < argc; i++) { if (strcmp(argv[i], "-sb") == 0) { doubleBuffer = GL_FALSE; } else if (strcmp(argv[i], "-db") == 0) { doubleBuffer = GL_TRUE; } else { printf("%s (Bad option).\n", argv[i]); return GL_FALSE; } } return GL_TRUE; } int main(int argc, char **argv) { GLenum type; char *s; char *extName1 = "GL_EXT_blend_logic_op"; char *extName2 = "GL_EXT_blend_minmax"; char *extName3 = "GL_EXT_blend_subtract"; char *version; glutInit(&argc, argv); if (Args(argc, argv) == GL_FALSE) { exit(1); } glutInitWindowPosition(0, 0); glutInitWindowSize( 800, 400); type = GLUT_RGB; type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE; glutInitDisplayMode(type); if (glutCreateWindow("Blend Equation") == GL_FALSE) { exit(1); } /* Make sure blend_logic_op extension is there. */ s = (char *) glGetString(GL_EXTENSIONS); version = (char*) glGetString(GL_VERSION); if (!s) exit(1); if (strstr(s,extName1)) { supportlogops = 1; use11ops = 0; printf("blend_logic_op extension available.\n"); } if (strncmp(version,"1.1",3)>=0) { supportlogops += 2; use11ops = 1; printf("1.1 color logic ops available.\n"); } if (supportlogops == 0) { printf("Blend_logic_op extension and GL 1.1 not present.\n"); exit(1); } if (strstr(s,extName2) == 0) { printf("Blend_minmax extension is not present.\n"); exit(1); } if (strstr(s,extName3) == 0) { printf("Blend_subtract extension is not present.\n"); exit(1); } Init(); glutReshapeFunc(Reshape); glutKeyboardFunc(Key); glutDisplayFunc(Draw); glutMainLoop(); return 0; }