git.mutantstargoat.com Git - glpixels/blob - glpixels.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <math.h>
   4 #include <assert.h>
   5 #define GL_GLEXT_PROTOTYPES     1
   6 #include <GL/glut.h>
   7
   8 enum {
   9         MODE_POINTS,
  10         MODE_DRAWPIX,
  11         MODE_TEXQUAD,
  12         MODE_TEXTRI,
  13
  14         NUM_MODES
  15 };
  16
  17 int init(void);
  18 void display(void);
  19 void idle(void);
  20 void reshape(int x, int y);
  21 void keyb(unsigned char key, int x, int y);
  22
  23 int win_width, win_height;
  24 int max_xscroll, max_yscroll;
  25
  26 #define IMG_W   1024
  27 #define IMG_H   1024
  28 unsigned int img[IMG_W * IMG_H];
  29 float *varr, *carr;
  30 unsigned int vbo_pos, vbo_col;
  31 int varr_sz, carr_sz;
  32
  33 int mode = MODE_POINTS;
  34
  35 int have_vbo = 1;       /* TODO */
  36
  37
  38 int main(int argc, char **argv)
  39 {
  40         glutInit(&argc, argv);
  41         glutInitWindowSize(800, 600);
  42         glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
  43         glutCreateWindow("GL pixel drawing methods");
  44
  45         glutDisplayFunc(display);
  46         glutReshapeFunc(reshape);
  47         glutKeyboardFunc(keyb);
  48         glutIdleFunc(idle);
  49
  50         if(init() == -1) {
  51                 return 1;
  52         }
  53         glutMainLoop();
  54         return 0;
  55 }
  56
  57
  58 int init(void)
  59 {
  60         int i, j, xor, r, g, b;
  61         unsigned int *ptr;
  62         unsigned int tex;
  63         float *vptr;
  64
  65         ptr = img;
  66         for(i=0; i<IMG_H; i++) {
  67                 for(j=0; j<IMG_W; j++) {
  68                         xor = i ^ j;
  69                         r = (xor >> 1) & 0xff;
  70                         g = xor & 0xff;
  71                         b = (xor << 1) & 0xff;
  72                         *ptr++ = r | (g << 8) | (b << 16);
  73                 }
  74         }
  75
  76         glPixelStorei(GL_UNPACK_ROW_LENGTH, IMG_W);
  77
  78         win_width = glutGet(GLUT_WINDOW_WIDTH);
  79         win_height = glutGet(GLUT_WINDOW_HEIGHT);
  80
  81         glGenTextures(1, &tex);
  82         glBindTexture(GL_TEXTURE_2D, tex);
  83         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
  84         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  85         glTexImage2D(GL_TEXTURE_2D, 1, GL_RGBA, win_width, win_height, 1, GL_RGBA, GL_UNSIGNED_BYTE, 0);
  86
  87         varr_sz = win_width * win_height * sizeof *varr * 2;
  88         if(!(varr = malloc(varr_sz))) {
  89                 fprintf(stderr, "failed to allocate vertex array\n");
  90                 return -1;
  91         }
  92         carr_sz = win_width * win_height * sizeof *carr * 3;
  93         if(!(carr = malloc(carr_sz))) {
  94                 fprintf(stderr, "failed to allocate color array\n");
  95                 return -1;
  96         }
  97
  98         vptr = varr;
  99         for(i=0; i<win_height; i++) {
 100                 for(j=0; j<win_width; j++) {
 101                         vptr[0] = j;
 102                         vptr[1] = i;
 103                         vptr += 2;
 104                 }
 105         }
 106
 107         if(have_vbo) {
 108                 glGenBuffers(1, &vbo_pos);
 109                 glBindBuffer(GL_ARRAY_BUFFER, vbo_pos);
 110                 glBufferData(GL_ARRAY_BUFFER, varr_sz, varr, GL_STATIC_DRAW);
 111
 112                 glGenBuffers(1, &vbo_col);
 113                 glBindBuffer(GL_ARRAY_BUFFER, vbo_col);
 114                 glBufferData(GL_ARRAY_BUFFER, carr_sz, 0, GL_STREAM_DRAW);
 115         }
 116
 117         return 0;
 118 }
 119
 120 void display(void)
 121 {
 122         int i, j;
 123         unsigned int tm = glutGet(GLUT_ELAPSED_TIME);
 124         float t = tm / 256.0f;
 125         int xoffs = (int)((sin(t) * 0.5f + 0.5f) * max_xscroll);
 126         int yoffs = (int)((cos(t) * 0.5f + 0.5f) * max_yscroll);
 127         unsigned int *start = img + yoffs * IMG_W + xoffs;
 128         float *vptr = varr;
 129
 130         switch(mode) {
 131         case MODE_POINTS:
 132                 /* draw with points */
 133                 vptr = carr;
 134                 for(i=0; i<win_height; i++) {
 135                         for(j=0; j<win_width; j++) {
 136                                 int r = start[j] & 0xff;
 137                                 int g = (start[j] >> 8) & 0xff;
 138                                 int b = (start[j] >> 16) & 0xff;
 139                                 vptr[0] = r / 255.0f;
 140                                 vptr[1] = g / 255.0f;
 141                                 vptr[2] = b / 255.0f;
 142                                 vptr += 3;
 143                         }
 144                         start += IMG_W;
 145                 }
 146
 147                 if(have_vbo) {
 148                         glBindBuffer(GL_ARRAY_BUFFER, vbo_pos);
 149                         glVertexPointer(2, GL_FLOAT, 0, 0);
 150                         glBindBuffer(GL_ARRAY_BUFFER, vbo_col);
 151                         glBufferSubData(GL_ARRAY_BUFFER, 0, carr_sz, carr);
 152                         glColorPointer(3, GL_FLOAT, 0, 0);
 153                         glBindBuffer(GL_ARRAY_BUFFER, 0);
 154                 } else {
 155                         glVertexPointer(2, GL_FLOAT, 0, varr);
 156                         glColorPointer(3, GL_FLOAT, 0, carr);
 157                 }
 158
 159                 glEnableClientState(GL_VERTEX_ARRAY);
 160                 glEnableClientState(GL_COLOR_ARRAY);
 161
 162                 glDrawArrays(GL_POINTS, 0, win_width * win_height);
 163
 164                 glDisableClientState(GL_VERTEX_ARRAY);
 165                 glDisableClientState(GL_COLOR_ARRAY);
 166                 break;
 167
 168         case MODE_DRAWPIX:
 169                 /* draw with glDrawPixels */
 170                 glDrawPixels(win_width, win_height, GL_RGBA, GL_UNSIGNED_BYTE, start);
 171                 break;
 172
 173         case MODE_TEXQUAD:
 174                 /* draw with textured quad */
 175                 break;
 176
 177         case MODE_TEXTRI:
 178                 /* draw with textured triangle */
 179                 break;
 180         }
 181
 182         glutSwapBuffers();
 183         assert(glGetError() == GL_NO_ERROR);
 184 }
 185
 186 void idle(void)
 187 {
 188         glutPostRedisplay();
 189 }
 190
 191 void reshape(int x, int y)
 192 {
 193         glViewport(0, 0, x, y);
 194
 195         glMatrixMode(GL_PROJECTION);
 196         glLoadIdentity();
 197         glOrtho(0, x, 0, y, -1, 1);
 198
 199         win_width = x;
 200         win_height = y;
 201         max_xscroll = IMG_W - win_width;
 202         max_yscroll = IMG_H - win_height;
 203         if(max_xscroll < 0) max_xscroll = 0;
 204         if(max_yscroll < 0) max_yscroll = 0;
 205 }
 206
 207 void keyb(unsigned char key, int x, int y)
 208 {
 209         switch(key) {
 210         case 27:
 211                 exit(0);
 212
 213         case ' ':
 214                 mode = (mode + 1) % NUM_MODES;
 215                 break;
 216
 217         default:
 218                 break;
 219         }
 220 }