progs/demos/copypix.c

   1 /**
   2  * glCopyPixels test
   3  *
   4  * Brian Paul
   5  * 14 Sep 2007
   6  */
   7
   8
   9 #define GL_GLEXT_PROTOTYPES
  10
  11 #include <stdio.h>
  12 #include <stdlib.h>
  13 #include <string.h>
  14 #include <GL/glut.h>
  15
  16 #include "readtex.h"
  17
  18 #define IMAGE_FILE "../images/arch.rgb"
  19
  20 static int ImgWidth, ImgHeight;
  21 static GLenum ImgFormat;
  22 static GLubyte *Image = NULL;
  23
  24 static int WinWidth = 800, WinHeight = 800;
  25 static int Xpos, Ypos;
  26 static int Scissor = 0;
  27 static float Xzoom, Yzoom;
  28 static GLboolean DrawFront = GL_FALSE;
  29 static GLboolean Dither = GL_TRUE;
  30
  31
  32 static void Reset( void )
  33 {
  34    Xpos = Ypos = 20;
  35    Scissor = 0;
  36    Xzoom = Yzoom = 1.0;
  37 }
  38
  39
  40 static void Display( void )
  41 {
  42    const int dx = (WinWidth - ImgWidth) / 2;
  43    const int dy = (WinHeight - ImgHeight) / 2;
  44
  45    if (DrawFront) {
  46       glDrawBuffer(GL_FRONT);
  47       glReadBuffer(GL_FRONT);
  48    }
  49    else {
  50       glDrawBuffer(GL_BACK);
  51       glReadBuffer(GL_BACK);
  52    }
  53
  54    glClear( GL_COLOR_BUFFER_BIT );
  55
  56    /* draw original image */
  57    glWindowPos2iARB(dx, dy);
  58    glDrawPixels(ImgWidth, ImgHeight, ImgFormat, GL_UNSIGNED_BYTE, Image);
  59
  60    if (Scissor)
  61       glEnable(GL_SCISSOR_TEST);
  62
  63    /* draw copy */
  64    glPixelZoom(Xzoom, Yzoom);
  65    glWindowPos2iARB(Xpos, Ypos);
  66    glCopyPixels(dx, dy, ImgWidth, ImgHeight, GL_COLOR);
  67    glPixelZoom(1, 1);
  68
  69    glDisable(GL_SCISSOR_TEST);
  70
  71    if (DrawFront)
  72       glFinish();
  73    else
  74       glutSwapBuffers();
  75 }
  76
  77
  78 static void Reshape( int width, int height )
  79 {
  80    WinWidth = width;
  81    WinHeight = height;
  82
  83    glViewport( 0, 0, width, height );
  84    glMatrixMode( GL_PROJECTION );
  85    glLoadIdentity();
  86    glOrtho( 0.0, width, 0.0, height, 0.0, 2.0 );
  87    glMatrixMode( GL_MODELVIEW );
  88    glLoadIdentity();
  89
  90    glScissor(width/4, height/4, width/2, height/2);
  91 }
  92
  93
  94 static void Key( unsigned char key, int x, int y )
  95 {
  96    (void) x;
  97    (void) y;
  98    switch (key) {
  99       case ' ':
 100          Reset();
 101          break;
 102       case 'd':
 103          Dither = !Dither;
 104          if (Dither)
 105             glEnable(GL_DITHER);
 106          else
 107             glDisable(GL_DITHER);
 108          break;
 109       case 's':
 110          Scissor = !Scissor;
 111          break;
 112       case 'x':
 113          Xzoom -= 0.1;
 114          break;
 115       case 'X':
 116          Xzoom += 0.1;
 117          break;
 118       case 'y':
 119          Yzoom -= 0.1;
 120          break;
 121       case 'Y':
 122          Yzoom += 0.1;
 123          break;
 124       case 'f':
 125          DrawFront = !DrawFront;
 126          printf("glDrawBuffer(%s)\n", DrawFront ? "GL_FRONT" : "GL_BACK");
 127          break;
 128       case 27:
 129          exit(0);
 130          break;
 131    }
 132    glutPostRedisplay();
 133 }
 134
 135
 136 static void SpecialKey( int key, int x, int y )
 137 {
 138    const int step = (glutGetModifiers() & GLUT_ACTIVE_SHIFT) ? 10 : 1;
 139    (void) x;
 140    (void) y;
 141    switch (key) {
 142       case GLUT_KEY_UP:
 143          Ypos += step;
 144          break;
 145       case GLUT_KEY_DOWN:
 146          Ypos -= step;
 147          break;
 148       case GLUT_KEY_LEFT:
 149          Xpos -= step;
 150          break;
 151       case GLUT_KEY_RIGHT:
 152          Xpos += step;
 153          break;
 154    }
 155    glutPostRedisplay();
 156 }
 157
 158
 159 static void Init( GLboolean ciMode, const char *filename )
 160 {
 161    printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
 162    printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
 163
 164    Image = LoadRGBImage( filename, &ImgWidth, &ImgHeight, &ImgFormat );
 165    if (!Image) {
 166       printf("Couldn't read %s\n", filename);
 167       exit(0);
 168    }
 169
 170    if (ciMode) {
 171       /* Convert RGB image to grayscale */
 172       GLubyte *indexImage = (GLubyte *) malloc( ImgWidth * ImgHeight );
 173       GLint i;
 174       for (i=0; i<ImgWidth*ImgHeight; i++) {
 175          int gray = Image[i*3] + Image[i*3+1] + Image[i*3+2];
 176          indexImage[i] = gray / 3;
 177       }
 178       free(Image);
 179       Image = indexImage;
 180       ImgFormat = GL_COLOR_INDEX;
 181
 182       for (i=0;i<255;i++) {
 183          float g = i / 255.0;
 184          glutSetColor(i, g, g, g);
 185       }
 186    }
 187
 188    printf("Loaded %d by %d image\n", ImgWidth, ImgHeight );
 189
 190    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 191    glPixelStorei(GL_UNPACK_ROW_LENGTH, ImgWidth);
 192
 193    Reset();
 194 }
 195
 196
 197 static void Usage(void)
 198 {
 199    printf("Keys:\n");
 200    printf("       SPACE  Reset Parameters\n");
 201    printf("     Up/Down  Move image up/down (SHIFT for large step)\n");
 202    printf("  Left/Right  Move image left/right (SHIFT for large step)\n");
 203    printf("           x  Decrease X-axis PixelZoom\n");
 204    printf("           X  Increase X-axis PixelZoom\n");
 205    printf("           y  Decrease Y-axis PixelZoom\n");
 206    printf("           Y  Increase Y-axis PixelZoom\n");
 207    printf("           s  Toggle GL_SCISSOR_TEST\n");
 208    printf("           f  Toggle front/back buffer drawing\n");
 209    printf("         ESC  Exit\n");
 210 }
 211
 212
 213 int main( int argc, char *argv[] )
 214 {
 215    GLboolean ciMode = GL_FALSE;
 216    const char *filename = IMAGE_FILE;
 217    int i = 1;
 218
 219    if (argc > i && strcmp(argv[i], "-ci")==0) {
 220       ciMode = GL_TRUE;
 221       i++;
 222    }
 223    if (argc > i) {
 224       filename = argv[i];
 225    }
 226
 227    glutInit( &argc, argv );
 228    glutInitWindowPosition( 0, 0 );
 229    glutInitWindowSize( WinWidth, WinHeight );
 230
 231    if (ciMode)
 232       glutInitDisplayMode( GLUT_INDEX | GLUT_DOUBLE );
 233    else
 234       glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE);
 235
 236    glutCreateWindow(argv[0]);
 237
 238    Init(ciMode, filename);
 239    Usage();
 240
 241    glutReshapeFunc( Reshape );
 242    glutKeyboardFunc( Key );
 243    glutSpecialFunc( SpecialKey );
 244    glutDisplayFunc( Display );
 245
 246    glutMainLoop();
 247    return 0;
 248 }