/*
 * Demo of off-screen Mesa rendering with 32-bit float color channels.
 * This requires the libOSMesa32.so library.
 *
 * Compile with something like this:
 *
 * gcc osdemo32.c -I../include -L../lib -lOSMesa32 -lm -o osdemo32
 */


#include <stdio.h>
#include <stdlib.h>
#include "GL/osmesa.h"
#include "GL/glut.h"


#define SAVE_TARGA


#define WIDTH 400
#define HEIGHT 400



static void render_image( void )
{
   GLfloat light_ambient[] = { 0.0, 0.0, 0.0, 1.0 };
   GLfloat light_diffuse[] = { 1.0, 1.0, 1.0, 1.0 };
   GLfloat light_specular[] = { 1.0, 1.0, 1.0, 1.0 };
   GLfloat light_position[] = { 1.0, 1.0, 1.0, 0.0 };
   GLfloat red_mat[]   = { 1.0, 0.2, 0.2, 1.0 };
   GLfloat green_mat[] = { 0.2, 1.0, 0.2, 0.5 };
   GLfloat blue_mat[]  = { 0.2, 0.2, 1.0, 1.0 };
   GLfloat white_mat[]  = { 1.0, 1.0, 1.0, 1.0 };
   GLfloat purple_mat[] = { 1.0, 0.2, 1.0, 1.0 };
   GLUquadricObj *qobj = gluNewQuadric();

   glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
   glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
   glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);
   glLightfv(GL_LIGHT0, GL_POSITION, light_position);
    
   glEnable(GL_LIGHTING);
   glEnable(GL_LIGHT0);
   glEnable(GL_DEPTH_TEST);

   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(-2.5, 2.5, -2.5, 2.5, -10.0, 10.0);
   glMatrixMode(GL_MODELVIEW);

   glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

   glPushMatrix();
   glRotatef(20.0, 1.0, 0.0, 0.0);

#if 0
   glPushMatrix();
   glTranslatef(-0.75, 0.5, 0.0); 
   glRotatef(90.0, 1.0, 0.0, 0.0);
   glMaterialfv( GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, red_mat );
   glutSolidTorus(0.275, 0.85, 20, 20);
   glPopMatrix();
#endif

   /* red square */
   glPushMatrix();
   glTranslatef(0.0, -0.5, 0.0); 
   glRotatef(90, 1, 0.5, 0);
   glScalef(3, 3, 3);
   glDisable(GL_LIGHTING);
   glColor4f(1, 0, 0, 0.5);
   glBegin(GL_POLYGON);
   glVertex2f(-1, -1);
   glVertex2f( 1, -1);
   glVertex2f( 1,  1);
   glVertex2f(-1,  1);
   glEnd();
   glEnable(GL_LIGHTING);
   glPopMatrix();

#if 0
   /* green square */
   glPushMatrix();
   glTranslatef(0.0, 0.5, 0.1); 
   glDisable(GL_LIGHTING);
   glColor3f(0, 1, 0);
   glBegin(GL_POLYGON);
   glVertex2f(-1, -1);
   glVertex2f( 1, -1);
   glVertex2f( 1,  1);
   glVertex2f(-1,  1);
   glEnd();
   glEnable(GL_LIGHTING);
   glPopMatrix();

   /* blue square */
   glPushMatrix();
   glTranslatef(0.75, 0.5, 0.3); 
   glDisable(GL_LIGHTING);
   glColor3f(0, 0, 0.5);
   glBegin(GL_POLYGON);
   glVertex2f(-1, -1);
   glVertex2f( 1, -1);
   glVertex2f( 1,  1);
   glVertex2f(-1,  1);
   glEnd();
   glEnable(GL_LIGHTING);
   glPopMatrix();
#endif
   glPushMatrix();
   glTranslatef(-0.75, -0.5, 0.0); 
   glRotatef(270.0, 1.0, 0.0, 0.0);
   glMaterialfv( GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, green_mat );
   glColor4f(0,1,0,0.5);
   glEnable(GL_BLEND);
   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
   gluCylinder(qobj, 1.0, 0.0, 2.0, 16, 1);
   glDisable(GL_BLEND);
   glPopMatrix();

   glPushMatrix();
   glTranslatef(0.75, 1.0, 1.0); 
   glMaterialfv( GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, blue_mat );
   gluSphere(qobj, 1.0, 20, 20);
   glPopMatrix();

   glPopMatrix();

   gluDeleteQuadric(qobj);

   {
      GLint r, g, b, a;
      glGetIntegerv(GL_RED_BITS, &r);
      glGetIntegerv(GL_GREEN_BITS, &g);
      glGetIntegerv(GL_BLUE_BITS, &b);
      glGetIntegerv(GL_ALPHA_BITS, &a);
      printf("channel sizes: %d %d %d %d\n", r, g, b, a);
   }
}



static void
write_targa(const char *filename, const GLfloat *buffer, int width, int height)
{
   FILE *f = fopen( filename, "w" );
   if (f) {
      int i, x, y;
      const GLfloat *ptr = buffer;
      printf ("osdemo, writing tga file \n");
      fputc (0x00, f);	/* ID Length, 0 => No ID	*/
      fputc (0x00, f);	/* Color Map Type, 0 => No color map included	*/
      fputc (0x02, f);	/* Image Type, 2 => Uncompressed, True-color Image */
      fputc (0x00, f);	/* Next five bytes are about the color map entries */
      fputc (0x00, f);	/* 2 bytes Index, 2 bytes length, 1 byte size */
      fputc (0x00, f);
      fputc (0x00, f);
      fputc (0x00, f);
      fputc (0x00, f);	/* X-origin of Image	*/
      fputc (0x00, f);
      fputc (0x00, f);	/* Y-origin of Image	*/
      fputc (0x00, f);
      fputc (WIDTH & 0xff, f);      /* Image Width	*/
      fputc ((WIDTH>>8) & 0xff, f);
      fputc (HEIGHT & 0xff, f);     /* Image Height	*/
      fputc ((HEIGHT>>8) & 0xff, f);
      fputc (0x18, f);		/* Pixel Depth, 0x18 => 24 Bits	*/
      fputc (0x20, f);		/* Image Descriptor	*/
      fclose(f);
      f = fopen( filename, "ab" );  /* reopen in binary append mode */
      for (y=height-1; y>=0; y--) {
         for (x=0; x<width; x++) {
            int r, g, b;
            i = (y*width + x) * 4;
            r = (int) (ptr[i+0] * 255.0);
            g = (int) (ptr[i+1] * 255.0);
            b = (int) (ptr[i+2] * 255.0);
            if (r > 255) r = 255;
            if (g > 255) g = 255;
            if (b > 255) b = 255;
            fputc(b, f); /* write blue */
            fputc(g, f); /* write green */
            fputc(r, f); /* write red */
         }
      }
   }
}


static void
write_ppm(const char *filename, const GLubyte *buffer, int width, int height)
{
   const int binary = 0;
   FILE *f = fopen( filename, "w" );
   if (f) {
      int i, x, y;
      const GLubyte *ptr = buffer;
      if (binary) {
         fprintf(f,"P6\n");
         fprintf(f,"# ppm-file created by osdemo.c\n");
         fprintf(f,"%i %i\n", width,height);
         fprintf(f,"255\n");
         fclose(f);
         f = fopen( filename, "ab" );  /* reopen in binary append mode */
         for (y=height-1; y>=0; y--) {
            for (x=0; x<width; x++) {
               i = (y*width + x) * 4;
               fputc(ptr[i], f);   /* write red */
               fputc(ptr[i+1], f); /* write green */
               fputc(ptr[i+2], f); /* write blue */
            }
         }
      }
      else {
         /*ASCII*/
         int counter = 0;
         fprintf(f,"P3\n");
         fprintf(f,"# ascii ppm file created by osdemo.c\n");
         fprintf(f,"%i %i\n", width, height);
         fprintf(f,"255\n");
         for (y=height-1; y>=0; y--) {
            for (x=0; x<width; x++) {
               i = (y*width + x) * 4;
               fprintf(f, " %3d %3d %3d", ptr[i], ptr[i+1], ptr[i+2]);
               counter++;
               if (counter % 5 == 0)
                  fprintf(f, "\n");
            }
         }
      }
      fclose(f);
   }
}



int main( int argc, char *argv[] )
{
   void *buffer;

   /* Create an RGBA-mode context */
#if OSMESA_MAJOR_VERSION * 100 + OSMESA_MINOR_VERSION >= 305
   /* specify Z, stencil, accum sizes */
   OSMesaContext ctx = OSMesaCreateContextExt( GL_RGBA, 16, 0, 0, NULL );
#else
   OSMesaContext ctx = OSMesaCreateContext( GL_RGBA, NULL );
#endif
   if (!ctx) {
      printf("OSMesaCreateContext failed!\n");
      return 0;
   }

   /* Allocate the image buffer */
   buffer = malloc( WIDTH * HEIGHT * 4 * sizeof(GLfloat));
   if (!buffer) {
      printf("Alloc image buffer failed!\n");
      return 0;
   }

   /* Bind the buffer to the context and make it current */
   if (!OSMesaMakeCurrent( ctx, buffer, GL_FLOAT, WIDTH, HEIGHT )) {
      printf("OSMesaMakeCurrent failed!\n");
      return 0;
   }
     
   render_image();

   if (argc>1) {
#ifdef SAVE_TARGA
      write_targa(argv[1], buffer, WIDTH, HEIGHT);
#else
      write_ppm(argv[1], buffer, WIDTH, HEIGHT);
#endif
   }
   else {
      printf("Specify a filename if you want to make an image file\n");
   }

   printf("all done\n");

   /* free the image buffer */
   free( buffer );

   /* destroy the context */
   OSMesaDestroyContext( ctx );

   return 0;
}
