void write_ppm(int ScreenHeight, int ScreenWidth)
{
	//glPixelStorei(GL_PACK_ALIGNMENT, 1);
	FILE *fp;
	fp = fopen("out.ppm","w");
	int height = ScreenHeight;
	int width = ScreenWidth;
	int max_ccv = 255;

	GLubyte* scrImage = new GLubyte[600*600*3];
	glReadPixels(0,0,ScreenWidth, ScreenHeight, GL_RGB, GL_UNSIGNED_BYTE, scrImage);
	fprintf(fp, "P3 %d %d %d\n", width, height, max_ccv);
	
	for (int j = ScreenWidth-1; j >= 0; j--)
		for (int i=0; i <  ScreenHeight; i++) 
			fprintf(fp, "%d\n%d\n%d\n", scrImage[3*j*width+3*i+0], scrImage[3*j*width+3*i+1], scrImage[3*j*width+3*i+2]); 


	fclose(fp);
	//glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
}