OpenGl texturing ........ ppm background - c++

Question

i am using a ppm loader to set image as a background , but there is a problem
in colors here is the code and the image that i am use .
http://imgur.com/w732d6j
http://imgur.com/mJr26Ik
here is the code .....
texture.h
#ifndef TEXTURE_H
#define TEXTURE_H
struct Image
{
unsigned char* pixels;
int width;
int height;
int numChannels;
};
class Texture
{
public:
Texture ();
void Prepare (int texN);
void ReadPPMImage (char *fn);
GLuint texName;
Image image;
};
#endif
texture.cpp
#include <fstream>
#include <glut.h>
#pragma warning (disable : 4996)
#include "Texture.h"
Texture::Texture ()
{
}
void Texture::Prepare (int texN)
{
texName = texN;
glPixelStorei (GL_UNPACK_ALIGNMENT, 1);
glBindTexture (GL_TEXTURE_2D, texName);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,GL_NEAREST);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, image.width,
image.height, 0, GL_RGB, GL_UNSIGNED_BYTE,
image.pixels);
}
void Texture::ReadPPMImage (char* fn)
{
int tmpint;
char str[100];
FILE* inFile = fopen (fn,"rb");
if (inFile == NULL)
{
printf ("Can't open input file %s. Exiting.\n",fn);
exit (1);
}
fscanf (inFile,"P%d\n", &tmpint);
if (tmpint != 6)
{
printf ("Input file is not ppm. Exiting.\n");
exit (1);
}
// skip comments embedded in header
fgets (str,100,inFile);
while (str[0]=='#')
fgets(str,100,inFile);
// read image dimensions
sscanf (str,"%d %d",&image.width, &image.height);
fgets (str,100,inFile);
sscanf (str,"%d",&tmpint);
if (tmpint != 255)
printf("Warning: maxvalue is not 255 in ppm file\n");
image.numChannels = 3;
image.pixels = (unsigned char*) malloc (image.numChannels * image.width * image.height * sizeof (unsigned char));
if (image.pixels == NULL)
{
printf ("Can't allocate image of size %dx%d. Exiting\n", image.width, image.height);
exit (1);
}
else
printf("Reading image %s of size %dx%d\n", fn, image.width, image.height);
fread (image.pixels, sizeof (unsigned char), image.numChannels * image.width * image.height, inFile);
fclose (inFile);
}
Main.cpp
#include <glut.h>
#include "Texture.h"
#pragma warning (disable : 4996)
const float fMinX = -5.0, fMinY = -5.0, fNearZ = 1.0,
fMaxX = 5.0 , fMaxY = 5.0 , fFarZ = 10.0;
Texture ImageOne ;
void Init ()
{
glClearColor (0.0, 0.0, 0.0, 0.0);
glEnable (GL_DEPTH_TEST);
glGenTextures (1, &ImageOne.texName);
ImageOne.ReadPPMImage("wood_1.ppm");
ImageOne.Prepare(1) ;
}
void Reshape (int width, int height)
{
glViewport (0, 0, width, height);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
glOrtho (fMinX, fMaxX, fMinY, fMaxY, fNearZ, fFarZ);
glMatrixMode (GL_MODELVIEW);
glLoadIdentity ();
}
void Display ()
{
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable (GL_TEXTURE_2D);
glTexEnvf (GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_BLEND);
glBindTexture (GL_TEXTURE_2D, ImageOne.texName);
glBegin(GL_QUADS);
glTexCoord2f(0,1);
glVertex3f(-5.5,5,-6);
glTexCoord2f(0,0);
glVertex3f(-5.5,-5,-6);
glTexCoord2f(1,0);
glVertex3f(5,-5,-6);
glTexCoord2f(1,1);
glVertex3f(5,5,-6);
glEnd();
glDisable(GL_TEXTURE_2D);
glutSwapBuffers ();
glFlush ();
}
void main (int argc, char **argv)
{
// init GLUT and create window
glutInit (&argc, argv);
glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowPosition(100,100);
glutInitWindowSize(500,500);
glutCreateWindow ("OpenGL - Rotating Cubes");
Init ();
// register callbacks
glutDisplayFunc (Display);
glutReshapeFunc (Reshape);
glutIdleFunc (Display); // used in animation
// enter GLUT event processing cycle
glutMainLoop();
}

Answer 1

Why are you using
glTexEnvf (GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_BLEND);
?
It does not make sense for your use case (and perfectly explays the "inversion" of the color values). You probably want GL_REPLACE or GL_MODULATE.