PPM Colors Issues

Question

any one please know what is the wrong with this code colors did not match ? iam using ppm loader to load an image but colors did not match the image when it loaded in the game .

when i pass a white image it is appear black , when i pass black it is appear white , when i pass 255 , 0 ,0 it is appear 0 ,255,255 , when i pass 128 , 128 , 192 it is appear 128 , 128 , 64

Fullscreen Image

#include <fstream>
#include <glut.h>
#include "Texture.h"
#include <iostream>
#pragma warning (disable : 4996)

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);
 }

Answer 1

It looks like you're not reading the header correctly and you are reading the pixel data offset from the actual start.

To begin with, I would remove the fgets after reading the dimensions. Then start checking what pixel values you expect to read and what you get, using a ground truth test image.