Displaying image in openGL with SOIL - c++

Question

I'm trying to display an image in openGL using SDL and SOIL but it isn't working.
Globals.h
#include <SDL.h>
#include <SDL_OpenGL.h>
#include <SOIL.h>
#include "player.h"
main.cpp
#include "Globals.h"
int main(int argc, char** argv){
//Begin SDL initialization
SDL_Init(SDL_INIT_EVERYTHING);
SDL_Surface* Screen = SDL_SetVideoMode(800, 600, 32, SDL_SWSURFACE|SDL_OPENGL);
SDL_Event Event;
//End SDL initialization
//Begin OpenGL initialization
glClearColor(1, 1, 1, 1);//Set colour for empty screen
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);//Enable transparency
glEnable(GL_TEXTURE_2D);
glShadeModel(GL_SMOOTH);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glOrtho(-400, 400, -300, 300, -1, 1);//Set grid for display
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
//End OpenGL initialization
Player Player(0, 0, 32, 64, 1, 0, 0, 0.5);
bool gameRunning = true;
while(gameRunning){
while(SDL_PollEvent(&Event)){
if(Event.type == SDL_QUIT)
gameRunning = false;
//If user closed the window in any way stop gameRunning
Player.Events(Event);
}
Player.Update();
glClear(GL_COLOR_BUFFER_BIT);//Clear screen
glPushMatrix();
Player.DisplayWithImage("Brick.png", 32, 64);
glPopMatrix();
SDL_GL_SwapBuffers();//Update screen with new shit
}
SDL_Quit();//Quit SDL
return 0;//End program
}
player.h
#pragma once
class Player{
public:
GLfloat X, Y, W, H, R, G, B, A;
bool movingUp, movingRight, movingDown, movingLeft;
GLuint image;
Player(GLfloat x, GLfloat y, GLfloat w, GLfloat h,
GLfloat r, GLfloat g, GLfloat b, GLfloat a);
void Events(SDL_Event &Event);
void Update();
void Display();
void DisplayWithImage(const char* filename, GLsizei w, GLsizei h);
};
player.cpp
#include "Globals.h"
Player::Player(GLfloat x, GLfloat y, GLfloat w, GLfloat h, GLfloat r, GLfloat g, GLfloat b, GLfloat a){
X = x;
Y = y;
W = w;
H = h;
R = r;
G = g;
B = b;
A = a;
movingUp = false;
movingRight = false;
movingDown = false;
movingLeft = false;
}
void Player::Events(SDL_Event &Event){
if(Event.type == SDL_KEYDOWN){
if(Event.key.keysym.sym == SDLK_w)
movingUp = true;
if(Event.key.keysym.sym == SDLK_d)
movingRight = true;
if(Event.key.keysym.sym == SDLK_s)
movingDown = true;
if(Event.key.keysym.sym == SDLK_a)
movingLeft = true;
}
if(Event.type == SDL_KEYUP){
if(Event.key.keysym.sym == SDLK_w)
movingUp = false;
if(Event.key.keysym.sym == SDLK_d)
movingRight = false;
if(Event.key.keysym.sym == SDLK_s)
movingDown = false;
if(Event.key.keysym.sym == SDLK_a)
movingLeft = false;
}
}
void Player::Update(){
if(movingUp)
Y ++;
if(movingRight)
X ++;
if(movingDown)
Y --;
if(movingLeft)
X --;
}
void Player::Display(){
glBegin(GL_QUADS);
glColor4f(R, G, B, A);
//bottom right
glVertex2f(X+(W/2), Y-(H/2));
//top right
glVertex2f(X+(W/2), Y+(H/2));
//top left
glVertex2f(X-(W/2), Y+(H/2));
//bottom left
glVertex2f(X-(W/2), Y-(H/2));
glEnd();
}
void Player::DisplayWithImage(const char* filename, GLsizei w, GLsizei h){
image = SOIL_load_OGL_texture // load an image file directly as a new OpenGL texture
(
filename,
SOIL_LOAD_AUTO,
SOIL_CREATE_NEW_ID,
SOIL_FLAG_MIPMAPS | SOIL_FLAG_INVERT_Y | SOIL_FLAG_NTSC_SAFE_RGB | SOIL_FLAG_COMPRESS_TO_DXT
);
glBindTexture(GL_TEXTURE_2D, image);
glBegin(GL_QUADS);
//bottom right
glTexCoord2f(0, 0); glVertex2f(X+(W/2), Y-(H/2));
//top right
glTexCoord2f(0, H); glVertex2f(X+(W/2), Y+(H/2));
//top left
glTexCoord2f(W, H); glVertex2f(X-(W/2), Y+(H/2));
//bottom left
glTexCoord2f(W, 0); glVertex2f(X-(W/2), Y-(H/2));
glEnd();
}

Answer 1

You have three problems in your code:
GL_TEXTURE_2D uses normalized texture coordinates (0.0 - 1.0). Unless H and W are 1.0 or less you do not want to use them for your texture coordinates. If you just want to stretch this texture across your quad one time, use 1.0 in-place of W and H.
Most Serious Issue: You are creating a new texture on each frame, you should load the texture one time and then pass the loaded texture handle to DisplayWithImage (...) instead of having that function load a texture each time you call it.
glOrtho (...) creates an orthographic projection matrix, any GL operation that uses the projection matrix in isolation (e.g. not Projection * ModelView) is going to fail to work properly if you use an identity projection matrix and an orthographic projection matrix for your modelview matrix. By the same token, things like vertex lighting will not work properly with a projection matrix serving as your modelview matrix...
You can correct bullet point 3 by re-writing part of your code this way:
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-400, 400, -300, 300, -1, 1);//Set grid for display
~~~~~~~ This should come AFTER you set the matrix mode to projection!