Simple pong game (SDL) - ball.cpp

//Simple pong game - ball.cpp
//created by thecplusplusguy
//     http://www.youtube.com/user/thecplusplusguy
#include "ball.h"

ball::ball(SDL_Surface* img,int x,int y,int w,int h,int xVel,int yVel)
{
    image=img;
    box.x=x;
    box.y=y;
    box.w=w;
    box.h=h;
    xvel=xVel;
    yvel=yVel;
}

ball::~ball()
{
    SDL_FreeSurface(image);
}

void ball::show()
{
    SDL_BlitSurface(image,NULL,SDL_GetVideoSurface(),&box);
}

void ball::move(SDL_Rect* player1,SDL_Rect* player2,Mix_Chunk* effect)
{
    box.x+=xvel;
    box.y+=yvel;
    if(box.y<=0)
        yvel=-yvel;
    if(box.y+box.h>=SDL_GetVideoSurface()->clip_rect.h)
        yvel=-yvel;
    if(collision(&box,player1))
    {
        Mix_PlayChannel(-1,effect,0);
        if(box.x+3<player1->x+player1->w)
            yvel=-yvel;
        else
            xvel=-xvel;
    }
    if(collision(&box,player2))
    {
        Mix_PlayChannel(-1,effect,0);
        if(box.x+box.w-3 > player2->x)
            yvel=-yvel;
        else
            xvel=-xvel;

    }
}

bool ball::collision(SDL_Rect* rec1,SDL_Rect* rec2)
{
    if(rec1->y >= rec2->y + rec2->h)
        return 0;
    if(rec1->x >= rec2->x + rec2->w)
        return 0;
    if(rec1->y + rec1->h <= rec2->y)
        return 0;
    if(rec1->x + rec1->w <= rec2->x)
        return 0;
    return 1;
}


int ball::isOut()
{
    if(box.x<=0)
        return 1;
    if(box.x>=SDL_GetVideoSurface()->clip_rect.w)
        return 2;
    return 0;
}


void ball::setBack(int x,int y,int w,int h,int xVel,int yVel)
{
    box.x=x;
    box.y=y;
    box.w=w;
    box.h=h;
    xvel=xVel;
    yvel=yVel;
}