New to SDL

Question

Xarver 0 Newbie Poster

15 Years Ago

I just started learning SDL so I can make games in C++,
but for some reason my code fails to compile.
The code:

#include "SDL/SDL.h"
#include <string>
using std::string;

int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
const int SCREEN_BPP = 32;

SDL_Surface *message = NULL;
SDL_Surface *background = NULL;
SDL_Surface *screen = NULL;

SDL_Surface *load_image(string filename)
{
    SDL_Surface* loadedImage = NULL;
    SDL_Surface* optimizedImage = NULL;
    loadedImage = SDL_LoadBMP(filename.c_str());
    if(loadedImage != NULL)
    {
        optimizedImage = SDL_Display_Format(loadedImage);
        SDL_FreeSurface(loadedImage);
    }

    return optimizedImage;
}
void applySurface(int x, int y, SDL_Surface* source, SDL_Surface* destination)
{
    SDL_Rect offset;
    offset.x = x;
    offset.y = y;
    SDL_BlitSurface(source, NULL, destination, &offset);
}

int main(int argc, char* args[])
{
    if(SDL_Init(SDL_INIT_EVERYTHING) == -1)
    {
        return 1;
    }
    screen = SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE);
    if(screen == NULL) { return 1; }
    SDL_WM_SetCaption("Hello World", NULL);
    message = load_image("message.bmp");
    background = load_image("background.bmp");
    apply_surface(0, 0, background, screen);
    apply_surface(200, 200, message, screen);
    if(SDL_Flip(screen) == -1) { return 1; }
    SDL_Delay(5000);
    SDL_FreeSurface(message);
    SDL_FreeSurface(background);

    SDL_Quit();
    return 0;
}

Here's the errors I got:

||=== Test_SDL, Release ===|
C:\Programming\C++\Newbie\TutorialStuff\Hello_SDL\main.cpp||In function `SDL_Surface* load_image(std::string)'
C:\Programming\C++\Newbie\TutorialStuff\Hello_SDL\main.cpp|20|error: `SDL_Display_Format' was not declared in this scope|
C:\Programming\C++\Newbie\TutorialStuff\Hello_SDL\main.cpp|20|warning: unused variable 'SDL_Display_Format'|
C:\Programming\C++\Newbie\TutorialStuff\Hello_SDL\main.cpp||In function `int SDL_main(int, char**)'
C:\Programming\C++\Newbie\TutorialStuff\Hello_SDL\main.cpp|40|error: `SetVideoMode' was not declared in this scope|
C:\Programming\C++\Newbie\TutorialStuff\Hello_SDL\main.cpp|45|error: `apply_surface' was not declared in this scope|
C:\Programming\C++\Newbie\TutorialStuff\Hello_SDL\main.cpp|40|warning: unused variable 'SetVideoMode'|
||=== Build finished: 3 errors, 2 warnings ===|

I don't know what went wrong, it's either the code or SDL isn't set up properly...
I would like someone to tell me what's wrong, and
be able to fix it and explain.

Any help appreciated!

~ Xarver

P.S. I have attached a zip file with the things.

c++

This attachment is potentially unsafe to open. It may be an executable that is capable of making changes to your file system, or it may require specific software to open. Use caution and only open this attachment if you are comfortable working with zip files.

Hello_SDL.zip (208.82 KB)

4 Contributors
12 Replies
352 Views
2 Days Discussion Span
Latest Post 15 Years Ago Latest Post by Xarver

ArkM 1,090 Postaholic

15 Years Ago

Read SDL tutorials carefully then correct misprints in you sources. Must be SDL_DisplayFormat, SDL_SetVideoMode etc...

mitrmkar 1,056 Posting Virtuoso

15 Years Ago

Well, by doing the following ...

...
background = load_image("background.bmp");

if(background == NULL)
{
    // load_image() failed ...
    cout << "load_image() failed, error: " << SDL_GetError() << endl;
}

apply_surface(100, 100, message, screen);
...

I got output as follows:

load_image() failed, error: File is not a Windows BMP file

Xarver commented: Thanks +1

minas1 1 Junior Poster in Training

15 Years Ago

Is it an image you changed manually from .jpg (for example) to bmp by just renaming the file?

Xarver commented: Thanks +1

Reply to this topic

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.

minas1 1 Junior Poster in Training · Answer 1 · 2008-11-05T15:45:02+00:00

Are you sure you added the library files from project settings?

ArkM 1,090 Postaholic · Answer 2 · 2008-11-05T15:58:02+00:00

Are you sure you added the library files from project settings?

IMHO, it's of no importance: there are obviously misspelled SDL function names in the source...

minas1 1 Junior Poster in Training · Answer 3 · 2008-11-05T16:06:27+00:00

Ok.

optimizedImage = SDL_Display_Format(loadedImage);
should be
optimizedImage = SDL_DisplayFormat(loadedImage);

----------------------------------------------------------------------------------------------

screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE);

You forgot SDL here.

----------------------------------------------------------------------------------------------

apply_surface(0, 0, background, screen);
apply_surface(200, 200, message, screen);

Your function's name is applySurface :)

It should be working now.

Xarver 0 Newbie Poster · Answer 4 · 2008-11-05T21:15:53+00:00

I fixed my program, but still a small problem.
It loads the message.bmp picture but doesn't load the background.
:(

#include "SDL/SDL.h"
#include <string>
using std::string;

const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
const int SCREEN_BPP = 32;

SDL_Surface *message = NULL;
SDL_Surface *background = NULL;
SDL_Surface *screen = NULL;

SDL_Surface *load_image(string filename)
{
    SDL_Surface* loadedImage = NULL;
    SDL_Surface* optimizedImage = NULL;
    loadedImage = SDL_LoadBMP(filename.c_str());
    if(loadedImage != NULL)
    {
        optimizedImage = SDL_DisplayFormat(loadedImage);
        SDL_FreeSurface(loadedImage);
    }

    return optimizedImage;
}
void apply_surface(int x, int y, SDL_Surface* source, SDL_Surface* destination)
{
    SDL_Rect offset;
    offset.x = x;
    offset.y = y;
    SDL_BlitSurface(source, NULL, destination, &offset);
}

int main(int argc, char* args[])
{
    if(SDL_Init(SDL_INIT_EVERYTHING) == -1)
    {
        return 1;
    }
    screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE);
    if(screen == NULL) { return 1; }
    SDL_WM_SetCaption("Hello World", NULL);
    message = load_image("message.bmp");
    background = load_image("background.bmp");
    apply_surface(0, 0, background, screen);
    apply_surface(100, 100, message, screen);
    if(SDL_Flip(screen) == -1) { return 1; }
    SDL_Delay(5000);
    SDL_FreeSurface(message);
    SDL_FreeSurface(background);

    SDL_Quit();
    return 0;
}

Here's a zip:

I don't know why it won't work. :|

Xarver 0 Newbie Poster · Answer 5 · 2008-11-06T02:43:28+00:00

Anyone know why it only loads message.bmp?

I need help here. :)

Xarver 0 Newbie Poster · Answer 6 · 2008-11-06T21:28:36+00:00

Xarver 0 Newbie Poster

15 Years Ago

I still need help here. :|

mitrmkar 1,056 Posting Virtuoso · Answer 7 · 2008-11-06T22:27:37+00:00

I still need help here. :|

Assuming that SDL is unable to load the image, you might place a call to SDL_GetError() immediately after the line: background = load_image("background.bmp"); to get a description of the cause of the failure.

Xarver 0 Newbie Poster · Answer 8 · 2008-11-07T02:52:42+00:00

I put SDL_GetError after it and it does nothing.
There's no errors, but the background image doesn't show.
Download the second zip I uploaded and maybe you can figure out the problem...
I need help with this. :)

Xarver 0 Newbie Poster · Answer 9 · 2008-11-08T03:19:19+00:00

Ah, GIMP didn't support BMP, but I saved it anyway... I'm going to make a new background.
Thanks for the solution! :)