Home
Blogs
Forums
News
Portfolios
Projects
Tutorials
30 users logged in
New? Learn about game development.
Before posting, review our community guidelines.
Follow Us
Chat in the GameDev.net Discord!
Mastodon
Back to For Beginners

Why wont SDL_DisplayFormat work?!?!?!

Started by
9 comments, last by TheBuzzSaw 13 years, 4 months ago
Im following lazy foo's SDL tutorial to set the color key on an image.
I did many of his tutorials and now I have a problem that didn't exist before.

I load img1 but the line SDL_DisplayFormat(img1) DOES NOTHING ( found this out during debug) and so the program exits.What am I doing wrong?

Here is the snippet:

SDL_Surface* loadimg(std::string filename){	SDL_Surface* img1 = NULL;	SDL_Surface* img2 =NULL;	img1 = IMG_Load(filename.c_str());	if(img1 !=NULL)	{		img2 = SDL_DisplayFormat(img1);		SDL_FreeSurface(img1); 		if(img2 != NULL)		SDL_SetColorKey(img2,SDL_SRCCOLORKEY,SDL_MapRGB(img2->format,0xFF,0xFF,0xFF));	}	return img1;}


Thanks in advance.
Advertisement
Quote:Original post by Mozly
I load img1 but the line SDL_DisplayFormat(img1) DOES NOTHING ( found this out during debug) and so the program exits.What am I doing wrong?
How do you know that line does nothing? What does 'nothing' mean to you?

Anyway, let's assume did actually work and the converted img1 is put into img2. That means you are leaking img2 and returning img1 after freeing it. I'd have written your code more like this:
SDL_Surface* loadimg(std::string filename){  SDL_Surface* img1 = IMG_Load(filename.c_str());  if(img1 ==NULL)  {    return NULL;  }  SDL_Surface* img2 = SDL_DisplayFormat(img1);  SDL_FreeSurface(img1);   if(img2 == NULL)  {    return NULL;  }  SDL_SetColorKey(img2,SDL_SRCCOLORKEY,SDL_MapRGB(img2->format,0xFF,0xFF,0xFF));  return img2;}
I dislike nesting statements unless necessary and I think "checking for failure and bailing immediately" makes more sense than "checking for success and continuing".

Hope this helps.

C++: A Dialog | C++0x Features: Part1 (lambdas, auto, static_assert) , Part 2 (rvalue references) , Part 3 (decltype) | Write Games | Fix Your Timestep!

Actually i did return img2; return img1 is a typo. it is display format that doesent work.
Quote:Original post by Mozly
Actually i did return img2; return img1 is a typo. it is display format that doesent work.
Still not sure what that means, but have you tried calling SDL_GetError after that line?

C++: A Dialog | C++0x Features: Part1 (lambdas, auto, static_assert) , Part 2 (rvalue references) , Part 3 (decltype) | Write Games | Fix Your Timestep!

the code now reads as you wrote it but SDL_DisplayFormat() is still not doing its job
Quote:Original post by Mozly
the code now reads as you wrote it but SDL_DisplayFormat() is still not doing its job
You keep saying what it isn't doing('its job'), but I think it might help if you say what it is doing. That is, does it return NULL or non-NULL? Does it cause your program to crash? Something entirely different?

Also, did you try SDL_GetError or not? If SDL_DisplayFormat returns non-NULL then SDL_GetError probably won't be helpful.

C++: A Dialog | C++0x Features: Part1 (lambdas, auto, static_assert) , Part 2 (rvalue references) , Part 3 (decltype) | Write Games | Fix Your Timestep!

ok, sdl_displayFormat() is supposed to set all the values of the image such as img->rectclips etc. none of the values are set. That is what im saying. Sorry if it sounded scetchy
Have you called SDL_Init? Have you already called SDL_SetVideoMode?
I recommend trying SDL_DisplayFormatAlpha (particularly since you are using SDL_image).
Amateurs practice until they do it right.Professionals practice until they never do it wrong.
Quote:Original post by Mozly
ok, sdl_displayFormat() is supposed to set all the values of the image such as img->rectclips etc. none of the values are set. That is what im saying. Sorry if it sounded scetchy


What makes you think this?

SDL_DisplayFormat optimises the image data. It does not preserve other data.

Looking through the source* it doesn't touch the "rectclips" member. You'll need to write a wrapper function that handles this.

* SDL_DisplayFormat (line 919)which delegates to SDL_ConvertSurface (line 719).
blog | twitter

This topic is closed to new replies.

Advertisement

Popular Topics

Aybe One
How do you manage yourself and your time as years pass on? GDNet Lounge
Jikoob
Too many managers? General and Gameplay Programming
ReignOnU
Do your part to stop global warming and climate change GDNet Lounge
aigan
The promise of freedom in story games Game Design and Theory
robertrobert
Facebook Ads for sales on steam, does it work? Games Business and Law
AliAbdulKareem
Understanding the wavy-like shape in alpha-testing magnification for text rendering Graphics and GPU Programming
Advertisement

Recommended Tutorials

Ruben Torres Bonet (The Gamedev Guru)
The Dark Side Of Ray-Traced Ambient Occlusion (RTAO) General and Gameplay Programming
Code_Analysis
A Long-Awaited Check of Unreal Engine 4 General and Gameplay Programming
Squared'D
How About UNICODE and UTF-8 General and Gameplay Programming
Myopic Rhino
Five Lessons I Learned From The GDC General and Gameplay Programming
Myopic Rhino
Algorithmic Forays Part 6 General and Gameplay Programming

Reticulating splines

About GameDev.net
Community Guidelines
Terms of Service
Privacy Policy
Contact Us
Copyright (c) 1999-2024 GameDev.net, LLC
Back to Top