Problem Copying SDL_Surfaces

[JesseGuarascia]

Hey all. It seems I've hit a sort of "nooby" problem in my latest endeavor. As the title pertains, I'm having a problem copying SDL_Surfaces. My problem is not that I don't know how to do it; it's too complex for something like that. My problem is that when I copy the image, based on it's format, it will not copy properly (at least that's my assumption). Here's a quick example of the code, and the result.

This code loads an image:

Code: Select all

	SDL_Surface *loadedImage = NULL;

	// Get the image location
	imageLoc = fileLoc;

	// Determine the type of image being loaded
	if (fileLoc.find("bmp") != std::string::npos){
		format = BMP;
	} else {
		format = PNG;
	}

	// Load an image file
	loadedImage = IMG_Load(fileLoc.c_str());

	// If the image wasn't loaded properly
	if (loadedImage == NULL){
		printf ("SDL Error loading image file '%s': %s", fileLoc, SDL_GetError());
		return false;
	}

	// Optimize the image
	sur = SDL_DisplayFormatAlpha(loadedImage);

	if (!sur){
		printf ("SDL Error optimizing image file '%s': %s", fileLoc, SDL_GetError());
		return false;
	}

	SDL_FreeSurface(loadedImage);

	return true;

Apart from copying, the above code actually turns a .PNG that I've loaded's BLUE mask, and makes it RED.

This code "copies" an image:

Code: Select all

	// Copy the given surface
	if (sur){
		SDL_FreeSurface(sur);
	}

	sur = SDL_CreateRGBSurface(SDL_SWSURFACE, image->w, image->h, 32,
								0xFF000000, 0x00FF0000, 0x0000FF00, 0x000000FF);

	SDL_BlitSurface(image, NULL, sur, NULL);

This is the ultimate result (not the expected/correct one):


So basically, two things. What's wrong with my image? Why is it's blue value being altered and turned to red (by the way, it's a PNG if that matters)? Also. Why can I not properly copy an image? I have another image, which is the copy of that ship, but it is not being rendered. Ultimately, I believe the problem is that I'm using OpenGL and the texturing is messing with SDL and what not; I'm not totally sure. Any help is appreciated

[dandymcgee]

Ultimately, I believe the problem is that I'm using OpenGL and the texturing is messing with SDL and what not; I'm not totally sure.

Wait, are you trying to render with both OpenGL and SDL at the same time?? You can't do that.

[JesseGuarascia]

Wait, are you trying to render with both OpenGL and SDL at the same time?? You can't do that.

Yeah, after going after my post it does seem like I'm saying that at some points. No no, I'm rendering with OpenGL, but using SDL to generate the surfaces and whatnot.

[dandymcgee]

Wait, are you trying to render with both OpenGL and SDL at the same time?? You can't do that.

Yeah, after going after my post it does seem like I'm saying that at some points. No no, I'm rendering with OpenGL, but using SDL to generate the surfaces and whatnot.

Can you show that code you're using to convert SDL_Surface to GL texture?

[JesseGuarascia]

Sure

Code: Select all

	// Generate the texture using the image given
	glGenTextures(1, &tex);

	glBindTexture(GL_TEXTURE_2D, tex);

	GLenum texFormat = GL_RGBA; // Format used for the texture

	// Decide which format to use
	if (img.GetImage()->format->BytesPerPixel == 4){
		texFormat = GL_RGBA;
	} else if (img.GetImage()->format->BytesPerPixel == 3){
		texFormat = GL_RGB;
	}

	// Create the texture
	glTexImage2D(GL_TEXTURE_2D, 0, 4, img.Width(), img.Height(), 
				0, texFormat, GL_UNSIGNED_BYTE, img.GetImage()->pixels);

	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

	// Get the sizes of the texture
	glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_WIDTH, &texWidth);
	glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_HEIGHT, &texHeight);

	if (glGetError() != GL_NO_ERROR){
		printf ("OpenGL Error - Creating textures failed!");
	}

[bnpph]

To fix the colors, just change RGB to BGR. Windows is backwards that way.

Do not know why copy isn't working - could you post more code?



But anyway, I do not get why you are using SDL surfaces with OpenGL. Why do you need them? If you need an image loader, you can always use something like DevIL or SOIL. Actually, loading textures is very easy, and you could even write the code yourself.

[JesseGuarascia]

To fix the colors, just change RGB to BGR. Windows is backwards that way.

Do not know why copy isn't working - could you post more code?



But anyway, I do not get why you are using SDL surfaces with OpenGL. Why do you need them? If you need an image loader, you can always use something like DevIL or SOIL. Actually, loading textures is very easy, and you could even write the code yourself.

Reason for SDL:

I like SDL, and am fluent with it. Apart from that, OpenGL internally does not deal with Window Management, something SDL does. SDL also deals with Sounds and Networking, Threading, etc. Some things any good game uses. I'm not using SDL exclusively for image loading (although I've heard DevIL is quite nice), I'm using it for all other components of the game.

More copying code:

Okay, I guess really, all I'm trying to achieve here, is clipping of an image. I'm doing this very stupidly I know, but it's all I could think of. Imagine you have a sprite sheet, all I'm trying to do is clip that texture and render it. If you know a better way then copying a certain portion of the SDL_Surface, then converting it to an OGL texture, that'd be nice

[bnpph]

I can understand using SDL for the things you mentioned, it just seems silly to me to use surfaces with OpenGL.

Why do you need to create different images? You could just set your texture coordinates to be 1 tile.

[JesseGuarascia]

I can understand using SDL for the things you mentioned, it just seems silly to me to use surfaces with OpenGL.

Why do you need to create different images? You could just set your texture coordinates to be 1 tile.

I think you mean split each tile into a different file, in which case: O_O no..

[Ginto8]

nope, he means to use texture coordinates (set via glTexCoord2f or such functions, or via glTexCoordPointer) to only draw a portion of the whole texture at a time. It's quite easy, orders of magnitude more efficient than splitting it into separate textures, and just overall works better.

[dandymcgee]

But anyway, I do not get why you are using SDL surfaces with OpenGL. Why do you need them? If you need an image loader, you can always use something like DevIL or SOIL. Actually, loading textures is very easy, and you could even write the code yourself.

Because he's using SDL for a bunch of other reasons. Why add another dependency when one of his current dependencies handles image loading just fine?