SDL_image to textured quad

icecubeflower · 2008-07-20T19:24:47

Hey I've a got 2D game going on. I used SDL and also OpenGL. For loading images I always use .TGA's and I load them myself with code I mostly took from NeHe's site. It's like this: I declare this data type: struct TextureImage { GLubyte *imageData; GLuint bpp; GLuint width; GLuint height; GLuint texID; }; Then I declare some variable: TextureImage *whatever; Then I declare this function: bool LoadTGA(TextureImage *texture, string &filename) { GLubyte TGAheader[12]={0,0,2,0,0,0,0,0,0,0,0,0}; GLubyte TGAcompare[12]; GLubyte header[6]; GLuint bytesPerPixel; GLuint imageSize; GLuint temp; GLuint type=GL_RGBA; FILE *file = fopen(filename.c_str(), "rb"); if(file==NULL|| fread(TGAcompare,1,sizeof(TGAcompare),file)!=sizeof(TGAcompare)|| memcmp(TGAheader,TGAcompare,sizeof(TGAheader))!=0|| fread(header,1,sizeof(header),file)!=sizeof(header)) { if(file!=NULL) fclose(file); return false; } texture->width = header[1] * 256 + header[0]; texture->height = header[3] * 256 + header[2]; if(texture->width<=0||texture->height<=0||(header[4]!=24 && header[4]!=32)) { fclose(file); return false; } texture->bpp=header[4]; bytesPerPixel=texture->bpp/8; imageSize=texture->width*texture->height*bytesPerPixel; texture->imageData = (GLubyte *)malloc(imageSize); //Ah, malloc, C's answer to "new". So when is this memory freed? //you have to free it yourself NeHe has a Deinitialize function if(texture->imageData==NULL||fread(texture->imageData, 1, imageSize, file)!=imageSize) { if(texture->imageData!=NULL) { free(texture->imageData); //well, I guess this is how you free it texture->imageData = NULL; } fclose(file); return false; } //for a fun time comment this out for(GLuint i=0; i<(unsigned int)imageSize; i+=bytesPerPixel) { temp=texture->imageData; texture->imageData = texture->imageData[i + 2]; texture->imageData[i + 2] = temp; } fclose (file); // Build A Texture From The Data glGenTextures(1, &texture[0].texID); //texture is a pointer to a TextureImage //why not just texture.texID? why &texture[0]?? wtf //the the address of a pointer? the first element of it? it has no elements, wtf? //wtf could [0] possibly mean? //oh I remember, you use -> for pointers instead of . like above //so here he wants to use . so maybe ampersand on a pointer "converts" it back to a regular data type? //I have no idea what's going on glBindTexture(GL_TEXTURE_2D, texture[0].texID); //And here it needs no ampersand. Why? I don't know. glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); if(texture[0].bpp==24) { type=GL_RGB; } //Here using . instead of -> so maybe [0] takes care of it? Then why the ampersand above? glTexImage2D(GL_TEXTURE_2D, 0, type, texture[0].width, texture[0].height,0, type, GL_UNSIGNED_BYTE, texture[0].imageData); return true; } So now I pass *whatever to that function along with the name of a .tga file and I can bind *whatever whenver I want and slap on some quads. glBindTexture(GL_TEXTURE_2D, whatever.texID); glBegin(GL_POLYGON); glTexCoord2f(0.0,1.0); glVertex3f(0,768,0.0); glTexCoord2f(1.0,1.0); glVertex3f(1024,768,0.0); glTexCoord2f(1.0,0.0); glVertex3f(1024,0,0.0); glTexCoord2f(0.0,0.0); glVertex3f(0,0,0.0); glEnd(); But TGA's always take up a few trillion terrabytes and no one's used them since Fred Flintstone so I want to start loading .PNG's instead. I want to use SDL_image loader and using SDL_image loader for an SDL game is easy enough except I want it to load the PNG into a data type that I can bind to an OpenGL texture like I'm doing above with .tga's. I cannot find how to do this. I don't think it would take more than a page of code, I figured there would be something out there I could just block copy and figure out later but I can't find anything. I don't know why, lots of people have probably loaded .png's with SDL_image and textured OpenGL quads with them.