OpenGL texture misaligned on quad
- by user308226
I've been having trouble with this for a while now, and I haven't gotten any solutions that work yet. Here is the problem, and the specifics:
I am loading a 256x256 uncompressed TGA into a simple OpenGL program that draws a quad on the screen, but when it shows up, it is shifted about two pixels to the left, with the cropped part appearing on the right side. It has been baffling me for the longest time, people have suggested clamping and such, but somehow I think my problem is probably something really simple, but I just can't figure out what it is!
Here is a screenshot comparing the TGA (left) and how it appears running in the program (right) for clarity. Also take note that there's a tiny black pixel on the upper right corner, I'm hoping that's related to the same problem.
Here's the code for the loader, I'm convinced that my problem lies in the way that I'm loading the texture.
Thanks in advance to anyone who can fix my problem.
bool TGA::LoadUncompressedTGA(char *filename,ifstream &texturestream)
{
cout << "G position status:" << texturestream.tellg() << endl;
texturestream.read((char*)header, sizeof(header)); //read 6 bytes into the file to get the tga header
width = (GLuint)header[1] * 256 + (GLuint)header[0]; //read and calculate width and save
height = (GLuint)header[3] * 256 + (GLuint)header[2]; //read and calculate height and save
bpp = (GLuint)header[4]; //read bpp and save
cout << bpp << endl;
if((width <= 0) || (height <= 0) || ((bpp != 24) && (bpp !=32))) //check to make sure the height, width, and bpp are valid
{
return false;
}
if(bpp == 24)
{
type = GL_RGB;
}
else
{
type = GL_RGBA;
}
imagesize = ((bpp/8) * width * height); //determine size in bytes of the image
cout << imagesize << endl;
imagedata = new GLubyte[imagesize]; //allocate memory for our imagedata variable
texturestream.read((char*)imagedata,imagesize); //read according the the size of the image and save into imagedata
for(GLuint cswap = 0; cswap < (GLuint)imagesize; cswap += (bpp/8)) //loop through and reverse the tga's BGR format to RGB
{
imagedata[cswap] ^= imagedata[cswap+2] ^= //1st Byte XOR 3rd Byte XOR 1st Byte XOR 3rd Byte
imagedata[cswap] ^= imagedata[cswap+2];
}
texturestream.close(); //close ifstream because we're done with it
cout << "image loaded" << endl;
glGenTextures(1, &texID); // Generate OpenGL texture IDs
glBindTexture(GL_TEXTURE_2D, texID);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glTexImage2D(GL_TEXTURE_2D, 0, type, width, height, 0, type, GL_UNSIGNED_BYTE, imagedata);
delete imagedata;
return true;
}
//Public loading function for TGA images. Opens TGA file and determines
//its type, if any, then loads it and calls the appropriate function.
//Returns: TRUE on success, FALSE on failure
bool TGA::loadTGA(char *filename)
{
cout << width << endl;
ifstream texturestream;
texturestream.open(filename,ios::binary);
texturestream.read((char*)header,sizeof(header)); //read 6 bytes into the file, its the header. //if it matches the uncompressed header's first 6 bytes, load it as uncompressed
LoadUncompressedTGA(filename,texturestream);
return true;
}
