OpenGL texture shifted somewhat to the left when applied to a quad
- by user308226
I'm a bit new to OpenGL and I've been having a problem with using textures. The texture seems to load fine, but when I run the program, the texture displays shifted a couple pixels to the left, with the section cut off by the shift appearing on the right side. I don't know if the problem here is in the my TGA loader or if it's the way I'm applying the texture to the quad.
Here is the loader:
#include "texture.h"
#include <iostream>
GLubyte uncompressedheader[12] = {0,0, 2,0,0,0,0,0,0,0,0,0};
GLubyte compressedheader[12] = {0,0,10,0,0,0,0,0,0,0,0,0};
TGA::TGA()
{
}
//Private loading function called by LoadTGA. Loads uncompressed TGA files
//Returns: TRUE on success, FALSE on failure
bool TGA::LoadCompressedTGA(char *filename,ifstream &texturestream)
{
return false;
}
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); // Bind Our Texture
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); // Linear Filtered
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
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;
}
GLubyte* TGA::getImageData()
{
return imagedata;
}
GLuint& TGA::getTexID()
{
return texID;
}
And here's the quad:
void Square::show()
{
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, texture.texID);
//Move to offset
glTranslatef( x, y, 0 );
//Start quad
glBegin( GL_QUADS );
//Set color to white
glColor4f( 1.0, 1.0, 1.0, 1.0 );
//Draw square
glTexCoord2f(0.0f, 0.0f); glVertex3f( 0, 0, 0 );
glTexCoord2f(1.0f, 0.0f); glVertex3f( SQUARE_WIDTH, 0, 0 );
glTexCoord2f(1.0f, 1.0f); glVertex3f( SQUARE_WIDTH, SQUARE_HEIGHT, 0 );
glTexCoord2f(0.0f, 1.0f); glVertex3f( 0, SQUARE_HEIGHT, 0 );
//End quad
glEnd();
//Reset
glLoadIdentity();
}
