SDL_ttf and OpenGL resizing, getting artifacts on text edges - opengl

Question

I'm using SDL_ttf for rendering text with OpenGL. However, I'm getting nasty artifacts at edges of text:
Here's the code:
#include <string>
#include "SDL.h"
#include "SDL_opengl.h"
#include <SDL_ttf.h>
using namespace std;
#define WINDOW_WIDTH 1280
#define WINDOW_HEIGHT 1024
struct Color
{
unsigned char R, G, B, A;
Color(unsigned char r, unsigned char g, unsigned char b, unsigned char a) :
R(r), G(g), B(b), A(a)
{}
};
void DrawRectangle(int left, int right, int top, int bottom, Color c, GLuint Texture);
void DrawTextGL(int left, int top, TTF_Font* font, string text);
GLuint SDLSurfaceToTexture(SDL_Surface* surface);
int main(int argc, char** argv)
{
SDL_Init(SDL_INIT_VIDEO);
SDL_Surface* screen = SDL_SetVideoMode(WINDOW_WIDTH, WINDOW_HEIGHT, 32, SDL_OPENGL);
TTF_Init();
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 0);
glEnable(GL_TEXTURE_2D);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);
glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0f, WINDOW_WIDTH, WINDOW_HEIGHT, 0.0f, -1.0f, 1.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
// Enabling transparency
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
SDL_Surface* temp = SDL_LoadBMP("New Bitmap Image.bmp");
GLuint WhiteTexture = SDLSurfaceToTexture(temp);
TTF_Font* Font;
Font = TTF_OpenFont("FreeSerif.ttf", 36);
DrawRectangle(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT, Color(0, 0, 0, 255), WhiteTexture);
SDL_GL_SwapBuffers();
DrawTextGL(300, 300, Font, "graveyard");
DrawTextGL(600, 600, Font, "graveyard");
SDL_GL_SwapBuffers();
system("pause");
SDL_Quit();
return 0;
}
void DrawRectangle(int left, int right, int top, int bottom, Color c, GLuint Texture)
{
glBindTexture(GL_TEXTURE_2D, Texture);
glColor4f(c.R/255.0f, c.G/255.0f, c.B/255.0f, c.A/255.0f);
glBegin(GL_QUADS);
//Top-left vertex (corner)
glTexCoord2i(0, 0);
glVertex2f(GLfloat(left), GLfloat(top));
//Top-right vertex (corner)
glTexCoord2i(1, 0);
glVertex2f(GLfloat(right), GLfloat(top));
//Bottom-right vertex (corner)
glTexCoord2i(1, 1);
glVertex2f(GLfloat(right), GLfloat(bottom));
//Bottom-left vertex (corner)
glTexCoord2i(0, 1);
glVertex2f(GLfloat(left), GLfloat(bottom));
glEnd();
}
void DrawTextGL(int left, int top, TTF_Font* font, string text)
{
SDL_Color color = {255, 255, 255, 255};
SDL_Surface* textSurface;
textSurface = TTF_RenderText_Blended(font, text.c_str(), color);
GLuint Texture = SDLSurfaceToTexture(textSurface);
DrawRectangle(left, left + 260, top, top + 80, Color(255, 255, 255, 255), Texture);
SDL_FreeSurface(textSurface);
glDeleteTextures(1, &Texture);
}
GLuint SDLSurfaceToTexture(SDL_Surface* surface)
{
GLuint texture;
GLint nOfColors;
GLenum texture_format;
// get the number of channels in the SDL surface
nOfColors = surface->format->BytesPerPixel;
if (nOfColors == 4) // contains an alpha channel
{
if (surface->format->Rmask == 0x000000ff)
texture_format = GL_RGBA;
else
texture_format = GL_BGRA;
}
else if (nOfColors == 3)
{
if (surface->format->Rmask == 0x000000ff)
texture_format = GL_RGB;
else
texture_format = GL_BGR;
}
else
{
printf("Picture with less than 24-bit color depth detected.\n");
return 0;
}
// Have OpenGL generate a texture object handle for us
glGenTextures(1, &texture);
// Bind the texture object
glBindTexture(GL_TEXTURE_2D, texture);
// Set the texture's stretching properties
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// Edit the texture object's image data using the information SDL_Surface gives us
glTexImage2D(GL_TEXTURE_2D, 0, nOfColors, surface->w, surface->h, 0,
texture_format, GL_UNSIGNED_BYTE, surface->pixels);
// Bind the texture to which subsequent calls refer to
glBindTexture(GL_TEXTURE_2D, texture);
return texture;
}
"New Bitmap Image.bmp" is just a bitmap with one white pixel in it. "FreeSerif.ttf" is a font taken from here.