problem blending properly in openGL

Question

I'm trying to draw a 2d character sprite on top of a 2d tilemap, but when I draw the character he's got odd stuff behind him. This isn't in the sprite, so I think its the blending.

This is how my openGL is set up:

void InitGL(int Width, int Height)          // We call this right after our OpenGL window is created.
{

    glViewport(0, 0, Width, Height);
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);       // This Will Clear The Background Color To Black
    glClearDepth(1.0);              // Enables Clearing Of The Depth Buffer
    glDepthFunc(GL_LESS);               // The Type Of Depth Test To Do
    glDisable(GL_DEPTH_TEST);           // Enables Depth Testing
    //glShadeModel(GL_SMOOTH);          // Enables Smooth Color Shading
    glEnable(GL_TEXTURE_2D);                        // Enable Texture Mapping ( NEW )
    glShadeModel(GL_FLAT);
    glMatrixMode(GL_PROJECTION);
    glEnable(GL_BLEND);
    glBlendFunc(GL_ONE , GL_ONE_MINUS_SRC_ALPHA);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
    glAlphaFunc(GL_GREATER, 0.5f);

    glMatrixMode(GL_PROJECTION);//configuring projection matrix now
    glLoadIdentity();//reset matrix
    glOrtho(0, Width, 0, Height, 0.0f, 100.0f);//set a 2d projection matrix

}

How should I set this up to work properly (ie drawing the sprite without odd stuff behind him.

This is what I am talking about: http://i.stack.imgur.com/cmotJ.png

PS: I need to be able to put transparent/semi-transparent images on top of each other and have whats behind them visible too

Answer 1

Does your sprite have premultiplied alpha? Your glBlendFunc setup is a little unusual, if you don't have premultiplied alpha it could definitely be causing the issue.