Sharpen Texture Example Program

Sharpen Texture Example Program

Example 6-2 illustrates the use of the sharpen texture example program. Because of space limitations, the sections dealing with X Window System setup and some of the keyboard input are omitted. The complete example is included in the source tree as sharpen.c.

Example 6-2 : Sharpen Texture Example

/* tree texture: high alpha in foreground, zero alpha in background */
#define B 0x00000000
#define F 0xA0A0A0ff
unsigned int tex[] = {
    B,B,B,B,B,B,B,B,B,B,B,B,B,B,B,B,
    B,B,B,B,B,B,B,F,F,B,B,B,B,B,B,B,
    B,B,B,B,B,B,B,F,F,B,B,B,B,B,B,B,
    B,B,B,B,B,B,F,F,F,F,B,B,B,B,B,B,
    B,B,B,B,B,B,F,F,F,F,B,B,B,B,B,B,
    B,B,B,B,B,F,F,F,F,F,F,B,B,B,B,B,
    B,B,B,B,B,F,F,F,F,F,F,B,B,B,B,B,
    B,B,B,B,F,F,F,F,F,F,F,F,B,B,B,B,
    B,B,B,B,F,F,F,F,F,F,F,F,B,B,B,B,
    B,B,B,F,F,F,F,F,F,F,F,F,F,B,B,B,
    B,B,B,F,F,F,F,F,F,F,F,F,F,B,B,B,
    B,B,F,F,F,F,F,F,F,F,F,F,F,F,B,B,
    B,B,F,F,F,F,F,F,F,F,F,F,F,F,B,B,
    B,B,B,B,B,B,F,F,F,F,B,B,B,B,B,B,
    B,B,B,B,B,B,F,F,F,F,B,B,B,B,B,B,
    B,B,B,B,B,B,B,B,B,B,B,B,B,B,B,B,
};

static void
init(void) {
    glEnable(GL_TEXTURE_2D);
    glMatrixMode(GL_PROJECTION);
    gluPerspective(60.0, 1.0, 1.0, 10.0 );
    glMatrixMode(GL_MODELVIEW);
    glTranslatef(0.,0.,-2.5);

    glColor4f(0,0,0,1);
    glClearColor(0.0, 0.0, 0.0, 1.0);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    /* sharpening just alpha keeps the tree outline crisp */
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
                    GL_LINEAR_SHARPEN_ALPHA_SGIS);
    /* generate mipmaps; levels 0 and 1 are needed for sharpening */
    gluBuild2DMipmaps(GL_TEXTURE_2D, 4, 16, 16, GL_RGBA, 
                      GL_UNSIGNED_BYTE, tex);
}

static void
draw_scene(void) {
    glClear(GL_COLOR_BUFFER_BIT);
    glBegin(GL_TRIANGLE_STRIP);
        glTexCoord2f( 0, 1); glVertex2f(-1,-1); 
        glTexCoord2f( 0, 0); glVertex2f(-1, 1); 
        glTexCoord2f( 1, 1); glVertex2f( 1,-1); 
        glTexCoord2f( 1, 0); glVertex2f( 1, 1); 
    glEnd();
    glFlush();
}