Finally. I found it a simple solution!
- c++
glPushMatrix();
glBegin(GL_QUADS);
float scale_texcoord = 0.7;
float top = 0.7;
float tx = scale_texcoord * top;
glTexCoord2f(-1 / 2, -1);
glVertex2f(-1.4, -1);
glTexCoord4f(0, 0, 0, tx);
glVertex2f(-top, 1);
glTexCoord4f( tx, 0, 0, tx);
glVertex2f( top, 1);
glTexCoord2f( 1, -1);
glVertex2f( 1.4, -1);
glEnd();
glPopMatrix();
- fragment:
uniform sampler2D sampler;
void main()
{
vec2 interpolated = vec2(gl_TexCoord[0].x / gl_TexCoord[0].w, gl_TexCoord[0].y);
gl_FragColor = texture2D(sampler, vec2(interpolated.x, interpolated.y));
}