#extension GL_ARB_texture_rectangle : enable

uniform sampler2DRect MyTex;
uniform float Sl,Sr,St,Sb; // shade size
varying vec2 pos;


void main (void)
{
    vec4 color = texture2DRect(MyTex, gl_TexCoord[0].st);

    color.a *=min(1.,pos.x/Sl);
    color.a *=min(1.,(1.-pos.x)/Sr);
    color.a *=min(1.,pos.y/St);
    color.a *=min(1.,(1.-pos.y)/Sb);

    gl_FragColor = color;
}