
// texcoords
varying vec2 texcoord0;
varying vec2 texdim0;

// samplers
uniform sampler2DRect tex0;

// resample dimensions
uniform vec4 crop;
uniform vec4 edge;
uniform vec2 zoom ; 
uniform vec2 offset ;
uniform float interp;

// entry point
void main()
{	
	// ramene coord [0-1] sur [0-texdim]
	vec4 cm = crop*vec4(texdim0.xyxy);
	vec4 am = edge*vec4(texdim0.xyxy);

	// calcul coord pixel fct zoom et offset
	vec2 fragcoord ;
	fragcoord = texcoord0/zoom - offset*texdim0 ; 

	
	// verifie que dans borne du crop
	bool bnd = all(bvec4(texcoord0.x>cm.x,texcoord0.x<cm.z,texcoord0.y>cm.y,texcoord0.y<cm.w));
	// recupere couleur pixel
	vec4 fragColor = texture2DRect(tex0,mix(floor(fragcoord),fragcoord,interp));
	float alpha = fragColor.a ; 
	
	// alpha blending hors des bornes
	if (bnd) {
		float ax = 1.;
		float ay = 1. ; 
	
	//	a = smoothstep (cm, am, texcoord0.xyxy) ;
			
		if (texcoord0.x<cm.x + am.x){
			ax = smoothstep (cm.x, cm.x+am.x, texcoord0.x) ;
		}else if (texcoord0.x>cm.z - am.z){
			ax = smoothstep (cm.z, cm.z-am.z, texcoord0.x) ;
		}
		if (texcoord0.y<cm.y + am.y){
			ay = smoothstep (cm.y, cm.y+am.y, texcoord0.y) ;
		}else if (texcoord0.y>cm.w - am.w){
			ay = smoothstep (cm.w, cm.w-am.w, texcoord0.y) ;
		}		
		
		
		fragColor.a = clamp(ax*ay, 0., alpha) ; 
	}
	else {
		fragColor.a = 0. ;
	}
	
	gl_FragColor = fragColor ;

}
