Demo.pde

PGraphics img;

void setup(){
	size(500, 500, P2D);
	
	createimg();
}

void draw(){
	background(40, 60, 200);

	// this part....
	beginShape();
    texture(img);
    vertex(50, 150, 0, 0);
    vertex(450, 150, img.width, 0);
    vertex(350, 350, img.width, img.height);
    vertex(150, 350, 0, img.height);
    endShape();
}

void createimg(){
	img = createGraphics(200, 200);
	img.beginDraw();
	img.background(200, 60, 40);
	img.stroke(10);
	for(float p = 0; p <= 1; p += 1.0/10){
		img.line(p*img.width, 0, p*img.width, img.height);
		img.line(0, p*img.height, img.width, p*img.height);
	}
	img.endDraw();
}