Pixel-Composer/shaders/sh_camera/sh_camera.fsh

//
// Simple passthrough fragment shader
//
varying vec2 v_vTexcoord;
varying vec4 v_vColour;

uniform sampler2D scene;
uniform vec2 scnDimension;
uniform vec2 camDimension;
uniform vec2 position;
uniform float zoom;
uniform float blur;
uniform int sampleMode;

vec4 sampleTexture(vec2 pos) {
	if(pos.x >= 0. && pos.y >= 0. && pos.x <= 1. && pos.y <= 1.)
		return texture2D(scene, pos);
	
	if(sampleMode == 0) 
		return vec4(0.);
	if(sampleMode == 1) 
		return texture2D(scene, clamp(pos, 0., 1.));
	if(sampleMode == 2) 
		return texture2D(scene, fract(pos));
	
	return vec4(0.);
}

void main() {
	vec2 pos = position + (v_vTexcoord - vec2(.5)) * (camDimension / scnDimension) * zoom;
    gl_FragColor = sampleTexture( pos );
}