Pixel-Composer/shaders/sh_skew/sh_skew.fsh

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

uniform vec2 dimension;
uniform vec2 center;
uniform int axis;
uniform float amount;
uniform int sampleMode;

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

void main() {
	vec2 pos = v_vTexcoord;
	vec2 cnt = center / dimension;
	
	if(axis == 0)
		pos.x += (pos.y - cnt.y) * amount;
	else
		pos.y += (pos.x - cnt.x) * amount;
	
    gl_FragColor = sampleTexture( pos );
}