PARTYMANX

use std::env;
use std::str;
use std::fs;
use std::fs::File;
use std::io::{ self, BufRead, BufReader };
use std::io::Seek;
use std::io::Read;
use std::io::Write;
use std::path::Path;
use std::io::SeekFrom;

PARTYMANX

// uv is input texture coord, srcRes is original texture resolution, returns filtered texture coords
vec2 filterCoord(vec2 uv, vec2 srcRes) {
	vec2 invSrc = 1.0 / srcRes;

	// calculate destination resolution
	vec2 duv1 = vec2(dFdx(uv.x), dFdy(uv.y));
	vec2 duv2 = vec2(dFdy(uv.x), dFdx(uv.y));
    
	vec2 duv = max(abs(duv1), abs(duv2));	// pick the larger derivatives (accounting for sideways sampling)