diff --git a/greyscale.txt b/grayscale.txt
similarity index 100%
rename from greyscale.txt
rename to grayscale.txt
diff --git a/poptimal.js b/poptimal.js
index 80b7414..84bbae1 100644
--- a/poptimal.js
+++ b/poptimal.js
@@ -2,6 +2,7 @@ import {  Resvg } from "@resvg/resvg-js";
 import { promises } from "fs";
 import { JSDOM } from "jsdom";
 import * as d3 from "d3";
+import * as d3c from "d3-color";
 import yargs from "yargs/yargs";
 import { hideBin } from "yargs/helpers";
 import spawn from "await-spawn";
@@ -19,7 +20,9 @@ const CELL = 10;
 const MAG = 2;
 const WIDTH = 20;
 const HEIGHT = WIDTH;
-const VISIBLE_DOG = 1000;
+// number of pixels which have to be visible for a colour to be
+// mentioned in the alt text
+const VISIBLE_DOG = 400;
 
 function randomise_params() {
 	const palette_name = random.choice(Array.from(PALETTES.keys()));
@@ -40,6 +43,28 @@ function randomise_params() {
 	}
 }
 
+async function load_or_random_params(paramf) {
+	if( paramf ) {
+		const pjson = await promises.readFile(paramf);
+  		const params = JSON.parse(pjson);
+		params.background = d3c.color(params.background);
+		params.patterns.forEach((p) => {
+			p.colour = d3c.color(p.colour);
+		});	
+		return params;
+	}
+	return randomise_params();
+}
+
+async function save_params(paramf, params) {
+	params.background = params.background.formatHex();
+	params.patterns.forEach((p) => {
+		p.colour = p.colour.formatHex();
+	});
+	await promises.writeFile(paramf, JSON.stringify(params));
+}
+
+
 
 // lol the best way I found to to this was imagemagick!
 
@@ -183,23 +208,26 @@ async function post_image(image, alt_text, cf) {
 
 async function main() {
 	const argv = yargs(hideBin(process.argv))
-		.usage("Usage: -s SIZE -o output.png -c config.json")
+		.usage("Usage: -s SIZE [-o output] -c config.json [-p params.json]")
 		.default('s', 1200)
 		.default('c', 'config.json').argv;
 
 	const cfjson = await promises.readFile(argv.c);
   	const cf = JSON.parse(cfjson);
 
+        const ts = String(Date.now());
 
-
-  	const fn = argv.o || String(Date.now()) + '.png';
+  	const fn = (argv.o || ts) + '.png';
+	const jsfn = (argv.o || ts) + '.json';
 
   	const imgfile = cf['working_dir'] + '/' + fn;
+	const paramsfile = cf['working_dir'] + '/' + jsfn;
 
-	const params = randomise_params();
+	const params = await load_or_random_params(argv.p);
 	const colourf = params.palette === 'grayscale' ? cf['grayscale'] : cf['colour'];
 
 	const namer = new ColourNamer();
+	console.log(`Loading colours ${colourf}`);
 	await namer.load_colours(colourf);
 
 
@@ -216,7 +244,6 @@ async function main() {
  	const pngData = resvg.render();
   	const pngBuffer = pngData.asPng();
 
-
   	await promises.writeFile(imgfile, pngBuffer);
 
   	// generate the alt_text last to check the image file histogram
@@ -224,6 +251,7 @@ async function main() {
   	const hist = await get_histogram(imgfile);
 	const alt_text = image_description(namer, params, hist);
 
+	await save_params(paramsfile, params);
 	console.log(alt_text);
 	console.log(imgfile);
   	if( cf['base_url'] ) {