From 114ba4279dea733f216b4e2d2b3cafb6c931c3bb Mon Sep 17 00:00:00 2001
From: Matthias Wirth <matthias.wirth@gmail.com>
Date: Mon, 20 Apr 2020 17:50:25 +0200
Subject: [PATCH] make negative dim and contrast work (not really useful)

---
 html/script.js | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/html/script.js b/html/script.js
index d7842c2..ba90ce2 100644
--- a/html/script.js
+++ b/html/script.js
@@ -3008,11 +3008,20 @@ function dim(evt) {
         evt.context.globalCompositeOperation = 'multiply';
         evt.context.fillStyle = 'rgba(0,0,0,'+dim+')';
         evt.context.fillRect(0, 0, evt.context.canvas.width, evt.context.canvas.height);
+    } else if (dim < -0.0001) {
+        evt.context.globalCompositeOperation = 'screen';
+        console.log(evt.context.globalCompositeOperation);
+        evt.context.fillStyle = 'rgba(255, 255, 255,'+(-dim)+')';
+        evt.context.fillRect(0, 0, evt.context.canvas.width, evt.context.canvas.height);
     }
     if (contrast > 0.0001) {
         evt.context.globalCompositeOperation = 'overlay';
         evt.context.fillStyle = 'rgba(0,0,0,'+contrast+')';
         evt.context.fillRect(0, 0, evt.context.canvas.width, evt.context.canvas.height);
+    } else if (contrast < -0.0001) {
+        evt.context.globalCompositeOperation = 'overlay';
+        evt.context.fillStyle = 'rgba(255, 255, 255,'+ (-contrast)+')';
+        evt.context.fillRect(0, 0, evt.context.canvas.width, evt.context.canvas.height);
     }
     evt.context.globalCompositeOperation = 'source-over';
 }