First commit.

It filters the colours by doing matrix multiplication in JS on the pixel array. It could almost definitely be made faster using a WebGL shader.

style.css

@@ -0,0 +1,36 @@
+:root {
+  --spacing: 1em;
+
+  color-scheme: light dark;
+}
+
+body {
+  font-family: sans-serif;
+}
+
+#grid {
+  margin: 5svh 0;
+  display: grid;
+  grid-template: repeat(2,1fr) / repeat(2,1fr);
+  width: 90svw;
+  height: 90svh;
+  gap: var(--spacing);
+}
+
+figure {
+    max-height: 100%;
+    display: grid;
+    overflow: hidden;
+    grid-template-rows: 1fr min-content;
+    margin: 0;
+}
+
+figcaption {
+  text-align: center;
+}
+
+img, canvas {
+  width: 100%;
+  height: 100%;
+  object-fit: cover;
+}