From a0ca7781ca50924ce89a1a6187c6f7cabef70a7f Mon Sep 17 00:00:00 2001
From: elioat <elioat@tilde.institute>
Date: Sun, 30 Jun 2024 16:23:29 -0400
Subject: *

---
 js/dither-video/video.js | 101 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 js/dither-video/video.js

(limited to 'js/dither-video/video.js')

diff --git a/js/dither-video/video.js b/js/dither-video/video.js
new file mode 100644
index 0000000..0da0157
--- /dev/null
+++ b/js/dither-video/video.js
@@ -0,0 +1,101 @@
+const toggleCameraButton = document.getElementById('toggleCamera');
+const video = document.getElementById('webcam');
+const canvas = document.getElementById('ditheredOutput');
+const context = canvas.getContext('2d');
+
+let stream = null;
+let isCameraOn = false;
+
+// FIXME: Sort out how to crop the image rather than squish and distort it.
+const lowResWidth = 160; // Gameboy camera resolution: 160×144
+const lowResHeight = 120; // If I use the GB camera resolution the image gets distorted
+
+toggleCameraButton.addEventListener('click', async () => {
+    if (!isCameraOn) {
+        try {
+            stream = await navigator.mediaDevices.getUserMedia({ video: true });
+            video.srcObject = stream;
+            video.style.display = 'block';
+            isCameraOn = true;
+            toggleCameraButton.textContent = 'Turn Camera Off';
+            video.addEventListener('loadeddata', () => {
+                canvas.width = lowResWidth;
+                canvas.height = lowResHeight;
+                requestAnimationFrame(processFrame);
+            });
+        } catch (err) {
+            console.error('Failed to access the camera: ', err);
+        }
+    } else {
+        stream.getTracks().forEach(track => track.stop());
+        video.style.display = 'none';
+        isCameraOn = false;
+        toggleCameraButton.textContent = 'Turn Camera On';
+    }
+});
+
+function processFrame() {
+    if (!isCameraOn) return;
+
+    context.drawImage(video, 0, 0, lowResWidth, lowResHeight);
+    const frame = context.getImageData(0, 0, lowResWidth, lowResHeight);
+    applyFloydSteinbergDithering(frame);
+    context.putImageData(frame, 0, 0);
+    requestAnimationFrame(processFrame);
+}
+
+
+function applyFloydSteinbergDithering(imageData) {
+    const { data, width, height } = imageData;
+
+    // Helpers to access and set pixel values
+    const getPixelIndex = (x, y) => (y * width + x) * 4;
+    const getPixelValue = (x, y) => data[getPixelIndex(x, y)];
+    const setPixelValue = (x, y, value) => {
+        const index = getPixelIndex(x, y);
+        data[index] = value;
+        data[index + 1] = value;
+        data[index + 2] = value;
+    };
+
+    // Helper that clamps a value between 0 and 255
+    const clamp = (value) => Math.max(0, Math.min(255, value));
+
+    // Process a single pixel
+    const processPixel = (x, y) => {
+        const oldPixel = getPixelValue(x, y);
+        const newPixel = oldPixel < 128 ? 0 : 255; // Threshold of the pixel value
+        setPixelValue(x, y, newPixel);
+        const quantError = oldPixel - newPixel;
+
+        // Spreads the error to neighboring pixels
+        if (x + 1 < width) {
+            const idx = getPixelIndex(x + 1, y);
+            data[idx] = clamp(data[idx] + quantError * 7 / 16);
+        }
+        if (x - 1 >= 0 && y + 1 < height) {
+            const idx = getPixelIndex(x - 1, y + 1);
+            data[idx] = clamp(data[idx] + quantError * 3 / 16);
+        }
+        if (y + 1 < height) {
+            const idx = getPixelIndex(x, y + 1);
+            data[idx] = clamp(data[idx] + quantError * 5 / 16);
+        }
+        if (x + 1 < width && y + 1 < height) {
+            const idx = getPixelIndex(x + 1, y + 1);
+            data[idx] = clamp(data[idx] + quantError * 1 / 16);
+        }
+    };
+
+    // TODO: This seems like a mad inefficient way to do this, but it does work. Noodle on if it is worth making this more efficient.
+    // Process all of the pixels
+    for (let y = 0; y < height; y++) {
+        for (let x = 0; x < width; x++) {
+            processPixel(x, y);
+        }
+    }
+}
+
+function clamp(value) {
+    return Math.max(0, Math.min(255, value));
+}
-- 
cgit 1.4.1-2-gfad0