Added image loading routines and a triangular lattice sampler

lib/image-functions.js

@@ -16,6 +16,77 @@ export function load_image_from_src(src) {
 	});
 }
 
+export class Bitfield_Image_Sampler {
+	constructor(width, height, data) {
+		Object.assign(this, { width, height, data });
+	}
+
+	static from_string(encoded) {
+		const [width_str, height_str, b64] = encoded.split(',');
+		const width = parseInt(width_str, 10);
+		const height = parseInt(height_str, 10);
+		const decoded = atob(b64);
+		const data = new Uint8Array(decoded.length);
+		for (let i = 0; i < decoded.length; i++) {
+			data[i] = decoded.charCodeAt(i);
+		}
+		return new this(width, height, data);
+	}
+
+	*iter_row(row) {
+		const { width, data } = this;
+		const row_offset = row * Math.ceil(width / 8);
+		let byte_index = row_offset;
+		let bit_mask = 1;
+		let byte = data[byte_index++] ?? 0;
+
+		for (let x = 0; x < width; x++) {
+			yield (byte & bit_mask) !== 0;
+			bit_mask <<= 1;
+			if (bit_mask === 256) {
+				bit_mask = 1;
+				byte = data[byte_index++] ?? 0;
+			}
+		}
+	}
+
+	*[Symbol.iterator]() {
+		for (let y = 0; y < this.height; y++) {
+			yield new Image_Row_Reference(this, y);
+		}
+	}
+
+	sample(rawx, rawy) {
+		const { width, height, data } = this;
+
+		const x = Math.floor(rawx);
+		const y = Math.floor(rawy);
+
+		if (x < 0 || y < 0 || x >= width || y >= height ) {
+			return undefined;
+		}
+
+		const row_offset = y * Math.ceil(width / 8);
+		let byte_index = row_offset + Math.floor(x / 8);
+
+		return data[byte_index] & (1 << x % 8)
+	}
+
+	pixel_map(cb) {
+		let y = 0;
+		for (const row of this) {
+			let x = 0;
+			for (const pixel of row) {
+				cb(x, y, pixel);
+				x++;
+			}
+			y++;
+		}
+	}
+
+}
+
+
 export class Image_Row_Reference {
 	constructor(sampler, row) {
 		Object.assign(this, { sampler, row });