Worked on image functions

lib/image-functions.js

@@ -0,0 +1,115 @@
+export function load_image_from_src(src) {
+	return new Promise((resolve, reject) => {
+		const image = new Image();
+		image.src = src;
+
+		image.addEventListener('load', ({ target }) => {
+			const canvas = document.createElement('canvas');
+			const ctx = canvas.getContext('2d');
+			canvas.width = target.width;
+			canvas.height = target.height;
+
+			ctx.drawImage(target, 0, 0);
+
+			resolve(ctx.getImageData(0, 0, target.width, target.height));
+		});
+	});
+}
+
+export class Image_Row_Reference {
+	constructor(sampler, row) {
+		Object.assign(this, { sampler, row });
+	}
+
+	*[Symbol.iterator]() {
+		yield* this.sampler.iter_row(this.row);
+	}
+}
+
+export class RGBA_unorm8 {
+	constructor(R=0, G=0, B=0, A=255) {
+		Object.assign(this, { R, G, B, A });
+	}
+
+	*[Symbol.iterator]() {
+		const {R, G, B, A} = this;
+		yield* [R, G, B, A];
+	}
+
+	get non_zero() {
+		const {R, G, B, A} = this;
+		return (A > 0) && ((R > 0) || (G > 0) || (B > 0));
+	}
+
+}
+
+export class Image_Data_Sampler {
+	constructor(image_data) {
+		Object.assign(this, { image_data });
+	}
+
+	encode_as_bitfield() {
+		//TODO - add alignment option
+		const { width, height } = this.image_data;
+		let result = '';
+		const bytes_per_row = Math.ceil(width / 8);
+
+		for (const row of this) {
+			let pending_value = 0;
+			let bit_value = 1;
+			for (const pixel of row) {
+
+				if (pixel.non_zero) {
+					pending_value |= bit_value;
+				}
+
+				bit_value <<= 1;
+				if (bit_value === 256) {
+					result += String.fromCharCode(pending_value);
+					pending_value = 0;
+					bit_value = 1;
+				}
+			}
+			if (bit_value > 1) { //If we have a tail we flush it here.
+				result += String.fromCharCode(pending_value);
+				pending_value = 0;
+				bit_value = 1;
+			}
+		}
+		return `${width},${height},${btoa(result)}`;
+	}
+
+	*iter_row(row) {
+		const { pixelFormat, data, width, height } = this.image_data;
+		switch(pixelFormat) {
+			case 'rgba-unorm8': {
+				const pixel_offset_y = row * width;
+				for (let x=0; x<width; x++) {
+					const pixel_offset_x = pixel_offset_y + x;
+					const data_offset = pixel_offset_x * 4;
+					yield new RGBA_unorm8(...data.slice(data_offset, data_offset + 4));
+				}
+				break;
+			}
+
+			default:
+				throw new Error(`Format ${pixelFormat} is not yet supported by ${this.constructor.name}.`);
+		}
+	}
+
+	*[Symbol.iterator]() {
+		const { pixelFormat, data, width, height } = this.image_data;
+		switch(pixelFormat) {
+			case 'rgba-unorm8': {
+				for (let y=0; y<height; y++) {
+					yield new Image_Row_Reference(this, y);
+				}
+				break;
+			}
+
+			default:
+				throw new Error(`Format ${pixelFormat} is not yet supported by ${this.constructor.name}.`);
+		}
+	}
+
+}