xiao/util/Canvas.js

module.exports = class CanvasUtil {
	static greyscale(ctx, x, y, width, height) {
		const data = ctx.getImageData(x, y, width, height);
		for (let i = 0; i < data.data.length; i += 4) {
			const brightness = (0.34 * data.data[i]) + (0.5 * data.data[i + 1]) + (0.16 * data.data[i + 2]);
			data.data[i] = brightness;
			data.data[i + 1] = brightness;
			data.data[i + 2] = brightness;
		}
		ctx.putImageData(data, x, y);
		return ctx;
	}

	static invert(ctx, x, y, width, height) {
		const data = ctx.getImageData(x, y, width, height);
		for (let i = 0; i < data.data.length; i += 4) {
			data.data[i] = 255 - data.data[i];
			data.data[i + 1] = 255 - data.data[i + 1];
			data.data[i + 2] = 255 - data.data[i + 2];
		}
		ctx.putImageData(data, x, y);
		return ctx;
	}

	static silhouette(ctx, x, y, width, height) {
		const data = ctx.getImageData(x, y, width, height);
		for (let i = 0; i < data.data.length; i += 4) {
			data.data[i] = 0;
			data.data[i + 1] = 0;
			data.data[i + 2] = 0;
		}
		ctx.putImageData(data, x, y);
		return ctx;
	}

	static sepia(ctx, x, y, width, height) {
		const data = ctx.getImageData(x, y, width, height);
		for (let i = 0; i < data.data.length; i += 4) {
			const brightness = (0.34 * data.data[i]) + (0.5 * data.data[i + 1]) + (0.16 * data.data[i + 2]);
			data.data[i] = brightness + 100;
			data.data[i + 1] = brightness + 50;
			data.data[i + 2] = brightness;
		}
		ctx.putImageData(data, x, y);
		return ctx;
	}

	static contrast(ctx, x, y, width, height) {
		const data = ctx.getImageData(x, y, width, height);
		const factor = (259 / 100) + 1;
		const intercept = 128 * (1 - factor);
		for (let i = 0; i < data.data.length; i += 4) {
			data.data[i] = (data.data[i] * factor) + intercept;
			data.data[i + 1] = (data.data[i + 1] * factor) + intercept;
			data.data[i + 2] = (data.data[i + 2] * factor) + intercept;
		}
		ctx.putImageData(data, x, y);
		return ctx;
	}

	static distort(ctx, amplitude, x, y, width, height, strideLevel = 4) {
		const data = ctx.getImageData(x, y, width, height);
		const temp = ctx.getImageData(x, y, width, height);
		const stride = width * strideLevel;
		for (let i = 0; i < width; i++) {
			for (let j = 0; j < height; j++) {
				const xs = Math.round(amplitude * Math.sin(2 * Math.PI * 3 * (j / height)));
				const ys = Math.round(amplitude * Math.cos(2 * Math.PI * 3 * (i / width)));
				const dest = (j * stride) + (i * strideLevel);
				const src = ((j + ys) * stride) + ((i + xs) * strideLevel);
				data.data[dest] = temp.data[src];
				data.data[dest + 1] = temp.data[src + 1];
				data.data[dest + 2] = temp.data[src + 2];
			}
		}
		ctx.putImageData(data, x, y);
		return ctx;
	}

	static drawImageWithTint(ctx, image, color, x, y, width, height) {
		const { fillStyle, globalAlpha } = ctx;
		ctx.fillStyle = color;
		ctx.drawImage(image, x, y, width, height);
		ctx.globalAlpha = 0.5;
		ctx.fillRect(x, y, width, height);
		ctx.fillStyle = fillStyle;
		ctx.globalAlpha = globalAlpha;
	}

	static shortenText(ctx, text, maxWidth) {
		let shorten = false;
		while (ctx.measureText(text).width > maxWidth) {
			if (!shorten) shorten = true;
			text = text.substr(0, text.length - 1);
		}
		return shorten ? `${text}...` : text;
	}

	static wrapText(ctx, text, maxWidth) {
		return new Promise(resolve => {
			if (ctx.measureText(text).width < maxWidth) return resolve([text]);
			if (ctx.measureText('W').width > maxWidth) return resolve(null);
			const words = text.split(' ');
			const lines = [];
			let line = '';
			while (words.length > 0) {
				let split = false;
				while (ctx.measureText(words[0]).width >= maxWidth) {
					const temp = words[0];
					words[0] = temp.slice(0, -1);
					if (split) {
						words[1] = `${temp.slice(-1)}${words[1]}`;
					} else {
						split = true;
						words.splice(1, 0, temp.slice(-1));
					}
				}
				if (ctx.measureText(`${line}${words[0]}`).width < maxWidth) {
					line += `${words.shift()} `;
				} else {
					lines.push(line.trim());
					line = '';
				}
				if (words.length === 0) lines.push(line.trim());
			}
			return resolve(lines);
		});
	}

	static centerImage(base, data) {
		const dataRatio = data.width / data.height;
		const baseRatio = base.width / base.height;
		let { width, height } = data;
		let x = 0;
		let y = 0;
		if (baseRatio < dataRatio) {
			height = data.height;
			width = base.width * (height / base.height);
			x = (data.width - width) / 2;
			y = 0;
		} else if (baseRatio > dataRatio) {
			width = data.width;
			height = base.height * (width / base.width);
			x = 0;
			y = (data.height - height) / 2;
		}
		return { x, y, width, height };
	}

	static centerImagePart(data, maxWidth, maxHeight, widthOffset, heightOffest) {
		let { width, height } = data;
		if (width > maxWidth) {
			const ratio = maxWidth / width;
			width = maxWidth;
			height *= ratio;
		}
		if (height > maxHeight) {
			const ratio = maxHeight / height;
			height = maxHeight;
			width *= ratio;
		}
		const x = widthOffset + ((maxWidth / 2) - (width / 2));
		const y = heightOffest + ((maxHeight / 2) - (height / 2));
		return { x, y, width, height };
	}
};