BarCode.js

// 左边的规则
function leftCode(number, o) {
    if(o == '1')
		return [
			'0001101', '0011001', '0010011', '0111101', '0100011',
			'0110001', '0101111', '0111011', '0110111', '0001011'][parseInt(number)%10];
	else {
		return [
			'0100111', '0110011', '0011011', '0100001', '0011101',
			'0111001', '0000101', '0010001', '0001001', '0010111'][parseInt(number)%10];
	}
}

// 右边的规则
function rightCode(number) {
	return [
		'1110010', '1100110', '1101100', '1000010', '1011100',
		'1001110', '1010000', '1000100', '1001000', '1110100'][parseInt(number)%10];
}

// 隐含数字的规则
function ISBNLeftRule(number) {
	return [
		'111111', '110100', '110010', '110001', '101100',
		'100110', '100011', '101010', '101001', '100101'][parseInt(number)%10];
}

function createEAN13(series) {
	var result = '101';
	var rule = ISBNLeftRule(series[0]);
	for(var i = 1; i < 7; ++i) {
		result += leftCode(series[i], rule[i-1]);
	}
	result += '01010';
	for(var i = 7; i < 13; ++i) {
		result += rightCode(series[i]);
	}
	result += '101';
	return result;
}

// 校验规则
function checkEAN13(series, mode) {
	var sum = 0;
	for(var i = 0; i < 6; ++i) {
		sum += parseInt(series[i*2]);
		sum += parseInt(series[i*2 + 1]) * 3;
	}
	sum = 10 - (sum % 10);
	if(mode == true)
		return sum + '';
	if(parseInt(series[12]) == sum)
		return true;
	return false;
}

function draw(ctx, series) {
	ctx.clearRect(0, 0, 1000, 1000);
	if(series.length == 12) {
		series = series + checkEAN13(series, true);
	} else if(checkEAN13(series) == false) {
		ctx.fillStyle = 'black';
		ctx.fillText('check failed!', 10, 30);
		return ;
	}
	var WIDTH = 4;		// 条码宽度
	var HEIGHT = 200;	// 条码高度
	var bc = createEAN13(series);
	ctx.fillStyle = 'black';
	for(i = 0; i < 3; ++i) {
		if(bc[i] == '1') {
			ctx.fillRect(i*WIDTH, 20, WIDTH, HEIGHT+25);
		}
	}
	for(; i < 45; ++i) {
		if(bc[i] == '1') {
			ctx.fillRect(i*WIDTH, 20, WIDTH, HEIGHT);
		}
	}
	for(; i < 50; ++i) {
		if(bc[i] == '1') {
			ctx.fillRect(i*WIDTH, 20, WIDTH, HEIGHT+25);
		}
	}
	for(; i < 92; ++i) {
		if(bc[i] == '1') {
			ctx.fillRect(i*WIDTH, 20, WIDTH, HEIGHT);
		}
	}
	for(; i < 95; ++i) {
		if(bc[i] == '1') {
			ctx.fillRect(i*WIDTH, 20, WIDTH, HEIGHT+25);
		}
	}
}

function create() {
	var ctx = document.getElementById('c').getContext('2d');
	var text = document.getElementById('in').value;
	draw(ctx, text);
}