我想使用JavaScript来计算字符串的宽度。如果不使用单行字体,这可能吗?
如果它不是内置的,我唯一的想法是为每个字符创建一个宽度表,但这是非常不合理的,特别是支持Unicode和不同的类型大小(以及所有浏览器)。
我想使用JavaScript来计算字符串的宽度。如果不使用单行字体,这可能吗?
如果它不是内置的,我唯一的想法是为每个字符创建一个宽度表,但这是非常不合理的,特别是支持Unicode和不同的类型大小(以及所有浏览器)。
当前回答
嘿,大家,我知道我来晚了一点,但我们开始吧
window.addEventListener("error",function(e){ alert(e.message); });
var canvas = new OffscreenCanvas(400, 50);
var ctx = canvas.getContext("2d");
ctx.font = "16px Ariel"; //this can be dynamic using getComputedStyle
const chars = ["a","b","c","d","e","f"," "," "];
const charWidths = new Map();
while(chars.length > 0){
var char = chars.shift();
var wide = ctx.measureText(char).width;
charWidths.set(char,wide);
}
然后你可以用它来做如下的事情:
var pixelWidth = charWidths.get("0");
//fyi css properties like letter-spacing need to be accounted for
其他回答
我喜欢你的“唯一的想法”只是做一个静态字符宽度地图!它实际上很适合我的目的。有时,出于性能原因,或者因为不容易访问DOM,您可能只想要一个快速的、独立的、校准为单一字体的计算器。这是一个用Helvetica字体校准的;传递一个字符串和字体大小:
const widths = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0.2796875,0.2765625,0.3546875,0.5546875,0.5546875,0.8890625,0.665625,0.190625,0.3328125,0.3328125,0.3890625,0.5828125,0.2765625,0.3328125,0.2765625,0.3015625,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.2765625,0.2765625,0.584375,0.5828125,0.584375,0.5546875,1.0140625,0.665625,0.665625,0.721875,0.721875,0.665625,0.609375,0.7765625,0.721875,0.2765625,0.5,0.665625,0.5546875,0.8328125,0.721875,0.7765625,0.665625,0.7765625,0.721875,0.665625,0.609375,0.721875,0.665625,0.94375,0.665625,0.665625,0.609375,0.2765625,0.3546875,0.2765625,0.4765625,0.5546875,0.3328125,0.5546875,0.5546875,0.5,0.5546875,0.5546875,0.2765625,0.5546875,0.5546875,0.221875,0.240625,0.5,0.221875,0.8328125,0.5546875,0.5546875,0.5546875,0.5546875,0.3328125,0.5,0.2765625,0.5546875,0.5,0.721875,0.5,0.5,0.5,0.3546875,0.259375,0.353125,0.5890625]
const avg = 0.5279276315789471
function measureText(str, fontSize) {
return Array.from(str).reduce(
(acc, cur) => acc + (widths[cur.charCodeAt(0)] ?? avg), 0
) * fontSize
}
这个巨大的丑陋数组是由字符代码索引的ASCII字符宽度。所以这只支持ASCII(否则它假设平均字符宽度)。幸运的是,宽度基本上是随字体大小线性缩放的,所以它在任何字体大小下都能很好地工作。它明显缺乏对字距或结扎之类的意识。
为了“校准”,我只是在svg上渲染了charCode 126(强大的波浪号)的每个字符,并获得了边界框并将其保存到这个数组中;这里有更多的代码、解释和演示。
这对我很有用……
// Handy JavaScript to measure the size taken to render the supplied text;
// you can supply additional style information too if you have it.
function measureText(pText, pFontSize, pStyle) {
var lDiv = document.createElement('div');
document.body.appendChild(lDiv);
if (pStyle != null) {
lDiv.style = pStyle;
}
lDiv.style.fontSize = "" + pFontSize + "px";
lDiv.style.position = "absolute";
lDiv.style.left = -1000;
lDiv.style.top = -1000;
lDiv.textContent = pText;
var lResult = {
width: lDiv.clientWidth,
height: lDiv.clientHeight
};
document.body.removeChild(lDiv);
lDiv = null;
return lResult;
}
我猜这和Depak的条目很相似,但这是基于Louis Lazaris在impressiveweb页面上发表的一篇文章
(function($){
$.fn.autofit = function() {
var hiddenDiv = $(document.createElement('div')),
content = null;
hiddenDiv.css('display','none');
$('body').append(hiddenDiv);
$(this).bind('fit keyup keydown blur update focus',function () {
content = $(this).val();
content = content.replace(/\n/g, '<br>');
hiddenDiv.html(content);
$(this).css('width', hiddenDiv.width());
});
return this;
};
})(jQuery);
fit事件用于在函数关联到控件之后立即执行函数调用。
例如:$(“输入”).autofit () .trigger(“适合”);
你可以使用画布,这样你就不必处理这么多css属性:
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
ctx.font = "20pt Arial"; // This can be set programmaticly from the element's font-style if desired
var textWidth = ctx.measureText($("#myElement").text()).width;
var textWidth = (function (el) {
el.style.position = 'absolute';
el.style.top = '-1000px';
document.body.appendChild(el);
return function (text) {
el.innerHTML = text;
return el.clientWidth;
};
})(document.createElement('div'));