我正在尝试做一些应该非常简单的事情，但我在失败和论坛之间度过了一天。
我想调整我的字体以匹配我的基线。在 indesign 中只需点击一下即可，但在 css 中这看起来是地球上最困难的事情。
让我们举一个有理值的简单例子。
在这张图片上，我每 20 像素就有一个基线。
所以对于我的<body> I do:
<style>
body {font-size:16px; line-height:20px;}
</style>
一切都很完美。我的段落与基线相符。
但是当我编写我的脚本时<h>这不再符合基线了..我做错了什么？这应该遵循我的基线，不是吗？
<style type="text/css">
body{font-size: 16px; line-height: 20px;}
h1{font-size: 5em; line-height: 1.25em;}
h2{font-size: 4em; line-height: 1.25em;}
h3{font-size: 3em; line-height: 1.25em;}
h4{font-size: 2em; line-height: 1.25em;}
</style>
PS：20/16=1.25em
在我的检查器中，计算返回预期值
h1{font-size: 84px; line-height: 100px;}
h2{font-size: 68px; line-height: 80px;}
h3{font-size: 52px; line-height: 60px;}
h4{font-size: 36px; line-height: 40px;}
So that should display something like this no? 
这有点复杂 - 你必须首先测量字体（就像 InDesign 所做的那样）并计算“行高”，即你所说的“bottom_gap”和其他一些东西
我很确定我们可以用 JavaScript 做一些事情..
你是对的 - 但对于 Typography JS 用于计算 CSS（取决于字体指标）
在这里演示了第一步（测量字体）https://codepen.io/sebilasse/pen/gPBQqm https://codepen.io/sebilasse/pen/gPBQqm它只是以图形方式显示测量的内容[针对技术背景]
需要进行这种测量，因为每种字体在“行”中的表现完全不同。
这是一个可以生成这样的 Typo CSS 的生成器:
https://codepen.io/sebilasse/pen/BdaPzN https://codepen.io/sebilasse/pen/BdaPzN
测量的函数可以基于<canvas>看起来像这样：
function getMetrics(fontName, fontSize) {
// NOTE: if there is no getComputedStyle, this library won't work.
if(!document.defaultView.getComputedStyle) {
throw("ERROR: 'document.defaultView.getComputedStyle' not found. This library only works in browsers that can report computed CSS values.");
}
if (!document.querySelector('canvas')) {
var _canvas = document.createElement('canvas');
_canvas.width = 220; _canvas.height = 220;
document.body.appendChild(_canvas);
}
// Store the old text metrics function on the Canvas2D prototype
CanvasRenderingContext2D.prototype.measureTextWidth = CanvasRenderingContext2D.prototype.measureText;
/**
* Shortcut function for getting computed CSS values
*/
var getCSSValue = function(element, property) {
return document.defaultView.getComputedStyle(element,null).getPropertyValue(property);
};
/**
* The new text metrics function
*/
CanvasRenderingContext2D.prototype.measureText = function(textstring) {
var metrics = this.measureTextWidth(textstring),
fontFamily = getCSSValue(this.canvas,"font-family"),
fontSize = getCSSValue(this.canvas,"font-size").replace("px",""),
isSpace = !(/\S/.test(textstring));
metrics.fontsize = fontSize;
// For text lead values, we meaure a multiline text container.
var leadDiv = document.createElement("div");
leadDiv.style.position = "absolute";
leadDiv.style.margin = 0;
leadDiv.style.padding = 0;
leadDiv.style.opacity = 0;
leadDiv.style.font = fontSize + "px " + fontFamily;
leadDiv.innerHTML = textstring + "<br/>" + textstring;
document.body.appendChild(leadDiv);
// Make some initial guess at the text leading (using the standard TeX ratio)
metrics.leading = 1.2 * fontSize;
// Try to get the real value from the browser
var leadDivHeight = getCSSValue(leadDiv,"height");
leadDivHeight = leadDivHeight.replace("px","");
if (leadDivHeight >= fontSize * 2) { metrics.leading = (leadDivHeight/2) | 0; }
document.body.removeChild(leadDiv);
// if we're not dealing with white space, we can compute metrics
if (!isSpace) {
// Have characters, so measure the text
var canvas = document.createElement("canvas");
var padding = 100;
canvas.width = metrics.width + padding;
canvas.height = 3*fontSize;
canvas.style.opacity = 1;
canvas.style.fontFamily = fontFamily;
canvas.style.fontSize = fontSize;
var ctx = canvas.getContext("2d");
ctx.font = fontSize + "px " + fontFamily;
var w = canvas.width,
h = canvas.height,
baseline = h/2;
// Set all canvas pixeldata values to 255, with all the content
// data being 0. This lets us scan for data[i] != 255.
ctx.fillStyle = "white";
ctx.fillRect(-1, -1, w+2, h+2);
ctx.fillStyle = "black";
ctx.fillText(textstring, padding/2, baseline);
var pixelData = ctx.getImageData(0, 0, w, h).data;
// canvas pixel data is w*4 by h*4, because R, G, B and A are separate,
// consecutive values in the array, rather than stored as 32 bit ints.
var i = 0,
w4 = w * 4,
len = pixelData.length;
// Finding the ascent uses a normal, forward scanline
while (++i < len && pixelData[i] === 255) {}
var ascent = (i/w4)|0;
// Finding the descent uses a reverse scanline
i = len - 1;
while (--i > 0 && pixelData[i] === 255) {}
var descent = (i/w4)|0;
// find the min-x coordinate
for(i = 0; i<len && pixelData[i] === 255; ) {
i += w4;
if(i>=len) { i = (i-len) + 4; }}
var minx = ((i%w4)/4) | 0;
// find the max-x coordinate
var step = 1;
for(i = len-3; i>=0 && pixelData[i] === 255; ) {
i -= w4;
if(i<0) { i = (len - 3) - (step++)*4; }}
var maxx = ((i%w4)/4) + 1 | 0;
// set font metrics
metrics.ascent = (baseline - ascent);
metrics.descent = (descent - baseline);
metrics.bounds = { minx: minx - (padding/2),
maxx: maxx - (padding/2),
miny: 0,
maxy: descent-ascent };
metrics.height = 1+(descent - ascent);
} else {
// Only whitespace, so we can't measure the text
metrics.ascent = 0;
metrics.descent = 0;
metrics.bounds = { minx: 0,
maxx: metrics.width, // Best guess
miny: 0,
maxy: 0 };
metrics.height = 0;
}
return metrics;
};
Note您还需要一个好的“reset.css”来重置浏览器边距和填充。
你点击“show CSS”，你还可以使用生成的CSS来混合多种字体：
如果它们具有不同的基本尺寸，请标准化第二个：
var factor = CSS1baseSize / CSS2baseSize;
现在重新计算 CSS2 中的每种字体
var size = size * factor;
请参阅演示https://codepen.io/sebilasse/pen/oENGev?editors=1100 https://codepen.io/sebilasse/pen/oENGev?editors=1100
如果涉及图像怎么办？ 以下演示使用两种具有相同规格的字体以及额外的 JS 部分。需要计算基线网格的媒体元素，例如图像：https://codepen.io/sebilasse/pen/ddopBj https://codepen.io/sebilasse/pen/ddopBj