如果文本中包含 "\n",我似乎无法将文本添加到画布上。我的意思是,换行符不会显示/起作用。
ctxPaint.fillText("s ome \n \\n <br/> thing", x, y);
以上代码将在一行上绘制"s ome \n <br/> thing"
。
这是fillText的限制还是我的问题?"\n"存在但没有被打印出来,也不起作用。
如果文本中包含 "\n",我似乎无法将文本添加到画布上。我的意思是,换行符不会显示/起作用。
ctxPaint.fillText("s ome \n \\n <br/> thing", x, y);
以上代码将在一行上绘制"s ome \n <br/> thing"
。
这是fillText的限制还是我的问题?"\n"存在但没有被打印出来,也不起作用。
如果您只想处理文本中的换行符,可以通过在换行符处拆分文本并多次调用fillText()
来模拟它。
类似于http://jsfiddle.net/BaG4J/1/
var c = document.getElementById('c').getContext('2d');
c.font = '11px Courier';
console.log(c);
var txt = 'line 1\nline 2\nthird line..';
var x = 30;
var y = 30;
var lineheight = 15;
var lines = txt.split('\n');
for (var i = 0; i<lines.length; i++)
c.fillText(lines[i], x, y + (i*lineheight) );
canvas{background-color:#ccc;}
<canvas id="c" width="150" height="150"></canvas>
我刚刚做了一个包裹的概念验证(在指定宽度上进行绝对换行,但尚未处理单词中断)
示例位于http://jsfiddle.net/BaG4J/2/
var c = document.getElementById('c').getContext('2d');
c.font = '11px Courier';
var txt = 'this is a very long text to print';
printAt(c, txt, 10, 20, 15, 90 );
function printAt( context , text, x, y, lineHeight, fitWidth)
{
fitWidth = fitWidth || 0;
if (fitWidth <= 0)
{
context.fillText( text, x, y );
return;
}
for (var idx = 1; idx <= text.length; idx++)
{
var str = text.substr(0, idx);
console.log(str, context.measureText(str).width, fitWidth);
if (context.measureText(str).width > fitWidth)
{
context.fillText( text.substr(0, idx-1), x, y );
printAt(context, text.substr(idx-1), x, y + lineHeight, lineHeight, fitWidth);
return;
}
}
context.fillText( text, x, y );
}
canvas{background-color:#ccc;}
<canvas id="c" width="150" height="150"></canvas>
这是一个单词换行(在空格处断开)的概念验证。
示例位于http://jsfiddle.net/BaG4J/5/
var c = document.getElementById('c').getContext('2d');
c.font = '11px Courier';
var txt = 'this is a very long text. Some more to print!';
printAtWordWrap(c, txt, 10, 20, 15, 90 );
function printAtWordWrap( context , text, x, y, lineHeight, fitWidth)
{
fitWidth = fitWidth || 0;
if (fitWidth <= 0)
{
context.fillText( text, x, y );
return;
}
var words = text.split(' ');
var currentLine = 0;
var idx = 1;
while (words.length > 0 && idx <= words.length)
{
var str = words.slice(0,idx).join(' ');
var w = context.measureText(str).width;
if ( w > fitWidth )
{
if (idx==1)
{
idx=2;
}
context.fillText( words.slice(0,idx-1).join(' '), x, y + (lineHeight*currentLine) );
currentLine++;
words = words.splice(idx-1);
idx = 1;
}
else
{idx++;}
}
if (idx > 0)
context.fillText( words.join(' '), x, y + (lineHeight*currentLine) );
}
canvas{background-color:#ccc;}
<canvas id="c" width="150" height="150"></canvas>
measureText()
方法,该方法显示在打印时字符串的长度(以像素为单位)。if
条件if(idx > 0)
的要求。idx
的初始值为1
,在if
条件之前没有任何地方对其进行减少。因此,if
条件将始终为true
。或者我有什么遗漏吗? - Nikunj Bhatt很遗憾,Canvas的fillText
存在一些限制,它不支持多行文本。更糟糕的是,没有内置的方法来测量行高,只能测量宽度,这使得自己实现变得更加困难!
许多人都编写了自己的多行文本支持,其中最著名的项目可能是Mozilla Skywriter。
你需要做的主要是多次进行fillText
调用,并在每次添加文本高度到y值中。 (我相信Skywriter中的人们测量M的宽度来近似文本。)
actualBoundingBoxAscent
来测量行高。 - Summer Sun可能我有些晚到这场派对,但我发现下面的教程非常适合在画布上换行文本。
http://www.html5canvastutorials.com/tutorials/html5-canvas-wrap-text-tutorial/
通过这个教程,我成功地让多行文本工作了(很抱歉 Ramirez,你的没能为我起作用!)。我的完整代码如下:
<script type="text/javascript">
// http: //www.html5canvastutorials.com/tutorials/html5-canvas-wrap-text-tutorial/
function wrapText(context, text, x, y, maxWidth, lineHeight) {
var cars = text.split("\n");
for (var ii = 0; ii < cars.length; ii++) {
var line = "";
var words = cars[ii].split(" ");
for (var n = 0; n < words.length; n++) {
var testLine = line + words[n] + " ";
var metrics = context.measureText(testLine);
var testWidth = metrics.width;
if (testWidth > maxWidth) {
context.fillText(line, x, y);
line = words[n] + " ";
y += lineHeight;
}
else {
line = testLine;
}
}
context.fillText(line, x, y);
y += lineHeight;
}
}
function DrawText() {
var canvas = document.getElementById("c");
var context = canvas.getContext("2d");
context.clearRect(0, 0, 500, 600);
var maxWidth = 400;
var lineHeight = 60;
var x = 20; // (canvas.width - maxWidth) / 2;
var y = 58;
var text = document.getElementById("text").value.toUpperCase();
context.fillStyle = "rgba(255, 0, 0, 1)";
context.fillRect(0, 0, 600, 500);
context.font = "51px 'LeagueGothicRegular'";
context.fillStyle = "#333";
wrapText(context, text, x, y, maxWidth, lineHeight);
}
$(document).ready(function () {
$("#text").keyup(function () {
DrawText();
});
});
</script>
其中c
是我的canvas的ID,text
是我的文本框的ID。
你可能已经看到我在使用非标准字体。你可以使用@font-face,只要你在操作canvas之前在某些文本上使用了该字体 - 否则canvas不会捕获该字体。
希望这能帮助到某些人。
将文本分成行,并单独绘制每一行:
function fillTextMultiLine(ctx, text, x, y) {
var lineHeight = ctx.measureText("M").width * 1.2;
var lines = text.split("\n");
for (var i = 0; i < lines.length; ++i) {
ctx.fillText(lines[i], x, y);
y += lineHeight;
}
}
这是我的解决方案,修改了已经在此处提供的流行的wrapText()函数。我使用JavaScript的原型功能,这样您就可以从画布上下文中调用该函数。
CanvasRenderingContext2D.prototype.wrapText = function (text, x, y, maxWidth, lineHeight) {
var lines = text.split("\n");
for (var i = 0; i < lines.length; i++) {
var words = lines[i].split(' ');
var line = '';
for (var n = 0; n < words.length; n++) {
var testLine = line + words[n] + ' ';
var metrics = this.measureText(testLine);
var testWidth = metrics.width;
if (testWidth > maxWidth && n > 0) {
this.fillText(line, x, y);
line = words[n] + ' ';
y += lineHeight;
}
else {
line = testLine;
}
}
this.fillText(line, x, y);
y += lineHeight;
}
}
基本用法:
var myCanvas = document.getElementById("myCanvas");
var ctx = myCanvas.getContext("2d");
ctx.fillStyle = "black";
ctx.font = "12px sans-serif";
ctx.textBaseline = "top";
ctx.wrapText("Hello\nWorld!",20,20,160,16);
这是我制作的一个演示:http://jsfiddle.net/7RdbL/
CanvasRenderingContext2D
并添加了两个功能:mlFillText和mlStrokeText。\n
并且还可以调整文字的对齐方式).function mlFillText(text,x,y,w,h,vAlign,hAlign,lineheight);
function mlStrokeText(text,x,y,w,h,vAlign,hAlign,lineheight);
< p >其中vAlign
可以是:top
,center
或button
hAlign
可以是:left
,center
,right
或justify
您可以在这里测试该库:http://jsfiddle.net/4WRZj/1/
这是该库的代码:
// Library: mltext.js
// Desciption: Extends the CanvasRenderingContext2D that adds two functions: mlFillText and mlStrokeText.
//
// The prototypes are:
//
// function mlFillText(text,x,y,w,h,vAlign,hAlign,lineheight);
// function mlStrokeText(text,x,y,w,h,vAlign,hAlign,lineheight);
//
// Where vAlign can be: "top", "center" or "button"
// And hAlign can be: "left", "center", "right" or "justify"
// Author: Jordi Baylina. (baylina at uniclau.com)
// License: GPL
// Date: 2013-02-21
function mlFunction(text, x, y, w, h, hAlign, vAlign, lineheight, fn) {
text = text.replace(/[\n]/g, " \n ");
text = text.replace(/\r/g, "");
var words = text.split(/[ ]+/);
var sp = this.measureText(' ').width;
var lines = [];
var actualline = 0;
var actualsize = 0;
var wo;
lines[actualline] = {};
lines[actualline].Words = [];
i = 0;
while (i < words.length) {
var word = words[i];
if (word == "\n") {
lines[actualline].EndParagraph = true;
actualline++;
actualsize = 0;
lines[actualline] = {};
lines[actualline].Words = [];
i++;
} else {
wo = {};
wo.l = this.measureText(word).width;
if (actualsize === 0) {
while (wo.l > w) {
word = word.slice(0, word.length - 1);
wo.l = this.measureText(word).width;
}
if (word === "") return; // I can't fill a single character
wo.word = word;
lines[actualline].Words.push(wo);
actualsize = wo.l;
if (word != words[i]) {
words[i] = words[i].slice(word.length, words[i].length);
} else {
i++;
}
} else {
if (actualsize + sp + wo.l > w) {
lines[actualline].EndParagraph = false;
actualline++;
actualsize = 0;
lines[actualline] = {};
lines[actualline].Words = [];
} else {
wo.word = word;
lines[actualline].Words.push(wo);
actualsize += sp + wo.l;
i++;
}
}
}
}
if (actualsize === 0) lines[actualline].pop();
lines[actualline].EndParagraph = true;
var totalH = lineheight * lines.length;
while (totalH > h) {
lines.pop();
totalH = lineheight * lines.length;
}
var yy;
if (vAlign == "bottom") {
yy = y + h - totalH + lineheight;
} else if (vAlign == "center") {
yy = y + h / 2 - totalH / 2 + lineheight;
} else {
yy = y + lineheight;
}
var oldTextAlign = this.textAlign;
this.textAlign = "left";
for (var li in lines) {
var totallen = 0;
var xx, usp;
for (wo in lines[li].Words) totallen += lines[li].Words[wo].l;
if (hAlign == "center") {
usp = sp;
xx = x + w / 2 - (totallen + sp * (lines[li].Words.length - 1)) / 2;
} else if ((hAlign == "justify") && (!lines[li].EndParagraph)) {
xx = x;
usp = (w - totallen) / (lines[li].Words.length - 1);
} else if (hAlign == "right") {
xx = x + w - (totallen + sp * (lines[li].Words.length - 1));
usp = sp;
} else { // left
xx = x;
usp = sp;
}
for (wo in lines[li].Words) {
if (fn == "fillText") {
this.fillText(lines[li].Words[wo].word, xx, yy);
} else if (fn == "strokeText") {
this.strokeText(lines[li].Words[wo].word, xx, yy);
}
xx += lines[li].Words[wo].l + usp;
}
yy += lineheight;
}
this.textAlign = oldTextAlign;
}
(function mlInit() {
CanvasRenderingContext2D.prototype.mlFunction = mlFunction;
CanvasRenderingContext2D.prototype.mlFillText = function (text, x, y, w, h, vAlign, hAlign, lineheight) {
this.mlFunction(text, x, y, w, h, hAlign, vAlign, lineheight, "fillText");
};
CanvasRenderingContext2D.prototype.mlStrokeText = function (text, x, y, w, h, vAlign, hAlign, lineheight) {
this.mlFunction(text, x, y, w, h, hAlign, vAlign, lineheight, "strokeText");
};
})();
以下是使用示例:
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
var T = "This is a very long line line with a CR at the end.\n This is the second line.\nAnd this is the last line.";
var lh = 12;
ctx.lineWidth = 1;
ctx.mlFillText(T, 10, 10, 100, 100, 'top', 'left', lh);
ctx.strokeRect(10, 10, 100, 100);
ctx.mlFillText(T, 110, 10, 100, 100, 'top', 'center', lh);
ctx.strokeRect(110, 10, 100, 100);
ctx.mlFillText(T, 210, 10, 100, 100, 'top', 'right', lh);
ctx.strokeRect(210, 10, 100, 100);
ctx.mlFillText(T, 310, 10, 100, 100, 'top', 'justify', lh);
ctx.strokeRect(310, 10, 100, 100);
ctx.mlFillText(T, 10, 110, 100, 100, 'center', 'left', lh);
ctx.strokeRect(10, 110, 100, 100);
ctx.mlFillText(T, 110, 110, 100, 100, 'center', 'center', lh);
ctx.strokeRect(110, 110, 100, 100);
ctx.mlFillText(T, 210, 110, 100, 100, 'center', 'right', lh);
ctx.strokeRect(210, 110, 100, 100);
ctx.mlFillText(T, 310, 110, 100, 100, 'center', 'justify', lh);
ctx.strokeRect(310, 110, 100, 100);
ctx.mlFillText(T, 10, 210, 100, 100, 'bottom', 'left', lh);
ctx.strokeRect(10, 210, 100, 100);
ctx.mlFillText(T, 110, 210, 100, 100, 'bottom', 'center', lh);
ctx.strokeRect(110, 210, 100, 100);
ctx.mlFillText(T, 210, 210, 100, 100, 'bottom', 'right', lh);
ctx.strokeRect(210, 210, 100, 100);
ctx.mlFillText(T, 310, 210, 100, 100, 'bottom', 'justify', lh);
ctx.strokeRect(310, 210, 100, 100);
ctx.mlStrokeText("Yo can also use mlStrokeText!", 0 , 310 , 420, 30, 'center', 'center', lh);
ctx.font ='40px Arial';
- 尝试将其放入您的fiddle中。 - psycho brmWords
(区分大小写)变量从哪里来的?它在任何地方都没有定义。只有当您更改字体时,代码的这部分才会被执行。 - psycho brm我在这种情况下创建了一个小型的库,链接在此处:Canvas-Txt
它可以在多行中呈现文本,并提供了不错的对齐模式。
如果你想使用它,你需要安装它或使用CDN。
npm install canvas-txt --save
import canvasTxt from 'canvas-txt'
var c = document.getElementById('myCanvas')
var ctx = c.getContext('2d')
var txt = 'Lorem ipsum dolor sit amet'
canvasTxt.fontSize = 24
canvasTxt.drawText(ctx, txt, 100, 200, 200, 200)
这将在一个不可见的框中渲染文本,该框具有以下位置/尺寸:
{ x: 100, y: 200, height: 200, width: 200 }
/* https://github.com/geongeorge/Canvas-Txt */
const canvasTxt = window.canvasTxt.default;
const ctx = document.getElementById('myCanvas').getContext('2d');
const txt = "Lorem ipsum dolor sit amet";
const bounds = { width: 240, height: 80 };
let origin = { x: ctx.canvas.width / 2, y: ctx.canvas.height / 2, };
let offset = { x: origin.x - (bounds.width / 2), y: origin.y - (bounds.height / 2) };
canvasTxt.fontSize = 20;
ctx.fillStyle = '#C1A700';
ctx.fillRect(offset.x, offset.y, bounds.width, bounds.height);
ctx.fillStyle = '#FFFFFF';
canvasTxt.drawText(ctx, txt, offset.x, offset.y, bounds.width, bounds.height);
body {
background: #111;
}
canvas {
border: 1px solid #333;
background: #222; /* Could alternatively be painted on the canvas */
}
<script src="https://unpkg.com/canvas-txt@2.0.6/build/index.js"></script>
<canvas id="myCanvas" width="300" height="160"></canvas>
ctx.fillText(txtline.trim(), textanchor, txtY)
。我只在您网站上的交互式演示中注意到了这一点。 - Mr. Polywhirl我用JavaScript开发了一个解决方案,虽然不是很美观但对我很有效:
function drawMultilineText(){
// set context and formatting
var context = document.getElementById("canvas").getContext('2d');
context.font = fontStyleStr;
context.textAlign = "center";
context.textBaseline = "top";
context.fillStyle = "#000000";
// prepare textarea value to be drawn as multiline text.
var textval = document.getElementByID("textarea").value;
var textvalArr = toMultiLine(textval);
var linespacing = 25;
var startX = 0;
var startY = 0;
// draw each line on canvas.
for(var i = 0; i < textvalArr.length; i++){
context.fillText(textvalArr[i], x, y);
y += linespacing;
}
}
// Creates an array where the <br/> tag splits the values.
function toMultiLine(text){
var textArr = new Array();
text = text.replace(/\n\r?/g, '<br/>');
textArr = text.split("<br/>");
return textArr;
}
ctx.textBaseline="bottom";
ctx.fillText("First line", x-position, y-position);
ctx.textBaseline="top";
ctx.fillText("Second line", x-position, y-position);
var wrapText = function (context, text, x, y, maxWidth, lineHeight) {
var paragraphs = text.split("\n");
var textLines = [];
// Loop through paragraphs
for (var p = 0; p < paragraphs.length; p++) {
var line = "";
var words = paragraphs[p].split(" ");
// Loop through words
for (var w = 0; w < words.length; w++) {
var testLine = line + words[w] + " ";
var metrics = context.measureText(testLine);
var testWidth = metrics.width;
// Make a line break if line is too long
if (testWidth > maxWidth) {
textLines.push(line.trim());
line = words[w] + " ";
}
else {
line = testLine;
}
}
textLines.push(line.trim());
}
// Move text up if centered vertically
if (context.textBaseline === 'middle')
y = y - ((textLines.length-1) * lineHeight) / 2;
// Render text on canvas
for (var tl = 0; tl < textLines.length; tl++) {
context.fillText(textLines[tl], x, y);
y += lineHeight;
}
};
fillText()
并使用字体高度进行分隔,要么使用 https://developer.mozilla.org/en-US/docs/Web/API/TextMetrics https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/measureText - 或者使用下面非常复杂的“解决方案”之一,但不使用 TextMetrics... - Andrew