javascript - Raphael JS 文本沿路径

Question

我正在寻找一个概念的例子或一些确认。希望在应用程序上使用 Raphael JS，并希望能够像 Illustrator 等图形设计应用程序那样扭曲文本。

Answer 1

这是对 Chris Wilson 代码的改编，被重构为一个插入函数，并添加了一些特性：

• IE8 / VML 模式支持和Gecko/Firefox 支持（通过定义旋转原点 - 没有这个，IE8 和 Firefox 会发疯地将文本扔到页面周围）
• 一个小调整，使 Gecko 浏览器（例如Firefox）中的文本不那么难看 - 没有这个，这些会任意增加字母间距
• 支持手动定义的字体大小和字母间距，以及动态“填充路径”大小和间距
• 支持手动字距调整（逐个字符微调字母间距）。路径上的文本通常会创建非常难看的字母空间；这允许您通过以下方式定义手动调整来修复这些问题：
  • 字符串中的数字位置，或者，
  • 性格，或者，
  • 字符对（应用于基于前一个字符的字符实例，例如下面的示例收紧 'ae' 对并加宽 'rn' 对）

JSBIN 演示

function textOnPath( message, path, fontSize, letterSpacing, kerning, geckoKerning) {
    // only message and path are required, other args are optional
    // if fontSize or letterSpacing are undefined, they are calculated to fill the path
    // 10% of fontSize is usually good for manual letterspacing

    // Gecko, i.e. Firefox etc, inflates and alters the letter spacing
    var gecko = /rv:([^\)]+)\) Gecko\/\d{8}/.test(navigator.userAgent||'') ? true : false;

    var letters = [], places = [], messageLength = 0;
    for (var c=0; c < message.length; c++) {
        var letter = paper.text(0, 0, message[c]).attr({"text-anchor" : "middle"});
        letters.push(letter);

        if (kerning) {
            if(gecko && geckoKerning) {
                kerning = geckoKerning;
            }
            var character = letter.attr('text'), kern = 0;
            var predecessor = letters[c-1] ? letters[c-1].attr('text') : '';

            if (kerning[c]) {
                kern = kerning[c];
            } else if (kerning[character]) {
                if( typeof kerning[character] === 'object' ) {
                    kern = kerning[character][predecessor] || kerning[character]['default'] || 0;
                } else {
                    kern = kerning[character];
                }
            }
            if(kerning['default'] ) {
                kern = kern + (kerning['default'][predecessor] || 0);
            }            
            messageLength += kern;
        }

        places.push(messageLength);
        //spaces get a width of 0, so set min at 4px
        messageLength += Math.max(4.5, letter.getBBox().width);
    }

    if( letterSpacing ){
        if (gecko) {
            letterSpacing = letterSpacing * 0.83;
        }
    } else {
        letterSpacing = letterSpacing || path.getTotalLength() / messageLength;
    }
    fontSize = fontSize || 10 * letterSpacing;

    for (c = 0; c < letters.length; c++) {
        letters[c].attr("font-size", fontSize + "px");
        p = path.getPointAtLength(places[c] * letterSpacing);
        var rotate = 'R' + (p.alpha < 180 ? p.alpha + 180 : p.alpha > 360 ? p.alpha - 360 : p.alpha )+','+p.x+','+p.y;
    letters[c].attr({ x: p.x, y: p.y, transform: rotate });
    }
}

Answer 2

正如 Kevin Nielsen 所建议的，使用 path.getPointAtLength 并不太难：

path = paper.path("M50,100c40,-50 270,50 300,0").attr("stroke", "#CCC");
message = "I want to do this in RaphaelJS";

//since not every letter is the same width, get the placement for each letter 
//along the length of the string
//however, Raphael appears to group the width of letters into intervals of 4px,
//so this won't be perfect        
for (; c < message.length; c += 1) {
        letter = paper.text(0, 0, message[c]).attr({"text-anchor" : "start"});
    letters.push(letter);
    places.push(message_length);
    //spaces get a width of 0, so set min at 4px
    message_length += Math.max(4, letter.getBBox().width);
}

ratio = path.getTotalLength() / message_length;
fontsize = 10 * ratio;

for (c = 0; c < letters.length; c += 1) {
    letters[c].attr("font-size", fontsize + "px"); 
    p = path.getPointAtLength(places[c] * ratio);
    //there does appear to be a bug in p.alpha around 180. Here's the fix
    letters[c].attr({ x: p.x, y: p.y, transform: 'r' + (p.alpha < 180 ? p.alpha + 180 : p.alpha)});
}

jsFiddle