Is there any way to center text with jsPDF?

问题:

I'm trying to create a simple pdf doc using javascript. I found jsPDF but I don't figure out how to center text. Is it possible?

回答1:

Yes it's possible. You could write a jsPDF plugin method to use.

One quick example is this:

    (function(API){
    API.myText = function(txt, options, x, y) {
        options = options ||{};
        /* Use the options align property to specify desired text alignment
         * Param x will be ignored if desired text alignment is 'center'.
         * Usage of options can easily extend the function to apply different text 
         * styles and sizes 
        */
        if( options.align == "center" ){
            // Get current font size
            var fontSize = this.internal.getFontSize();

            // Get page width
            var pageWidth = this.internal.pageSize.width;

            // Get the actual text's width
            /* You multiply the unit width of your string by your font size and divide
             * by the internal scale factor. The division is necessary
             * for the case where you use units other than 'pt' in the constructor
             * of jsPDF.
            */
            txtWidth = this.getStringUnitWidth(txt)*fontSize/this.internal.scaleFactor;

            // Calculate text's x coordinate
            x = ( pageWidth - txtWidth ) / 2;
        }

        // Draw text at x,y
        this.text(txt,x,y);
    }
})(jsPDF.API);

And you use it like this

var doc = new jsPDF('p','in');
doc.text("Left aligned text",0.5,0.5);
doc.myText("Centered text",{align: "center"},0,1);

回答2:

This works in the scratchpad on the jsPdf homepage:

var centeredText = function(text, y) {
    var textWidth = doc.getStringUnitWidth(text) * doc.internal.getFontSize() / doc.internal.scaleFactor;
    var textOffset = (doc.internal.pageSize.width - textWidth) / 2;
    doc.text(textOffset, y, text);
}

回答3:

WootWoot, just in case you need more layout options, you could also take a look at my pdfmake library

It supports:

• text alignments, lists, margins
• styling (with style inheritance)
• tables with auto/fixed/star sized columns, auto-repeated headers, col/row spans
• page headers and footers
• font embedding, and a couple of other options

It works on client-side (pure JS) or server-side (an npm module)

Take a look at the playground to see what's possible

Good luck

回答4:

I have found that the current version of jsPdf supports a parameter 'align' with the function signature like this:

API.text = function (text, x, y, flags, angle, align)

So the following should give you a center-aligned text:

doc.text('The text', doc.internal.pageSize.width, 50, null, null, 'center');

However, at the current point in time, an error is thrown in the library when strict mode is on because a 'var' is missing. There is an issue and pull request for it, but the fix hasn't made it in: https://github.com/MrRio/jsPDF/issues/575

Whoever is looking for this, one day, you might be able to use this to make it easier to center text.

回答5:

I had the same problem and a lot of others while creating PDF-Files (e.g. auto-pagebreak, total-pageCount). So i started writing a little lib, which depends on jsPDF but gives you a lot of features in a way you know them (form HTML/CSS and jQuery). You can find it on GitHub. I hope it makes PDF-Creating easier... =)

回答6:

Based on @Tsilis answer I have snippet out a plugin here https://gist.github.com/Purush0th/7fe8665bbb04482a0d80 which can align the text left, right and center in the given text container width.

(function (api, $) {
'use strict';
api.writeText = function (x, y, text, options) {
    options = options || {};

    var defaults = {
        align: 'left',
        width: this.internal.pageSize.width
    }

    var settings = $.extend({}, defaults, options);

    // Get current font size
    var fontSize = this.internal.getFontSize();

    // Get the actual text's width
    /* You multiply the unit width of your string by your font size and divide
     * by the internal scale factor. The division is necessary
     * for the case where you use units other than 'pt' in the constructor
     * of jsPDF.
    */
    var txtWidth = this.getStringUnitWidth(text) * fontSize / this.internal.scaleFactor;

    if (settings.align === 'center')
        x += (settings.width - txtWidth) / 2;
    else if (settings.align === 'right')
        x += (settings.width - txtWidth);

    //default is 'left' alignment
    this.text(text, x, y);

}
})(jsPDF.API, jQuery);

Usage

var doc = new jsPDF('p', 'pt', 'a4');
//Alignment based on page width
doc.writeText(0, 40 ,'align - center ', { align: 'center' });
doc.writeText(0, 80 ,'align - right ', { align: 'right' });
//Alignment based on text container width
doc.writeText(0, 120 ,'align - center : inside container',{align:'center',width:100});

回答7:

doc.text(text,left,top,'center') can be used to center text. It can be used with array of lines as well but when it is used with array the center does not work right so I have used it in a loop for every object in the array.

var lMargin=15; //left margin in mm
var rMargin=15; //right margin in mm
var pdfInMM=210;  // width of A4 in mm
var pageCenter=pdfInMM/2;

var doc = new jsPDF("p","mm","a4");
var paragraph="Apple's iPhone 7 is officially upon us. After a week of pre-orders, the latest in the iPhone lineup officially launches today.\n\nEager Apple fans will be lining up out the door at Apple and carrier stores around the country to grab up the iPhone 7 and iPhone 7 Plus, while Android owners look on bemusedly.\n\nDuring the Apple Event last week, the tech giant revealed a number of big, positive changes coming to the iPhone 7. It's thinner. The camera is better. And, perhaps best of all, the iPhone 7 is finally water resistant.\n\nStill, while there may be plenty to like about the new iPhone, there's plenty more that's left us disappointed. Enough, at least, to make smartphone shoppers consider waiting until 2017, when Apple is reportedly going to let loose on all cylinders with an all-glass chassis design.";

var lines =doc.splitTextToSize(paragraph, (pdfInMM-lMargin-rMargin));
var dim = doc.getTextDimensions('Text');
var lineHeight = dim.h
for(var i=0;i<lines.length;i++){
  lineTop = (lineHeight/2)*i
  doc.text(lines[i],pageCenter,20+lineTop,'center'); //see this line
}
doc.save('Generated.pdf');