I am implementing a
PdfPageEventHelper event to add a footer as shown in this code snippet:
ColumnText.showTextAligned(cb, Element.ALIGN_RIGHT, new Phrase(String.format(" %d ", writer.getPageNumber()), footerFont), document.right() - 2 , document.bottom() - 20, 0);
I need to add 3 lines, but I don't find how to calculate the distance between the lines. Each line has different font size. What should I use as
XXX value in
document.bottom() - XXX?
The difference between two lines is the
leading. You can pick your own leading, but it is custom to use 1.5 times the font size. You are drawing line by line yourself, using different font sizes, so you'll have to adjust the Y value based on that font size. Note that
Canvas.showTextAligned() uses the Y value as the baseline of the text you're adding, so if you have some text with font size of 12pt, you'd need to take into account a leading of 18pt. If you have a font size 8pt, you make sure you have 12pt.
That's the easy solution: based on "convention". If you really want to know how much horizontal space some specific takes, you need to calculate the ascender and the descender. If
bf is your font (a
text is your text (a
size is your font size (a
float), then the height of your text is equal to
float aboveBaseline = bf.getAscent(text, size); float underBaseline = bf.getDescent(text, size); float height = aboveBaseline - underBaseline;
y is the Y-coordinate used in
showTextAligned() make sure you keep the space between
y + aboveBaseline and
y + underBaseline free. This is the accurate solution.
document.bottom() - 20 looks somewhat strange. I would expect
document.bottom() + 20 as the Y-axis of the PDF coordinate system points upwards, not downwards.
Click this link if you want to see how to answer this question in iText 5.