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https://issues.apache.org/jira/browse/PDFBOX-3464?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15435348#comment-15435348
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Daniel Persson commented on PDFBOX-3464:
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You might be right about that all fonts in PDFs should have an EM square of
size 1000 but both Opentype and Truetype defines unitsPerEm in their head block
and when applied to your calculations the actual height seems accurate.
Opentype head
https://www.microsoft.com/typography/otspec/head.htm
TrueType head
https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6head.html
> character height 3 times higher than expected
> ---------------------------------------------
>
> Key: PDFBOX-3464
> URL: https://issues.apache.org/jira/browse/PDFBOX-3464
> Project: PDFBox
> Issue Type: Bug
> Components: Text extraction
> Reporter: Roman
> Priority: Minor
> Attachments: notHelped.png, nowItsHelped.png, screenshot-1.png,
> screenshot.png, subnode.docx.pdf
>
>
> The issue basically same as PDFBOX-2749, but wrong sample was attached to it
> by mistake. Correct PDF is attached here.
> The core of the problem is that font height for this specific font is
> determined incorrectly, please see code with comments below.
> The issue was reproduced on Pdfbox 1.8.4, but as we tested before, same
> result we get on 1.8.9 and 2.0 versions.
> {code}
> public class Extractor extends PDFTextStripper {
> //<...CUT...>
> protected void writePage() throws IOException {
> for (List<TextPosition> textList : charactersByArticle) {
> //charactersByArticle was inherited from base class
> Iterator textIter = textList.iterator();
> //<...CUT...>
> while (textIter.hasNext()) {
> TextPosition position = (TextPosition)
> textIter.next();
> //<...CUT...>
> PDFontDescriptor fontDescriptor =
> position.getFont().getFontDescriptor();
> //<...CUT...>
> float yscale = position.getTextPos().getYScale();
> float asc = Math.abs(fontDescriptor.getAscent() / 1000 *
> yscale);
> float rh =
> Math.abs(fontDescriptor.getFontBoundingBox().getUpperRightY() / 1000 *
> yscale);
> float desc = Math.abs(fontDescriptor.getDescent() / 1000 *
> yscale);
> float capHeight = Math.abs(fontDescriptor.getCapHeight() / 1000
> * yscale);
> if (capHeight == 0)
> capHeight = position.getHeight();
> float h = (rh + Math.max(Math.max(capHeight,
> position.getHeight()), asc)) / 2;
> //"h" evaluates to 37.39 (should be between 11 and 12)
> //"desc" evaluates to 2.664
> //"capHeight" evaluates to 37.39
> //"position.getHeight()" evaluates to 33.48
> {code}
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