PDSimpleFont. Font height reported as zero.
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Key: PDFBOX-611
URL: https://issues.apache.org/jira/browse/PDFBOX-611
Project: PDFBox
Issue Type: Bug
Components: PDModel
Affects Versions: 0.8.0-incubator
Environment: Win and Linux
Reporter: Peter Costello
Fix For: 0.8.0-incubator
The logic for PDSimpleFont.getFontHeight() can return a value of zero.
This will corrupt or compromise text extraction and layout.
In particular, test with
'http://www.encana.com/investor/financial/shareholder/pdfs/info-circular-french.pdf',
pg 12
When a PDFontDescriptor is used, the current logic uses:
1) an average of xHeight and capHeight.
xHeight is the height from the baseline to the top of a lower case
letter like 'x'.
CapHeight is the height from the baseline to the top of an upper
case latin char.
2) xHeight
3) capHeight
4) ascent
5) zero
This is really bizarre. 'xHeight' is an optional parameter, and 'capHeight' is
often missing.
The font bounding box is a required parameter and is the height that is used by
Acrobat Reader when you select a line of text.
The bounding box is not perfect, because it often overlaps the line above, but
it is a consistent value. The problem with the
current logic is that the reported height varies way too much, and a zero value
can be reported.
I have modified the logic as follows. The goal was to make the nominal values
the same as the current logic,
but return a very similar number when parameters go missing.
PDFontDescriptor desc = getFontDescriptor();
if( desc != null ) {
float height = desc.getCapHeight();
// Top of Cap to baseline (eg 715)
if (height==0) {
height=desc.getAscent();
// Max height from baseline (eg 715);
if (height==0) {
PDRectangle bbox = desc.getFontBoundingBox();
height = bbox.getHeight()/2;
// Max height less max depth (eg (1006-(-325))=1331/2=665)
if (height==0) {
height=desc.getXHeight();
// Top of lower-case to baseline (eg 518)
height-=desc.getDescent();
// Depth below baseline (eg 209, to get total of 727)
}
}
}
retval=height;
}
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