Write rectangles with the precision of real numbers - #385
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Write(PdfRectangle) rounded the coordinates to three decimal places, while Write(double) and Write(PdfReal) use seven. Writing a document therefore changed its geometry, e.g. the /MediaBox of an ISO A4 page created by another producer became 595.276 instead of 595.2756. That is a change of the page for every digital signature the document already contains: adding a second signature to a signed document made validators report the pages of the first revision as changed. /MediaBox, /CropBox, /BleedBox, /TrimBox, /ArtBox, /Rect and /BBox now round-trip unchanged. Note that the coordinates are written as they are, while Write(double) converts a real number to a single first. Doing that for rectangles as well would defeat the purpose, because the single nearest to 595.2756 is 595.27557, which does not round-trip either. An alternative would be to write the value that was parsed, as PRESERVE_PARSED_VALUES does for numbers. That preserves every number of a file and not only rectangles, but it needs the parsed value to survive until the document is written, which is not the case for rectangles today.
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PdfWriter.Write(PdfRectangle)rounds the coordinates to three decimal places, whileWrite(double)andWrite(PdfReal)use seven:Writing a document therefore changes its geometry. The
/MediaBoxof an ISO A4 page created by another producer becomes595.276instead of595.2756.For a signed document that is a changed page: adding a second signature to a document that already contains one makes validators report the pages of the first revision as changed.
With seven decimal places
/MediaBox,/CropBox,/BleedBox,/TrimBox,/ArtBox,/Rectand/BBoxround-trip unchanged.Why not convert to a single first, as
Write(double)does? That would defeat the purpose: the single nearest to595.2756is595.27557, which does not round-trip either.Alternative you may prefer: writing the value that was parsed, as
PRESERVE_PARSED_VALUESalready does for numbers. That preserves every number of a file and not only rectangles, but it needs the parsed value to survive until the document is written, which is not the case for rectangles today. Happy to go that way instead if you consider it the better fix.Test (
IO/WriterTests.cs): a page with a/MediaBoxof four decimal places is written and read back; the test checks both the bytes in the file and the values after reading.Verified on top of current
master: fullPdfSharp.Testssuite green (253 passed, 0 failed).This PR is independent of my other PRs; each of them applies to
masteron its own.