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Bezier curve precision

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  • Bezier curve precision

    Hi there

    I have noticed a small error in the precision of bezier curves as printed via your tool from Express PCB, a circuit board design tool. It's a rather old version of the Express PCB software, 7.0.2, but I need to use it to solve a problem with an old file.

    I've attached a simple PDF (uncompressed for convenience) which shows the issue. Notice that the two red curves don't quite line up.

    The PDF code which creates the two curves is:

    q 0.24 0 0 -0.24 0 595.276 cm 3.5 w 1 J 1 j 1 0 0 SC 1214.5 1598.75 m 1214.5 1582.313 1201.188 1569 1184.75 1569 c S Q 
    q 0.24 0 0 -0.24 0 595.276 cm 3.5 w 1 J 1 j 1 0 0 SC 1215 1598.75 m 1215 1598.75 1215 1598.75 1215 1598.75 c 1215 1615.156 1228.313 1628.5 1244.75 1628.5 c 1244.75 1628.5 1244.75 1628.5 1244.75 1628.5 c S Q
    These are intended to be segments of a circle. I know that PDF beziers cannot create perfect circles but the ends should line up properly. Viewed at normal scale it is not very obvious but the error is about 1/600 of an inch, I think the number 1214.5 should proably be 1215 in a PDF with 300dpi scaling.

    Is this likely to be an issue with Foxit software, or with Express PCB? How do you get those coordinates? Is there anything we can do to fix it?

    The error changes in various places on the page if I use lots of different curves. I wonder if it is a rounding error?

    Thanks for any information

    Attached Files

  • #2
    Hfuy ,I apologize for any hassle and inconvenience this may cause for you. I am sorry that I am still not clear about how you create the attached PDF file with bezier curves included.
    Would you please help to use the LiceCap tool to generate an animated gif that shows us the whole procedures for creating the DPF file from Express PCB for our referencing.
    Here's the download link:
    (Unzip it, then double-click on licecap file, you can then specify the recording area then hit "Record", it requires naming the file first then start recording.)
    And we also need to know which Foxit Software you used to create PDF file from Express PCB?