Precision issues with high dpis and drawquad #6
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The preceding code resulted in errors making the circles and ellipses look odd, compared to the ps's ones. The magic value b had to be replaced by a double, for precision purposes. Large dpis cause overflow on `ch*cv`. To address this problem, we multiply the signs instead of the numbers themselves.
ints are 32-bit. Some users may use very high dpis (eg, 720000). pdfpos00(x*100, y*100) makes for frequent overflows, since x, y and dev_res can be very large. Doubles in pdfpos and pdfunit calculations: This is very important when precision is required (eg, when using grap). When ints are used instead, the output is very choppy since lines' ends fall only on points with integer coordinates (this problem doesn't arise in ps because coordinates are not divided by dev_res, so integer coordinates are almost like floats because they are so dense). This is also very problematic for tbl.
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Hello,
This pull request includes 2 commits very useful when using high DPIs (7200 is enough to trigger bugs).
The first makes drawquad more aligned with what a true circle quadrant should like using Bézier curves. Moreover, when using high DPIs, the calculations would overflow (especially the sign test). To fix overflow and precision issues, replacing long's by double's is enough.
The second commit fixes pdfpos and pdfunit. For similar reasons, these 2 functions concentrated much of the overflows of neatpdf. Replacing 32-bit integers by 64-bit might have been enough, but the calculations used to simulate decimal numbers are the source of many rounding errors, which are problematic when precision is needed (eg, when using grap). Replacing the long's by double's is, here too, sufficient.
Thanks for the work you put in your very fine pieces of code,
Regards,
Elie Le Vaillant