Rounding errors in image size when printing to png/jpg etc.

[amir]

I see some sort of rounding error when saving to png or jpg. 
The size of the image is very often slightly off by 1 or 2 pixels on the y-
or x-axis.
When using fltk, the code needs to be invoked twice to start scaling.

I hope that the scaling algorithm does not take into acount the dpi settings 
(a pixel is a pixel, and if I say 480 pixel wide image, I mean a 480 pixel
wide image).
Just guessing, though.

Thanks
Amir
----------------------------------------------
graphics_toolkit ("fltk");
plot( linspace ( 0,1,11));
print('a.png','-dpng','-S4800,3200');
print('b.png','-dpng','-S2400,1600');
print('c.png','-dpng','-S480,320');
print('d.png','-dpng','-S481,321');
print('e.png','-dpng','-S482,322');


Result, 1st run:
a.png 1333,917
b.png 2400,1600
c.png 479,319
d.png 479,321
e.png 481,321

Result, 2nd run:
a.png 4800,3200
b.png 2400,1600
c.png 479,319
d.png 479,321
e.png 481,321

- - - - - - - - -
Restart octave

graphics_toolkit ("gnuplot");
plot( linspace ( 0,1,11));
print('a.png','-dpng','-S4800,3198');
print('b.png','-dpng','-S2400,1600');
print('c.png','-dpng','-S480,320');
print('d.png','-dpng','-S481,321');
print('e.png','-dpng','-S482,322');


Result, 1st run:
a.png 4800,3198
b.png 2400,1600
c.png 479,319
d.png 479,321
e.png 481,321

Result, 2nd run:
like first run.



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