40400: Why does the customer's timetable look different on screen than on the printout, although it is "what you see is what you get"?

The problem is the significantly different resolution (number of dots) between the screen and most printers: while a screen has about 100 pixels per inch, the resolution for printers is in the order of 600 to several thousand dots per inch (dpi = dots per inch), which is about a factor of 10 higher. If a character on the printer, has for example a size of 75 points, it should be 7.5 points at 1:10 on the screen, which is not possible, of course, because you cannot light up half a pixel. So, it only remains to draw the character with 7 or 8 points, and thus not precisely as in the output. Normally this round error does not interfere very much. However, if, as with the customer's timetable, a very large number of very small characters are to be output in succession, all of which have the same round error, the error accumulates up to an order of magnitude which is no longer negligible. Then it can happen, that suddenly something fits on the sheet when printing, which did not fit on the screen - or vice versa. Since this error is system-related, you can watch it regularly with software that handles many small characters.

The computational effort to compensate for this error on the screen (e.g. by alternately drawing 7 and 8 point high characters in the above example) would require that other algorithms would be used for expression than for output on the screen. However, this would not be in line with the principle "what you see is what you get". In addition, the output on the screen would have to be dependent on the current printer and its resolution. Therefore, we cannot offer you 100% "WYSIWYG" unfortunately. However, the FBS print preview avoids the problem to a large extent and therefore provides a more realistic image of an imminent print. Hence, when working with the customer's timetable, expect the sheet division to change, when printing, as it depends on the actual print resolution (dpi of the printer).

As a rule of thumb, the view ratios on the screen correspond to those of the expression, if they are only sufficiently enlarged. Thus, at a ratio of 1:10 between screen resolutions and the printer, there would be no error on the screen with a "zoom level" of 1000%. You can easily test this experimentally: when switching between lower "zoom levels", the display on the screen often jumps; from about 1000% up, however, the relative distances always stay the same.

The PDF output that is integrated into FBS is not subject to the restrictions of the screen: it has a "virtual" resolution of 7200 dots per inch. Thus, even in the most modern, high-resolution printers, there are no deviations in PDF files generated directly from FBS.


Last update on 20.03.2020 by iRFP Support.

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