[Qgis-developer] Blend modes for printer/pdf outputs - advice?

[Larry Shaffer]

Hi Nyall,

On Thu, May 2, 2013 at 5:57 PM, Nyall Dawson <nyall.dawson at gmail.com> wrote:

> Hi all,
>
> I'm after some advice on the best way to handle pdf or printer output
> of compositions when the composition or map contains blending.
>
> Since QPrinter doesn't support the QPainter composition modes, any
> blending options are currently ignored when exporting a composition to
> pdf/printer. There's two options I can see to handle this, and I'm
> wondering what everyone thinks is the best approach.
>
> Option 1 - Automatically export compositions with blending using rasters.
> This approach would check whether the composition contains any
> blending, and if so would use the "print as raster" option to
> effectively flatten the output before exporting. This is probably the
> most user-friendly approach, since the user doesn't need to do
> anything extra to get the printout looking correct.
>
> Option 2 - Warn the user that blending requires 'print as raster' checked
> This approach would display a warning dialog when attempting to
> print/pdf a composition containing blending (similar to how svg
> outputs currently show a warning). The warning would tell the user to
> check "print as raster" if they want the blending modes used in the
> export.
>

How about option 3: do option 2, but right below the warning offer a "Print
as raster" checkbox (on by default, IMO).

This way a user is warned and can just choose the option to skip
rasterization, without closing the dialog. Then, only a single "Continue"
button (along with Cancel) would be needed and the dialog would work for
preceding both PDF exporting and printing.

Oh, just saw Nathan's similar reply. Therefore, just adding my 2 cents
worth.

Regards,

Larry


> The advantage with option 2 is that it leaves the possibility for
> vector-based exports even when blending has been used. This way, a
> user who wants to further edit a composition in a vector illustration
> program (inkscape/illustrator/etc) can still export to an editable pdf
> to tweak the map and re-apply the blending in the external program.
> Option 1 would make this impossible, since any blending would force
> the output into raster format and prevent any manual editing of the
> composition.
>
> For this reason my gut feeling is that option 2 is a better way to go,
> but I thought I'd raise it with the list for other opinions.
>
> Nyall
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