Which resizing method is better?

[Timur Born]

Hello.

I wonder if there is any difference in method and outcome between enlarging a page via "Resize Pages" option or just use "Fit to Printer Margins" to print a PDF on larger paper than the original size?

[Tracker Supp-Stefan]

Hello Timur,

If the content is vector based - then it should not really matter - as it will just be scaled up proportionally both times.
However if there are raster objects - they might be recompressed when you resize the page, and then when sending to the printer - depending on how it processes images - there might be a second processing of the same image, and given that in the majority of cases those reprocessings are lossy - it is possible that you will get some change in the quality. So I'd rather recommend you to do the scaling if and when you need it directly on paper, and leave the PDF file itself with as few edits as possible.

Regards,
Stefan

[Timur Born]

Usually I use Photoshop to upscale bitmap images to the scale I need and in the same step resample them to 360 DPI, the latter of which being the native resolution of my Epson 3880 in normal quality print mode. That way I ensure that the print driver does not upscale the final print image using its inferior resampling method (likely simple bilinear).

I don't know which method Editor uses to resample images (up or down) when the size of a page containing bitmap images is changed?! Is it anything more sophisticated than bilinear? Recompression might be an issue, especially since Editor's implementation of JPG compression is a bit untrustworthy.

Likely the the best quality would be achieved by editing images externally (Photoshop) and then re-import them after Editor changed the size of the page. Of course this also is the most work intensive method.

[Tracker Supp-Stefan]

Hello Timur,

Actually our devs just told me that it should not matter which way you use to resize a PDF file with our products. Whether you resize the page directly, or only when you print it. In both cases we do not resample raster images, rather we just change the "scaling coefficient" in the display matrix.So the image will be used with it's original resolution when passed to the printer (+ the scaling info).

Regards,
Stefan

[Timur Born]

Great information. I assume that anti-aliasing will be applied at original resolution then as well and then left to the printer driver to upscale along with the image? If this is the case then resampling images outside of Editor makes sense when superior image quality is needed.

[Tracker Supp-Stefan]

Hi Timur,

I do not think we would apply AA when directly sending the image to the printer, but when displayin it from a source that is with a lower resolution - we might.
Indeed if you want good quality images printed - the source should also be with good quality (and if upscaling of the image is needed - a dedicated image processing tool to do the job is recommended).

Regards,
Stefan

[Timur Born]

What kind of resampling is used when images are resized to a different aspect ratio? Simple bilinear, bikubic or anything else? Or does the "scaling coefficient" handle this situation as well, with different scales for horizontal and vertical sizes?

[Tracker Supp-Stefan]

Hello Timur,

I have feedback on this from our devs:
No scaling is ever done by the editor, and the only time that we will manipulate an image is when cropping a page and choosing "remove content outside..." Otherwise the image will not be changed in any way. In most cases, when printing, scaling is handled directly by the printer, or no scaling is done at all. so your printer would be doing all of this.

Regards,
Stefan

[Timur Born]

Thank you, but I am confused by this answer. When I use Editor to resize a page from Letter to DIN A4 without keeping the original aspect ratio then the printer driver is not involved. Document -> More for pages -> Resize page does that without printing,

[TrackerSupp-Daniel]

Hello Timur,

when using the resize functions like that, you will notice that the images do not change in dimensions. They will be resized, and repositioned to fit the document, but in term of the images itself, nothing is changed, you can resize the bounding box to its original size and you will see the exact same image fidelity that was originally in place. The Editor will not alter the image itself, even when it may change how it is displayed temporarily.

this is most noticeable if you try to convert a document from portrait to landscape orientation by using the resize function. Please try this to see what I mean regarding the images.

[Timur Born]

I see. Thanks for the information, it's well appreciated.

Are there any plans to allow user preferences for changing Editor's own display resampling (is it simple bilinear at this point)? What I mean is the resampling done in order to display images at different zoom settings and when resizing is done at different ratios (even if only for the display without altering the original image).

[Tracker Supp-Stefan]

Hello Timur,

No plans for the moment to allow such rendering customizations I am afraid!

Regards,
Stefan