Unexpected rasterisation when printing

[dpt]

Hi,

I've got an Affinity Designer document here that I've just printed out and found unexpected mushy pixel halos around some shapes. The problem shapes are plain vectors, but semi-transparent. Clearly these shapes have been rasterised but I'm failing to find an option in AD to stop it from happening.

Not wanting to burn through my ink and paper I'm testing this by using the Print dialogue and using PDF > Open in Preview. Is this the same stream that the print driver receives?

I've tried boosting the DPI in the Document Setup dialogue but that has had no effect. I can however export PDFs which dodge the issue.

AD 10.10.4 running on macOS Big Sur 11.6.2

Regards,
Dave

[walt.farrell]

Sometimes it is necessary to Export to PDF, and then print the PDF.

What kind of printer do you have, and what color format is your document?

What options for color management are you using in the Print dialog?

[dpt]

33 minutes ago, walt.farrell said:

Sometimes it is necessary to Export to PDF, and then print the PDF.

So I'm interested to know how "sometimes" is defined. Is AD's Print dialogue essentially unpredictable for .. printing?

The printers are a couple of Canons, but I'm not sure knowing that helps much. I can meddle colour formats and management options all day long and hit the same basic problem: a simple, albeit semi-transparent, shape prints as mush.

[walt.farrell]

There are perhaps several factors, but I am not an expert so I can't be very specific. But from what I've read here, Exporting to PDF is the recommended option if direct printing doesn't work as needed.

First, I think that many (most?) consumer-grade printers expect RGB data. So, if you have a CMYK document, and Affinity is doing the color management, Affinity will convert the document to RGB before sending it to the printer. (I'm pretty sure that is true on Windows, but it may behave differently on Mac.)

I'm also not sure what happens if you tell Affinity to let the printer manage the color, vs Affinity managing it. And, again, color management is different on Mac than on Windows.

Next, to a printer, at least a consumer-grade printer, I think that transparency is a raster attribute, not a vector attribute. So some rasterization may be required when printing semi-transparent vector objects. I think that even vector lines must be in raster format for printing on some printers.

 

[R C-R]

5 hours ago, walt.farrell said:

In think that even vector lines must be in raster format for printing on some printers.

I am far from an expert on any of this but I think everything must be rasterized unless possibly you are outputting vector content to a plotter. Doesn't the "R" in "RIP" stand for 'raster'?

[v_kyr]

33 minutes ago, R C-R said:

Doesn't the "R" in "RIP" stand for 'raster'?

Well it probably depends on ... if you mean in the printing domain (a Raster Image Processor =  RIP), or instead more the undertaker domain (Rest In Peace = RIP). 😉

Another older forum thread, but dealing instead with color variances between vector & raster, was:

• Color Variance when Printing Vector vs Raster

 

Other than that and just to give a different example here and one more for Adobe specific vector output:

I'm also no expert in printing and the printing domain in general, but AFAIK Illustrator for example outputs Postscript data for printing. But most end-user inkjet printers do not have a Postscript RIP (Raster Image Processor). Without a RIP, the printer will output the low resolution preview image of an AI file rather than the actual postscript data, because the printer can not process the postscript data.

There is no way to correct this directly for a printer lacking a postscript RIP. However, there is a workaround one can use...

• Save the AI file as a PDF, then print the PDF from Acrobat or Reader.

PDF/Acrobat is a software RIP and processes the actual postscript data to a high resolution preview image. Then the printer can print that high resolution image as opposed to the embedded low resolution preview image.

• One can also merely open the AI file with Photoshop and then print from within Photoshop. Photoshop has an internal RIP and will output a high-resolution raster image an inkjet will understand.
• In case of Postscript, the third option is to upgrade the printer to one with a Postscript RIP or trying out instead to use Ghostscript as a RIP.

 

However, that's as far as I know, but don't take my words for it, some of our other forum users here, like @MikeW, do know the printing domain for sure much better and thus can also tell much better here, also from a daily practise!

 

[R C-R]

13 minutes ago, v_kyr said:

Other than that and just to give a different example here and one more for Adobe specific vector output:

But in all these instances, isn't the output to the printer in raster format, whatever RIP (Postscript or otherwise) is involved in the process?

IOW, are there any printers besides plotters that can print vectors without rasterizing them?

[lacerto]

If it is a problem with transparency, and the printer expects RGB data, it is best to manually rasterize objects that have transparencies in the document before printing. I do not think that there is another way to do transparency flattening in RGB mode (without rasterizing the whole job) when using Affinity apps (e.g., they cannot flatten transparencies when exporting to RGB mode PDFs).

Transparencies will be flattened when exporting to PDF/X-1a and PDF/X-3, but these methods convert the job at least partially to CMYK (the former 100%), which possiblty is not wanted, and might cause problems if there are imported PDF files placed to be passed through. But these methods would allow non-destructive export time transparency flattening and might resolve the problem.

[dpt]

It's a question of knowing when and where in the print process that AD is going to transform objects, to avoid surprises - I wasted ink and paper discovering this.

The surprise for me was that when printing AD is rasterising semi-transparent shapes by some (apparently uncontrollable) DPI value. I'd at least have expected a small warning on the print dialogue saying "(Some areas will be rasterised)" like you get on the export dialogue.

[v_kyr]

25 minutes ago, R C-R said:

But in all these instances, isn't the output to the printer in raster format, whatever RIP (Postscript or otherwise) is involved in the process?

Yes, since that's what the name RIP also implies here, a raster image processor (RIP) is a component used in a printing system which produces a raster image also known as what we call commonly a bitmap. - Further also all modern inkjet printers have a RIP, aka ...

Quote

...To determine the positions at which the individual droplets are sprayed onto the paper, a raster image processor is used, which uses dithering and color separation (in color printers) to convert the pixels of an image to be printed into print cells (dither cells or, in the case of grayscale printing, "halftone cells"), that is, in groups of ink dots in the print image that reproduce the color and brightness of the image dots as precisely as possible by superimposing and combining the droplets with regard to number, color, possibly size and arrangement. The actual resolution of pixels (determined as ppi, points per inch) that can be achieved by a printer thus depends on the positioning resolution of the individual droplets (e.g. specified as dpi, dots per inch) and the size of the print cells. For example, a printer with a nominal resolution of 5000 dpi with a print cell size of 5 × 5 print pixels has a resolution of the pixels of 1000 ppi. In so-called dithering with error diffusion, no dither cells are formed, but the image is analyzed line by line and a quantization error is calculated in the software for each point, which is then distributed to the neighboring pixels. The processes used to convert images into ink droplet patterns on the medium contribute significantly to the quality of the print and are part of the know-how of printer manufacturers.

 

33 minutes ago, R C-R said:

IOW, are there any printers besides plotters that can print vectors without rasterizing them?

Good question, I believe plotters are mostly associated with vector printing here, since graphics & CAD/CAM etc. and the availability for huge paper sizes were their main domain. Though nowadays there are also other wide-format printers which might do an equally good job here also for vector based printing.

[lacerto]

On 12/22/2021 at 3:13 AM, dpt said:

The surprise for me was that when printing AD is rasterising semi-transparent shapes by some (apparently uncontrollable) DPI value.

Basically rasterizing should happen at document DPI (in Publisher, File > Document Setup). But when printing and exporting, it is possible to specify an overriding rasterizing DPI.

When print artifacts appear (kind of antialiasing fringes, black objects, objects with background the color of which differs from the rest of the background, etc.), there is a good chance that transparencies are flattened (color values calculated) in different color space than where rasterization of the rest of the image has happened, so therefore ensuring non-mixed color space  (like when exporting to PDF/X-1a making everything device CMYK), or flattening transparent areas manually already before printing/exporting to RGB mode,  leaves no room for color space conflicts in final rasterization.

There are however situations where transparencies get prematurely rasterized: when exporting to PDF/X-1 and PDF/X-3, Affinity apps do transparency flattening by rasterizing the overlapping colors in vector objects (rather than clipping them as separate vector shapes with resolved color values) which can result in a situation where edges of affected areas have been rasterized e.g. at 300 dpi while the remaining parts of the "same object",  are still in vector mode and would eventually get rendered by using a higher accuracy.

What you describe above as "mushy pixel halos" might be results of this, but it is impossible to say without seeing the actual printouts. Anyway, an enlarged image below (from one of my earlier posts) is an example of such transparency flattening in a Publisher-created PDF/X-1a document (rasterizing the transparencies in the document would make the lower blue edge similarly jagged as the rest of the edges) :

These kinds of inconsistencies do not necessarily show in final print as artifacts (without looking at very close distant or using a lupe), but might still cause a feel of some general fuzziness or unevenness (like above where one edge is non-antialiased, two edges antialiased and one edge non-rasterized).

[walt.farrell]

6 hours ago, Lagarto said:

Affinity apps do transparency flattening by rasterizing the overlapping colors in vector objects (rather than clipping them as separate vector shapes with resolved color values) which can result in a situation where edges of affected areas have been rasterized e.g. at 300 dpi while the remaining parts of the "same object" ,  are still in vector mode and would eventually get rendered by using a higher accuracy.

In the Print dialog (on Windows) there's a Rasterize section in the options that includes a "Clip Transparency" option. (I'm not at that computer right now, so the names may be a bit different.) I haven't found an explanation for what it does, but it sounds like it could be related to what you've described.

[lacerto]

 

1 hour ago, walt.farrell said:

In the Print dialog (on Windows) there's a Rasterize section in the options that includes a "Clip Transparency" option.

It is a different thing:

 

...and appears to be related to clipping off transparent background ("completely transparent pixels") rather than handling of overlapping transparent areas. Anyway, I tried it with my PostScript printer printing to file and having the setting on or off with overlapping transparencies did not make any difference. Besides, I was referring to transparency flattening related to PDF/X1a and PDF/X3. OP used PDF option in the context of macOS Print dialog (and I am also not sure whether this has anything to do with the actual print stream -- I do not think so, though), but it seems there are no Rasterization options at all in context of macOS printing.

 

[R C-R]

8 hours ago, BofG said:

Usually there is an intermediary format, a page description, PostScript is a very advanced one for example, the lower end is something like PCL. Vector data can be within this. The print driver is technically the RIP, it interprets the page description and produces the final raster for the printer.

Whatever the intermediate format, one way or another the vector data has to be rasterized for a conventional printer to print the page. Plotters are, as far as I know, the only kind of printing device that can print vector data directly, without processing it into raster image data ('dots').

[dpt]

So I've spotted the trigger - transparency was applied to a group. It was intended and that auto-rasterisation is happening is understandable, but it's the cause.

[R C-R]

1 minute ago, BofG said:

Think of it a writing the state of each of the printer's physical dots.

What would you call that besides rasterizing the image? Isn't that exactly what a Raster Image Processor does?