Wednesday, 8 March 2017

Paper to Pixel to Paper Again: Part 9

A guide to creating the best looking line art in print in the new digital print world

Part 9
Batch Processing + Cleaning Line Art Originals


This is the ninth installment of Paper to Pixel to Paper Again, a series that explains (in an overly thorough manner) the how-to's of preparing line art (and later in the series, color art!) for print.

And as always, if you have any questions, please let me know in the comments!

In our last installment, we finished a Photoshop action for adjusting and setting up all of our line art originals for cleaning. Now it's time to run our action!

With no files open, go to File-> Scripts -> Image Processor.

This is definitely the easiest Photoshop dialogue for batch processing of this type (not the aptly-named "Batch" function, which is useful for other purposes, but more cumbersome for this). Select the target folder for processing, and set a destination folder. I make a separate destination folder called "[Name of book and type of file] Cleaned", and have all the processed originals go there, saved in PSD (Photoshop) format. And at the bottom of the dialogue you can select your Action for running.

Now hit Run, and let that puppy go! Photoshop will soon start flashing with small slices of images that it's opening, processing, and closing. This process might take a while.

It's worth noting though that it will take significantly LESS time than if you were opening each file, running the script, then saving. This is because every process is more efficient if your computer isn't compelled to perform any normal display functions—it can operate in a much more processor-efficient manner while batch processing like this.

When it's done, you might have a few files remaining open that didn't get saved. If this happens, this is most likely because they're too large to be saved as PSD files and need to be saved as PSB files (large document Photoshop format) instead. Go ahead and do so by hand for any remaining open images.

And now, assuming everything went well, we can at long last...

Clean Some Originals

Okay! Here's the drill! I'm going to present many techniques for cleaning images in this section (and possibly next week, depending on how much time I have), with an emphasis on the type of techniques that might apply to line art originals. We'll talk about a few of these techniques in greater detail when we get into newsprint originals in a layer installment.

There are MANY WAYS to do these things, many of which, I'm sure, I don't know! So any and all feedback about this, things I missed etc, is welcome in the comments.

Without further ado...

I'm in the midst of working on Jaka's Story, one of my favorite Cerebus books, not only because of the gorgeous, stylish art, but because of the pacing, which starts relaxed and leisurely, taking its time with the intertwining relationships of the characters, before accelerating to disaster. Here's a leisurely double-page spread, later redrawn with a tweaked viewpoint for the cover of the volume.

Our goal is to eliminate anything that we don't want to reproduce in the final book—any noise, ink splotch, extra corner doodling, whatever—while preserving all of the things that we might lose without this additional step—watery lines, super duper fine lines, etc.

Even at this zoomed-out vantage point we can see a few items that need eliminating, mainly, the "Issue__ Page__" chop at the upper left of the page, that were indicators to the printer of page order for the monthly volumes. We'll take care of this and any other noise in the margins with one easy to use method:

Cleaning method A: Selection and Fill

Hit M to bring up the Marquee Selection tool, which allows you to select rectangular units in your image. I quickly use this tool to select the outer parts of the image that are intended to be white, and, since there are big chunks of white space inside the image as well, I select these too. I see that the cut line on the top and bottom of the text paste-up is also visible, so I make sure my selection also overlaps these areas.

Here's my selection (notice the "marching ants," indicating the area that's selected).

Now I'm going to hit G to bring up the paintbucket tool. I've selected White from my color swatches, and, making sure my Cleanup layer is selected, I click in my selection, which dumps white into the entire selected area, essentially masking any noise or grit in these areas.

Here's what my cleanup layer now looks like, sans image layers.

Now hit CTRL-D, which De-selects.

Now we're going to take care of something that I already know is a chronic problem with these pages. Although it looks hand-drawn, the border of this image was actually made with Letratape, a type of border tape consisting of a black border and a clear sticky carrier backing, used for paste-up layouts. Over time, the edge of that sticky carrier has accumulated dust and debris, and we need to clean that edge in order for it to not reproduce (even if it ends up not being very noticable).

If we left this alone, it would cause a little stippled line on the edge of the carrier film to be visible in the printed book.

Fortunately, there's an easy way to take care of this, or any other similar noise problem. (I only wish I figured it out earlier!)

Cleaning Method B: Select and Median Noise Filter
Hit M to select the Marquee tool again, and select your Sharpened layer from the layers panel.

Now use the Marquee tool to select the border tape and border tape schmutz, careful to not overlap any lines with your selection.

Now zoom in on an area of the noise, and then go to Filter -> Noise -> Median.

This is one of those incredibly simple filters that are so basic they tend to get overlooked for filters with more bells and whistles. All the Median filter does is look for and apply an average of neigboring pixels to any selection, at a user-determined radius. In this case, any radius between 4 and 6 pixels completely eliminates my specs of debris without affecting my border tape at all. If the radius is too low, it doesn't get the big specks of dirt. If the radius is too high, it starts to soften the edge of my border tape. 

Well, that was quick! We're about a minute into our cleanup and we've done most of what we need to do to this page (mostly because there's no mechanical tone on this page! The real time-suck on this project).

But before we move on from using our Median filter, we're going to check out one other area. From previous pages, I know that the big chunk of text on the right-hand side of the page was either photocopied or printed on a laser printer, and thus might have noise problems as well.

And so it does. We'll try the same solution as previous, bring up the Median filter and seeing if there's a radius that will knock out all of our noise without affecting our letter forms at all.

Oh, hey, a 4 px radius did the trick. 

Now we're going to scan the page with our eyes, turning the Threshold adjustment layer on and off, looking for any areas of the page that have watery lines or super fine lines that might break up when Threshold is on. And in the lower left-hand corner, I find what I'm looking for. The lines indicating the snow are blowing out when the Threshold adjustment layer is on, and, at least after our adjustment, they look pretty gray compared to their neighbors.

(If this were a systematic problem with many or all pages, and the originals didn't also look that gray, then we might have a problem with our script. But my script seems otherwise fine, so I'm going to assume this is just the way it appears in the original art)

Here's the area in question:

Click to embiggen.

There are a bunch (a bunch!) of ways to deal with this, but since it's mostly affecting one area of our drawing, let's try...

Cleaning Method C: Selection and Levels Command

I'm going to hit L to bring up the Lasso tool, which enables you to freehand a selection. Then I'll select the area, and make sure that my Sharpened layer is selected in my layers menu. Then I'll hit CTRL-L to bring up my Levels command:

Click to embiggen.

And here we have our almost-instant fix. I've raised the black point just a bit, and moved the Mid Point (i.e. the gamma control) far to the right, watching the lines become blacker as it moves. Then I move around the White point to make sure there's no additional filling-in happening, only the gray lines becoming jet black.

In the days of manual darkroom development, this would have been a cumbersome process of masking off the area and overexposing it to get the desired fill-in. If the exposure were too long, the area would become clunky and clogged, the fine details in the hatching filling-in along with the lines. But now, it's a whole lot easier, at least if you happen to know how to do it.

And that's it until next week! Hit me up in the comments for any questions or comments. 

Sean Michael Robinson is a writer, artist, and musician. See more at


Carson Grubaugh said...

WARLOCK! Burn it!!!

So grateful for these.

Jeff Seiler said...

Sean, when I think of the joint efforts that go into these remasters, I tend to think of you (with your digital technology skills) as the Wizard and me (with my OED), to stretch a metaphor, as the alchemist off in the dark corner of the basement.

Somehow, with Dave cast as The Grand Poobah, it all works. (!)