There's no way to do that using the threshold filter alone. There's no single effect that will do this, but it's possible using a combination of techniques.
Anyway, here's one possible method using Photoshop.
Start with the original image of the mountain, and add a background layer under it filled white.
Make sure the mountain layer is selected in the ...
Illustrator is the easier option for this job.
Apply your threshold and reduce your resolution to the desired values in Photoshop. Take note of the size of your image in pixels (25 x 17 in your example).
Copy a flattened raster version of this image and paste it in Illustrator. Yes, it's tiny.
Select the object and choose Object > Create Object Mosaic.......
In single color printing blurry effects such as glow or drop shadow the color of the effect should be set only white (=paper) or the used print color.
The effect settings contain also blending mode. It should be = normal; other blending modes can behave differently than with CMYK or RGB colors.
If you expect the effect blur around object A be visible on ...
If you want to go down your workaround route using the black plate, I think you'll need to speak to your printer to check it's OK with them. There's no reason why it shouldn't work technically. A plate is just a plate - it has no colour until it's inked on the press. Edit: See note in comments
BTW "Computer to Plate" isn't a fully digital printing ...
Just use the "Nearest neighbor" method, present on many programs.
This will duplicate the rows and columns.
Try to think in multiples, for example 60px x 10 = 600px. Or multiplied by 20 will give you 1200px.
If you do not choose exact multiples some rows will have let's say 11 "clones" and some will have 10, making the resampled pixels ...
There are probably dozens of ways you could go about this. Here's a simple one:
Paint shapes/blobs with a large soft-edged brushes onto a darker coloured background.
Then create a 50% grey filled layer above that, apply the noise filter to it. And set the layer blending mode to Multiply, and perhaps reduce the opacity a little.
The grain/noise will look ...
Manual painting to a layer below the actual objects surely creates complex variety, but you can convert layer style Outer Glow at first to a layer and use it as your starting point. It makes a halo around an object with zero effort if the object has transparent background.
Filter Render > Clouds can create useful forms with little effort. The effect can ...
I don't think this is created from a gradient. As mentioned in comments it seems to just be a simple geometric pattern consisting of a lot of circles on top of some rectangles.
You could probably use all sorts of transform magic to make it easier, but here I just want to show you how to draw the pattern with the mouse and keyboard using Ellipse Tool, ...
I would try the following image trace options. You want to make sure your corners are set to 100%. The end result is about 41kb SVG.
I think it turns out pretty good.
You could also try Object -> Create Object Mosaic. You will have to mess around with the amount of tiles you use.
In Illustrator set up the new document to the size you want. In your case, that will be 57.15mm x 88.9mm. You don't need to worry about the ppi at this point. Create your artwork, or import your artwork into that new document.
Here are the settings I used for the example below.
When you need to output your work as raster, proceed as follows:
Do File > ...
Take your screenshot. Note in Windows screenshots are 96ppi by default
Open the screenshot in Photoshop, do Image > Image Size. Set PPI to 72, disable the Resample option. If the image is already 72ppi you can skip the Photoshop steps.
Save the image as PNG
Open Illustrator, create a new document, choosing one of the Web presets. This will ensure Align ...
Ok. Wait. Something is not right.
Have you talked to them and see if they print spot inks?
Here is a screenshot of their personalized decks:
The ones from the right are most likely digital prints, which definitely will not use spot inks. (They will probably use RGB files).
A company that big will probably not use spot inks because this slows down the ...
This is a really interesting question. And will be a followup from this one
How to make a given color a bit darker or lighter?
I will not address how to mask properly an aliased border, I will talk about colors and opacity components.
Let's explore how theoretically the colors will respond as transparent over a white or black background.
I stumbled upon this superuser post that seemed related and was able to make the GIMP instructions work reasonably well
Open the image in GIMP 2.10
Right click the image and choose Layer >> Transparency >> Color-to-alpha
The default white choice was nearly exactly the effect required, though the red appeared slightly transparent. I was able to ...