Trouble with brushes and creating an image to mask with

[SonjaThompson]

This is what I'm trying to do, that I could do in Serif CraftArtist 2.0 before, and loved:

The shown brush is one that CraftArtist uses to produce the effect.  While it is a PNG file, there is no transparency in it.

It appears that Edge brushes are different from other brushes, and Affinity doesn't support them.  I'm going to have work to get the same effect, and I'm willing.  But I'm having trouble making that happen, and I could really use some advice.

Obviously CraftArtist does some masking under the covers, but I sure can't figure out which algorithm it uses.   For example, in Affinity, if you use "Mask to Below," anything opaque reveals the layer below it, and transparency obscures it from view, with semi-transparent colors showing some transparency in the layer below.  But if you use "Rasterize to Mask," white reveals the layer below, while black and transparency obscures it from view, with colors showing some transparency in the layer below, depending on their closeness to black.  I have no idea what CraftArtist does, but this brush image won't do for Affinity, so I filled the bottom white pixels with black.

My plan is to create the Smudge brush and outline a black rectangle with it, white to the outside, then apply an Invert adjustment to get a white shape with black around the outside.  To keep things simple, it will be for the "Rasterize to Mask" algorithm.  And I've tried, but I ran into so many problems.  Here's my story:

I pulled up Affinity Designer Version 2.1, made a pure black rectangle with a pure black stroke.  Then tried to build the brush.  I didn't know which brush to build -- textured intensity or textured image.  Both take a single image as their basis, using the "repeat" method.  So I built and tried both. 

Here's what the textured intensity brush looked like, at 24 pt, aligned to the center of the line, with the rectangle behind the line:

It's not bad, but the fine transparency that should be inside the rectangle is covered up.  I proceeded anyway, and added the Invert adjustment, and got:

I really expected a white center with a black outline.  Nope.  So I tried the textured image brush instead and got:

And the brush is upside down!  After I while, I figured out I could select the middle top handled and pull it down past the bottom edge of the rectangle (which is a really weird thing to do) and I got this:

This not only puts the brush in the right position, but also gives back transparency over the rectangle, although there appears to be a line where the brush starts.  Obviously, the brush image is not made with pure black.  Not only that, but the brush doesn't look like it's held it shape well -- either squashed horizontally, or stretched vertically.  So I inverted it, anyway, and it looked like:

Not even close to what I expected.  WHY IS THIS?  What am I doing wrong, and is there a better way to do this?

Thanks!

[thomaso]

If I understand your first picture right you want to mask the paper edge with a rough brush and get the masked area transparent? If yes, it appears to work with the default brush Masking > Textured Mask Brush 01 painted on a Mask layer. Like so:

Sorry I did not understand what you want to achieve with inverting etc. – but working with masks maybe a different subject. As far I know Mask layers ignore adjustments, at least in my V1, it maybe different in V2. In case you want the masking brush strokes as black pixel layer you could paint on a Pixel layer, not a Mask layer.

[SonjaThompson]

Unfortunately, the Textured Mask Brushes are pixel brushes, and can't be applied to a line around the objects, so I can't use it to create a mask.

Inverting the image was an attempt to change black to white and white to black, which is does in most cases.  

I've discovered that, for some strange reason, RGB 0,0,0 in Affinity converts to this in CMYK:

It's not supposed to do that.  At least K should be 100, and it doesn't matter what C, M, and Y do.

[thomaso]

Ah, I didn't know that you want to use a vector brush and/or apply a stroke to the image, – as mac user I didn't experience Serif CraftArtist 2.0.

In AD you can apply a vector brush stroke to an image + apply the blend mode "Erase" to the stroke only + apply several strokes to one object + apply colour opacity to a stroke. For instance:

  + 

In APub you can't set a stroke blend mode separately from the fill colour or the containing image and you can't apply several strokes to an object – thus in APub you would need separate objects for this result.

6 hours ago, SonjaThompson said:

I've discovered that, for some strange reason, RGB 0,0,0 in Affinity converts to this in CMYK:

It is not converted, it gets displayed only with its equivalent in CMYK because of the activated lock button left to the menu. As long this lock is activated every colour will be displayed in the space that is currently set in the menu and every new colour you define / save as swatch will be created in this space, too.

6 hours ago, SonjaThompson said:

It's not supposed to do that.  At least K should be 100, and it doesn't matter what C, M, and Y do.

In Affinity you will never get RGB 0,0,0 either displayed or converted to CMYK 0,0,0,100. Consider that RGB 0,0,0 is darker than 100 K because it uses 3 channels, different to the single K channel of CMYK. Accordingly 100 K would appear as dark gray only compared to the rich black of RGB 0,0,0.

What exactly happens in the Colour panel not only depends on the currently selected colour space when defining a colour or saving a swatch but also depends on your document colour space and profile.

Also note, the black + 50% gray swatches of the 4 default swatches in the Swatches panel right to the palette menu    also depend on the current document colour space: In a CMYK document they are defined as 100 and 50 K whereas in an RGB document they are defined as RGB.

[SonjaThompson]

Wow, thomaso, that was realy great information!  I know I have a lot to learn.  I'm not a Mac user, so there may be some differences.  It's too bad you never knew CraftArtist.  It was a really fun and intuitive tool!  I could really focus on my projects.

You are right about CMYK 0,0,0,100 being lighter than RGB 0,0,0, but I've also discovered since my last post that CMYK 100,100,100,100 is darker than RGB 0,0,0.  I guess the CMY values do matter after all.

So I tried the Erase blend mode on the brush edge, which was cool. Thanks for the tip on that. There's a couple of problems.  It looks like some brushes are fine, but once in a while I get a bad corner.  I don't know what to do about that.

When I use MY brush this way, the tops of the brush edge get cut off.  I've tried all the alignments, and it's the best I can get with my brush.  The vertical stretching of the brush image is still annoying.

 

 

[thomaso]

3 hours ago, SonjaThompson said:

CMYK 100,100,100,100 is darker than RGB 0,0,0.  I guess the CMY values do matter after all.

Not sure what you mean. You hardly will print 400% ink in CMYK. In an RGB document this difference doesn't exist.
In CMYK documents I prefer to keep the CMYK lock activated + use CMYK swatches only.

3 hours ago, SonjaThompson said:

It looks like some brushes are fine, but once in a while I get a bad corner.  I don't know what to do about that.
(...)
When I use MY brush this way, the tops of the brush edge get cut off. 

These are quite likely matters of the stroke options (-> Stroke panel), or the current brush options (-> Context Toolbar), or of the brush properties (-> Brushes panel -> double-click a brush). It might help if you inspect those / or show screenshots with brush settings for the two issues, and possibly upload the file of your "MY" brush.

[SonjaThompson]

Yeah, I've been brushing up on what I thought I knew...and I have been operating on some wrong assumptions.  I better go do my homework better before I try this again.  Brushes are total different in Affinity...

Thanks for your patience with me.

[thomaso]

On 7/14/2023 at 9:42 AM, SonjaThompson said:

It looks like some brushes are fine, but once in a while I get a bad corner.  I don't know what to do about that.

Just noticed a related thread to this specific vector brush corner occurrence. It is a general, known issue and seems to have as solution: Open the curve + adjust nodes manually.