Recolor line art in Photo

[nitrospectide]

I have some scanned line art I want to recolor from black to blue. In Photoshop, I would always copy the art, paste into an alpha channel, and then load that as a selection and fill. How can I do it in Photo?

[Alfred]

One simple way to recolour black or greyscale artwork in any image editor is to create a new layer on top of the image layer, set its blend mode to 'Screen' and flood-fill it with the desired colour.

[Butler To Cats]

A simple alternative:

Open your scanned image, add a layer adjustment, select Curves, select the Blue channel only, make the blue curve a simple horizontal line across the top at the highest value.

 

 

A vaguely similar technique to your Photoshop technique:

 

1. Duplicate the layer (copy and paste).

2. Invert the uppermost layer (layer adjustments) and merge the adjustment layer.

 

You should now have an inverted version of your line art (white on black) as a layer above your line art (black on white).

 

3. With the top (inverted) layer selected: Layer menu, Rasterise to Mask.

4. Select the lowermost layer and paint or fill.

 

5. You can group these two layers so the mask does not affect any other layers, or alternatively drag the uppermost Mask layer down onto the Pixel line art layer.

[nitrospectide]

I will give these a look. Is there no way to work in an alpha channel with a grayscale image?

[MEB]

Hi nitrospectide,

I'm not sure i understood your question. I believe you want to work/paint on a mask as a greyscale layer. If so press ⌥ (option/alt) and click the mask's thumbnail in the Layers panel to switch to greyscale mode. 

[nitrospectide]

In Photoshop, I can work with a grayscale image in an alpha channel, and the grayscale values determine what is/isn't selected when I load a selection from the alpha channel. So, If I bring in a black and white photo, I can load that as a selection, then paint across the selection in whatever color I want. The end result is the photo in the color I am using to paint.

[nitrospectide]

One simple way to recolour black or greyscale artwork in any image editor is to create a new layer on top of the image layer, set its blend mode to 'Screen' and flood-fill it with the desired colour.

This worked nicely for my current need. Thanks!

 

The advantage of using the alpha channel / selection though, is that all of my negative space is transparent, so I can place something as line art, and then fill in layers behind to show through it.

[nitrospectide]

An simple alternative:

Open your scanned image, add a layer adjustment, select Curves, select the Blue channel only, make the blue curve a simple horizontal line across the top at the highest value.

 

 

A vaguely similar technique to your Photoshop technique:

 

1. Duplicate the layer (copy and paste).

2. Invert the uppermost layer (layer adjustments) and merge the adjustment layer.

 

You should now have an inverted version of your line art (white on black) as a layer above your line art (black on white).

 

3. With the top (inverted) layer selected: Layer menu, Rasterise to Mask.

4. Select the lowermost layer and paint or fill.

 

5. You can group these two layers so the mask does not affect any other layers, or alternatively drag the uppermost Mask layer down onto the Pixel line art layer.

Your Rasterize to Mask works as well, AND it makes the negative space in the line art transparent!

 

I don't understand what it's doing though. If I drag the layer onto the other, it only masks according to the rectangle outline of the line art. If I use "Mask to Below" in the Layers palette, it also uses only the rectangle of the line art. What is going on with the Rasterize to Mask that it actually does what I want? How is it different? I don't see anything in the Help.

[JimmyJack]

I'll toss my hat in.

 

Copy your image. If you want add a b&w adjustment, adjust levels... whatever. Rasterize to mask (later you can turn it off). Go the the channels panel and right click on the mask alpha and choose Create Spare Channel. Right click on the spare channel and choose Load to Pixel Selection. Invert the pixel selection (Select dropdown). Fill.

 

You can skip the spare channel step and load the pixel selection right from the composite alpha if you're only dealing with the one image in the work space, or if you turn off visibility of unwanted objects/layers.

 

 

[nitrospectide]

I'll toss my hat in.

 

Copy your image. If you want add a b&w adjustment, adjust levels... whatever. Rasterize to mask (then you can turn it off). Go the the channels panel and right click on the mask alpha and choose Create Spare Channel. Right click on the spare channel and choose Load to Pixel Selection. Invert the pixel selection (Select dropdown). Fill.

 

You can skip the spare channel step and load the pixel selection right from the composite alpha if you're only dealing with the one image in the work space, or if you turn off visibility of unwanted objects/layers.

 

Screen Shot 2017-05-09 at 2.48.53 PM.png  Screen Shot 2017-05-09 at 2.49.06 PM.png

This is nearly the same as what I had described. Thank you. It seems a bit convoluted, though. Why do I have to rasterize to a mask, and pick it up as the alpha channel?

 

In Pshop, I could just create and work on a channel directly, pasting an image in, retouching, adjusting levels, until I got what I wanted, and then load as a selection after I was finished. I don't see any way to edit (or even see) the spare channel in this though.

[JimmyJack]

HA! Why indeed!

 

Why can't we draw a marquee selection out from the center?? I dunno.

(sorry... mini rant out of nowhere. Boom. Drops mic  :D )

 

....Scroll down to the bottom of the Channels Panel to see the spares.

[nitrospectide]

HA! Why indeed!

 

Why can't we draw a marquee selection out from the center?? I dunno.

(sorry... mini rant out of nowhere. Boom. Drops mic  :D )

 

....Scroll down to the bottom of the Channels Panel to see the spares.

Sorry - I can see the spare channel in the Channels palette, but I want to look at it in the main view and edit it.

[JimmyJack]

Sorry - I can see the spare channel in the Channels palette, but I want to look at it in the main view and edit it.

 

Ah! Well then, I guess, we're back to MEB's suggestion?

If you want to manipulate it in real time as it's masking, paint on the mask with black/white/grey.

[Butler To Cats]

Your Rasterize to Mask works as well, AND it makes the negative space in the line art transparent!

 

Yes, sorry, I typically want to re-colour the line art itself AND colour the space (basically, cartoon/comic work from line art).

Oh, hang on, your reply to Alfred says you can use that for some cases. Good-oh.

 

I don't understand what it's doing though. If I drag the layer onto the other, it only masks according to the rectangle outline of the line art. If I use "Mask to Below" in the Layers palette, it also uses only the rectangle of the line art. What is going on with the Rasterize to Mask that it actually does what I want? How is it different? I don't see anything in the Help.

 

Mask Below or drag creates a small 'm' masking layer, which is still a Pixel layer: if a pixel is transparent in the masking layer, it will be transparent in the masked layer, so you can use paint or an eraser to define/edit the mask. Think "frisket" (liquid or cutout shapes) - the mask transparency indicates where you can paint, or not. 

 

Rasterise to Mask creates a big 'M' Mask layer, a different type of layer like an alpha adjustment layer: white is opaque, black is transparent.

 

You can also (this might seem more like your Photoshop thinking):

1) Shift+Ctrl+click (is it Cmmd rather than Ctrl on a Mac?) on the thumbnail of the line art layer (creates a selection based on luminosity),

2) then Select menu, Invert Pixel Selection (since you want the non-luminous line art to be the selected area),

3) then paint over the line art using that selection,

 

or (if you want to keep and/or edit the mask)

1) Shift+Ctrl+click (is it Cmmd rather than Ctrl on a Mac?) on the thumbnail of the line art layer  (creates a selection based on luminosity), 

2) then Select menu, Invert Pixel Selection (since you want the non-luminous line art to be the selected area),

3) click the Mask Layer button under the layer panel to turn the selection into a (big 'M') Mask layer only for this layer. 

4) Ctrl+D (Cmmd+D) or Select menu, Deselect to turn off the selection (since you now have a Mask, you don't need a selection) and

5) click the line art thumbnail so you are painting on the line art, not the Mask.

You can right-click the Mask thumbnail and Edit Mask to view and edit the Mask using black/white/grey, or normal single-click the Mask thumbnail to edit the Mask while viewing the line art.