Computer Graphics with Photoshop - Overlapping single colour layers

Author

Overlapping single colour layers

James McNangle

2005-06-12, 11:14 pm

I want to compare two similar shapes, and would like to put masks of each shape
on separate layers, with each layer coloured in a single primary colour, and
overlap the layers in such a way that both colours are printed where the two
shapes overlap, but only the corresponding colour is printed where one shape is
larger than the other. As far as I can see, the only way to do this is to give
the top layer of 50% transparency, making its colour diluted.

Is there a way to print both colours at full intensity?

James McNangle

edjh

2005-06-12, 11:14 pm

James McNangle wrote:
> I want to compare two similar shapes, and would like to put masks of each shape
> on separate layers, with each layer coloured in a single primary colour, and
> overlap the layers in such a way that both colours are printed where the two
> shapes overlap, but only the corresponding colour is printed where one shape is
> larger than the other. As far as I can see, the only way to do this is to give
> the top layer of 50% transparency, making its colour diluted.
>
> Is there a way to print both colours at full intensity?
>
>
> James McNangle

Not sure what you're after but have you tried the Blending Modes? Top of
the Layers palette "Mode". Set upper layers to Multiply or Overlay for
instance at 100% Opacity.

--
Comic book sketches and artwork:
http://www.sover.net/~hannigan/edjh.html
Comics art for sale:
http://www.sover.net/~hannigan/batsale.html

johnboy

2005-06-12, 11:14 pm

"James McNangle" <mcnangle@westnet.com.au> wrote in message
news:hihpa15p02fe1olt6pv6g119d3e11hveqa@4ax.com...
>I want to compare two similar shapes, and would like to put masks of each
>shape
> on separate layers, with each layer coloured in a single primary colour,
> and
> overlap the layers in such a way that both colours are printed where the
> two
> shapes overlap, but only the corresponding colour is printed where one
> shape is
> larger than the other. As far as I can see, the only way to do this is to
> give
> the top layer of 50% transparency, making its colour diluted.

Play with layer modes. You might try Screen first.

Peter Wollenberg

2005-06-13, 7:14 am

James McNangle <mcnangle@westnet.com.au> wrote:

>I want to compare two similar shapes, and would like to put masks of each shape
>on separate layers, with each layer coloured in a single primary colour, and
>overlap the layers in such a way that both colours are printed where the two
>shapes overlap, but only the corresponding colour is printed where one shape is
>larger than the other. As far as I can see, the only way to do this is to give
>the top layer of 50% transparency, making its colour diluted.
>
>Is there a way to print both colours at full intensity?
>

Sure,

set:
Background: white
Layer 1: Solid color with shape 1 as layer mask: 100R 0G 0B

Layer 2: Solid color with shape 2 as layer mask: 100R 0G 100B (= M!);
Layer Mode of Layer 2: Difference

Layer 3: Selective color adjustment layer with blues adjusted to:
-100C -100M +100Y

This gives you red and green as the colors of the shapes without
overlap and yellow (R + G) in the overlapping area.
With proper adjustments every combination of primaries is possible.
The layer masks should be sharpenend to minimize black dots at the
boundaries as far as possible. For a final printout, merge down and
blur slightly in order to prevent jaggies.

HTH, Peter

johnboy

2005-06-13, 7:16 pm

"James McNangle" <mcnangle@westnet.com.au> wrote in message
news:c5qqa1dmgftfa7qlor0or3h2lf8qqgejbb@4ax.com...

> Thank you for this suggestion. I put some diagrams showing what I was
> trying to
> achieve on my web page, before I read your suggestion. These are shown at
> http://www.corybas.com/Overlays.htm. 'Multiply' gives the effect I was
> looking
> for. I am not sure what 'Overlay' does, but it doesn't give this effect.

It would be easier if you used the RGB model.

Peter Wollenberg

2005-06-13, 7:16 pm

James McNangle <mcnangle@westnet.com.au> wrote:
....
>
>Thank you for this suggestion. I put some diagrams showing what I was trying to
>achieve on my web page, before I read your suggestion. These are shown at
>http://www.corybas.com/Overlays.htm. 'Multiply' gives the effect I was looking
>for. I am not sure what 'Overlay' does, but it doesn't give this effect.
>
>
Seeing what you actually want, the solution is quite simple:

RGB model, white Background
Layer 1: shape with 255 R 255 G 0 B; mode = Normal
Layer 2: shape with 255 R 0 G 0 B; mode = Difference
Layer 3: shape with 0 R 255 G 0 B; mode = Difference;
that's all

BTW, IMHO you have a misconception of "adding" colors. You want the
colors to subtract, not to add! CMY are the subtractive primaries and
black represents zero luminosity.

Peter

James McNangle

2005-06-14, 7:16 pm

jenelisepasceci@web.de (Peter Wollenberg) wrote:

..........
>Seeing what you actually want, the solution is quite simple:
>
>RGB model, white Background
>Layer 1: shape with 255 R 255 G 0 B; mode = Normal
>Layer 2: shape with 255 R 0 G 0 B; mode = Difference
>Layer 3: shape with 0 R 255 G 0 B; mode = Difference;
>that's all
>
>BTW, IMHO you have a misconception of "adding" colors. You want the
>colors to subtract, not to add! CMY are the subtractive primaries and
>black represents zero luminosity.

Thank you for your interest. I know what you mean about colours adding, but for
me school paints came first, so I normally think blue plus yellow equals green,
etc.

To try to get a better idea of what was going on, I set up three experiments.

1. I set up a new file, white background and RGB colour mode. Then I created
three overlapping circles on separate layers, set each layer to 'Difference',
and coloured them respectively 100% red, green and blue. Rather to my surprise,
each layer came up as the complementary colour, but these combined as I
expected, with true black in the middle. However the individual colours
appeared rather desaturated compared with the following experiments.

2. I set up another new file, as before, but this time I set each layer to
'Multiply', and coloured them 100% cyan, magenta and yellow. This looked much
the same as the first diagram, except that the individual colours appeared more
fully saturated, but the black in the middle was less saturated.

3. I set up a third new file using CMYK colour mode, and used the same
arrangement of layers as in experiment 2. This time the black was fully black,
and the reds greens and blues appeared stronger than in experiment two.

When I sampled the colours in each region of each image, I found that in
experiment 1 the primary colours were each 100% of the opposite two colours (ie
the nominally red region was 100% green and 100% blue), the secondary colours
were 100% of a single colour, and the triple colour was true black.

In experiment 2 each region was the appropriate combination of C M & Y, but
these were achieved by various combinations of R, G & B, but generally at
significantly less than 100%. This made the single and double colours appear
more saturated than in experiment 1, but the triple colour had quite large
percentages of R, G., and B, so that it was really a dark grey.

In experiment 3 (with the CMYK colour scheme) the double and triple colours had
significant components of K. In particular the triple colour had 90% K, and R,
G., and B were all zero.

When I used the techniques of experiment 2 for an actual test case, I found that
it did not work nearly as well as I had hoped, because I tended to see the
overlap region as a separate shape, so that was difficult to visualise the two
shapes I was actually comparing. So now I am wondering about alternative ways
of achieving a similar result. I suspect I might do better if I drew constant
width outlines around each shape, in different colours, and only displayed the
outlines.

Anyone know a good way to draw a constant width outline around an irregular
shape?

James McNangle

KatWoman

2005-06-14, 7:17 pm

Layer effect>stroke

"James McNangle" <mcnangle@westnet.com.au> wrote in message
news:ej2ta1hecl5vojpa1q0jnh7bcp37qt1glh@4ax.com...
> jenelisepasceci@web.de (Peter Wollenberg) wrote:
>
> .........
>
> Thank you for your interest. I know what you mean about colours adding,
> but for
> me school paints came first, so I normally think blue plus yellow equals
> green,
> etc.
>
> To try to get a better idea of what was going on, I set up three
> experiments.
>
> 1. I set up a new file, white background and RGB colour mode. Then I
> created
> three overlapping circles on separate layers, set each layer to
> 'Difference',
> and coloured them respectively 100% red, green and blue. Rather to my
> surprise,
> each layer came up as the complementary colour, but these combined as I
> expected, with true black in the middle. However the individual colours
> appeared rather desaturated compared with the following experiments.
>
> 2. I set up another new file, as before, but this time I set each layer to
> 'Multiply', and coloured them 100% cyan, magenta and yellow. This looked
> much
> the same as the first diagram, except that the individual colours appeared
> more
> fully saturated, but the black in the middle was less saturated.
>
> 3. I set up a third new file using CMYK colour mode, and used the same
> arrangement of layers as in experiment 2. This time the black was fully
> black,
> and the reds greens and blues appeared stronger than in experiment two.
>
> When I sampled the colours in each region of each image, I found that in
> experiment 1 the primary colours were each 100% of the opposite two
> colours (ie
> the nominally red region was 100% green and 100% blue), the secondary
> colours
> were 100% of a single colour, and the triple colour was true black.
>
> In experiment 2 each region was the appropriate combination of C M & Y,
> but
> these were achieved by various combinations of R, G & B, but generally at
> significantly less than 100%. This made the single and double colours
> appear
> more saturated than in experiment 1, but the triple colour had quite large
> percentages of R, G., and B, so that it was really a dark grey.
>
> In experiment 3 (with the CMYK colour scheme) the double and triple
> colours had
> significant components of K. In particular the triple colour had 90% K,
> and R,
> G., and B were all zero.
>
> When I used the techniques of experiment 2 for an actual test case, I
> found that
> it did not work nearly as well as I had hoped, because I tended to see the
> overlap region as a separate shape, so that was difficult to visualise the
> two
> shapes I was actually comparing. So now I am wondering about alternative
> ways
> of achieving a similar result. I suspect I might do better if I drew
> constant
> width outlines around each shape, in different colours, and only displayed
> the
> outlines.
>
> Anyone know a good way to draw a constant width outline around an
> irregular
> shape?
>
>
> James McNangle

James McNangle

2005-06-17, 11:14 pm

"KatWoman" <JoliePrincessKatana@hotmail.com> wrote:

>Layer effect>stroke

Thank you for this. It has some tricks to it, but it can be persuaded to work.

To allow the shapes to overlap transparently you have to set their mode to
'difference', then fill them with black. If you try to delete the contents of
the layer, the border gets much wider, with gaps at 90°. And if you try to
select the object and then move it, the border doesn't move.

Also, although the layer is in 'difference' mode the borders aren't, so where
they overlap the top one obliterates the lower ones. The only way I can see to
overcome this, if it matters, is to put each shape on a different page, put a
border on it and fill it with white, so that only the border shows. Combine the
layers so that all the layer information is lost, then copy all the shapes to a
new page, so that the individual borders becomes separate normal layers, which
you can then define as 'difference'. The border colours would be inverted in
the process so you would have to correct for this somewhere along the line.

James McNangle

Peter Wollenberg

2005-06-20, 7:14 am

James McNangle <mcnangle@westnet.com.au> wrote:

>"KatWoman" <JoliePrincessKatana@hotmail.com> wrote:
>
>
>Thank you for this. It has some tricks to it, but it can be persuaded to work.
>
>To allow the shapes to overlap transparently you have to set their mode to
>'difference', then fill them with black. If you try to delete the contents of
>the layer, the border gets much wider, with gaps at 90°. And if you try to
>select the object and then move it, the border doesn't move.
>
>Also, although the layer is in 'difference' mode the borders aren't, so where
>they overlap the top one obliterates the lower ones. The only way I can see to
>overcome this, if it matters, is to put each shape on a different page, put a
>border on it and fill it with white, so that only the border shows. Combine the
>layers so that all the layer information is lost, then copy all the shapes to a
>new page, so that the individual borders becomes separate normal layers, which
>you can then define as 'difference'. The border colours would be inverted in
>the process so you would have to correct for this somewhere along the line.
>
>
Better use "Stroke" as a layer effect on your shapes and not Edit->
Stroke.

Peter