Converting to a single-color image (duotone sans black channel)

[Alex Graul]

Hello,

Apologies if I'm missing something obvious, I'm trying to work out how to convert an image to a single colour - much like grayscale but colorised. Effectively what I'm trying to do is replicate the effect of Photoshop's Screen blending mode when the top layer is a solid color. I've put up an example to compensate for my inability to articulate this properly here: Loading Image...

I can do a duotone easily enough but this has me stumped. It would also make my life notably easier if it was a single invocation of convert.

Any guidance would be greatly appreciated.

Kind Regards,
Alex

[Fred Weinhaus]

Post by Alex Graul
Hello,
Apologies if I'm missing something obvious, I'm trying to work out
how to convert an image to a single colour - much like grayscale but
colorised. Effectively what I'm trying to do is replicate the effect
of Photoshop's Screen blending mode when the top layer is a solid
color. I've put up an example to compensate for my inability to
articulate this properly here: http://sho.ch/otterconvert.jpg
I can do a duotone easily enough but this has me stumped. It would
also make my life notably easier if it was a single invocation of
convert.
Any guidance would be greatly appreciated.

see -tint and related techniques at
http://www.imagemagick.org/Usage/color/#tinting

also if you are on unix, see my script tintilize at
http://www.fmwconcepts.com/imagemagick/index.php


Fred

[Fred Weinhaus]

Post by Alex Graul
Hello,
Apologies if I'm missing something obvious, I'm trying to work out
how to convert an image to a single colour - much like grayscale but
colorised. Effectively what I'm trying to do is replicate the effect
of Photoshop's Screen blending mode when the top layer is a solid
color. I've put up an example to compensate for my inability to
articulate this properly here: http://sho.ch/otterconvert.jpg
I can do a duotone easily enough but this has me stumped. It would
also make my life notably easier if it was a single invocation of
convert.
Any guidance would be greatly appreciated.

see -tint and related techniques at
http://www.imagemagick.org/Usage/color/#tinting

also if you are on unix, see my script tintilize at
http://www.fmwconcepts.com/imagemagick/index.php


Fred


P.S. On second thought after re-reviewing your example, a better
method would appear to be

+level-colors blue,white

see http://www.imagemagick.org/Usage/color/#level-colors

[Anthony Thyssen]

On Mon, 14 Jun 2010 21:17:11 -0700
magick-users-***@imagemagick.org wrote:
| >Hello,
| >
| >Apologies if I'm missing something obvious, I'm trying to work out
| >how to convert an image to a single colour - much like grayscale but
| >colorised. Effectively what I'm trying to do is replicate the effect
| >of Photoshop's Screen blending mode when the top layer is a solid
| >color. I've put up an example to compensate for my inability to
| >articulate this properly here: http://sho.ch/otterconvert.jpg
| >
| >I can do a duotone easily enough but this has me stumped. It would
| >also make my life notably easier if it was a single invocation of
| >convert.
| >
| >Any guidance would be greatly appreciated.
|
|
| see -tint and related techniques at
| http://www.imagemagick.org/Usage/color/#tinting
|
| also if you are on unix, see my script tintilize at
| http://www.fmwconcepts.com/imagemagick/index.php
|
|
| Fred
|
|
| P.S. On second thought after re-reviewing your example, a better
| method would appear to be
|
| +level-colors blue,white
|
| see http://www.imagemagick.org/Usage/color/#level-colors

Note you should greyscale the image first then apply +level-colors

Remember +level-colors is still a -level operator, just getting its
values (+level -> map black and white to given levels) from the colors
you have specified. each channel will still be modified individually.

So use...
-colorspace Gray +level-colors blue,white

You can also use -gamma afetr the -colorspace operator to adjust the
mid-tone brightness, if you want to.



Anthony Thyssen ( System Programmer ) <***@griffith.edu.au>
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