[Gimp-user] global color changes

[rich404 <forums gimpusers com>]

> Rich....I have attempted to implement what I thought was your
> suggestion.
> I have stated it below. In trying to make my mask....I encountered a
> problem.
> I could not select a portion of my mask pattern to repeat by pasting
> and anchoring.
> Can you tell me what I might be doing incorrectly?
>
> Goal
> Create a test pattern of 24 pairs of vertical lines (one  black, one
> of four colors) for an electronic sign 112 pixels wide and 48 pixels
> high.  The color lines of the pair are Red or Green or Blue, or White.

You only asked about color-to-alpha and swapping black/white. However

First the arithmetic does not work with Gimp. 112 pixels in 24 (pairs) = 4.66
pixels. You can not split pixels.

Assuming you sort that out, I think you are over-complicating things.

You can use Filters -> Render -> Pattern -> Grid to generate vertical black and
white stripes 1 pair = 4 pix (2 + 2 )

I put up a set of guides = 28 to indicate the lack of match.  example:
https://i.imgur.com/5lAgF7f.jpg

note the guides fall on pixel boundaries so are not all equal width.

Sets of black/red , black/green , black/blue most easily done by adding coloured
layers with those layers in 'multiply mode'

Turn visibility on or off for colour, export as png's for individual images.
example: https://i.imgur.com/A5ARfHj.jpg

attached the xcf to play with.

Attachments:
* http://www.gimpusers.com/system/attachments/1054/original/rgb-b-w-stripes.xcf

-- 
rich404 (via www.gimpusers.com/forums)