how to invert greyscale values only... leaving colors alone
Rich Evans wrote:
I have an RGB image that is basically a black background with many colorful objects and white text. --- I'd like to invert the image so that it is a white background with black text but a simple invert inverts the colors in all the colored objects as well. Is there a technique or tool to invert any part of the image that is only a shade of grey? i.e. invert pixeils with a saturation of ~0 (if that is how you say it). I could imagine a filter that does a simple RGB invert for any pixel whose calculated RGB saturation value is below a set threshold. Does this type of tool/script exist?
Here's how I'd do this:
First, I'd make a copy of the original image.
Second, working with the copy, I'd add a new layer, filled with white,
and move that layer to the bottom of the layer stack.
Third, I'd make a copy of the original image, and move the copy to the
top of the stack, if it doesn't happen to be there at the beginning. If
necessary, I'd switch the color paletes so that black is the active
color. Then I'd use the facility to select by color tool to select the
white areas, making certain that there were not highlights of some of
the "many colorful objects" which got included as well. I'd then paint
or bucket fill as necessary to convert the formerly white areas to black.
Fourth, returning to the original layer, I'd select all of the areas
which are black, and remove them.
Finally, merge the layers together, and you should have achieved the
effect you wish.
ns
