GIMP Version: 2.6.12
Operating System: Linux
OS Version: Windows7 (64-bit) and Fedora 16
GIMP Experience: Basic Level

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This has never happened to me before, I am doing Dracs metal again and when it says Colors > invert, instead of the darker green, I get purple. In my color selection boxes, it shows that I have the two different shades of green selected.
Now this could only happen to me...I think. Is there anyone that can tell me how to fix this?

You're confusing value invert with invert.

Invert inverts the individual values of each RGB channel independently. Thus you get purple from green, as those are complementary colours.

Value invert only inverts the value and leaves the hue & saturation intact.

Also, neither are affected by what colours you have selected. If you want to simply change the colour to the colour you've selected, simply lock the alpha channel and fill the layer with the colour of your choice.

Thank you dd.
I am still confused tho, cuz it worked when I was using the colors that Drac was using on his tute. (two shades of brown) Anyway, I will do what you mentioned as long as I get where I want to go. I just couldn't understand why this happened.

Molly, you are using two shades of green instead of brown, so the results will be different.

Briefly, the inverted color is:
A) the color on the opposite side of the color wheel,
which also is:
B) the color with a hue that is different by 180 degrees.

I did a color pick on your two colors and as the screen shot shows, the hue of the two colors is different by 180 degrees.

Thank you bkh1914 - Great explanation of the Color Invert process. Never really thought about it much so it's good information to know. It never ceases to amaze me at the knowledge base represented her on GC.

Molly - I'm not sure what step you were on with the Invert process. I use /Colors>Desaurate to get to a greyscale sometimes before inverting but I don't remember any part of the tut with that step. More than likely I was referring to Inverting the selection to cut away the metal image from outside a panel layer selection like in Step 8.

Don't know if this is even related to the tut or not but I just thought I would throw it out there just in case.

It was step 3 Drac...says invert

AHHHHH. Yeah I was working with gray colors so the invert process would certainly work differently with a colored layer.

Woo Hoo, I wasn't crazy after all.

But crazy is good though right?

Black, White are special colors: the absence of all color (Black) and the maximum presence of all colors (White). They live in the center and edge of a shaded color wheel. They have no hue value, although for convenience GIMP assigns them a hue of 0. Changing the position of the hue slider has no effect on the resulting color.

Gray is all the shades between Black and White. Like Black and White, Gray has no hue because all the colors are equally present. For example 50% gray (neutral gray) is the combination of 50% red, 50% green and 50% blue (RGB color system). Inverting a gray color produces the complimentary gray color: 30% Gray (70% White) inverts to 70% Gray (30% White).

I hope this helps, rather than adding to the confusion.

The color wheel is such a basic concept in art that it is well worth a little time to learn it and understand it.

Note: the color wheel for pigments is different from the color wheel for light (i.e. digital art).

Great point. Wasn't it you that posted something a while back regarding blending of colored layers using a particular layer Mode to get the combination of colors to produce secondary colors? I found that quite interesting and useful.

I am very familiar with the colour wheel in art but I didn't tie it in with Gimp tools. I took art for around 3 yrs but I didn't associate the tools in Gimp with it. I will know the next time, I just assumed that when you click invert, it would change to the foreground colour. Live and learn. .
Thanks

Actually, the "invert" function doesn't care about the HSV values at all, because it works strictly on RGB space. What I'm saying is, your explanation is basically correct, but I think you're explaining it in a sort of roundabout way...

Invert simply inverts each colour channel R, G, B to their inverse values, ie. they are substracted from 255 so that for example (0,255,0) becomes (255,0,255) and so on. A channel value of 100 would become (255 - 100 = 155).

The reason why invert works differently on black, white or any grayscale colour is because in grayscale colours (ie. colours where saturation is 0) all the RGB values are the same, eg. black is (0,0,0), white is (255,255,255) and middle gray is (128,128,128)... so when they're all inverted, they'll again all be the same, resulting in another grayscale value.

A saturated colour ends up with the complementary colour (ie. 180 degrees on the colour wheel) because of the way HSV is mapped on the RGB space. Saturation and Value do not necessarily stay the same, though.


"Value invert", on the other hand, does work on the HSV space, as the name implies - it converts each colour to HSV space, then inverts the Value, keeping H&S the same, and then converts it back to RGB.