CODEWITHSUNDEEP
mathrgb
AK.
AK.

Reputation: 33

Can we find out the difference between 2 RGb colors to find out a 3rd color?

2 colors are mixed together. If i have the RGB for the resultant color and RGB for one of the colors mixed, then somehow i could calculate the 2nd color?

I will try to explain visually what i am trying to say. Here is a flickr link

http://www.flickr.com/photos/48150615@N08/4407414157

I know that the circle in the middle has an opacity of 20%

Is there any way to know the color value of the circle so that i can deduct that to get the same color value as the background color.

Upvotes: 1

Views: 2736

Answers (4)

Ross
Ross

Reputation: 2096

CIELAB color space is specially designed for calculating differences between colors, but it might be a overkill in you case. Probably HSV is easy solution for you.

Upvotes: 1

nickf
nickf

Reputation: 546025

Firstly it depends how you're going to mix them. That is, you could average the RGB components (this means blue (0,0,255) + yellow (255,255,0) == grey (128,128,128)), or you could work on Hues, Saturation and Value, which often gives a much more "as expected" result.

Anyway, in either case, it's some simple maths:

  • if the way to get the average is C3 = (C1 + C2) / 2
  • then the way to find C2 is C2 = (C3 * 2) - C1

Upvotes: 3

David Pfeffer
David Pfeffer

Reputation: 39833

Just subtract each component. The components are often stored in hexadecimal format, in which case you will need to convert the numbers to decimal or do hex math.

Upvotes: 0

Andrey
Andrey

Reputation: 60065

if i understood the task correctly...

let's do some school math

c is color of initial image, t is color of transparent color, a (for alpha) is transparency, c' is result color.

c' = (1 - a) * t + a * c

you want to find c.

c = (c' - (1 - a) * t) / a

you need to know a, t and c'

Upvotes: 3

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