CODEWITHSUNDEEP
c++scale
flavia
flavia

Reputation: 31

How to go from linear axis to log?

I have a c++ program which the user will click on two points on the screen and I have to create a logarithym scale from that.. Like:

10 100 1000 10000

given that my first point is at 10 supossed pixel 5 and 10000 is given at pixel 200

So how do I calculate the equation that would make my mouse show the log value when it points to the screen.

Thanks.

Upvotes: 3

Views: 3392

Answers (1)

Shahbaz
Shahbaz

Reputation: 47513

All you need is the log function. Let's first assume no offset. If you are given a value of x on the X-axis, you can get it's log value (e.g. in base 10) by:

log(x) / log(10)

If you want x to count from a certain offset (say x0), you should adjust x:

log(x - x0) / log(10)

If you want the resulting point to be offset at a point (say lx0), well just do it:

log(x - x0) / log(10) + lx0

Upvotes: 2

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