Simple math question about frame buffers

How do you get row back out of n?

local n = row * cols + col
local c开发者_如何转开发 = n % cols
local r = ?

Using some simple arithmetic...

You have

n = rows * cols + col

subtract col from both sides

n - col = rows * cols

divide by cols on both sides

(n - col) / cols = rows

Assuming col < cols holds, you could do it with integer division as rows = n / cols.

local r = int( n / cols )