affine v0.1.0 Affine.LinearMap

Generating 2D graphics, either for charting, design or other reasons, can require reassignment of a space on the drawing canvas for a part of the graphic. For instance, creating the x-axis in a chart that goes for 0-21 for the data in the area from pixel 143 to pixel 200 on the drawing canvas can use a transform to easily convert from data space to canvas space.

A special type of ‘create’ parameter list can be used to generate the transform for the very example just stated. Here’s how it looks:

t =
  [type: :linear_map, x1_in: 0.0, x1_out: 143.0, x2_in: 21.0, x2_out: 200.0]
  |> Affine.create

This code generates a 1D transform with translation and scaling such that a value of 0 in will generate 143 and a value of 21 in will generate a 200.

point = Affine.map (t, 0.0)
assert point == 143
point = Affine.map (t, 21.0)
assert point == 200

Summary

Types

matrix()

Functions

linear_map(parms)

Generates a linear map transform from parameters describing the requried mapping. See the documentation above for the format of the parameters keyword list. A transform is returned that can perform the mapping

map(t, value)

Given a 1 dimensional transform set up using the Affine.create function using the :linear_map type, the map function will map an input value to an output value. See the description above for examples

Types

matrix()

matrix() :: [[number]]

Functions

linear_map(parms)

linear_map(list) :: matrix

map(t, value)

map(matrix, number) :: number

Given a 1 dimensional transform set up using the Affine.create function using the :linear_map type, the map function will map an input value to an output value. See the description above for examples.