exif-orientation-math

Small library to compose multiple exif orientation values and convert an orientation into flip and rotate instructions.

Methods

compose (Number, Number) -> Number

Given two EXIF orientation numbers (1-8), returns the EXIF orientation of the result of doing both operations in sequence. This could be useful if you are applying an additional EXIF orientation (say, from a database) on top of what is stored in a file.

const exifmath = require('exif-orientation-math')
const neworientation = exifmath.compose(5, 7)
// neworientation: 3

operations (Number, { flop: Boolean }) -> { flip: Boolean, angle: Number }

Given an EXIF orientation, returns the meaning in an object defining whether or not to flip first, and a rotation angle to apply after the flip.

const operations = exifmath.operations(5)
// operations: { flip: true, angle: 270 }

flop option should be used if the image manipulation library being used supports a vertical flip. Will return an additional flop: Boolean in the return to represent the vertical flip operation. This will result in the minimum number of operations.

const operations = exifmath.operations(4, { flop: true })
// operations: { flip: false, flop: true, angle: 0 }