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