Sharp: how can i crop by percentage?

[aryeharmon]

i'd like to slice an image into 2 (bottom half + top half)

[lovell]

Hello, if I've understood you correctly, a combination of metadata and extract should help here, something like (untested):

sharp(input)
  .metadata()
  .then(({ width, height }) => {
    const halfHeight = Math.round(height / 2);
    return [
      sharp(input)
        .extract({ top: 0, left: 0, width, height: halfHeight })
        .toBuffer(),
      sharp(input)
        .extract({ top: halfHeight, left: 0, width, height: height - halfHeight })
        .toBuffer()
    ];
  })
  .then(([upper, lower]) => { ... });

[lovell]

Hope this helped. Feel free to re-open with more details if not.