How to preserve the DPI of cropped images?

[IB21-A]

I need to accept images that are 150+ DPI for print, and let the user crop them. However it appears cropper is outputting a 72 dpi image after cropping? How can I ensure that the DPI of the image is preserved?

[fengyuanchen]

If you want to print an image with 240x2400px (150DPI), you can crop an image with 500x500px (72 DPI):

const ratio = 150 / 72;
const targetSize = 240;
const sourceSize = targetSize * ratio; // 500