How to properly compress an image knowing the final height in pixels?

Question

JavaScript

Good afternoon!
Tell me, is there a formula or a method by which you can calculate the image compression size knowing that at the output it should not exceed 200px in height
In general, how to correctly calculate the width of the output image,
The image is loaded by the user, then it should be drawn in the Canvas window? If you set the compression in the canvas,
then it does not compress correctly!
Thanks in advance.

Answer 1

function calcSize(w, h, limitW, limitH) {
    if (h <= limitH && w <= limitW) {
        return [w, h];
    }
    const r = Math.min(limitW / w, limitH / h);
    return [Math.round(r * w), Math.round(r * h)];
}

const realSizes = calcSize(imgW, imgH, Infinity, 200);

Proportionally sized to fit within width and height limits