API endpoint -
Resize - resizes image with preserving aspect ratio and optimizes it using lossy compression. If you need the exact size then use fit operation.
size - new size (in pixels) of the image in the format
WIDTH and xHEIGHT.
You can specify only one dimension and the second will be calculated according to aspect ratio of the image.
Please, feel free to test this in your browser to see how it works.
Image after Pixboost transformation