Preserve the aspect ratio of picture objects when resizing by their corners
If I resize an imported picture by its corner, the aspect ratio of the picture should be preserved. If I want to change the aspect ratio (which would not be very often), I can resize the picture by its edges. This behaviour is the same as how Microsoft Office treats pictures.
Frédéric Harvey-Lavergne commented
Thanks @Zulkifli Mohd Ali, that's what I was looking for. But still, when importing your picture, you need to define borders in which your picture will fit in, that's where it messes with the aspect ratio.
Zulkifli Mohd Ali commented
Have you try to hold the SHIFT key to resize the image proportionally?