How to apply a gradient to an image so that the gradient does not go beyond the edges?

Question

PHP

Hello. How to make the gradient not go beyond the edges of the image? It is necessary that the gradient be only in the area in which the picture of the knife. The option for svg is fine too, left svg commented out. (On LAN, the background of the picture is transparent). Thanks in advance, feel free to suggest your implementation. Preferably with a picture.
https://jsfiddle.net/5agb4c1x/4/

Answer 1

Try changing your browser's encoding first. When you find it, add Header to the code.

Answer 2

In Photoshop, why does the client need extra calculations