Change Image Attributes in WordPress

I need change Image Attributes in WordPress.
Remove styl css class=“alignnone wp-image-15 size-medium” and remove img
width=“300” height=“225”. Thank you


It seems you already know what to do?
So what is your question?

to remove all classes on images

I’d like my images to have no classes assigned to them by default.

img class=“alignnone wp-image-15 size-medium”
img class=“mycss”
and remove default img width=“300” height=“225”, I want without width, height
example tag
img class=“mycss"src=”/" alt=“/”