n image represented as a 3D array with shape <cite>(w, h, n)</cite>,
where <cite>w</cite> and <cite>h</cite> are the width and height, and <cite>n</cite> is the number of color channels (typically <strong>3 for RGB</strong> or <strong>4 for RGBA</strong>).
It uses a <strong>5x5 Gaussian kernel</strong> for smoothing, applied through <strong>two-pass convolution</strong> (horizontal + vertical).
The function modifies the input array in-place, avoiding unnecessary memory allocation.</p>
<p><strong>Feature