For some cases, the function ‘savefig’ with ‘bbox_inches=’tight” doesn’t work well and still generates images with borders that you want to remove.

plt.savefig('fn.jpg', dpi = 300, bbox_inches='tight')

One way to avoid this is to look into the axes properties before calling the function ‘savefig’. Basically, you just need to create an axes object without border/frame and add it to the pre-generated figure window.

def save_image(data, cm, fn):
  
    sizes = np.shape(data)
    height = float(sizes[0])
    width = float(sizes[1])
    
    fig = plt.figure()
    fig.set_size_inches(width/height, 1, forward=False)
    ax = plt.Axes(fig, [0., 0., 1., 1.])
    ax.set_axis_off()
    fig.add_axes(ax)

    ax.imshow(data, cmap=cm)
    plt.savefig(fn, dpi = height) 
    plt.close()