I am trying neural style transfer here is my code
class Vgg16(torch.nn.Module):
    def __init__(self):
        super(Vgg16, self).__init__()
        features = list(vgg16(pretrained = True).features)[:23]
        self.features = nn.ModuleList(features).eval() 
        
    def forward(self, x):
        results = []
        for ii,model in enumerate(self.features):
            x = model(x)
            if ii in {3,8,15,22}:
                results.append(x)
        return results
normalization_mean = torch.tensor([0.485, 0.456, 0.406])
normalization_std = torch.tensor([0.229, 0.224, 0.225])
class Normalization(nn.Module):
    def __init__(self, mean, std):
        super(Normalization, self).__init__()
        self.mean = torch.tensor(mean).view(-1, 1, 1)
        self.std = torch.tensor(std).view(-1, 1, 1)
    def forward(self, img):
        return (img - self.mean) / self.std
normalization = Normalization(normalization_mean, normalization_std)
def style_loss(style,actual_style):
    q,w,e,r=style.shape
    s_loss=(gram_matrix(style)-gram_matrix(actual_style)).pow(2).sum()
    return s_loss
def gram_matrix(inp):
    q,w,e,r=inp.shape
    reshape=inp.view(q*w,e*r)
    g_mat=torch.mm(reshape,reshape.t())
    return g_mat/(q*w*e*r)
def content_loss(content,actual_content):
    q,w,e,r=content.shape
    c_loss=(content-actual_content).pow(2).sum()
    return c_loss/(q*w*e*r)
content_im=cv2.imread('/home/jatin/ML_intern/challenge-master/hij.jpeg')
style_im=cv2.imread('/home/jatin/ML_intern/challenge-master/download.jpeg')
s=128
c_im=cv2.resize(content_im,(s,s))
c_im=torch.from_numpy(c_im)
c_im=c_im.view(3,s,s)
c_im=normalization(c_im)
c_im=c_im.view(1,3,s,s)
c_im=c_im.float()
c_im=c_im/255
s_im=cv2.resize(style_im,(s,s))
s_im=torch.from_numpy(s_im)
s_im=s_im.view(3,s,s)
s_im=s_im.float()
s_im=s_im/255
#s_im=(s_im-0.4)/0.2
s_im=normalization(s_im)
s_im=s_im.view(1,3,s,s)
print(s_im)
y_con=net(c_im.float())
y_sty=net(s_im.float())
def loss_fn(y_pred,y_con,y_sty,y):
    s_loss=style_loss(y_pred[1],y_sty[1])
    c_loss=0
    for ij in range(len(y_pred)):
        if ij==1:
            c_loss+=content_loss(y_pred[ij],y_con[ij])
        else:
            s_loss+=style_loss(y_pred[ij],y_sty[ij])
    loss=c_loss+100*s_loss
    print('s_loss=',s_loss)
    print('c_loss=',c_loss)
    return loss
inp=torch.randn(1,3,s,s,requires_grad=True)
optimizer = optim.LBFGS([inp])
or i in range(2000):
    def closure():
        inp.data.clamp_(0,1)
        optimizer.zero_grad()
        y_pred=net(inp.float())
        loss=loss_fn(y_pred,y_con,y_sty,inp)
        loss.backward(retain_graph=True)
        return loss
    optimizer.step(closure)
    print('#########################################################################################',i)
    if i%5==0:
        with torch.no_grad():
            bc=inp.view(s,s,3)
            bc.data.clamp_(0,1)
            bc=bc*255
            bc=bc.detach()
            bc=bc.numpy()    
            bc=bc.astype(np.uint8)
            bc=cv2.cvtColor(bc,cv2.COLOR_BGR2RGB)
        plt.imshow(bc)
        plt.show()

But after I normalised the input images the loss was initially decreasing after some iterations the loss was constant