New features include ".t7" Torch7 model support, Inception, ResNet, etc... architecture support, DeepDream, FC layers (caffemodels only) can be used as content layers and DeepDream layers, the ability to use label files, and an experimental pixel decay/L2 latent state regularizer.

neural_style_l2_dd_fc_labels_t7.lua

-- Original DeepDream code by github.com/jcjohnson
-- Simaltaneous DeepDream and style transfer modifications by github.com/ProGamerGov

-- The FC layers as content layers feature, and the label file features come from: 
-- github.com/htoyryla's gist.github.com/htoyryla/806ca4d978f0528114282cd00022ad71 

-- Torch model and architecture support from https://github.com/szagoruyko/neural-style/tree/torch

require 'torch'
require 'nn'
require 'image'
require 'optim'

require 'loadcaffe'


local cmd = torch.CmdLine()

-- Basic options
cmd:option('-style_image', 'examples/inputs/seated-nude.jpg',
           'Style target image')
cmd:option('-style_blend_weights', 'nil')
cmd:option('-content_image', 'examples/inputs/tubingen.jpg',
           'Content target image')
cmd:option('-image_size', 512, 'Maximum height / width of generated image')
cmd:option('-gpu', '0', 'Zero-indexed ID of the GPU to use; for CPU mode set -gpu = -1')
cmd:option('-multigpu_strategy', '', 'Index of layers to split the network across GPUs')

-- Optimization options
cmd:option('-content_weight', 5e0)
cmd:option('-style_weight', 1e2)
cmd:option('-fc_weight', 5e2)
cmd:option('-tv_weight', 1e-3)
cmd:option('-num_iterations', 1000)
cmd:option('-normalize_gradients', false)
cmd:option('-init', 'random', 'random|image')
cmd:option('-init_image', '')
cmd:option('-optimizer', 'lbfgs', 'lbfgs|adam')
cmd:option('-learning_rate', 1e1)
cmd:option('-lbfgs_num_correction', 0)

-- Output options
cmd:option('-print_iter', 50)
cmd:option('-save_iter', 100)
cmd:option('-output_image', 'out.png')

-- Other options
cmd:option('-style_scale', 1.0)
cmd:option('-original_colors', 0)
cmd:option('-pooling', 'max', 'max|avg')
cmd:option('-proto_file', 'models/VGG_ILSVRC_19_layers_deploy.prototxt')
cmd:option('-model_file', 'models/VGG_ILSVRC_19_layers.caffemodel')
cmd:option('-label_file', '')
cmd:option('-backend', 'nn', 'nn|cudnn|clnn')
cmd:option('-cudnn_autotune', false)
cmd:option('-seed', -1)

cmd:option('-content_layers', 'relu4_2', 'layers for content')
cmd:option('-style_layers', 'relu1_1,relu2_1,relu3_1,relu4_1,relu5_1', 'layers for style')

-- Options for DeepDream
cmd:option('-deepdream_layers', '')
cmd:option('-deepdream_weights', '')

-- Experimental leongatys/NeuralImageSynthesis features
cmd:option('-l2_weight', '0')

labels = {}

local function main(params)
  
  if params.label_file ~= '' then
    f = io.open(params.label_file)  
    if f then
      for line in f:lines() do
        table.insert(labels, line)
      end
    end
  end

  local dtype, multigpu = setup_gpu(params)

  local loadcaffe_backend = params.backend
  if params.backend == 'clnn' then loadcaffe_backend = 'nn' end
  local cnn
  local is_caffemodel = params.model_file:find'caffemodel' 
  if is_caffemodel then
    cnn = loadcaffe.load(params.proto_file, params.model_file, loadcaffe_backend):type(dtype)
  else
    cnn = torch.load(params.model_file):type(dtype)
    if cnn.unpack then cnn = cnn:unpack() end
    --cnn = (cnn):type(dtype)
  end

  local content_image = image.load(params.content_image, 3)
  content_image = image.scale(content_image, params.image_size, 'bilinear')
  local content_image_caffe = preprocess(content_image):float()

  local style_size = math.ceil(params.style_scale * params.image_size)
  local style_image_list = params.style_image:split(',')
  local style_images_caffe = {}
  for _, img_path in ipairs(style_image_list) do
    local img = image.load(img_path, 3)
    img = image.scale(img, style_size, 'bilinear')
    local img_caffe = preprocess(img):float()
    table.insert(style_images_caffe, img_caffe)
  end

  local init_image = nil
  if params.init_image ~= '' then
    init_image = image.load(params.init_image, 3)
    local H, W = content_image:size(2), content_image:size(3)
    init_image = image.scale(init_image, W, H, 'bilinear')
    init_image = preprocess(init_image):float()
  end

  -- Handle style blending weights for multiple style inputs
  local style_blend_weights = nil
  if params.style_blend_weights == 'nil' then
    -- Style blending not specified, so use equal weighting
    style_blend_weights = {}
    for i = 1, #style_image_list do
      table.insert(style_blend_weights, 1.0)
    end
  else
    style_blend_weights = params.style_blend_weights:split(',')
    assert(#style_blend_weights == #style_image_list,
      '-style_blend_weights and -style_images must have the same number of elements')
  end
  -- Normalize the style blending weights so they sum to 1
  local style_blend_sum = 0
  for i = 1, #style_blend_weights do
    style_blend_weights[i] = tonumber(style_blend_weights[i])
    style_blend_sum = style_blend_sum + style_blend_weights[i]
  end
  for i = 1, #style_blend_weights do
    style_blend_weights[i] = style_blend_weights[i] / style_blend_sum
  end

  local content_layers = params.content_layers:split(",")
  local style_layers = params.style_layers:split(",")
  local deepdream_layers = params.deepdream_layers:split(",")

  -- Set up the network, inserting style and content loss modules
  local content_losses, style_losses, deepdream_losses = {}, {}, {}
  local next_content_idx, next_style_idx, next_deepdream_idx = 1, 1, 1
  local net = nn.Sequential()
  if params.tv_weight > 0 then
    local tv_mod = nn.TVLoss(params.tv_weight):type(dtype)
    net:add(tv_mod)
  end
  if params.l2_weight ~= 0 then
    local l2_mod = nn.L2Penalty(params.l2_weight):type(dtype)
    net:add(l2_mod)
  end
  for i = 1, #cnn do
    local layer = cnn:get(i)
    -- Makes FC Layers usable as content layers. 
    if (torch.type(layer) == "nn.View") then 
      addlayer = nn.SpatialAdaptiveMaxPooling(7,7):type(dtype)
      net:add(addlayer)
    end 
    if next_content_idx <= #content_layers or next_style_idx <= #style_layers then
      --local layer = cnn:get(i)
      --local name = layer.name
      local name = is_caffemodel and layer.name or tostring(i)
      local layer_type = torch.type(layer)
      local is_pooling = (layer_type == 'cudnn.SpatialMaxPooling' or layer_type == 'nn.SpatialMaxPooling')
      if is_pooling and params.pooling == 'avg' then
        assert(layer.padW == 0 and layer.padH == 0)
        local kW, kH = layer.kW, layer.kH
        local dW, dH = layer.dW, layer.dH
        local avg_pool_layer = nn.SpatialAveragePooling(kW, kH, dW, dH):type(dtype)
        local msg = 'Replacing max pooling at layer %d with average pooling'
        print(string.format(msg, i))
        net:add(avg_pool_layer)
      else
        if params.label_file ~= '' then
          if layer_type ~= "nn.Dropout" then
            layer:type(dtype)         
            net:add(layer)
          end
         else
           net:add(layer)
         end
      end
      if name == content_layers[next_content_idx] then
        print("Setting up content layer", i, ":", layer.name)
        local norm = params.normalize_gradients
        local cweight = params.content_weight
        if is_caffemodel then
     	  local pos, _ = string.find(layer.name, "fc")
	  if pos == 1 then  -- this is an fc layer
	    cweight = params.fc_weight
	  end
        end
        local loss_module = nn.ContentLoss(cweight, norm):type(dtype)
        net:add(loss_module)
        table.insert(content_losses, loss_module)
        next_content_idx = next_content_idx + 1
      end
      if name == style_layers[next_style_idx] then
        print("Setting up style layer  ", i, ":", layer.name)
        local norm = params.normalize_gradients
        local loss_module = nn.StyleLoss(params.style_weight, norm):type(dtype)
        net:add(loss_module)
        table.insert(style_losses, loss_module)
        next_style_idx = next_style_idx + 1
      end
      if name == deepdream_layers[next_deepdream_idx] then
        print("Setting up Deepdream layer  ", i, ":", layer.name)
        local dweight = params.deepdream_weights
        if is_caffemodel then
	  local pos, _ = string.find(layer.name, "fc")
	  if pos == 1 then  -- this is an fc layer
	    dweight = params.fc_weight
	  end
        end
        local loss_module = nn.DeepDreamLoss(dweight):type(dtype)
        net:add(loss_module)
        table.insert(deepdream_losses, loss_module)
        next_deepdream_idx = next_deepdream_idx + 1
      end
    else
      if params.label_file ~= '' then
        if layer_type ~= "nn.Dropout" then
          layer:type(dtype)
          net:add(layer)
        end
      end
    end
  end
  
  if params.label_file ~= '' then
    --vgg16 places lacks softmax at the end, so insert one
    local prob = nn.SoftMax():type(dtype)
    net:add(prob)
  end
  
  if multigpu then
    net = setup_multi_gpu(net, params)
  end
  net:type(dtype)

  -- Capture content targets
  for i = 1, #content_losses do
    content_losses[i].mode = 'capture'
  end
  print 'Capturing content targets'
  print(net)
  content_image_caffe = content_image_caffe:type(dtype)
  net:forward(content_image_caffe:type(dtype))

  -- Capture style targets
  for i = 1, #content_losses do
    content_losses[i].mode = 'none'
  end
  for i = 1, #style_images_caffe do
    print(string.format('Capturing style target %d', i))
    for j = 1, #style_losses do
      style_losses[j].mode = 'capture'
      style_losses[j].blend_weight = style_blend_weights[i]
    end
    net:forward(style_images_caffe[i]:type(dtype))
  end
  
  -- Capture deepdream targets
  if params.deepdream_layers ~= '' then
    for i = 1, #deepdream_losses do
      deepdream_losses[i].mode = 'capture'
    end
    print 'Capturing deepdream targets'
    --print(net)
  end

  -- Set all loss modules to loss mode
  for i = 1, #content_losses do
    content_losses[i].mode = 'loss'
  end
  for i = 1, #style_losses do
    style_losses[i].mode = 'loss'
  end
  if params.deepdream_layers ~= '' then
    for i = 1, #deepdream_losses do
      deepdream_losses[i].mode = 'loss'
    end
  end

  -- We don't need the base CNN anymore, so clean it up to save memory.
  cnn = nil
  for i=1, #net.modules do
    local module = net.modules[i]
    if torch.type(module) == 'nn.SpatialConvolutionMM' then
        -- remove these, not used, but uses gpu memory
        module.gradWeight = nil
        module.gradBias = nil
    end
  end
  collectgarbage()

  -- Initialize the image
  if params.seed >= 0 then
    torch.manualSeed(params.seed)
  end
  local img = nil
  if params.init == 'random' then
    img = torch.randn(content_image:size()):float():mul(0.001)
  elseif params.init == 'image' then
    if init_image then
      img = init_image:clone()
    else
      img = content_image_caffe:clone()
    end
  else
    error('Invalid init type')
  end
  img = img:type(dtype)

  if params.label_file ~= '' then
    --try the network with content image to detect features
    cimg = content_image_caffe:clone():float()
    cimg = cimg:type(dtype)
    if f then
      local p = net:forward(cimg)  
      print("----------- Detected Features --------------")
      for i=1, #labels do
        if p[i] > 0.03 then
          print(string.format("%.4f   %s", p[i], labels[i]))
        end
      end 
    end
  end
  
  -- Run it through the network once to get the proper size for the gradient
  -- All the gradients will come from the extra loss modules, so we just pass
  -- zeros into the top of the net on the backward pass.
  local y = net:forward(img)
  local dy = img.new(#y):zero()

  -- Declaring this here lets us access it in maybe_print
  local optim_state = nil
  if params.optimizer == 'lbfgs' then
    optim_state = {
      maxIter = params.num_iterations,
      verbose=true,
      tolX=-1,
      tolFun=-1,
    }
    if params.lbfgs_num_correction > 0 then
      optim_state.nCorrection = params.lbfgs_num_correction
    end
  elseif params.optimizer == 'adam' then
    optim_state = {
      learningRate = params.learning_rate,
    }
  else
    error(string.format('Unrecognized optimizer "%s"', params.optimizer))
  end

  local function maybe_print(t, loss, p)
    local verbose = (params.print_iter > 0 and t % params.print_iter == 0)
    if verbose then
      print(string.format('Iteration %d / %d', t, params.num_iterations))
      for i, loss_module in ipairs(content_losses) do
        print(string.format('  Content %d loss: %f', i, loss_module.loss))
      end
      for i, loss_module in ipairs(style_losses) do
        print(string.format('  Style %d loss: %f', i, loss_module.loss))
      end
      print(string.format('  Total loss: %f', loss))
      if f then
        for i=1, #labels do
          if p[i] > 0.03 then
            print(string.format("%.4f   %s", p[i], labels[i]))
          end
        end 
      end
    end
  end

  local function maybe_save(t)
    local should_save = params.save_iter > 0 and t % params.save_iter == 0
    should_save = should_save or t == params.num_iterations
    if should_save then
      local disp = deprocess(img:double())
      disp = image.minmax{tensor=disp, min=0, max=1}
      local filename = build_filename(params.output_image, t)
      if t == params.num_iterations then
        filename = params.output_image
      end

      -- Maybe perform postprocessing for color-independent style transfer
      if params.original_colors == 1 then
        disp = original_colors(content_image, disp)
      end

      image.save(filename, disp)
    end
  end

  -- Function to evaluate loss and gradient. We run the net forward and
  -- backward to get the gradient, and sum up losses from the loss modules.
  -- optim.lbfgs internally handles iteration and calls this function many
  -- times, so we manually count the number of iterations to handle printing
  -- and saving intermediate results.
  local num_calls = 0
  local function feval(x)
    num_calls = num_calls + 1
    local p
    if params.label_file ~= '' then
      p = net:forward(x)
    else 
      net:forward(x)
    end
    local grad = net:updateGradInput(x, dy)
    local loss = 0
    for _, mod in ipairs(content_losses) do
      loss = loss + mod.loss
    end
    for _, mod in ipairs(style_losses) do
      loss = loss + mod.loss
    end
    if params.deepdream_layers ~= '' then
      for _, mod in ipairs(deepdream_losses) do
        loss = loss + mod.loss
      end
    end
    if params.label_file ~= '' then
      maybe_print(num_calls, loss, p)
    else 
      maybe_print(num_calls, loss)
    end
    maybe_save(num_calls)

    collectgarbage()
    -- optim.lbfgs expects a vector for gradients
    return loss, grad:view(grad:nElement())
  end

  -- Run optimization.
  if params.optimizer == 'lbfgs' then
    print('Running optimization with L-BFGS')
    local x, losses = optim.lbfgs(feval, img, optim_state)
  elseif params.optimizer == 'adam' then
    print('Running optimization with ADAM')
    for t = 1, params.num_iterations do
      local x, losses = optim.adam(feval, img, optim_state)
    end
  end
end


function setup_gpu(params)
  local multigpu = false
  if params.gpu:find(',') then
    multigpu = true
    params.gpu = params.gpu:split(',')
    for i = 1, #params.gpu do
      params.gpu[i] = tonumber(params.gpu[i]) + 1
    end
  else
    params.gpu = tonumber(params.gpu) + 1
  end
  local dtype = 'torch.FloatTensor'
  if multigpu or params.gpu > 0 then
    if params.backend ~= 'clnn' then
      require 'cutorch'
      require 'cunn'
      if multigpu then
        cutorch.setDevice(params.gpu[1])
      else
        cutorch.setDevice(params.gpu)
      end
      dtype = 'torch.CudaTensor'
    else
      require 'clnn'
      require 'cltorch'
      if multigpu then
        cltorch.setDevice(params.gpu[1])
      else
        cltorch.setDevice(params.gpu)
      end
      dtype = torch.Tensor():cl():type()
    end
  else
    params.backend = 'nn'
  end

  if params.backend == 'cudnn' then
    require 'cudnn'
    if params.cudnn_autotune then
      cudnn.benchmark = true
    end
    cudnn.SpatialConvolution.accGradParameters = nn.SpatialConvolutionMM.accGradParameters -- ie: nop
  end
  return dtype, multigpu
end


function setup_multi_gpu(net, params)
  local DEFAULT_STRATEGIES = {
    [2] = {3},
  }
  local gpu_splits = nil
  if params.multigpu_strategy == '' then
    -- Use a default strategy
    gpu_splits = DEFAULT_STRATEGIES[#params.gpu]
    -- Offset the default strategy by one if we are using TV
    if params.tv_weight > 0 then
      for i = 1, #gpu_splits do gpu_splits[i] = gpu_splits[i] + 1 end
    end
  else
    -- Use the user-specified multigpu strategy
    gpu_splits = params.multigpu_strategy:split(',')
    for i = 1, #gpu_splits do
      gpu_splits[i] = tonumber(gpu_splits[i])
    end
  end
  assert(gpu_splits ~= nil, 'Must specify -multigpu_strategy')
  local gpus = params.gpu

  local cur_chunk = nn.Sequential()
  local chunks = {}
  for i = 1, #net do
    cur_chunk:add(net:get(i))
    if i == gpu_splits[1] then
      table.remove(gpu_splits, 1)
      table.insert(chunks, cur_chunk)
      cur_chunk = nn.Sequential()
    end
  end
  table.insert(chunks, cur_chunk)
  assert(#chunks == #gpus)

  local new_net = nn.Sequential()
  for i = 1, #chunks do
    local out_device = nil
    if i == #chunks then
      out_device = gpus[1]
    end
    new_net:add(nn.GPU(chunks[i], gpus[i], out_device))
  end

  return new_net
end


function build_filename(output_image, iteration)
  local ext = paths.extname(output_image)
  local basename = paths.basename(output_image, ext)
  local directory = paths.dirname(output_image)
  return string.format('%s/%s_%d.%s',directory, basename, iteration, ext)
end


-- Preprocess an image before passing it to a Caffe model.
-- We need to rescale from [0, 1] to [0, 255], convert from RGB to BGR,
-- and subtract the mean pixel.
function preprocess(img)
  local mean_pixel = torch.DoubleTensor({103.939, 116.779, 123.68})
  local perm = torch.LongTensor{3, 2, 1}
  img = img:index(1, perm):mul(256.0)
  mean_pixel = mean_pixel:view(3, 1, 1):expandAs(img)
  img:add(-1, mean_pixel)
  return img
end


-- Undo the above preprocessing.
function deprocess(img)
  local mean_pixel = torch.DoubleTensor({103.939, 116.779, 123.68})
  mean_pixel = mean_pixel:view(3, 1, 1):expandAs(img)
  img = img + mean_pixel
  local perm = torch.LongTensor{3, 2, 1}
  img = img:index(1, perm):div(256.0)
  return img
end


-- Combine the Y channel of the generated image and the UV channels of the
-- content image to perform color-independent style transfer.
function original_colors(content, generated)
  local generated_y = image.rgb2yuv(generated)[{{1, 1}}]
  local content_uv = image.rgb2yuv(content)[{{2, 3}}]
  return image.yuv2rgb(torch.cat(generated_y, content_uv, 1))
end


-- Define an nn Module to compute content loss in-place
local ContentLoss, parent = torch.class('nn.ContentLoss', 'nn.Module')

function ContentLoss:__init(strength, normalize)
  parent.__init(self)
  self.strength = strength
  self.target = torch.Tensor()
  self.normalize = normalize or false
  self.loss = 0
  self.crit = nn.MSECriterion()
  self.mode = 'none'
end

function ContentLoss:updateOutput(input)
  if self.mode == 'loss' then
    self.loss = self.crit:forward(input, self.target) * self.strength
  elseif self.mode == 'capture' then
    self.target:resizeAs(input):copy(input)
  end
  self.output = input
  return self.output
end

function ContentLoss:updateGradInput(input, gradOutput)
  if self.mode == 'loss' then
    if input:nElement() == self.target:nElement() then
      self.gradInput = self.crit:backward(input, self.target)
    end
    if self.normalize then
      self.gradInput:div(torch.norm(self.gradInput, 1) + 1e-8)
    end
    self.gradInput:mul(self.strength)
    self.gradInput:add(gradOutput)
  else
    self.gradInput:resizeAs(gradOutput):copy(gradOutput)
  end
  return self.gradInput
end


local Gram, parent = torch.class('nn.GramMatrix', 'nn.Module')

function Gram:__init()
  parent.__init(self)
end

function Gram:updateOutput(input)
  assert(input:dim() == 3)
  local C, H, W = input:size(1), input:size(2), input:size(3)
  local x_flat = input:view(C, H * W)
  self.output:resize(C, C)
  self.output:mm(x_flat, x_flat:t())
  return self.output
end

function Gram:updateGradInput(input, gradOutput)
  assert(input:dim() == 3 and input:size(1))
  local C, H, W = input:size(1), input:size(2), input:size(3)
  local x_flat = input:view(C, H * W)
  self.gradInput:resize(C, H * W):mm(gradOutput, x_flat)
  self.gradInput:addmm(gradOutput:t(), x_flat)
  self.gradInput = self.gradInput:view(C, H, W)
  return self.gradInput
end


-- Define an nn Module to compute style loss in-place
local StyleLoss, parent = torch.class('nn.StyleLoss', 'nn.Module')

function StyleLoss:__init(strength, normalize)
  parent.__init(self)
  self.normalize = normalize or false
  self.strength = strength
  self.target = torch.Tensor()
  self.mode = 'none'
  self.loss = 0

  self.gram = nn.GramMatrix()
  self.blend_weight = nil
  self.G = nil
  self.crit = nn.MSECriterion()
end

function StyleLoss:updateOutput(input)
  self.G = self.gram:forward(input)
  self.G:div(input:nElement())
  if self.mode == 'capture' then
    if self.blend_weight == nil then
      self.target:resizeAs(self.G):copy(self.G)
    elseif self.target:nElement() == 0 then
      self.target:resizeAs(self.G):copy(self.G):mul(self.blend_weight)
    else
      self.target:add(self.blend_weight, self.G)
    end
  elseif self.mode == 'loss' then
    self.loss = self.strength * self.crit:forward(self.G, self.target)
  end
  self.output = input
  return self.output
end

function StyleLoss:updateGradInput(input, gradOutput)
  if self.mode == 'loss' then
    local dG = self.crit:backward(self.G, self.target)
    dG:div(input:nElement())
    self.gradInput = self.gram:backward(input, dG)
    if self.normalize then
      self.gradInput:div(torch.norm(self.gradInput, 1) + 1e-8)
    end
    self.gradInput:mul(self.strength)
    self.gradInput:add(gradOutput)
  else
    self.gradInput = gradOutput
  end
  return self.gradInput
end


local DeepDreamLoss, parent = torch.class('nn.DeepDreamLoss', 'nn.Module')

-- Deepdream from jcjohnson/fast-neural-style
function DeepDreamLoss:__init(strength, max_grad)
  parent.__init(self)
  self.strength = strength or 1e-5
  self.max_grad = max_grad or 100.0
  self.clipped = torch.Tensor()
  self.loss = 0
end

function DeepDreamLoss:updateOutput(input)
  self.output = input
  -- Contrast fix
  self.output = self.output:mul(1/self.output:max())
  return self.output
end

function DeepDreamLoss:updateGradInput(input, gradOutput)
  self.gradInput:resizeAs(gradOutput):copy(gradOutput)
  self.clipped:resizeAs(input):clamp(input, -self.max_grad, self.max_grad)
  self.gradInput:add(-self.strength, self.clipped)
  return self.gradInput
end


local TVLoss, parent = torch.class('nn.TVLoss', 'nn.Module')

function TVLoss:__init(strength)
  parent.__init(self)
  self.strength = strength
  self.x_diff = torch.Tensor()
  self.y_diff = torch.Tensor()
end

function TVLoss:updateOutput(input)
  self.output = input
  return self.output
end

-- TV loss backward pass inspired by kaishengtai/neuralart
function TVLoss:updateGradInput(input, gradOutput)
  self.gradInput:resizeAs(input):zero()
  local C, H, W = input:size(1), input:size(2), input:size(3)
  self.x_diff:resize(3, H - 1, W - 1)
  self.y_diff:resize(3, H - 1, W - 1)
  self.x_diff:copy(input[{{}, {1, -2}, {1, -2}}])
  self.x_diff:add(-1, input[{{}, {1, -2}, {2, -1}}])
  self.y_diff:copy(input[{{}, {1, -2}, {1, -2}}])
  self.y_diff:add(-1, input[{{}, {2, -1}, {1, -2}}])
  self.gradInput[{{}, {1, -2}, {1, -2}}]:add(self.x_diff):add(self.y_diff)
  self.gradInput[{{}, {1, -2}, {2, -1}}]:add(-1, self.x_diff)
  self.gradInput[{{}, {2, -1}, {1, -2}}]:add(-1, self.y_diff)
  self.gradInput:mul(self.strength)
  self.gradInput:add(gradOutput)
  return self.gradInput
end


local L2Penalty, parent = torch.class('nn.L2Penalty','nn.Module')

--This module acts as an L2 latent state regularizer, adding the 
--[gradOutput] to the gradient of the L2 loss. The [input] is copied to 
--the [output]. 

-- L2Penalty module from leongatys/NeuralImageSynthesis
function L2Penalty:__init(l2weight, sizeAverage, provideOutput)
    parent.__init(self)
    self.l2weight = l2weight 
    self.sizeAverage = sizeAverage or false  
    if provideOutput == nil then
       self.provideOutput = true
    else
       self.provideOutput = provideOutput
    end
end
    
function L2Penalty:updateOutput(input)
    local m = self.l2weight 
    if self.sizeAverage == true then 
      m = m/input:nElement()
    end
    local loss = m*input:norm(2)/2
    self.loss = loss  
    self.output = input 
    return self.output 
end

function L2Penalty:updateGradInput(input, gradOutput)
    local m = self.l2weight 
    if self.sizeAverage == true then 
      m = m/input:nElement() 
    end
    
    self.gradInput:resizeAs(input):copy(input):mul(m)
    
    if self.provideOutput == true then 
        self.gradInput:add(gradOutput)  
    end 

    return self.gradInput 
end


local params = cmd:parse(arg)
main(params)