forked from luanfujun/deep-photo-styletransfer
-
Notifications
You must be signed in to change notification settings - Fork 0
/
deepmatting_seg.lua
607 lines (503 loc) · 20.2 KB
/
deepmatting_seg.lua
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
require 'torch'
require 'nn'
require 'image'
require 'optim'
require 'loadcaffe'
require 'libcuda_utils'
require 'cutorch'
require 'cunn'
local matio = require 'matio'
local cmd = torch.CmdLine()
-- Basic options
cmd:option('-style_image', 'examples/inputs/seated-nude.jpg', 'Style target image')
cmd:option('-content_image', 'examples/inputs/tubingen.jpg','Content target image')
cmd:option('-style_seg', '', 'Style segmentation')
cmd:option('-style_seg_idxs', '', 'Style seg idxs')
cmd:option('-content_seg', '', 'Content segmentation')
cmd:option('-content_seg_idxs', '', 'Content seg idxs')
cmd:option('-init_image', 'examples/inputs/init.jpg', 'Initial image')
cmd:option('-gpu', 0, 'Zero-indexed ID of the GPU to use; for CPU mode set -gpu = -1')
-- Optimization options
cmd:option('-content_weight', 5e0)
cmd:option('-style_weight', 1e2)
cmd:option('-tv_weight', 1e-3)
cmd:option('-num_iterations', 1000)
-- Local affine params
cmd:option('-lambda', 1e4)
cmd:option('-patch', 3)
cmd:option('-eps', 1e-7)
-- Reconstruct best local affine using joint bilateral smoothing
cmd:option('-f_radius', 7)
cmd:option('-f_edge', 0.05)
-- Output options
cmd:option('-print_iter', 1)
cmd:option('-save_iter', 100)
cmd:option('-output_image', 'out.png')
cmd:option('-index', 1)
cmd:option('-serial', 'serial_example')
-- Other options
cmd:option('-proto_file', 'models/VGG_ILSVRC_19_layers_deploy.prototxt')
cmd:option('-model_file', 'models/VGG_ILSVRC_19_layers.caffemodel')
cmd:option('-backend', 'nn', 'nn|cudnn|clnn')
cmd:option('-cudnn_autotune', false)
cmd:option('-seed', 612)
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')
local function main(params)
cutorch.setDevice(params.gpu + 1)
cutorch.setHeapTracking(true)
torch.manualSeed(params.seed)
idx = cutorch.getDevice()
print('gpu, idx = ', params.gpu, idx)
-- content: pitie transferred input image
local content_image = image.load(params.content_image, 3)
local content_image_caffe = preprocess(content_image):float():cuda()
local content_layers = params.content_layers:split(",")
-- style: target model image
local style_image = image.load(params.style_image, 3)
local style_image_caffe = preprocess(style_image):float():cuda()
local style_layers = params.style_layers:split(",")
local c, h, w = content_image:size(1), content_image:size(2), content_image:size(3)
local _, h2, w2 = style_image:size(1), style_image:size(2), style_image:size(3)
local index = params.index
-- init: used for initialize the image
local init_image = image.load(params.init_image, 3)
init_image = image.scale(init_image, w, h, 'bilinear')
local init_image_caffe = preprocess(init_image):float():cuda()
-- segmentation images
--[
local content_seg = image.load(params.content_seg, 3)
content_seg = image.scale(content_seg, w, h, 'bilinear')
local style_seg = image.load(params.style_seg, 3)
style_seg = image.scale(style_seg, w2, h2, 'bilinear')
local color_codes = {'blue', 'green', 'black', 'white', 'red', 'yellow', 'grey', 'lightblue', 'purple'}
local color_content_masks, color_style_masks = {}, {}
for j = 1, #color_codes do
local content_mask_j = ExtractMask(content_seg, color_codes[j])
local style_mask_j = ExtractMask(style_seg, color_codes[j])
table.insert(color_content_masks, content_mask_j)
table.insert(color_style_masks, style_mask_j)
end
--]]
-- Set up the network, inserting style and content loss modules
local content_losses, style_losses = {}, {}
local next_content_idx, next_style_idx = 1, 1
local net = nn.Sequential()
if params.tv_weight > 0 then
local tv_mod = nn.TVLoss(params.tv_weight):float():cuda()
net:add(tv_mod)
end
-- load VGG-19 network
local cnn = loadcaffe.load(params.proto_file, params.model_file, params.backend):float():cuda()
-- load matting laplacian
local CSR_fn = 'gen_laplacian/Input_Laplacian_'..tostring(params.patch)..'x'..tostring(params.patch)..'_1e-7_CSR' .. tostring(index) .. '.mat'
print('loading matting laplacian...', CSR_fn)
local CSR = matio.load(CSR_fn).CSR:cuda()
paths.mkdir(tostring(params.serial))
print('Exp serial:', params.serial)
for i = 1, #cnn do
if next_content_idx <= #content_layers or next_style_idx <= #style_layers then
local layer = cnn:get(i)
local name = layer.name
local layer_type = torch.type(layer)
local is_pooling = (layer_type == 'nn.SpatialMaxPooling' or layer_type == 'cudnn.SpatialMaxPooling')
local is_conv = (layer_type == 'nn.SpatialConvolution' or layer_type == 'cudnn.SpatialConvolution')
net:add(layer)
if is_pooling then
for k = 1, #color_codes do
color_content_masks[k] = image.scale(color_content_masks[k], math.ceil(color_content_masks[k]:size(2)/2), math.ceil(color_content_masks[k]:size(1)/2))
color_style_masks[k] = image.scale(color_style_masks[k], math.ceil(color_style_masks[k]:size(2)/2), math.ceil(color_style_masks[k]:size(1)/2))
end
elseif is_conv then
local sap = nn.SpatialAveragePooling(3,3,1,1,1,1):float()
for k = 1, #color_codes do
color_content_masks[k] = sap:forward(color_content_masks[k]:repeatTensor(1,1,1))[1]:clone()
color_style_masks[k] = sap:forward(color_style_masks[k]:repeatTensor(1,1,1))[1]:clone()
end
end
color_content_masks = deepcopy(color_content_masks)
color_style_masks = deepcopy(color_style_masks)
if name == content_layers[next_content_idx] then
print("Setting up content layer", i, ":", layer.name)
local target = net:forward(content_image_caffe):clone()
local loss_module = nn.ContentLoss(params.content_weight, target, false):float():cuda()
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 gram = GramMatrix():float():cuda()
local target_features = net:forward(style_image_caffe):clone()
local target_grams = {}
for j = 1, #color_codes do
local l_style_mask_ori = color_style_masks[j]:clone():cuda()
local l_style_mask = l_style_mask_ori:repeatTensor(1,1,1):expandAs(target_features)
local l_style_mean = l_style_mask_ori:mean()
local masked_target_features = torch.cmul(l_style_mask, target_features)
local masked_target_gram = gram:forward(masked_target_features):clone()
if l_style_mean > 0 then
masked_target_gram:div(target_features:nElement() * l_style_mean)
end
table.insert(target_grams, masked_target_gram)
end
local loss_module = nn.StyleLossWithSeg(params.style_weight, target_grams, color_content_masks, color_codes, next_style_idx, false):float():cuda()
net:add(loss_module)
table.insert(style_losses, loss_module)
next_style_idx = next_style_idx + 1
end
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()
local mean_pixel = torch.CudaTensor({103.939, 116.779, 123.68})
local meanImage = mean_pixel:view(3, 1, 1):expandAs(content_image_caffe)
local img = init_image_caffe
-- 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 = {
maxIter = params.num_iterations,
tolX = 0, tolFun = -1,
verbose=true,
}
local function maybe_print(t, loss)
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))
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 = params.serial .. '/out' .. tostring(index) .. '_t_' .. tostring(t) .. '.png'
image.save(filename, disp)
end
end
local num_calls = 0
local function feval(AffineModel)
num_calls = num_calls + 1
local output = torch.add(img, meanImage)
local input = torch.add(content_image_caffe, meanImage)
net:forward(img)
local gradient_VggNetwork = net:updateGradInput(img, dy)
local gradient_LocalAffine = MattingLaplacian(output, CSR, h, w):mul(params.lambda)
if num_calls % params.save_iter == 0 then
local best = SmoothLocalAffine(output, input, params.eps, params.patch, h, w, params.f_radius, params.f_edge)
fn = params.serial .. '/best' .. tostring(params.index) .. '_t_' .. tostring(num_calls) .. '.png'
image.save(fn, best)
end
local grad = torch.add(gradient_VggNetwork, gradient_LocalAffine)
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
maybe_print(num_calls, loss)
-- maybe_save(num_calls)
collectgarbage()
-- optim.lbfgs expects a vector for gradients
return loss, grad:view(grad:nElement())
end
-- Run optimization.
local x, losses = optim.lbfgs(feval, img, optim_state)
end
function MattingLaplacian(output, CSR, h, w)
local N, c = CSR:size(1), CSR:size(2)
local CSR_rowIdx = torch.CudaIntTensor(N):copy(torch.round(CSR[{{1,-1},1}]))
local CSR_colIdx = torch.CudaIntTensor(N):copy(torch.round(CSR[{{1,-1},2}]))
local CSR_val = torch.CudaTensor(N):copy(CSR[{{1,-1},3}])
local output01 = torch.div(output, 256.0)
local grad = cuda_utils.matting_laplacian(output01, h, w, CSR_rowIdx, CSR_colIdx, CSR_val, N)
grad:div(256.0)
return grad
end
function SmoothLocalAffine(output, input, epsilon, patch, h, w, f_r, f_e)
local output01 = torch.div(output, 256.0)
local input01 = torch.div(input, 256.0)
local filter_radius = f_r
local sigma1, sigma2 = filter_radius / 3, f_e
local best01= cuda_utils.smooth_local_affine(output01, input01, epsilon, patch, h, w, filter_radius, sigma1, sigma2)
return best01
end
function ErrorMapLocalAffine(output, input, epsilon, patch, h, w)
local output01 = torch.div(output, 256.0)
local input01 = torch.div(input, 256.0)
local err_map, best01, Mt_M, invMt_M = cuda_utils.error_map_local_affine(output01, input01, epsilon, patch, h, w)
return err_map, best01
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
function deepcopy(orig)
local orig_type = type(orig)
local copy
if orig_type == 'table' then
copy = {}
for orig_key, orig_value in next, orig, nil do
copy[deepcopy(orig_key)] = deepcopy(orig_value)
end
setmetatable(copy, deepcopy(getmetatable(orig)))
else -- number, string, boolean, etc
copy = orig
end
return copy
end
-- Define an nn Module to compute content loss in-place
local ContentLoss, parent = torch.class('nn.ContentLoss', 'nn.Module')
function ContentLoss:__init(strength, target, normalize)
parent.__init(self)
self.strength = strength
self.target = target
self.normalize = normalize or false
self.loss = 0
self.crit = nn.MSECriterion()
end
function ContentLoss:updateOutput(input)
if input:nElement() == self.target:nElement() then
self.loss = self.crit:forward(input, self.target) * self.strength
else
print('WARNING: Skipping content loss')
end
self.output = input
return self.output
end
function ContentLoss:updateGradInput(input, gradOutput)
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)
return self.gradInput
end
-- Returns a network that computes the CxC Gram matrix from inputs
-- of size C x H x W
function GramMatrix()
local net = nn.Sequential()
net:add(nn.View(-1):setNumInputDims(2))
local concat = nn.ConcatTable()
concat:add(nn.Identity())
concat:add(nn.Identity())
net:add(concat)
net:add(nn.MM(false, true))
return net
end
-- Define an nn Module to compute style loss in-place
local StyleLoss, parent = torch.class('nn.StyleLoss', 'nn.Module')
function StyleLoss:__init(strength, target, normalize)
parent.__init(self)
self.normalize = normalize or false
self.strength = strength
self.target = target
self.loss = 0
self.gram = GramMatrix()
self.G = nil
self.crit = nn.MSECriterion()
end
function StyleLoss:updateOutput(input)
self.G = self.gram:forward(input)
self.G:div(input:nElement())
self.loss = self.crit:forward(self.G, self.target)
self.loss = self.loss * self.strength
self.output = input
return self.output
end
function StyleLoss:updateGradInput(input, gradOutput)
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)
return self.gradInput
end
function ExtractMask(seg, color)
local mask = nil
if color == 'green' then
mask = torch.lt(seg[1], 0.1)
mask:cmul(torch.gt(seg[2], 1-0.1))
mask:cmul(torch.lt(seg[3], 0.1))
elseif color == 'black' then
mask = torch.lt(seg[1], 0.1)
mask:cmul(torch.lt(seg[2], 0.1))
mask:cmul(torch.lt(seg[3], 0.1))
elseif color == 'white' then
mask = torch.gt(seg[1], 1-0.1)
mask:cmul(torch.gt(seg[2], 1-0.1))
mask:cmul(torch.gt(seg[3], 1-0.1))
elseif color == 'red' then
mask = torch.gt(seg[1], 1-0.1)
mask:cmul(torch.lt(seg[2], 0.1))
mask:cmul(torch.lt(seg[3], 0.1))
elseif color == 'blue' then
mask = torch.lt(seg[1], 0.1)
mask:cmul(torch.lt(seg[2], 0.1))
mask:cmul(torch.gt(seg[3], 1-0.1))
elseif color == 'yellow' then
mask = torch.gt(seg[1], 1-0.1)
mask:cmul(torch.gt(seg[2], 1-0.1))
mask:cmul(torch.lt(seg[3], 0.1))
elseif color == 'grey' then
mask = torch.cmul(torch.gt(seg[1], 0.5-0.1), torch.lt(seg[1], 0.5+0.1))
mask:cmul(torch.cmul(torch.gt(seg[2], 0.5-0.1), torch.lt(seg[2], 0.5+0.1)))
mask:cmul(torch.cmul(torch.gt(seg[3], 0.5-0.1), torch.lt(seg[3], 0.5+0.1)))
elseif color == 'lightblue' then
mask = torch.lt(seg[1], 0.1)
mask:cmul(torch.gt(seg[2], 1-0.1))
mask:cmul(torch.gt(seg[3], 1-0.1))
elseif color == 'purple' then
mask = torch.gt(seg[1], 1-0.1)
mask:cmul(torch.lt(seg[2], 0.1))
mask:cmul(torch.gt(seg[3], 1-0.1))
else
print('ExtractMask(): color not recognized, color = ', color)
end
return mask:float()
end
-- Define style loss with segmentation
local StyleLossWithSeg, parent = torch.class('nn.StyleLossWithSeg', 'nn.Module')
--function StyleLossWithSeg:__init(strength, target_grams, color_content_masks, content_seg_idxs, layer_id)
function StyleLossWithSeg:__init(strength, target_grams, color_content_masks, color_codes, layer_id)
parent.__init(self)
self.strength = strength
self.target_grams = target_grams
self.color_content_masks = deepcopy(color_content_masks)
self.color_codes = color_codes
--self.content_seg_idxs = content_seg_idxs
self.loss = 0
self.gram = GramMatrix()
self.crit = nn.MSECriterion()
self.layer_id = layer_id
end
function StyleLossWithSeg:updateOutput(input)
self.output = input
return self.output
end
function StyleLossWithSeg:updateGradInput(input, gradOutput)
self.loss = 0
self.gradInput = gradOutput:clone()
self.gradInput:zero()
for j = 1, #self.color_codes do
local l_content_mask_ori = self.color_content_masks[j]:clone():cuda()
local l_content_mask = l_content_mask_ori:repeatTensor(1,1,1):expandAs(input)
local l_content_mean = l_content_mask_ori:mean()
local masked_input_features = torch.cmul(l_content_mask, input)
local masked_input_gram = self.gram:forward(masked_input_features):clone()
if l_content_mean > 0 then
masked_input_gram:div(input:nElement() * l_content_mean)
end
local loss_j = self.crit:forward(masked_input_gram, self.target_grams[j])
loss_j = loss_j * self.strength * l_content_mean
self.loss = self.loss + loss_j
local dG = self.crit:backward(masked_input_gram, self.target_grams[j])
dG:div(input:nElement())
local gradient = self.gram:backward(masked_input_features, dG)
if self.normalize then
gradient:div(torch.norm(gradient, 1) + 1e-8)
end
self.gradInput:add(gradient)
end
self.gradInput:mul(self.strength)
self.gradInput:add(gradOutput)
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
function TVGradient(input, gradOutput, strength)
local C, H, W = input:size(1), input:size(2), input:size(3)
local gradInput = torch.CudaTensor(C, H, W):zero()
local x_diff = torch.CudaTensor()
local y_diff = torch.CudaTensor()
x_diff:resize(3, H - 1, W - 1)
y_diff:resize(3, H - 1, W - 1)
x_diff:copy(input[{{}, {1, -2}, {1, -2}}])
x_diff:add(-1, input[{{}, {1, -2}, {2, -1}}])
y_diff:copy(input[{{}, {1, -2}, {1, -2}}])
y_diff:add(-1, input[{{}, {2, -1}, {1, -2}}])
gradInput[{{}, {1, -2}, {1, -2}}]:add(x_diff):add(y_diff)
gradInput[{{}, {1, -2}, {2, -1}}]:add(-1, x_diff)
gradInput[{{}, {2, -1}, {1, -2}}]:add(-1, y_diff)
gradInput:mul(strength)
gradInput:add(gradOutput)
return gradInput
end
local params = cmd:parse(arg)
main(params)