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local SpatialPadding, parent = torch.class('nn.SpatialPadding', 'nn.Module')
function SpatialPadding:__init(pad_l, pad_r, pad_t, pad_b)
parent.__init(self)
-- usage
if not pad_l then
error(xlua.usage('nn.SpatialPadding',
'a 2D padder module for images, zero-padding', nil,
{type='number', help='left padding', req=true},
{type='number', help='right padding'},
{type='number', help='top padding'},
{type='number', help='bottom padding'}))
end
self.pad_l = pad_l
self.pad_r = pad_r or self.pad_l
self.pad_t = pad_t or self.pad_l
self.pad_b = pad_b or self.pad_l
end
function SpatialPadding:forward(input)
if input:dim() ~= 3 then error('input must be 3-dimensional') end
local h = input:size(2) + self.pad_t + self.pad_b
local w = input:size(3) + self.pad_l + self.pad_r
if w < 1 or h < 1 then error('input is too small') end
self.output:resize(input:size(1), h, w)
self.output:zero()
-- crop input if necessary
local c_input = input
if self.pad_t < 0 then c_input = c_input:narrow(2, 1 - self.pad_t, c_input:size(2) + self.pad_t) end
if self.pad_b < 0 then c_input = c_input:narrow(2, 1, c_input:size(2) + self.pad_b) end
if self.pad_l < 0 then c_input = c_input:narrow(3, 1 - self.pad_l, c_input:size(3) + self.pad_l) end
if self.pad_r < 0 then c_input = c_input:narrow(3, 1, c_input:size(3) + self.pad_r) end
-- crop outout if necessary
local c_output = self.output
if self.pad_t > 0 then c_output = c_output:narrow(2, 1 + self.pad_t, c_output:size(2) - self.pad_t) end
if self.pad_b > 0 then c_output = c_output:narrow(2, 1, c_output:size(2) - self.pad_b) end
if self.pad_l > 0 then c_output = c_output:narrow(3, 1 + self.pad_l, c_output:size(3) - self.pad_l) end
if self.pad_r > 0 then c_output = c_output:narrow(3, 1, c_output:size(3) - self.pad_r) end
-- copy input to output
c_output:copy(c_input)
return self.output
end
function SpatialPadding:backward(input, gradOutput)
if input:dim() ~= 3 then error('input must be 3-dimensional') end
self.gradInput:resizeAs(input):zero()
-- crop gradInput if necessary
local cg_input = self.gradInput
if self.pad_t < 0 then cg_input = cg_input:narrow(2, 1 - self.pad_t, cg_input:size(2) + self.pad_t) end
if self.pad_b < 0 then cg_input = cg_input:narrow(2, 1, cg_input:size(2) + self.pad_b) end
if self.pad_l < 0 then cg_input = cg_input:narrow(3, 1 - self.pad_l, cg_input:size(3) + self.pad_l) end
if self.pad_r < 0 then cg_input = cg_input:narrow(3, 1, cg_input:size(3) + self.pad_r) end
-- crop gradOutout if necessary
local cg_output = gradOutput
if self.pad_t > 0 then cg_output = cg_output:narrow(2, 1 + self.pad_t, cg_output:size(2) - self.pad_t) end
if self.pad_b > 0 then cg_output = cg_output:narrow(2, 1, cg_output:size(2) - self.pad_b) end
if self.pad_l > 0 then cg_output = cg_output:narrow(3, 1 + self.pad_l, cg_output:size(3) - self.pad_l) end
if self.pad_r > 0 then cg_output = cg_output:narrow(3, 1, cg_output:size(3) - self.pad_r) end
-- copy gradOuput to gradInput
cg_input:copy(cg_output)
return self.gradInput
end
function SpatialPadding:write(file)
parent.write(self, file)
file:writeInt(self.pad_l)
file:writeInt(self.pad_r)
file:writeInt(self.pad_t)
file:writeInt(self.pad_b)
end
function SpatialPadding:read(file)
parent.read(self, file)
self.pad_l = file:readInt()
self.pad_r = file:readInt()
self.pad_t = file:readInt()
self.pad_b = file:readInt()
end
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