140 lines
4 KiB
Lua
140 lines
4 KiB
Lua
local gm = require 'graphicsmagick'
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local ffi = require 'ffi'
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local iproc = require 'iproc'
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require 'pl'
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local image_loader = {}
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local clip_eps8 = (1.0 / 255.0) * 0.5 - (1.0e-7 * (1.0 / 255.0) * 0.5)
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local clip_eps16 = (1.0 / 65535.0) * 0.5 - (1.0e-7 * (1.0 / 65535.0) * 0.5)
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local background_color = 0.5
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function image_loader.encode_png(rgb, depth)
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depth = depth or 8
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rgb = iproc.byte2float(rgb)
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if depth < 16 then
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rgb = rgb:clone():add(clip_eps8)
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rgb[torch.lt(rgb, 0.0)] = 0.0
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rgb[torch.gt(rgb, 1.0)] = 1.0
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rgb = rgb:mul(255):long():float():div(255)
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else
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rgb = rgb:clone():add(clip_eps16)
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rgb[torch.lt(rgb, 0.0)] = 0.0
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rgb[torch.gt(rgb, 1.0)] = 1.0
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rgb = rgb:mul(65535):long():float():div(65535)
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end
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local im
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if rgb:size(1) == 4 then -- RGBA
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im = gm.Image(rgb, "RGBA", "DHW")
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elseif rgb:size(1) == 3 then -- RGB
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im = gm.Image(rgb, "RGB", "DHW")
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elseif rgb:size(1) == 1 then -- Y
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im = gm.Image(rgb, "I", "DHW")
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-- im:colorspace("GRAY") -- it does not work
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end
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return im:depth(depth):format("PNG"):toString(9)
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end
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function image_loader.save_png(filename, rgb, depth)
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depth = depth or 8
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local blob = image_loader.encode_png(rgb, depth)
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local fp = io.open(filename, "wb")
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if not fp then
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error("IO error: " .. filename)
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end
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fp:write(blob)
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fp:close()
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return true
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end
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function image_loader.decode_float(blob)
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local load_image = function()
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local im = gm.Image()
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local alpha = nil
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local gamma_lcd = 0.454545
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im:fromBlob(blob, #blob)
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if im:colorspace() == "CMYK" then
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im:colorspace("RGB")
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end
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local gamma = math.floor(im:gamma() * 1000000) / 1000000
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if gamma ~= 0 and gamma ~= gamma_lcd then
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local cg = gamma / gamma_lcd
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im:gammaCorrection(cg, "Red")
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im:gammaCorrection(cg, "Blue")
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im:gammaCorrection(cg, "Green")
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end
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-- FIXME: How to detect that a image has an alpha channel?
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if blob:sub(1, 4) == "\x89PNG" or blob:sub(1, 3) == "GIF" then
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-- split alpha channel
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im = im:toTensor('float', 'RGBA', 'DHW')
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local sum_alpha = (im[4] - 1.0):sum()
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if sum_alpha < 0 then
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alpha = im[4]:reshape(1, im:size(2), im:size(3))
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-- drop full transparent background
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local mask = torch.le(alpha, 0.0)
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im[1][mask] = background_color
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im[2][mask] = background_color
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im[3][mask] = background_color
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end
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local new_im = torch.FloatTensor(3, im:size(2), im:size(3))
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new_im[1]:copy(im[1])
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new_im[2]:copy(im[2])
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new_im[3]:copy(im[3])
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im = new_im
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else
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im = im:toTensor('float', 'RGB', 'DHW')
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end
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return {im, alpha, blob}
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end
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local state, ret = pcall(load_image)
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if state then
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return ret[1], ret[2], ret[3]
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else
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return nil, nil, nil
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end
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end
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function image_loader.decode_byte(blob)
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local im, alpha
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im, alpha, blob = image_loader.decode_float(blob)
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if im then
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im = iproc.float2byte(im)
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-- hmm, alpha does not convert here
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return im, alpha, blob
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else
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return nil, nil, nil
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end
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end
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function image_loader.load_float(file)
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local fp = io.open(file, "rb")
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if not fp then
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error(file .. ": failed to load image")
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end
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local buff = fp:read("*a")
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fp:close()
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return image_loader.decode_float(buff)
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end
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function image_loader.load_byte(file)
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local fp = io.open(file, "rb")
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if not fp then
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error(file .. ": failed to load image")
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end
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local buff = fp:read("*a")
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fp:close()
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return image_loader.decode_byte(buff)
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end
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local function test()
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torch.setdefaulttensortype("torch.FloatTensor")
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local a = image_loader.load_float("../images/lena.png")
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local blob = image_loader.encode_png(a)
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local b = image_loader.decode_float(blob)
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assert((b - a):abs():sum() == 0)
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a = image_loader.load_byte("../images/lena.png")
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blob = image_loader.encode_png(a)
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b = image_loader.decode_byte(blob)
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assert((b:float() - a:float()):abs():sum() == 0)
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end
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--test()
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return image_loader
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