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Saving and Loading

This sections includes functions for saving and loading different types of images to and from disk.

[res] image.load([dst,] filename, [depth, [tensortype, [noscale]]])

Loads an image located at path filename having depth channels (1 or 3) into a Tensor. You can either specify the type of the res tensor via tensortype (float, double or byte) or provide a dst tensor that will be resized to store the image. If noscale is specified, the range will not be rescaled between 0 and 1.

The image format is determined from the filename's extension suffix. Supported formats are JPEG, PNG, PPM and PGM.

The returned res Tensor has size nChannel x height x width where nChannel is 1 (greyscale) or 3 (usually RGB or YUV.

Usage:

--To load as byte tensor for rgb imagefile
local img = image.load(imagefile,3,'byte')

--To load as byte tensor for gray imagefile
local img = image.load(imagefile,1,'byte')

image.save(filename, tensor)

Saves Tensor tensor to disk at path filename. The format to which the image is saved is extrapolated from the filename's extension suffix. The tensor should be of size nChannel x height x width. To save with a minimal loss, the tensor values should lie in the range [0, 1] since the tensor is clamped between 0 and 1 before being saved to the disk.

[res] image.decompress([dst,] tensor, [depth, [tensortype, [noscale]]])

Decompresses an image from a ByteTensor in memory having depth channels (1 or 3) into a Tensor You can either specify the type of the res tensor via tensortype (float, double or byte) or provide a dst tensor that will be resized to store the image. If noscale is specified, the range will not be rescaled between 0 and 1.

This function support both JPG and PNG inputs.

Usage:

local fin = torch.DiskFile(imfile, 'r')
fin:binary()
fin:seekEnd()
local file_size_bytes = fin:position() - 1
fin:seek(1)
local img_binary = torch.ByteTensor(file_size_bytes)
fin:readByte(img_binary:storage())
fin:close()
-- Then when you're ready to decompress the ByteTensor:
im = image.decompress(img_binary)

[res] image.compressJPG(tensor, [quality])

Compresses an image to a ByteTensor in memory. Optional quality is between 1 and 100 and adjusts compression quality.