How to save the image correctly?

[yyuuliang]

hi
thanks for this lib. I have a question about saving img.
I can use the plot to plot a correct color img, however, I don't know how to save it correctly. The color in the saved img is quite different from the plotting. Will you please show a example of img saving?

[KelSolaar]

Hi @yyuuliang,

So assuming you have an image:

image = demosaicing_CFA_Bayer_Malvar2004(CFA)

It is float64 linear at this stage, so you could either save it as an EXR linear file:

colour.write_image(image, 'my_image.exr')

or as a PNG file, but this would require non-linear encoding, e.g. sRGB:

colour.write_image(colour.cctf_encoding(image), 'my_image.png')

[KelSolaar]

Hi @vigneshgarrapally,

It seems like the image you started with was already non-linearly encoded, please make sure that you are working with linear data, then for viewing (and storage in a 8-bit file) you will need to non-linearly encode it.

Cheers,

Thomas

[vigneshgarrapally]

Hi Thomas,
Thanks for the reply. Do you have any idea on how to convert non linear data to linear data. I am not aware of the differences actually. Currently, I am trying to demosaic the bayer data that I get from the machine vision cameras.

Regards
Vignesh

[KelSolaar]

You would need to know how the image is encoded by the machine vision camera, they typically use a power function, ~gamma encoding. The manual should give you that information.

[vigneshgarrapally]

Thanks for the quick reply. I have gone through the docs and as you mentioned it is gamma encoding. How to convert it to send it to demosaicing algorithms.

Regards
Vignesh

[KelSolaar]

Using the colour.gamma_function:

import colour
colour.gamma_function(0.18, 2.2)