Python bindings for lcms2 about swatchbooker HOT 13 CLOSED

Continuation...
So I reply to Richard directly (accidentally off-list) with

Yes please :)

So Richard replies

I can do an example that does a colorspace conversion.

Yes please :)

So I had a try at this just now, but my python knowledge is lacking.
I'm not sure how you get access to the raw bytes in an image from
python and what coding conventions you'd use in a library. Ideas
welcome here. I've included the incomplete code below. I'm happy to
add more functionality into libcolord if this is required (e.g. if we
want to pass an array of "ddd" to the process function).

Richard

import gi
gi.require_version('Colord', '1.0')

from gi.repository import Colord
from gi.repository import Gio

# load sRGB (without using the daemon)
icc_src = Colord.Icc.new()
h = Gio.file_new_for_path('/usr/share/color/icc/colord/sRGB.icc')
icc_src.load_file(h, Colord.IccLoadFlags.NONE)

# load AdobeRGB (without using the daemon)
icc_dst = Colord.Icc.new()
h = Gio.file_new_for_path('/usr/share/color/icc/colord/AdobeRGB1998.icc')
icc_dst.load_file(h, Colord.IccLoadFlags.NONE)

# set up the transform
transform = Colord.Transform.new()
transform.set_input_pixel_format(Colord.PIXEL_FORMAT_RGB24)
transform.set_input_icc(icc_src)
transform.set_output_icc(icc_dst)
transform.set_output_pixel_format(Colord.PIXEL_FORMAT_RGB24)
transform.set_rendering_intent(Colord.RenderingIntent.PERCEPTUAL)
transform.set_bpc(True)

# hmm, not sure how to make process() accept raw image data
data_in = [0.5,0.6,0.7]
transform.process(data_in, data_in, 1, 1, 1, None)

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Above Richard writes:

So I had a try at this just now, but my python knowledge is lacking.
I'm not sure how you get access to the raw bytes in an image from
python and what coding conventions you'd use in a library. Ideas
welcome here. I've included the incomplete code below. I'm happy to
add more functionality into libcolord if this is required (e.g. if we
want to pass an array of "ddd" to the process function).

So I'm CCing some possible help from friends:
@berteh
@sk1project
@aoloe
@QuLogic

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According to this, functions with bare gpointer should not be exposed over introspection. They should instead be annotated with the expected array dimensions. However, this seems a bit difficult since the function accepts an array in multiple dimensions with varied data types.

You can create the memory pointer using NumPy arrays. I'm not sure why the example uses [0.5, 0.6, 0.7]; the settings are PIXEL_FORMAT_RGB24 which should be 3 bytes of 0-255, not floats.

This works but since you are passing around pointers and stuff, you should check the caveats and ensure your array is allocated suitably:

data_in = np.array([0.5*255, 0.6*255, 0.7*255],
                   dtype=np.uint8)  # NOTE: Use correct type here, not floats!
print(data_in)
transform.process(data_in.ctypes.data, data_in.ctypes.data, 1, 1, 1, None)
print(data_in)

and outputs:

[127 153 178]
[134 152 176]

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There's now some bindings for Python3: https://bitbucket.org/johnpfjefferies/little-cms-python-bindings/

No idea what it would take to convert it to python 2...

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True but since I have no clue about C programming or Python packaging, I have no idea how to use it with SwatchBooker.

PIL/Pillow also has lcms2 bindings but only with a limited set of features that don't match the few ones I need...

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the functions I'm using in SwatchBooker are:

cmsOpenProfileFromFile
cmsCreate_sRGBProfile
cmsCreateLab4Profile
cmsCreateXYZProfile
cmsCreateTransform
cmsCloseProfile
cmsDoTransform
cmsDeleteTransform

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PIL bitmaps are converted directly inside PIL but their binding don't expose the "simple" color transform functions...

In the meantime I did manage to have it working with an updated version of ctypesgen and the THR version of the functions so there's no emergency anymore.

Thank you anyway!

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Just released 0.7.5 with the lcms2 bindings.

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