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Hey It NOT ISSUES But i need colormap Add cubehelix #2191

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KristapsSDRSharp opened this issue Jun 30, 2024 · 3 comments
Open

Hey It NOT ISSUES But i need colormap Add cubehelix #2191

KristapsSDRSharp opened this issue Jun 30, 2024 · 3 comments

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@KristapsSDRSharp
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Colormap

@f4exb
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f4exb commented Jun 30, 2024

It is pretty difficult to retrieve values from a picture. In SDRangel color maps are stored as 256 (R,G,B) floating point values (0.0 to 1.0) from lower (left on the picture) to higher (right on the picture). If you can provide these values it will be no big deal to add this color map.

@f4exb
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f4exb commented Jul 25, 2024

This can be done in Python...
Firstly install pillow:

pip install pillow

Then this snippet should print out the colormap structure to be inserted in sdrgui\gui\colormap.cpp:

from PIL import Image

im = Image.open('cubehelix.png') 
pix = im.load()
xsize = im.size[0]

print("const float ColorMap::m_cubehelix[m_size] =")
print("{")

for xi in range(256):
    x = int((xsize/256)*xi)
    colortuple = pix[x, 0][:-1]
    rf = colortuple[0] / 256
    gf = colortuple[1] / 256
    bf = colortuple[2] / 256
    print(f"    {rf:.4f},   {gf:.4f},   {bf:.4f},")

print("};")

@f4exb
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f4exb commented Jul 25, 2024

The explanation that goes with this palette seems to be here: https://people.phy.cam.ac.uk/dag9/CUBEHELIX/ Could be nice indeed.

Alternatively it has a link to a Javascript page that can also print out the RGB values: https://people.phy.cam.ac.uk/dag9/CUBEHELIX/cubetry.html

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