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Merge pull request #27866 from JayPol559:4.x

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Fix HDR tutorial result mismatch by adding gamma note #27866

This PR fixes #22219 by clarifying the gamma correction value in the HDR tutorial.

The function cv.createTonemap() has a default gamma value of 1.0. To match the tutorial example results, gamma should be explicitly set to 2.2. This note has been added to the Tonemap HDR image section of the tutorial.
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Jay Pol 2025-10-21 15:00:58 +05:30 committed by GitHub
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doc/py_tutorials/py_photo/py_hdr/py_hdr.markdown
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@ -83,10 +83,15 @@ We map the 32-bit float HDR data into the range [0..1].
Actually, in some cases the values can be larger than 1 or lower the 0, so notice
we will later have to clip the data in order to avoid overflow.
@note: The function `cv.createTonemap()` uses a default gamma value of 1.0.
Set it explicitly to 2.2 to match standard display brightness and ensure consistent tone mapping results.
@code{.py}
# Tonemap HDR image
# Tonemap HDR images using gamma correction (set gamma=2.2 for standard display brightness)
tonemap1 = cv.createTonemap(gamma=2.2)
res_debevec = tonemap1.process(hdr_debevec.copy())
res_robertson = tonemap1.process(hdr_robertson.copy())
@endcode
### 4. Merge exposures using Mertens fusion
@ -125,6 +130,8 @@ You can see the different results but consider that each algorithm have addition
extra parameters that you should fit to get your desired outcome. Best practice is
to try the different methods and see which one performs best for your scene.
The results below were generated with a gamma value of 2.2 during tonemapping.
### Debevec:
![image](images/ldr_debevec.jpg)