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Software ISP is currently fully automatic and doesn't allow image
modifications by explicitly set control values. The user has no means
to make the image looking better.
This patch introduces support for contrast control, which can improve
e.g. a flat looking image. Based on the provided contrast value, it
applies a simple S-curve modification to the image.
The contrast algorithm just handles the provided values, while the
S-curve is applied in the gamma algorithm on the computed gamma curve
whenever the contrast value changes. Since the algorithm is applied
only on the lookup table already present, its overhead is negligible.
The contrast value range is 0..2 and corresponds to the whole range from
a completely flat contrast to an infinite contrast, 1.0 being the normal
value. This makes the user visible range intuitive and easy to use in
GUI sliders, while complying with Contrast control definition. There is
no unified range in the hardware pipelines, for example rkisp1 uses
0..1.993 range while rpi uses 0..10 range.
This is a preparation patch without actually providing the control
itself, which is done in the following patch.
Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
Tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
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It's more natural to represent color gains as floating point numbers
rather than using a particular pixel-related representation.
double is used rather than float because it's a more common floating
point type in libcamera algorithms. Otherwise there is no obvious
reason to select one over the other here.
The constructed color tables still use integer representation for
efficiency.
Black level still uses pixel (integer) values, for consistency with
other libcamera parts.
Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
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After black level handling has been moved to an algorithm module, white
balance and the construction of color tables can be moved to algorithm
modules too.
This time, the moved code is split between stats processing and
parameter construction methods. It is also split to two algorithm
modules:
- White balance computation.
- Gamma table computation and color lookup tables construction. While
this applies the color gains computed by the white balance algorithm,
it is not directly related to white balance. And we may want to
modify the color lookup tables in future according to other parameters
than just gamma and white balance gains.
Gamma table computation and color lookup tables construction could be
split to separate algorithms too. But there is no big need for that now
so they are kept together for simplicity.
This is the only part of the software ISP algorithms that sets the
parameters so emitting setIspParams can be moved to prepare() method.
A more natural representation of the gains (and black level) would be
floating point numbers. This is not done here in order to minimize
changes in code movements. It will be addressed in a followup patch.
Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Acked-by: Umang Jain <umang.jain@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
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