ipa: rkisp1: Add WDR algorithm

Add a WDR algorithm to do global tone mapping. Global tone mapping is used to increase the perceived dynamic range of an image. The typical effect is that in areas that are normally overexposed, additional structure becomes visible. The overall idea is that the algorithm applies an exposure value correction to underexpose the image to the point where only a small number of saturated pixels is left. This artificial underexposure is then mitigated by applying a tone mapping curve. This algorithm implements 4 tone mapping strategies: - Linear - Power - Exponential - Histogram equalization Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com> Reviewed-by: Paul Elder <paul.elder@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
2025-09-19 11:40:33 +02:00
parent 026f25f32b
commit f62a1498e9
8 changed files with 637 additions and 1 deletions
@@ -1283,5 +1283,67 @@ controls:
        \sa SensorTimestamp

        The FrameWallClock control can only be returned in metadata.
+  - WdrMode:
+      type: int32_t
+      direction: inout
+      description: |
+        Set the WDR mode.
+
+        The WDR mode is used to select the algorithm used for global tone
+        mapping. It will automatically reduce the exposure time of the sensor
+        so that there are only a small number of saturated pixels in the image.
+        The algorithm then compensates for the loss of brightness by applying a
+        global tone mapping curve to the image.
+      enum:
+        - name: WdrOff
+          value: 0
+          description: Wdr is disabled.
+        - name: WdrLinear
+          value: 1
+          description:
+            Apply a linear global tone mapping curve.
+
+            A curve with two linear sections is applied. This produces good
+            results at the expense of a slightly artificial look.
+        - name: WdrPower
+          value: 2
+          description: |
+            Apply a power global tone mapping curve.
+
+            This curve has high gain values on the dark areas of an image and
+            high compression values on the bright area. It therefore tends to
+            produce noticeable noise artifacts.
+        - name: WdrExponential
+          value: 3
+          description: |
+            Apply an exponential global tone mapping curve.
+
+            This curve has lower gain values in dark areas compared to the power
+            curve but produces a more natural look compared to the linear curve.
+            It is therefore the best choice for most scenes.
+        - name: WdrHistogramEqualization
+          value: 4
+          description: |
+            Apply histogram equalization.
+
+            This curve preserves most of the information of the image at the
+            expense of a very artificial look. It is therefore best suited for
+            technical analysis.
+  - WdrStrength:
+      type: float
+      direction: in
+      description: |
+        Specify the strength of the wdr algorithm. The exact meaning of this
+        value is specific to the algorithm in use. Usually a value of 0 means no
+        global tone mapping is applied. A values of 1 is the default value and
+        the correct value for most scenes. A value above 1 increases the global
+        tone mapping effect and can lead to unrealistic image effects.
+  - WdrMaxBrightPixels:
+      type: float
+      direction: in
+      description: |
+        Percentage of allowed (nearly) saturated pixels. The WDR algorithm
+        reduces the WdrExposureValue until the amount of pixels that are close
+        to saturation is lower than this value.

 ...