HI3518 image appears yellow circle

OV9712 Sensor output image in the middle of a concentric circular yellow circle, resulting in a partial color.

Reason:OV9712 CRA and monitoring lens mismatch, the physical structure of the lens to determine the center of the sensor than the periphery can receive more light, relative to the center of the periphery is a shadow, this phenomenon is called the Halo (vignetting). Lens shadow correction is used to compensate the dark angle of the image. For the brightness correction, the R, G, B three components can use the same parameters, and when color correction, the individual calibration parameters are used.

Solution: Through the ISP Lens Shadow correction module to solve. OV9712 's CMOS.C has a set of default correction parameters, but the lens shadow is associated with the lens itself, the default parameters do not match each shot perfectly, and need to be corrected with your own lens. In the lens parameters, the length of the coke and the size of the aperture are most affected.

The lens shadow correction API provided in the HiSilicon SDK is as follows:

Hi_mpi_isp_setshadingattr: Sets the dark angle correction attribute.

Hi_mpi_isp_getshadingattr: Gets the dark corner correction attribute.

Hi_mpi_isp_setshadingtable: Set the lens dark angle compensation lookup table.

Hi_mpi_isp_getshadingtable: Gets the lens dark angle compensation lookup table.

typedef structhiisp_shading_attr_s

{

Hi_bool Enable;

} isp_shading_attr_s;

Where the benable values are as follows:

Hi_false: Turn off lens shading correction function;

Hi_true: Enables lens shading correction function. The default value is Hi_false.

Note: When the illumination is low, normal illuminance under normal correction parameters, will cause a large noise around, and higher brightness. So in low illumination, you can switch to the maximum gain of the calibration table, or close the lens shadow

Correction function.