imageprocessing/geometry/rectifier/docs/usecase1.md

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# Copyright (c) 2019-2020 NVIDIA CORPORATION.  All rights reserved.

@page rectifier_usecase1 Rectifier Workflow

@note SW Release Applicability: This tutorial is applicable to modules in both **NVIDIA DriveWorks** and **NVIDIA DRIVE Software** releases.

This tutorial will show you how to convert images captured with a camera model into a different camera model.

In this example we'll use as input a camera from our rig configuration file:

```{.cpp}
dwInitialize(&contextHandle, DW_VERSION, &sdkParams)
dwRig_initializeFromFile(&rigConf, contextHandle, rigConfigFilename);
dwRig_findSensorByName(&sensorId, cameraName, rigConf)

dwCameraModelHandle_t cameraModelIn = DW_NULL_HANDLE;
dwCameraModel_initialize(&cameraModelIn, sensorId, rigConf)
```

The following two snippets demonstrate how to initialize different output camera models.<br>
`contextHandle` is assumed to be previously initialized `::dwContextHandle_t`.

#### Example of camera for rectification (undistortion)

```{.cpp}
    // Settings
    dwPinholeCameraConfig cameraConf = {};
    cameraConf.distortion[0] = 0.f;
    cameraConf.distortion[1] = 0.f;
    cameraConf.distortion[2] = 0.f;
    // CODE: other settings of camera
    dwCameraModel_initializePinhole(&cameraModelOut, &cameraConf, contextHandle);
```

#### Example of camera for model projection (simulation)

```{.cpp}
    // CODE: create settings of simulated ocam
    dwCameraModel_initializeOCam(&cameraModelOut, &cameraConf, contextHandle);
```

#### Use of the rectifier

The rectifier module can be initialized with the camera models that we have just created:

```{.cpp}
    dwRectifier_initialize(&rectifier, cameraModelIn, cameraModelOut, contextHandle);
```

And can be used on images coming from a live sensor or from a recording:

```{.cpp}
    while(loop) {
        // CODE: get image from camera, stream it (optional)
        dwRectifier_setHomography(&homography, rectifier); //optional
        dwRectifier_warp(&rectifiedImage, inputImage, rectifier);
    }
```

For simplicity, the actual sensor management, including retrieving images from a camera, is omitted in this tutorial.<br>
For more information see @ref camera_usecase1.

Finally all handles can be released:

```{.cpp}
dwCameraModel_release(cameraModelIn);
dwCameraModel_release(cameraModelOut);
dwRectifier_release(rectifier);
dwRelease(contextHandle);
```

For the full implementation refer to @ref dwx_video_rectifier_sample.<br>
See @ref rig_mainsection for more information on Calibrated Cameras.