image/docs/usecase1.md

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

@page image_usecase1 Image Capture
@tableofcontents

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

This tutorial demonstrates how to utilize the FrameCapture module to capture images from a window rendered on screen.<br>

The FrameCapture module is accessed through a handle:

```{.cpp}
dwFrameCaptureHandle_t frameCapture = DW_NULL_HANDLE;
```
@section image_usecase1_initializing Initializing the FrameCapture Module

The ::dwFrameCaptureHandle_t handle initializes the FrameCapture module with the following parameters, once they are declared and assigned.

```{.cpp}
    dwFrameCaptureParams frameParams{};
    std::string params = "type=disk";
    params += ",format=h264";
    params += ",bitrate=8000000";
    params += ",framerate=30";
    params += ",file=video.h264";
    frameParams.params.parameters = params.c_str();
    frameParams.width = imageWidth;
    frameParams.height = imageHeight;
    frameParams.mode = DW_FRAMECAPTURE_MODE_SCREENCAP | DW_FRAMECAPTURE_MODE_SERIALIZE;
    frameParams.serializationType = DW_IMAGE_GL;

    dwFrameCapture_initialize(frameCapture,frameParams,dwSALHandle,dwContextHandle);
```
For a complete description of all parameters, please refer to ::dwFrameCaptureParams.

For simplicity, steps to render this window are left out of this tutorial. Please refer to @ref dwx_render_engine_sample for more information.<br>

@section image_usecase1_capturing Capturing the Window's Content

To capture the content inside the window:

```{.cpp}
    dwRect roiCapture = {0, 0, WINDOW_WIDTH, WINDOW_HEIGHT};
    const dwImageGL* imgGL = nullptr;
    dwFrameCapture_screenCapture(&imgGL, roiCapture,frameCapture);
    dwFrameCapture_appendFrameGL(imgGL,frameCapture);
```

@section image_usecase1_releasing_handle Releasing the Handle

To release the handle:

```{.cpp}
    dwFrameCapture_release(frameCapture);
```

To see a full demonstration of this workflow, please refer to @ref dwx_image_capture_sample.