Stereo Disparity

Overview

The Stereo Disparity application receives left and right stereo pair images and returns the disparity between them, which is a function of image depth. The result is saved into disparity.png.

This sample shows the following VPI features:

• Creating and destroying a VPI device.
• Wrapping an image hosted on CPU (the input) to be used by VPI.
• Creating a VPI-managed 2D image where output will be written to
• Create a properly-configured StereoProcess algorithm and submit it to the device.
• Simple device synchronization.
• Image locking to access its contents from CPU side.
• Error handling.
• Environment clean up.

Instructions

The usage is:

./vpi_sample_02_stereo_disparity <backend> <input image>

where

• backend: either cpu, cuda or pva; it defines the backend that will perform the processing.
• left image: left input image of a stereo pair, it accepts png, jpeg and possibly others.
• right image: right input image of a stereo pair.

Here's one example:

./vpi_sample_02_stereo_disparity cuda ../assets/chair_stereo_left.png ../assets/chair_stereo_right.png

This is using the CUDA backend and the provided sample images. You can try with other stereo pair images, respecting the constraints imposed by the algorithm.

Source code

For convenience, here's the code that is also installed in the samples directory.

/*
* Copyright (c) 2019, NVIDIA CORPORATION. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*  * Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
*  * Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*  * Neither the name of NVIDIA CORPORATION nor the names of its
*    contributors may be used to endorse or promote products derived
*    from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
 
#include <vpi/Image.h>
#include <vpi/Stream.h>
#include <vpi/algo/StereoDisparityEstimator.h>
 
#include <cstring> // for memset
#include <iostream>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/imgproc.hpp>
 
#define CHECK_STATUS(STMT)                                      \
    do                                                          \
    {                                                           \
        VPIStatus status = (STMT);                              \
        if (status != VPI_SUCCESS)                              \
        {                                                       \
            throw std::runtime_error(vpiStatusGetName(status)); \
        }                                                       \
    } while (0);
 
int main(int argc, char *argv[])
{
    VPIImage left      = nullptr;
    VPIImage right     = nullptr;
    VPIImage disparity = nullptr;
    VPIStream stream   = nullptr;
    VPIPayload stereo  = nullptr;
 
    int retval = 0;
 
    try
    {
        if (argc != 4)
        {
            throw std::runtime_error(std::string("Usage: ") + argv[0] + " <cpu|pva|cuda> <left image> <right image>");
        }
 
        std::string strDevType = argv[1];
        std::string strLeftFileName = argv[2];
        std::string strRightFileName = argv[3];
 
        // Load the input images
        cv::Mat cvImageLeft = cv::imread(strLeftFileName, cv::IMREAD_GRAYSCALE);
        if (cvImageLeft.empty())
        {
            throw std::runtime_error("Can't open '" + strLeftFileName + "'");
        }
 
        cv::Mat cvImageRight = cv::imread(strRightFileName, cv::IMREAD_GRAYSCALE);
        if (cvImageRight.empty())
        {
            throw std::runtime_error("Can't open '" + strRightFileName + "'");
        }
 
        // Currently we only accept unsigned 16bpp inputs.
        cvImageLeft.convertTo(cvImageLeft, CV_16UC1);
        cvImageRight.convertTo(cvImageRight, CV_16UC1);
 
        // Now process the device type
        VPIDeviceType devType;
 
        if(strDevType == "cpu")
        {
            devType = VPI_DEVICE_TYPE_CPU;
        }
        else if(strDevType == "cuda")
        {
            devType = VPI_DEVICE_TYPE_CUDA;
        }
        else if(strDevType == "pva")
        {
            devType = VPI_DEVICE_TYPE_PVA;
        }
        else
        {
            throw std::runtime_error("Backend '" + strDevType + "' not recognized, it must be either cpu, cuda or pva.");
        }
 
        // Create the stream for the given backend.
        CHECK_STATUS(vpiStreamCreate(devType, &stream));
 
        // We now wrap the loaded images into a VPIImage object to be used by VPI.
        {
            // First fill VPIImageData with the, well, image data...
            VPIImageData imgData;
            memset(&imgData, 0, sizeof(imgData));
            imgData.type                = VPI_IMAGE_TYPE_Y16;
            imgData.numPlanes           = 1;
            imgData.planes[0].width     = cvImageLeft.cols;
            imgData.planes[0].height    = cvImageLeft.rows;
            imgData.planes[0].rowStride = cvImageLeft.step[0];
            imgData.planes[0].data      = cvImageLeft.data;
 
            // Wrap it into a VPIImage. VPI won't make a copy of it, so the original
            // image must be in scope at all times.
            CHECK_STATUS(vpiImageWrapHostMem(&imgData, 0, &left));
 
            imgData.planes[0].width     = cvImageRight.cols;
            imgData.planes[0].height    = cvImageRight.rows;
            imgData.planes[0].rowStride = cvImageRight.step[0];
            imgData.planes[0].data      = cvImageRight.data;
 
            CHECK_STATUS(vpiImageWrapHostMem(&imgData, 0, &right));
        }
 
        // Create the image where the disparity map will be stored.
        CHECK_STATUS(vpiImageCreate(cvImageLeft.cols, cvImageLeft.rows, VPI_IMAGE_TYPE_Y16, 0, &disparity));
 
        // Create the payload for Harris Corners Detector algorithm
 
        VPIStereoDisparityEstimatorParams params;
        params.windowSize   = 5;
        params.maxDisparity = 64;
        CHECK_STATUS(vpiCreateStereoDisparityEstimator(stream, cvImageLeft.cols, cvImageLeft.rows, VPI_IMAGE_TYPE_Y16,
                                                       params.maxDisparity, &stereo));
 
        // Submit it with the input and output images
        CHECK_STATUS(vpiSubmitStereoDisparityEstimator(stereo, left, right, disparity, &params));
 
        // Wait until the algorithm finishes processing
        CHECK_STATUS(vpiStreamSync(stream));
 
        // Now let's retrieve the output
        {
            // Lock output to retrieve its data on cpu memory
            VPIImageData data;
            CHECK_STATUS(vpiImageLock(disparity, VPI_LOCK_READ, &data));
 
            // Make an OpenCV matrix out of this image
            cv::Mat cvOut(data.planes[0].height, data.planes[0].width, CV_16UC1, data.planes[0].data,
                          data.planes[0].rowStride);
 
            // Scale result and write it to disk
            double min, max;
            minMaxLoc(cvOut, &min, &max);
            cvOut.convertTo(cvOut, CV_8UC1, 255.0 / (max - min), -min);
 
            imwrite("disparity_"+strDevType+".png", cvOut);
 
            // Done handling output, don't forget to unlock it.
            CHECK_STATUS(vpiImageUnlock(disparity));
        }
    }
    catch (std::exception &e)
    {
        std::cerr << e.what() << std::endl;
        retval = 1;
    }
 
    // Clean up
    vpiImageDestroy(left);
    vpiImageDestroy(right);
    vpiImageDestroy(disparity);
    vpiPayloadDestroy(stereo);
    vpiStreamDestroy(stream);
 
    return retval;
}

Results

Left input image	Right input image
Stereo disparity