Hi,
Please refer to the following sample:
static GstFlowReturn
get_converted_mat (GstDsExample * dsexample, NvBufSurface *input_buf, gint idx,
NvOSD_RectParams * crop_rect_params, gdouble & ratio, gint input_width,
gint input_height)
{
NvBufSurfTransform_Error err;
NvBufSurfTransformConfigParams transform_config_params;
NvBufSurfTransformParams transform_params;
NvBufSurfTransformRect src_rect;
NvBufSurfTransformRect dst_rect;
NvBufSurface ip_surf;
cv::Mat in_mat, out_mat;
ip_surf = *input_buf;
ip_surf.numFilled = ip_surf.batchSize = 1;
ip_surf.surfaceList = &(input_buf->surfaceList[idx]);
gint src_left = GST_ROUND_UP_2(crop_rect_params->left);
gint src_top = GST_ROUND_UP_2(crop_rect_params->top);
gint src_width = GST_ROUND_DOWN_2(crop_rect_params->width);
gint src_height = GST_ROUND_DOWN_2(crop_rect_params->height);
//g_print("ltwh = %d %d %d %d \n", src_left, src_top, src_width, src_height);
guint dest_width, dest_height;
dest_width = src_width;
dest_height = src_height;
NvBufSurface *nvbuf;
NvBufSurfaceCreateParams create_params;
create_params.gpuId = dsexample->gpu_id;
create_params.width = dest_width;
create_params.height = dest_height;
create_params.size = 0;
create_params.colorFormat = NVBUF_COLOR_FORMAT_RGBA;
create_params.layout = NVBUF_LAYOUT_PITCH;
#ifdef __aarch64__
create_params.memType = NVBUF_MEM_DEFAULT;
#else
create_params.memType = NVBUF_MEM_CUDA_UNIFIED;
#endif
NvBufSurfaceCreate (&nvbuf, 1, &create_params);
// Configure transform session parameters for the transformation
transform_config_params.compute_mode = NvBufSurfTransformCompute_Default;
transform_config_params.gpu_id = dsexample->gpu_id;
transform_config_params.cuda_stream = dsexample->cuda_stream;
// Set the transform session parameters for the conversions executed in this
// thread.
err = NvBufSurfTransformSetSessionParams (&transform_config_params);
if (err != NvBufSurfTransformError_Success) {
GST_ELEMENT_ERROR (dsexample, STREAM, FAILED,
("NvBufSurfTransformSetSessionParams failed with error %d", err), (NULL));
goto error;
}
// Calculate scaling ratio while maintaining aspect ratio
ratio = MIN (1.0 * dest_width/ src_width, 1.0 * dest_height / src_height);
if ((crop_rect_params->width == 0) || (crop_rect_params->height == 0)) {
GST_ELEMENT_ERROR (dsexample, STREAM, FAILED,
("%s:crop_rect_params dimensions are zero",__func__), (NULL));
goto error;
}
#ifdef __aarch64__
if (ratio <= 1.0 / 16 || ratio >= 16.0) {
// Currently cannot scale by ratio > 16 or < 1/16 for Jetson
goto error;
}
#endif
// Set the transform ROIs for source and destination
src_rect = {(guint)src_top, (guint)src_left, (guint)src_width, (guint)src_height};
dst_rect = {0, 0, (guint)dest_width, (guint)dest_height};
// Set the transform parameters
transform_params.src_rect = &src_rect;
transform_params.dst_rect = &dst_rect;
transform_params.transform_flag =
NVBUFSURF_TRANSFORM_FILTER | NVBUFSURF_TRANSFORM_CROP_SRC |
NVBUFSURF_TRANSFORM_CROP_DST;
transform_params.transform_filter = NvBufSurfTransformInter_Default;
//Memset the memory
NvBufSurfaceMemSet (nvbuf, 0, 0, 0);
GST_DEBUG_OBJECT (dsexample, "Scaling and converting input buffer\n");
// Transformation scaling+format conversion if any.
err = NvBufSurfTransform (&ip_surf, nvbuf, &transform_params);
if (err != NvBufSurfTransformError_Success) {
GST_ELEMENT_ERROR (dsexample, STREAM, FAILED,
("NvBufSurfTransform failed with error %d while converting buffer", err),
(NULL));
goto error;
}
// Map the buffer so that it can be accessed by CPU
if (NvBufSurfaceMap (nvbuf, 0, 0, NVBUF_MAP_READ) != 0){
goto error;
}
// Cache the mapped data for CPU access
NvBufSurfaceSyncForCpu (nvbuf, 0, 0);
// Use openCV to remove padding and convert RGBA to BGR. Can be skipped if
// algorithm can handle padded RGBA data.
in_mat =
cv::Mat (dest_height, dest_width,
CV_8UC4, nvbuf->surfaceList[0].mappedAddr.addr[0],
nvbuf->surfaceList[0].pitch);
out_mat =
cv::Mat (cv::Size(dest_width, dest_height), CV_8UC3);
cv::cvtColor (in_mat, out_mat, CV_RGBA2BGR);
static gint dump = 0;
if (dump < 150) {
char filename[64];
snprintf(filename, 64, "/home/nvidia/image%03d.jpg", dump);
cv::imwrite(filename, out_mat);
dump++;
}
if (NvBufSurfaceUnMap (nvbuf, 0, 0)){
goto error;
}
NvBufSurfaceDestroy(nvbuf);
#ifdef __aarch64__
// To use the converted buffer in CUDA, create an EGLImage and then use
// CUDA-EGL interop APIs
if (USE_EGLIMAGE) {
if (NvBufSurfaceMapEglImage (dsexample->inter_buf, 0) !=0 ) {
goto error;
}
// dsexample->inter_buf->surfaceList[0].mappedAddr.eglImage
// Use interop APIs cuGraphicsEGLRegisterImage and
// cuGraphicsResourceGetMappedEglFrame to access the buffer in CUDA
// Destroy the EGLImage
NvBufSurfaceUnMapEglImage (dsexample->inter_buf, 0);
}
#endif
/* We will first convert only the Region of Interest (the entire frame or the
* object bounding box) to RGB and then scale the converted RGB frame to
* processing resolution. */
return GST_FLOW_OK;
error:
return GST_FLOW_ERROR;
}
It creates a NvBufSurface for each object and saves it to a jpg file.