VPI - Vision Programming Interface

2.0 Release

Box Filter


Box Filter is a low-pass filter that smooths the image by making each output pixel the average of the surrounding ones, removing details, noise and and edges from images.

Input Window size Output

C API functions

For list of limitations, constraints and backends that implements the algorithm, consult reference documentation of the following functions:

Function Description
vpiSubmitBoxFilter Runs a 2D box filter over an image.


The Box filter is implemented as a convolution operation on the input image using the following kernel:

\[ box_{m,n} = \frac{1}{mn} \begin{bmatrix} 1 & 1 & \dots & 1 \\ 1 & 1 & \dots & 1 \\ \vdots & \vdots & \ddots & \vdots \\ 1 & 1 & \dots & 1 \end{bmatrix}_{m \times n} \]


  1. Import VPI module
    import vpi
  2. Use the CUDA backend to filter input image with a 5x5 box kernel, using ZERO boundary condition. Input and output are VPI images.
    with vpi.Backend.CUDA:
    output = input.box_filter(5, border=vpi.Border.ZERO)
  1. Initialization phase
    1. Include the header that defines the box filter function.
      Declares functions that implement the Box Filter algorithm.
    2. Define the input image object.
      VPIImage input = /*...*/;
      struct VPIImageImpl * VPIImage
      A handle to an image.
      Definition: Types.h:256
    3. Create the output image. It gets its dimensions and format from the input image.
      int32_t w, h;
      vpiImageGetSize(input, &w, &h);
      vpiImageGetFormat(input, &type);
      VPIImage output;
      vpiImageCreate(w, h, type, 0, &output);
      uint64_t VPIImageFormat
      Pre-defined image formats.
      Definition: ImageFormat.h:94
      VPIStatus vpiImageGetFormat(VPIImage img, VPIImageFormat *format)
      Get the image format.
      VPIStatus vpiImageCreate(int32_t width, int32_t height, VPIImageFormat fmt, uint64_t flags, VPIImage *img)
      Create an empty image instance with the specified flags.
      VPIStatus vpiImageGetSize(VPIImage img, int32_t *width, int32_t *height)
      Get the image dimensions in pixels.
    4. Create the stream where the algorithm will be submitted for execution.
      VPIStream stream;
      vpiStreamCreate(0, &stream);
      struct VPIStreamImpl * VPIStream
      A handle to a stream.
      Definition: Types.h:250
      VPIStatus vpiStreamCreate(uint64_t flags, VPIStream *stream)
      Create a stream instance.
  2. Processing phase
    1. Submit the algorithm to the stream along with other parameters. In this case it's a 5x5 box filter with clamp border extension. It'll be executed by the CUDA backend.
      vpiSubmitBoxFilter(stream, VPI_BACKEND_CUDA, input, output, 5, 5, VPI_BORDER_ZERO);
      VPIStatus vpiSubmitBoxFilter(VPIStream stream, uint64_t backend, VPIImage input, VPIImage output, int32_t kernelWidth, int32_t kernelHeight, VPIBorderExtension border)
      Runs a 2D box filter over an image.
      CUDA backend.
      Definition: Types.h:93
      All pixels outside the image are considered to be zero.
      Definition: Types.h:278
    2. Optionally, wait until the processing is done.
      VPIStatus vpiStreamSync(VPIStream stream)
      Blocks the calling thread until all submitted commands in this stream queue are done (queue is empty)...
  3. Cleanup phase
    1. Free resources held by the stream and the input and output images.
      void vpiImageDestroy(VPIImage img)
      Destroy an image instance.
      void vpiStreamDestroy(VPIStream stream)
      Destroy a stream instance and deallocate all HW resources.

For more information, see Box Filter in the "C API Reference" section of VPI - Vision Programming Interface.


For information on how to use the performance table below, see Algorithm Performance Tables.
Before comparing measurements, consult Comparing Algorithm Elapsed Times.
For further information on how performance was benchmarked, see Performance Benchmark.