VPI - Vision Programming Interface

3.0 Release

Gaussian Pyramid Generator


Gaussian pyramid generator takes one input image and fills the output image pyramid with downscaled versions of the input.

Input Output


The function is implemented by generating the Gaussian pyramid from the base (level 0) to coarser levels.

If the input image actually wraps the first level of the image pyramid, nothing is done for this level. If not, the input image contents will be copied to the first image pyramid level.

The coarser levels are generated by taking the previous level, convolving it using a clamp border extension with the following kernel:

\[ k = \begin{bmatrix} 1 \\ 4 \\ 6 \\ 4 \\ 1 \end{bmatrix} \cdot \begin{bmatrix} 1 & 4 & 6 & 4 & 1 \end{bmatrix} \]

Because only 2x downscaling is supported, the result is then downsampled by keeping all pixels with even coordinates.

The algorithm repeats until all levels are generated.

C API functions

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

Function Description
vpiSubmitGaussianPyramidGenerator Computes the Gaussian pyramid from the input image.


  1. Import VPI module
    import vpi
  2. Returns the 4-level Gaussian pyramid created from the input image using the CUDA backend. Input is a VPI image, and output is a VPI pyramid.
    with vpi.Backend.CUDA:
    output = input.gaussian_pyramid(4)
  1. Initialization phase
    1. Include the header that defines the Gaussian pyramid generator function.
      Declares functions that handle gaussian pyramids.
    2. Define the input image object.
      VPIImage input = /*...*/;
      struct VPIImageImpl * VPIImage
      A handle to an image.
      Definition: Types.h:256
    3. Create the output pyramid with the desired number of levels (4) and scale factor (0.5). It gets its dimensions and format from the input image.
      int32_t w, h;
      vpiImageGetSize(input, &w, &h);
      vpiImageGetFormat(input, &type);
      VPIPyramid output;
      vpiPyramidCreate(w, h, type, 4, 0.5, 0, &output);
      uint64_t VPIImageFormat
      Pre-defined image formats.
      Definition: ImageFormat.h:94
      VPIStatus vpiImageGetFormat(VPIImage img, VPIImageFormat *format)
      Get the image format.
      VPIStatus vpiImageGetSize(VPIImage img, int32_t *width, int32_t *height)
      Get the image dimensions in pixels.
      VPIStatus vpiPyramidCreate(int32_t width, int32_t height, VPIImageFormat fmt, int32_t numLevels, float scale, uint64_t flags, VPIPyramid *pyr)
      Create an empty image pyramid instance with the specified flags.
      struct VPIPyramidImpl * VPIPyramid
      A handle to an image pyramid.
      Definition: Types.h:262
    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 the input image and output pyramid. It'll be executed by the CPU backend.
      VPIStatus vpiSubmitGaussianPyramidGenerator(VPIStream stream, uint64_t backend, VPIImage input, VPIPyramid output, VPIBorderExtension border)
      Computes the Gaussian pyramid from the input image.
      CPU backend.
      Definition: Types.h:92
      Border pixels are repeated indefinitely.
      Definition: Types.h:279
    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, the input image and the output pyramid.
      void vpiImageDestroy(VPIImage img)
      Destroy an image instance.
      void vpiPyramidDestroy(VPIPyramid pyr)
      Destroy an image pyramid instance as well as all resources it owns.
      void vpiStreamDestroy(VPIStream stream)
      Destroy a stream instance and deallocate all HW resources.

For more information, see Gaussian Pyramid Generator 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.