Image Blurring OpenCL

This is an OpenCL Project for Image Blurring Application comparing the performance between OpenCV builtin blur method and implementation with GPU parallel programming using OpenCL. Within the OpenCL implementation, different data structured is tested to see if can affect the memory access time and the overall performance.

Averaging Blur

The implementation of the image blur is based on averaging blur. Three different implementations were tested which includes OpenCV builtin, OpenCL with vector<uchar>, and OpenCL with vector<uchar3>.

Implementation Methodology

• Image:

The image data is read and uncompressed using OpenCV's method Mat imread(const String& filename, int flags=IMREAD_COLOR )

• OpenCV:

The builtin OpenCV cv::blur ( InputArray src, OutputArray dst, Size ksize, Point anchor = Point(-1,-1), int borderType = BORDER_DEFAULT ) was used for the base line of the tests.

• OpenCL:

The OpenCL implementation includes converting the including converting Mat data provided by the image into vector<uchar> and sending that to the GPU with a kernel method. Lastly, converting the vector<uchar> back into 'Mat'.

• OpenCL Data Structure:

OpenCL Data Structure is similar to the previous OpenCL implementation, except that the data passed into the kernel is vector<uchar3>. The vector<uchar> that was converted from Mat is converted into vector<uchar3> with another kernel method using the GPU and convert back after the blur operation is done into Mat.

Performance Time:

The performance of each implementation is measured by the total time spent from reading the image to opening an window to show the blurred image. The operations that is included for each implementation is listed below.

• OpenCV:

  • Read Image
  • Blur

• OpenCL:

  • Read Image
  • Convert Mat to vector<uchar>
  • Set up kernel function
  • Blur (GPU)
  • Convert vector<uchar> to `Mat'

• OpenCL Data Structure:

  • Read Image
  • Convert Mat to vector<uchar>
  • Set up kernel functions
  • Convert vector<uchar> to vector<uchar3> (GPU)
  • Blur (GPU)
  • Convert vector<uchar3> to vector<uchar> (GPU)
  • Convert vector<uchar> to `Mat'

Result:

Original:

OpenCV:

OpenCL:

OpenCL - Data:

5x5 window

Implementation	Average Time
OpenCV	0.120641 seconds
OpenCL	0.0454018 seconds
OpenCL-Data	0.258974 seconds

9x9 window

Implementation	Average Time
OpenCV	0.116062 seconds
OpenCL	0.044688 seconds
OpenCL-Data	0.257319 seconds

15x15 window

Implementation	Average Time
OpenCV	0.116528 seconds
OpenCL	0.116528 seconds
OpenCL-Data	0.116528 seconds

Average

Implementation	Average Time
OpenCV	0.117744 seconds
OpenCL	0.045961 seconds
OpenCL-Data	0.258592 seconds