Created by Rob Golshan (uteid: rpg499)

Credit: main.cpp: GL functions / idea of the image loop taken from NVIDIA cuda sample code convolution.cu: Algorithms implemented based on convolutionSeparable.pdf in cuda sample code and a parallel implementation of algorithms in https://web.archive.org/web/20060718054020/http://www.acm.uiuc.edu/siggraph/workshops/wjarosz_convolution_2001.pdf

What does the program do?

This is an implementation of several image processesing algorithms utilizing the parallelism of an NVIDIA GPU via CUDA. Algorithms implemented are:

1. 2D Convolution in parallel that works with any kernel (i.e. filter matrix)

• O(radius^2) assuming all blocks run in parallel

2. 2D Convolution in parallel similar to #1, but uses shared memory. Works with any kernel.

• This is faster than #1.
• Shared memory requirements are (BLOCK_SIZE x kernel radius) squared
• Could possibly be faster (but same time complexity) by loading the source image in a texture

3. 2D Convolution in parallel with SEPARABLE kernels ONLY.

• Split into two functions that compute convolution of rows or convolution of columns
• O(radius) assuming all blocks run in parallel

4. Boxfilter

• Similar to #3, but uses properties of box filters to keep time low when using a big radius
• O(width+height) assuming all blocks run in parallel
• Could possibly be faster (but same time complexity) by loading the source image in a texture
• Time taken independent of radius size
• Multiple iterations of this similate a Guassian filter

Filters I purposely did not implement:

1. FFT filter

• Requires more math knowledge than I currently have
• Implementation would be padding kernel/image and using FFT library in cuda
• Slower than separable implementation
• Should only really be needed with using BIG kernels that are not separable

2. Guassian filters

• We can either use a separable filter (#3) or a box filter several times (#4) to get the same result

Any other filters I didn't implement were either because I thought it was already a filter mentioned earlier, or I missed it in my research

Why use this over NVIDIA sample code? There is no reason. I doubt my implementations are any faster than the samples provided.

BUILDING

Build with make

Tested and built on a single GPU system with a GTX 980 (compute capability 5.2) Have Xwindow system enabled to visually see results

Must either use the sample lena.ppm or have your own ppm image file

Running

./convolution --image [path to image]

While the program is running and the XWindow is in focus, press h for a help command.