PPM Image filtering

Applying filters on ppm images using C++

PPM

"A PPM file is a 24-bit color image formatted using a text format. It stores each pixel with a number from 0 to 65536, which specifies the color of the pixel. PPM files also store the image height and width, whitespace data, and the maximum color value."

The Filters

Every filter except laplace has parameters.

• gamma: Has 1 parameter γ, every color channel of the pixel is raised to the power of γ.
• linear: Has 6 parameters, 2 for each color channel of the pixel. Each channel is multiplied with and then added to the correspondant values.
• laplace: Edge detector. Each pixel is a weighted sum of it's 3x3 neighboring valid pixels. The weights are determined by a specidied 3x3 matrix.
• blur: Has 1 parameter N. Each pixel is the average value of it's NxN neighboring valid pixels.

HowTo

1. Download all files into one folder.
2. Open Assignment.sln with visual studio (created on visual studio 2013)
3. Build the solution.
4. Go to Debug/Release folder, depending on which build you did.
5. Open cmd
6. Use filterd etc./filter etc. depending on which build you did. (Release is faster)

input image must be in the same folder

To transform an image input.ppm into it's negative version and save it as filtered_input.ppm

filter -f linear -1 -1 -1 1 1 1 input.ppm

You can also supply a list of multiple filters to be applied successively, for example

filter -f laplace -f blur 3 -f gamma 2 -f linear 2 2 2 0 0 0 -f blur 1 input.ppm