Image border color extraction

Find the hex color value of the average color around an image's border

Gets the pixels from the outer 5% of an image, discards outlier values, and returns the average color in hex (as a string)

Usage

python image-decoder.py -i path/to/image.jpg

Downscale the source image to have a width of 200px, keeping the aspect ratio. We don't need to keep the original (large) resolution.
Choose a percentage of the image's border on each axis to use for the color calculation (I use 5%), and put the coordinates of these pixels into a list.
Split the scaled image to individual lists of R, G, B color channels.
Using the coordinates list, populate 3 more lists of just the color values (0-255) for the perimeter pixels of each channel.
Use numpy to remove statistically significant outliers from each of the lists made in the previous step.
Calculate the average value for each channel from the result of the previous step.
Merge the averages of each channel (an RGB(1, 2, 3) value) into hex (#123456) and return it.
Optionally display the input image overlaid over the calculated background color using a GUI with PIL.Image.show().