Rendering ASCII
With most exams written I finally found the time to work on some cool projects again, first of which is a Image to ASCII Art converter.I first had the idea when checking out nothings single header file libraries, of which
image.h provides a really simple way for working with all the image formats and does the heavy lifting of working with the different formats for you.In my previous project PNGenius I used
libpng itself, which was overkill for the simple functionality I actually needed (and used).For rendering ascii I had to goals:
- Resemble the source image as closely as possible by calculating the actual lumiance of each char in the font
- Create a simple edge detection algorithm to outline areas of high contrast using
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To calculate a luminance value for each letter I created a python script which renders every character using
pillow, calculates the luminance and stores it. Chars that have almost the same luminance are thrown out so there is a mostly even distribution.The actual rendering is done in C, where I read the image, convert it to gray scale and then use the gray value to determine the luminance (and thus the char) to be rendered.
For the edge detection I used a simple 2x2 kernel that scans the image, calculating a vector for each cell that points in the direction of the contrast (the details can be found in the implementation), the kernel also calculates the average luminance of the 4 pixel, it then decides whether to draw an edge or luminance char based on the magnitude of the vector and a threshhold that can be modified for different results.
Example showing the 2x2 kernel result and source image
More details on the kernel and the entire project can be found in its repository