MNIST classifier in C++

This is a simple MNIST classifier I wrote for school in C++ from scratch.

Compiling and Running

1. Download the MNIST dataset from https://archive.org/download/mnist-dataset
2. Convert all images in MNIST_Dataset/trainingSet/* to the PPM P6 format:

for d in ./*; do
    cd "$d"
    parallel -j 8 'ffmpeg -y -i {} {.}.ppm && rm {}' ::: *.jpg
    cd ..
done

(or something like that, parallel makes it a lot faster)

3. Extend the MNIST dataset using mnist-ext by cp -r mnist-ext/* MNIST_Dataset/trainingSet
4. make clean && make && ./mnist-classify
5. watch the magic happen :)

You may use the pre-built model at modelis.txt with 99% or so accuracy. (sorry for the unoptimised code, I only had time til today's evening)

If you want to classify own images, feel free to use the https://ari.lt/ppm tool to draw your own, ensure:

1. Width and height are both 28 pixels, press "save canvas" before anything.
2. Set the brush size to 2
3. Draw your number :)

... or open the ppm.html file in your browser.

Cross-Compiling to Windows

rm -rf build
mkdir build
cd build
cmake -DCMAKE_TOOLCHAIN_FILE=../toolchain-mingw64.cmake ..
cmake --build .

Compiling on Windows using MSVC

Open the Developer Command Prompt and navigate to the project's root directory, then execute the following commands:

rm -rf build
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release ..
cmake --build . -j4 --config Release