I'm looking to create a small javascript program to take any popular image format and convert it to a format that is able to be read by a microcontroller. The output file needs to have a specific 50 byte header, after the header the image data is the same as a bitmap file. The microcontroller reads the file as bytes. Ideally all of the image conversion happens client side, resulting in a downloadable file for the user.
So far I am able to display the image and edit it however I am unsure where to start generating the converted file.
I am very new to programming and a push in the right direction would be greatly appreciated.