i want to learn image processing with stm32f4 in c,
*where should i start?
*do you have any suggestion?
Understand C, thoroughly.
Understand how data, and image are represented in memory.
I might also suggest doing it on a PC first, where you have a file system, can read/process image files, or videos, and generate output. Debug and become comfortable with what you are working with, and what is required to handle data real-time.
Image processing would be advanced level on a microcontroller.
As Clive said, start from a PC, maybe experiment on a linux based solution (RPI or else), then dig down to embedded.
For embedded, hunt for a discovery with camera example (if possible with display) as it may help you avoid startup from scratch. Otherwise, audio processing would be a better start before going "2D" with graphics.
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