Upload a photo, move the controls, and watch OpenCV transform it in real time. Four tools, four concepts from class: arithmetic, thresholding, alpha masks and annotation.
Image arithmetic. Brightness uses cv.add / cv.subtract,
contrast uses cv.multiply. Turn clipping off to watch values overflow and wrap around.
Thresholding. Turn a shadowy photo of notes or sheet music into clean black and white. Compare one global threshold with adaptive thresholding.
// All five methods side by side
Alpha channels & masks. A threshold builds a mask, cv.bitwise_not
flips it when needed, and cv.merge adds it as the 4th (alpha) channel.
Drawing & annotation. cv.putText for the caption,
cv.rectangle / cv.circle to highlight something, cv.line to draw an arrow pointing at it.