Question

how do i find out pixel value at certain degree on the circumference of a circle if I know the pixel co-ordinates of the center of the circle, radius of the circle ,and perpendicular angle.
Basically, I am trying to draw the hands of a clock at various times ( 1 o clock , 2 o clock etc )

Answer 1

Let h be the hour as a floating point number (h=2.25 would be 02:15, etc.) between 0 and 12. (cX,cY) are the coordinates of the center. hLength and mLength are the lengths of the hour and min hands.

// Hour hand
hAngle = 2.0*Pi*h/12.0; // 0..12 mapped to 0..2*Pi
hX = cX + hLength * sin(hAngle);
hY = cY - hLength * cos(hAngle);

// Min hand
mAngle = 2.0*Pi*h; // 0..1 mapped to 0..2*Pi, etc.
mX = cX + mLength * sin(mAngle);
mY = cY - mLength * cos(mAngle);