I found an algorithm which allows to convert latitude/longitude to (x, y) of a screen. The problem is a picture on a map is rotated. If it is not rotated then I use the following calculations:
minLat, minLong, maxLat, maxLong - coords of a rect on a map
mapWidth, mapHeight - screen (rect) width and height
x, y - coords I need
Calculations
xScale = mapWidth / (maxLong - minLong)
yScale = mapHeight / (maxLat - minLat)
x = (lon - minLong) * xScale
y = (lat - minLat) * yScale
How to fix these calculations to take into account a rotation?