It is difficult for me to calculate the latitude and longitude values of the image that I place inside the div tag on my web page. I can easily determine the x, y (pixel) coordinates of the image and save them in a variable inside my script. Here's the hard part ...
The map is not a projection of the Mercator, so I can’t just linearly interpolate the coordinates of the x, y pixels on the lat and lon values. However, I have the luxury of knowing the latitude and longitude of all four corners of the image (see the Placed Chart), the projection of the map onto the image, the central meridian and the latitude of origin.
800x600 U.S., , x, y . , - .