Javascript/Html for selecting (x,y) pixel coordinates from images.

Hello, I need some javascript and html code to allow the user to locate and save pixel coordinate locations from an image. I intend to use this code on the Mturk platform. The images will have an almost square map image within the overall image. I would like to create a data file of the x,y pixel locations of each of the corners of the inset square. Since the image is not perfectly square and not perfectly aligned each of the corners will need to be identified. The image files are .jpg or .tif with 9500 X 7500 pixels. With this resolution the tool will require some zoom capabilities. I am open to suggestions. One option would be two viewing screens. One would have the full image and allow the user to put a box around one of the corners. This would put a zoomed image of the boxed in section on the second screen. The user would be able to click the second screen to identify a pixel location and then select which quadrant it is in (upper left, upper right, lower left, lower right). The pixel location would need to be converted to pixel location in the entire file. I would recommend that the second screen be about 600% enlargement of the raw image. There should also be a way for the user to select or submit a null value for any of those coordinate points, in case a corner is missing. The user also needs a way of resetting the values and also submitting the results. Submitting would save the .csv file with the matching file name and then reset the values and load the next image. This is one layout option: [login to view URL] On the Android platform the box locks into position, which is what I would want it to do. On windows it continues to move with the mouse, which isn't what I would want it to do. This sample discusses the Mturk structure: [login to view URL] If you have any questions, please ask. The goal is to extract the coordinates from hundreds of images. Accuracy is very important. Thank you for considering this project. I appreciate your knowledge, ideas, and suggestions.