gistfile1.js

function generateClickMap(id) {
            var imageData, data, width, height;

            var c = document.createElement('canvas');
            var ctx = c.getContext('2d');
            var imageObj = this.director.getImage(id);
            var clickMap = [];

            width = imageObj.width;
            height = imageObj.height;
            c.width = width;
            c.height = height;

            ctx.drawImage(imageObj, 0, 0);

            imageData = ctx.getImageData(0, 0, width, height);
            data = imageData.data;

            for (var i = 0, n = data.length; i < n; i += 4) {
                var row = Math.floor((i / 4) / width);
                var col = (i / 4) - (row * width);
                if (!clickMap[row]) clickMap[row] = [];
                clickMap[row][col] = data[i + 3] == 0 ? 0 : 1;
            }

            return clickMap;
        }