单击或悬停在画布中的多个图像上？

Question

I am working on a project for my programming class. I'd like to essentially have a canvas with a background element (say a room.jpg) and then maybe three interactive objects in the room (lamp.jpg, couch.jpg, desk.jpg). I'd like for it to be that if you hover over the lamp a small box or text pops out, giving you some information. Or maybe have it so if you click an image, the same concept happens. You know, something interactive with the objects in the canvas. Again, I'm new to canvas but we have to use it in our assignment. My current code is:

function loadImages(sources, callback) {
            var images = {};
            var loadedImages = 0;
            var numImages = 0;
            // get num of sources
            for(var src in sources) {
                numImages++;
                }
            for(var src in sources) {
                images[src] = new Image();
                images[src].onload = function() {
                if(++loadedImages >= numImages) {
                callback(images);
                    }
                };
            images[src].src = sources[src];
                }
            }

            var sources = {
            room: 'room.jpg',
            title: 'title.jpg'
            };

            loadImages(sources, function(images) {
            context.drawImage(images.room, 0,0);
            context.drawImage(images.title, 0,0);
            });
            }

But from what I understand, it makes the two jpegs a "permanent" canvas element (unable to be messed with). I had been trying to get it so that when I clicked I'd go from the title.jpg to the room.jpg but I've since given up. Essentially, all I want now is just to have the room.jpg appear when the page is first loaded, and have three other png objects on top (as objects in the room). Are these able to be interacted with, or do I have to put the images into the canvas in another way? Thanks for all your help and your patience!

Answer 1

// --- Image Loader ----
var images = {};
var loadedImages = 0;
var pictures = {
    room: 'room.jpg',
    title: 'title.jpg'
    lamp1: 'lampoff.jpg'
    lamp2: 'lampon.jpg'
};
function loadImages(sources, callback) {
    var numImages = 0;
    for(var src in sources)numImages++;

    for(var src in sources) {
        images[src] = new Image();
        images[src].onload = function() {
            if(++loadedImages >= numImages) {
                callback(images);
            }
        };
        images[src].src = sources[src];
    }
}



// --- Mouse Down Functionality ----
$('#canvas').addEventListener('mouseDown', function(e){
    if(e.clientX){
        var rect = this.getBoundingClientRect();
        if(rect)            clickCanvas(e.clientX - rect.left, e.clientY - rect.top)
        else                clickCanvas(e.clientX  - this.offsetLeft, e.clientY - this.offsetTop);
    }else if(e.offsetX)     clickCanvas(e.offsetX, e.offsetY);
    else if(e.layerX)       clickCanvas(e.layerX, e.layerY);
    else console.warn("Couldn't Determine Mouse Coordinates");
})


var lampOn;

function drawCanvas(showLamp){
    lampOn = showLamp;
    canvas.width = canvas.width //clears canvas
    context.drawImage(images.room, 0,0);
    context.drawImage(images.title, 0,0);
    if(lampOn){ 
        context.drawImage(images.lamp2, 100,100);
    }else{
        context.drawImage(images.lamp1, 100,100);
    }
}   

function clickCanvas(x,y){
    console.log('clicked canvas at:',x,y)
    if(clickedLamp){
        drawCanvas(!lampOn)
    }
}

loadImages(pictures, function(images) {
    drawCanvas(false)
});

Make sure to replace "clickedLamp" and "#canvas"! The idea here is that you redraw the same canvas, using the same function. Everytime you modify any of it, you rerender ALL of it. See if you can get this example working, it will help clarify alot. If you don't understand something comment