所以让我首先说我正在尝试创建一个大图像或房间，比如5000乘3750，并且画布或观看区域只有800乘599，总是跟随播放器块。我确实找到了一个如何做到这一点的好指南，使用了java脚本中绘制的背景和播放器（不是从精灵表中获取）。但我所拥有的是带有背景的精灵表，而玩家，我让玩家在JavaScript的背景上工作，但不是像我想要的那样从精灵表中获取。 以下是一些代码：
// wrapper for "class" Map
(function(){
function Map(width, height){
// map dimensions
this.width = width;
this.height = height;
// map texture
this.image = null;
}
// generate an example of a large map
Map.prototype.generate = function(){
ctxBg.drawImage(imgSprite,0,2250,5000,3750,0,0,5000,3750);
}
// draw the map adjusted to camera
Map.prototype.draw = function(context, xView, yView){
var sx, sy, dx, dy;
var sWidth, sHeight, dWidth, dHeight;
// offset point to crop the image
sx = xView;
sy = yView;
// dimensions of cropped image
sWidth = 800;
sHeight = 599;
// if cropped image is smaller than canvas we need to change the source dimensions
if(800 - sx < sWidth){
sWidth = 800 - sx;
}
if(599 - sy < sHeight){
sHeight = 599 - sy;
}
// location on canvas to draw the croped image
dx = 0;
dy = 0;
// match destination with source to not scale the image
dWidth = sWidth;
dHeight = sHeight;
context.drawImage(imgSprite, sx, sy, sWidth, sHeight, dx, dy, dWidth, dHeight);
}
// add "class" Map to our Game object
Game.Map = Map;
})();
// Game Script
(function(){
// prepaire our game canvas
var canvas = document.getElementById("gameCanvas");
var context = canvas.getContext("2d");
// game settings:
var FPS = 30;
var INTERVAL = 1000/FPS; // milliseconds
var STEP = INTERVAL/1000 // seconds
// setup an object that represents the room
var room = {
width: 5000,
height: 3750,
map: new Game.Map(5000, 3750)
};
room.map.generate();
继承了camra / player代码：
(function(){
function Rectangle(left, top, width, height){
this.left = left || 0;
this.top = top || 0;
this.right = (left + width) || 0;
this.bottom = (top + height) || 0;
}
Rectangle.prototype.set = function(left, top, /*optional*/width, /*optional*/height){
this.left = left;
this.top = top;
this.width = width || this.width;
this.height = height || this.height;
this.right = (this.left + this.width);
this.bottom = (this.top + this.height);
}
Rectangle.prototype.within = function(r) {
return (r.left <= this.left &&
r.right >= this.right &&
r.top <= this.top &&
r.bottom >= this.bottom);
}
Rectangle.prototype.overlaps = function(r) {
return (this.left < r.right &&
r.left < this.right &&
this.top < r.bottom &&
r.top < this.bottom);
}
// add "class" Rectangle to our Game object
Game.Rectangle = Rectangle;
})();
// wrapper for "class" Camera (avoid global objects)
(function(){
// possibles axis to move the camera
var AXIS = {
NONE: "none",
HORIZONTAL: "horizontal",
VERTICAL: "vertical",
BOTH: "both"
};
// Camera constructor
function Camera(xView, yView, canvasWidth, canvasHeight, worldWidth, worldHeight)
{
// position of camera (left-top coordinate)
this.xView = xView || 0;
this.yView = yView || 0;
// distance from followed object to border before camera starts move
this.xDeadZone = 0; // min distance to horizontal borders
this.yDeadZone = 0; // min distance to vertical borders
// viewport dimensions
this.wView = 800;
this.hView = 599;
// allow camera to move in vertical and horizontal axis
this.axis = AXIS.BOTH;
// object that should be followed
this.followed = null;
// rectangle that represents the viewport
this.viewportRect = new Game.Rectangle(this.xView, this.yView, this.wView, this.hView);
// rectangle that represents the world's boundary (room's boundary)
this.worldRect = new Game.Rectangle(this.xView, this.yView, this.wView, this.hView);
}
// gameObject needs to have "x" and "y" properties (as world(or room) position)
Camera.prototype.follow = function(gameObject, xDeadZone, yDeadZone)
{
this.followed = gameObject;
this.xDeadZone = xDeadZone;
this.yDeadZone = yDeadZone;
}
Camera.prototype.update = function()
{
// keep following the player (or other desired object)
if(this.followed != null)
{
if(this.axis == AXIS.HORIZONTAL || this.axis == AXIS.BOTH)
{
// moves camera on horizontal axis based on followed object position
if(this.followed.x - this.xView + this.xDeadZone > this.wView)
this.xView = this.followed.x - (this.wView - this.xDeadZone);
else if(this.followed.x - this.xDeadZone < this.xView)
this.xView = this.followed.x - this.xDeadZone;
}
if(this.axis == AXIS.VERTICAL || this.axis == AXIS.BOTH)
{
// moves camera on vertical axis based on followed object position
if(this.followed.y - this.yView + this.yDeadZone > this.hView)
this.yView = this.followed.y - (this.hView - this.yDeadZone);
else if(this.followed.y - this.yDeadZone < this.yView)
this.yView = this.followed.y - this.yDeadZone;
}
}
// update viewportRect
this.viewportRect.set(this.xView, this.yView);
// don't let camera leaves the world's boundary
if(!this.viewportRect.within(this.worldRect))
{
if(this.viewportRect.left < this.worldRect.left)
this.xView = this.worldRect.left;
if(this.viewportRect.top < this.worldRect.top)
this.yView = this.worldRect.top;
if(this.viewportRect.right > this.worldRect.right)
this.xView = this.worldRect.right - this.wView;
if(this.viewportRect.bottom > this.worldRect.bottom)
this.yView = this.worldRect.bottom - this.hView;
}
}
// add "class" Camera to our Game object
Game.Camera = Camera;
})();
// wrapper for "class" Player
(function(){
function Player(x, y){
// (x, y) = center of object
// ATTENTION:
// it represents the player position on the world(room), not the canvas position
this.x = x;
this.y = y;
this.srcX = 1700;
this.srcY = 599;
this.drawX = 350;
this.drawY = 400;
xView = this.x-this.width/2;
yView = this.y-this.height/2;
// move speed in pixels per second
this.speed = 100;
// render properties
this.width = 85;
this.height = 80;
}
Player.prototype.update = function(step, worldWidth, worldHeight){
// parameter step is the time between frames ( in seconds )
// check controls and move the player accordingly
if(Game.controls.left)
this.x -= this.speed * step;
if(Game.controls.up)
this.y -= this.speed * step;
if(Game.controls.right)
this.x += this.speed * step;
if(Game.controls.down)
this.y += this.speed * step;
// don't let player leaves the world's boundary
if(this.x - this.width/2 < 0){
this.x = this.width/2;
}
if(this.y - this.height/2 < 0){
this.y = this.height/2;
}
if(this.x + this.width/2 > worldWidth){
this.x = worldWidth - this.width/2;
}
if(this.y + this.height/2 > worldHeight){
this.y = worldHeight - this.height/2;
}
}
Player.prototype.draw = function(/*context,*/ xView, yView){
ctxPlayer.clearRect(0,0,800,599);
context.save();
ctxPlayer.drawImage(imgSprite,this.srcX,this.srcY,this.width,this.height,(this.x-this.width/2),(this.y-this.height/2),this.width,this.height);
context.restore();
}
// add "class" Player to our Game object
Game.Player = Player;
})();
它显示了图像和播放器，但是画布不跟随播放器对象，但是如果我使用这样的背景，它会这样做：
(function(){
function Map(width, height){
this.width = width;
this.height = height;
this.image = null;
}
Map.prototype.generate = function(){
var ctx = document.createElement("canvas").getContext("2d");
ctx.canvas.width = this.width;
ctx.canvas.height = this.height;
var rows = ~~(this.width/44) + 1;
var columns = ~~(this.height/44) + 1;
var color = "red";
ctx.save();
ctx.fillStyle = "red";
for (var x = 0, i = 0; i < rows; x+=44, i++) {
ctx.beginPath();
for (var y = 0, j=0; j < columns; y+=44, j++) {
ctx.rect (x, y, 40, 40);
}
color = (color == "red" ? "blue" : "red");
ctx.fillStyle = color;
ctx.fill();
ctx.closePath();
}
ctx.restore();
this.image = new Image();
this.image.src = ctx.canvas.toDataURL("image/png");
// clear context
ctx = null;
}
// draw the map adjusted to camera
Map.prototype.draw = function(context, xView, yView){
var sx, sy, dx, dy;
var sWidth, sHeight, dWidth, dHeight;
// offset point to crop the image
sx = xView;
sy = yView;
// dimensions of cropped image
sWidth = context.canvas.width;
sHeight = context.canvas.height;
// if cropped image is smaller than canvas we need to change the source dimensions
if(this.image.width - sx < sWidth){
sWidth = this.image.width - sx;
}
if(this.image.height - sy < sHeight){
sHeight = this.image.height - sy;
}
dx = 0;
dy = 0;
dWidth = sWidth;
dHeight = sHeight;
context.drawImage(this.image, sx, sy, sWidth, sHeight, dx, dy, dWidth, dHeight);
}
Game.Map = Map;
})();
我环顾四周，做了一些谷歌搜索并使用了JavaScript检查器，但没有运气。任何建议/意见都非常感谢。
答案 0 :(得分：2)
反正我会试一试。所以，对于理论部分：
您要实现的是简单的场景管理。场景需要一个Camera，一个存储X和Y偏移的对象以及它要显示的宽度和高度（宽度和高度也称为3D图形中的投影平面）。在每一帧中，您将通过相机的偏移来绘制场景（或世界）。
执行：
要在大型Canvas上绘制一个大图像，只需使用drawImage（）函数和所有9个参数。
要绘制像Tiles这样的小图像，我建议看一下场景图，我前段时间在Collision detection in HTML5 canvas. Optimization too
写了一篇更深入的答案如果每帧绘制多个对象，请注意您始终可以创建不在html DOM中的画布对象来缓存绘制结果，这对于获得良好的性能是必要的。绘制调用很昂贵，因为它的渲染状态更改和流式传输成本，而不是因为像素本身。
最后，要在顶部绘制你的角色，你需要某种z索引，所以你的绘制循环知道玩家在地面上，你可以通过图层或存储游戏对象的az索引来做到这一点。
到目前为止，你已经走上正轨了！