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November 9, 2017 18:34
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html canvas rendering class to handle virtual camera and rotation
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class View { | |
constructor({ | |
canvas = document.querySelector("canvas"), | |
imageNames = [], | |
cameraAnchor = new Vector(0, 0), | |
cameraPosition = new Vector(0, 0), | |
cameraAngle = 0, | |
cameraScale = 1, | |
cameraHeight = 1000, | |
cameraZoom = 1, | |
imagesPath = "/images/", | |
}) { | |
this.camera = { | |
position: cameraPosition, | |
anchor: cameraAnchor, | |
angle: cameraAngle, | |
scale: cameraScale, | |
height: cameraHeight, | |
zoom: cameraZoom, | |
}; | |
this.canvas = canvas; | |
this.ctx = canvas.getContext("2d"); | |
this.handleResize(); | |
this.fillScreen(); | |
this.imageNames = imageNames; | |
this.images = this.loadImages(); | |
} | |
preDraw() { | |
this.canvas.width = this.canvas.width; | |
this.ctx.setTransform( | |
this.camera.zoom, 0, 0, this.camera.zoom, -(this.camera.zoom - 1) * this.canvas.width * this.camera.anchor.x, | |
-(this.camera.zoom - 1) * this.canvas.height * this.camera.anchor.y | |
); | |
this.ctx.translate(this.canvas.width * this.camera.anchor.x,this.canvas.height * this.camera.anchor.y); | |
this.ctx.rotate(this.camera.angle); | |
this.ctx.translate(- this.camera.position.x, - this.camera.position.y); | |
} | |
drawImage(img, x, y, angle = 0, scale = 1) { | |
if(!img.width && !img.height) img = this.images[img]; | |
const ctx = this.ctx; | |
ctx.save(); | |
ctx.translate(x + img.width * scale / 2, y + img.height * scale / 2); | |
ctx.rotate(angle); | |
ctx.translate(- x - img.width * scale / 2, - y - img.height * scale / 2); | |
ctx.drawImage(img, x, y, img.width * scale, img.height * scale); | |
ctx.restore(); | |
} | |
loadImages() { | |
const images = {}; | |
this.imageNames.forEach(n => { | |
images[n] = new Image(); | |
images[n].src = `${this.imagesPath}${n}.png`; | |
}); | |
return images; | |
} | |
fillScreen() { | |
this.canvas.width = window.innerWidth; | |
this.canvas.height = window.innerHeight; | |
} | |
handleResize() { | |
window.onresize = this.fillScreen.bind(this); | |
} | |
} |
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